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  • phytoplankton
  • saline lakes
  • Springer  (205)
  • 1995-1999  (205)
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  • 1
    Electronic Resource
    Electronic Resource
    A weighted-averaging regression and calibration model for inferring lakewater salinity from fossil diatom assemblages in saline lakes of the Vestfold Hills: a new tool for interpreting Holocene lake histories in Antarctica (1998)
    Springer
    Journal of paleolimnology 19 (1998), S. 99-113 
    Details
    ISSN: 1573-0417
    Keywords: Antarctica ; saline lakes ; weightedaveraging ; transfer function ; diatom analysis ; palaeolimnology ; climate change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The relationship between surface sediment diatom assemblages and measured limnological variables in thirty-three coastal Antarctic lakes from the Vestfold Hills was examined by constructing a diatom-water chemistry dataset. Previous analysis of this dataset by canonical correspondence analysis revealed that salinity accounted for a significant amount of the variation in the distribution of the diatom assemblages. Weighted-averaging regression and calibration of this diatom-salinity relationship was used to establish a transfer function for the reconstruction of past lakewater salinity from fossil diatom assemblages. Weighted-averaging regression and calibration with classical deshrinking provided the best model for salinity reconstructions and this was applied to the fossil diatom assemblages from one of the saline lakes in the Vestfold Hills in order to assess its potential for palaeosalinity and palaeoclimate reconstruction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007947402927
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  • 2
    Electronic Resource
    Electronic Resource
    A diatom-conductivity transfer function for Spanish salt lakes (1998)
    Springer
    Journal of paleolimnology 19 (1998), S. 399-416 
    Details
    ISSN: 1573-0417
    Keywords: saline lakes ; paleolimnology ; paleoclimate ; diatoms ; transfer functions ; Spain ; CCA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Diatom-salinity transfer functions for interpretation of palaeosalinity and palaeoclimate change have been developed successfully for parts of North America and North and East Africa, but there is a need for data-sets in other saline lake regions of the world. A data-set of 74 modern diatom samples and associated water chemistry data is described from Spain. The influence of conductivity and other environmental variables on diatom distribution is explored using canonical correspondence analysis (CCA) and partial CCAs. A transfer function is derived for conductivity (70 samples) whose apparent predictive ability is high (apparent r2 = 0.91). Performance under jackknifing is poor due to the heterogeneous nature of the data-set and poor coverage of the freshwater end of the salinity gradient. There is a lack of suitable low-salinity sites in Spain, and the accuracy of estimated salinity optima and tolerance ranges may be improved by merging this data-set with those of other regions. The Spanish transfer function has strong affinities with the African data-set and contributes important ecological data for diatom taxa which are absent or poorly represented in the modern flora of African lakes, and for which, in fossil material, there were previously no good modern analogues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007934627134
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  • 3
    Electronic Resource
    Electronic Resource
    Quaternary charophytes from Salina del Bebedero, Argentina: their relation with extant taxa and palaeolimnological significance (1999)
    Springer
    Journal of paleolimnology 21 (1999), S. 307-323 
    Details
    ISSN: 1573-0417
    Keywords: charophytes ; gyrogonite morphology ; saline lakes ; palaeoecology ; Palaeobiogeography ; Argentina ; microfossils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Charophyte (Charales, green macroscopic algae) assemblages found in Quaternary shoreline sediments from Salina del Bebedero, Argentina, are described in detail, illustrated, and statistically analysed. Fossil gyrogonites, Late Pleistocene and Holocene in age, of Chara cf. hispida var. major (Hartman) Wood, Chara halina García, Chara hornemannii Wallmann, Chara bulbillifera (Donterberg) García, Lamprothamnium haesseliae Donterberg and Lamprothamnium succinctum (Braun ex Ascherson) Wood were identified. A comparison with extant charophyte species of similar ecological requirements allowed for an accurate systematical determination and provided useful data for complementary palaeoecological and palaeobiogeographical approaches. On this basis, a reconstruction of palaeo-salinities for the Salina del Bebedero lake, represented by eleven palaeo-beaches, is proposed. Also the associations of charophytes with the ostracods Cyprideis sp., Limnocythere sp., Pampacythere sp., Cypridopsis sp., Darwinula sp., Ilyocypris gibba (Randohr) Brady and Norman, and the foraminifers Ammonia sp., Elphidium gunteri Cole, Quinqueloculina sp., and one species of Discorbacea are analysed, since they are present in both the fossil and modern environments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008067112334
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  • 4
    Electronic Resource
    Electronic Resource
    Diatom preservation in the recent sediment record of Spanish saline lakes: implications for palaeoclimate study (1998)
    Springer
    Journal of paleolimnology 19 (1998), S. 129-137 
    Details
    ISSN: 1573-0417
    Keywords: saline lakes ; paleolimnology ; paleoclimate ; diatoms ; taphonomy ; preservation ; Spain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract In palaeoclimate research, fossil diatoms from saline lakes can be excellent indicators of past salinity, a proxy for climate change, although they are sometimes poorly preserved in sediment cores. Spain has numerous salt lakes but the potential of diatoms for studies of climate change has never been investigated. A comprehensive survey of diatom preservation is described based on modern and fossil diatoms from short cores (〈50 cm depth) in a representative data-set of 59 sites, and the main factors affecting preservation are investigated using principal components analysis (PCA). Most lakes do not preserve a diatom record; four sites in southern Spain are identified which both contain diatoms and have suitable limnological characteristics for a climate study. Many lakes are ephemeral and the physical effects of desiccation, coupled with other factors such as turbidity and high salinity, are the main factors enhancing diatom dissolution or their failure to be incorporated into the sediment record.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007948600780
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  • 5
    Electronic Resource
    Electronic Resource
    Glutamine Synthetase activity in limnetic phytoplankton (1996)
    Springer
    Aquatic sciences 58 (1996), S. 103-119 
    Details
    ISSN: 1420-9055
    Keywords: Lake ; phytoplankton ; N-assimilation ; N-uptake ; Glutamine Synthetase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The seasonal distribution of potential Glutamine Synthetase (GS) activities was studied in eutrophic Lake Aydat (France, Massif Central). The validity of this index of N-assimilation in field studies was tested by a comparison with the coupling of distributions of inorganic nitrogen uptake rate based on14C incorporation into proteins and the amino acids to protein ratio together with several abiotic and biotic parameters. The potential GS activities recorded during the seasonal succession of phytoplankton (characterized by the dominance of diatoms) were in the same order of magnitude of those reported from the very poor literature on this subject. Over high N-NO 3 - availability, the potential GS activities recorded were close to indirect estimations of N-uptake rates. During nitrogen depletion, high potential GS activities (which coincided with a development of small diatoms) were recorded suggesting that cell metabolism adapted to N-nutrient constraints. In addition, potential GS activity evolved concomitantly to other indicators of N-uptake and N-status. However, N-assimilation rates based on the enzymatic approach were lower than those obtained through indirect isotopic determination of uptakes rates. We suggest therefore that GS was not the unique pathway of ammonium assimilation in field populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877110
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  • 6
    Electronic Resource
    Electronic Resource
    Time series of multivariate data in aquatic ecology (1995)
    Springer
    Aquatic sciences 57 (1995), S. 185-198 
    Details
    ISSN: 1420-9055
    Keywords: Time series ; multivariate data ; phytoplankton ; abiotic factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Coupling of multivariate methods and time series analysis can be ueful for studying dynamics of aquatic communities. This is demonstratred with a data set from the pelagic area of an oligo-mesotrophic lake in Central Spain during 61 consecutive days of Autumn overturn. Abiotic variables, phytoplankton species and their total biomass were traced. Species abundance and specific biomass were considered as indices of community structure and resource partitioning, respectively. Abiotic and algal data sets were subjected to factor analyses of cases separately. Atmospheric forcing and nitrogen could be considered as the main (2) driving variables of the abiotic matrix. The coupling of motile abilities and cell size was associated to the main factors of the community structure matrix whereas phosphorus limitation and species responses to buoyancy represented the main factors of the biomass matrix. Coordinates of the two first factors could be used to mimic the trajectories in the data space. Significant short term lags (1–4 days) were found in most time series. Lagged responses of atmospheric forcing and nitrogen on phytoplankton community structure and resource partitioning at scales of 1–7 days were also shown. Overall phytoplankton biomass did not show significant delayed responses, thereby suggesting that it might be resulting from the interplay of other non-studied factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877426
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  • 7
    Electronic Resource
    Electronic Resource
    Eicosanoids and Egg-Hatching Synchrony in Barnacles: Evidence Against a Dietary Precursor to Egg-Hatching Pheromone (1997)
    Springer
    Journal of chemical ecology 23 (1997), S. 2299-2312 
    Details
    ISSN: 1573-1561
    Keywords: Eicosanoids ; pheromone ; egg-hatcing ; barnacle ; phytoplankton ; lipoxygenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The boreoarctic barnacle, Semibalanus balanoides (= Balanus balanoides) (L.), has the ability to synchronize the release of its nauplii with the spring phytoplankton bloom, thereby ensuring that the larvae can start their planktotrophic development successfully. Hatching is induced by an egg-hatching pheromone (an hydroxy fatty acid) released by the adult. Here, the possibility that the pheromone is an excretory metabolite of dietary eicosapentaenoic acid (EPA) is examined. Egg hatching could be induced by feeding gravid adult barnacles on Skeletonema costatum, but neither a concentrated culture of this diatom nor cell-free culture medium induced egg hatching in vitro. Following a 15-min incubation of EPA in seawater, a product with egg hatching activity was obtained, presumably by autooxidation. Egg hatching was not induced by feeding barnacles with lecithin liposomes containing EPA. Likewise, radiolabeled egg-hatching pheromone was not released by adult barnacles that had been fed with [14C]EPA liposomes. Egg-hatching pheromone was not released by barnacles that were actively feeding on S. costatum prior to egg-hatching. The production of egg-hatching pheromone was inhibited in vitro and in vivo by lipoxygenase inhibitors. Taken together, the results suggest that egg-hatching pheromone is not an excretory metabolite but is derived from EPA released from membrane phospholipid and acted upon by a lipoxygenase. The nature of the stimulus to precursor fatty acid release has yet to be established, but a link with molting appears tenuous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/B:JOEC.0000006675.61630.f0
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  • 8
    Electronic Resource
    Electronic Resource
    Responses of phyto- and zooplankton to liming in a small acidified humic lake (1995)
    Springer
    Water, air & soil pollution 85 (1995), S. 943-948 
    Details
    ISSN: 1573-2932
    Keywords: acidification ; liming ; phytoplankton ; zooplankton ; humic lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Liming resulted in an immediate and transitory decrease of plankton biomass and phytoplankton primary production in the limed part of an acidified humic lake. In the longer term liming has changed species composition and dominance of phyto- and zooplankton. Due to increased transparency and improved oxygen conditions plankton biomass peaked deeper in the water column after liming. During the three years post-liming period phyto- and zooplankton communities have changed less than reported in several other studies. This is largely because liming was carried out well before the collapse of perch population, which has controlled zooplankton both in the pre- and post-treatment period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00476951
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  • 9
    Electronic Resource
    Electronic Resource
    MAJOR PATHWAYS FOR NITROGEN REMOVAL IN WASTE WATER STABILIZATION PONDS (1997)
    Springer
    Water, air & soil pollution 94 (1997), S. 125-136 
    Details
    ISSN: 1573-2932
    Keywords: nitrogen removal ; waste stabilization pond ; phytoplankton ; nitrification and denitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A study on the factors influencing nitrogen removal in waste water stabilization ponds was undertaken in an eight-pond series in Werribee, Australia. Nitrogen species including Kjeldahl nitrogen, total ammonia nitrogen, nitrite and nitrate were monitored monthly from March 1993 to January 1994. At the same time, pH, temperature, chlorophyll a content and dissolved oxygen were also recorded. Highest nitrogen removal occurred during the period with highest levels of chlorophyll a content and dissolved oxygen, but the rate of nitrogen removal was not related to temperature and pH. Enhanced photosynthetic activities resulting from an increased phytoplankton abundance due to prolonged detention time caused an increase in dissolved oxygen, and created an optimum condition for nitrification to occur. In this process, ammonia was oxidized to nitrite and nitrate which were subsequently reduced to elemental nitrogen. Apart from nitrification-denitrification which was the major nitrogen removal pathway in the study system, algal uptake of ammonium, nitrate and nitrite as nutrient sources also contributed to the nitrogen removal. The role of phytoplankton and zooplankton in the treatment process in waste stabilization ponds was discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026438730507
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  • 10
    Electronic Resource
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    Dynamic modelling of photosynthesis in marine and estuarine ecosystems (1997)
    Springer
    Environmental modeling and assessment 2 (1997), S. 83-93 
    Details
    ISSN: 1573-2967
    Keywords: ecological model ; phytoplankton ; productivity ; mixing ; dynamic simulation ; OOP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The relationship between primary productivity and light intensity is usually modelled as a static representation of photosynthesis, assuming that the parameters describing the response to light are constant. However, these parameters have a dynamic behaviour justifying the development of dynamic models in order to improve the description of photosynthesis in the sea. In this work a mathematical model is used to simulate several situations where the phytoplankton exposure to light is controlled by the temporal variation of light intensity and the vertical advective and diffusive flux. The model includes both a static and a dynamic description of photosynthesis. It uses object‐oriented methods to switch between different types of productivity response to light intensity and to potential photoinhibition effects. The main conclusions emerging from the simulations performed are that the dynamic behaviour of the production–light curves is relevant in the simulation of primary productivity, and that this relevance is more pronounced under high light conditions and/or in the absence of vertical mixing. It is suggested that large scale models, where the time and spatial scales are too large to include the dynamic behaviour of the photosynthetic light response, may be parameterized by smaller scale simulations including the mentioned dynamic behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019044907648
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  • 11
    Electronic Resource
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    Estimation of phytoplankton photosynthesis and nutrient limitation in the Eastern Scheldt estuary using variable fluorescence (1999)
    Springer
    Aquatic ecology 33 (1999), S. 101-104 
    Details
    ISSN: 1573-5125
    Keywords: chlorophyll fluorescence ; nutrient limitation ; phytoplankton ; photosynthesis ; quantum efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009900124650
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  • 12
    Electronic Resource
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    Experimental study of the impacts of silver carp on plankton communities of eutrophic Villerest reservoir (France) (1999)
    Springer
    Aquatic ecology 33 (1999), S. 193-204 
    Details
    ISSN: 1573-5125
    Keywords: biomanipulation ; eutrophic reservoir ; mesocosm ; phytoplankton ; silver carp ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the impact of five silver carp biomass levels (0, 8, 16, 20, and 32 g m−3) on plankton communities and water quality of Villerest eutrophic reservoir (France). We realized the experiments using outdoor mesocosms. The presence of silver carp led to changes in zooplankton and phytoplankton assemblages. High fish biomass strongly reduced cladoceran abundance (through predation). Silver carp inefficiently grazed down particles 〈 20 μm. More importantly, however, the suppression of herbivorous cladocerans resulted in the increase of small size algae which were relieved from grazing and benefit from high nutrient concentrations. In contrast, in mesocosms without fish, the dominance of cladocerans (mainly Daphnia) controlled small size algae and probably also larger size algae (colonial chlorophytes, cyanobacteria). Thus, the Secchi disc transparency increased markedly. Through cascade effects, the modification of grazers communities led to changes in the utilization patterns of the added nutrients by phytoplankton communities. In high fish biomass treatments, nutrients were more efficiently accumulated into particulate fractions compared with no-fish and low-fish biomass treatments that were characterized by higher dissolved nutrients concentrations. Zooplankton was an essential source of food for silver carp. The productivity of zooplankton sustained a moderate silver carp biomass (up to 16 g m−3). In the presence of the highest fish biomass, the productivity of zooplankton was not large enough and silver carps fed on additional phytoplankton. Although mesocosms with high fish biomass were characterized by a slight cyanobacteria development compared with other fish mesocosms, silver carp was not effective in reducing cyanobacteria dominance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009984713183
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  • 13
    Electronic Resource
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    Phytoplankton dynamics in the River Meuse as affected by pollution (1995)
    Springer
    Aquatic ecology 29 (1995), S. 103-116 
    Details
    ISSN: 1573-5125
    Keywords: River Meuse ; pollution ; phytoplankton ; ecological rehabilitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The temporal and spatial dynamics of phytoplankton in the River Meuse and a number of physical and chemical parameters were analyzed to gain insight into the pollution level in the river affecting the phytoplankton community. During 1993, samples were taken every two months at eight stations along the River Meuse for physical, chemical and biological characterization of the water. In February, water samples were also taken for laboratory incubations of the natural plankton community. The algae showed a rapid successive development with highest densities (up to 77 mg chlorophylla l−1) in the middle reach of the river in spring and summer. During winter algal biomass remained very low. A substantial input of nutrients (nitrogen, phosphorus) was observed in the middle reach of the river. Concurrently, an increase in temperature and a reduction in pH was observed. Furthermore, the toxicity of polar organic compounds in the Microtox test showed a strong increase up to the city of Liège and the Belgian/Dutch border; the water quality improved further downstream. The relatively high toxicity at the location Liège was reflected in relatively low growth rates of phytoplankton in the laboratory experiments using water from these locations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02061793
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  • 14
    Electronic Resource
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    Using XAD resins to study the effects of reduced organic micropollutant concentrations in River Rhine and Meuse water on phytoplankton growth (1995)
    Springer
    Aquatic ecology 29 (1995), S. 151-156 
    Details
    ISSN: 1573-5125
    Keywords: phytoplankton ; specific growth rate ; XAD-4 ; XAD-8 ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Laboratory incubation experiments were used to study the effect of reduced concentrations of organic micropollutants in water from the rivers Rhine and Meuse on the specific growth rate of the river phytoplankton community. Before incubation, part of the water sampled was treated with XAD-4 and XAD-8 resins to absorb dissolved organic compounds. Four dilutions were made by mixing untreated water with XAD-treated water in the ratios 100:0 (control), 70:30, 40:60 and 0:100. The phytoplankton specific growth rate increased significantly with the increased fraction treated with XAD in all but one incubation experiment. In these experiments, the specific growth rate was on average 9% higher in the fraction in which 100% was treated with XAD than in the controls. In the Rhine and Meuse river water, phytoplankton growth seemed to be inhibited by organic compounds. This inhibition was ascribed to the presence of dissolved organic micropollutants. Removing organic micropollutants using XAD resins to study the toxic effects of these compounds on field phytoplankton communities can be concluded to be a promising tool for risk assessment of micropollutants but needs to be supported by additional methodological research.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02336044
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  • 15
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    Spatial and temporal variation of physico-chemical conditions and phytoplankton during a dry year in the Tagus estuary (Portugal) (1995)
    Springer
    Aquatic ecology 29 (1995), S. 323-332 
    Details
    ISSN: 1573-5125
    Keywords: estuary ; phytoplankton ; spatio-temporal variations ; multivariate analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During monthly synoptic surveys in a dry year, physicochemical and biological data were collected at 15 stations throughout the Tagus estuary. A Principal Component Analysis (PCA) was used to identify the major sources of variation in the data. The most important variations in the Tagus estuary were the spatial variations, mainly the longitudinal ones showing clearly the riverine and the sea water influenced zones of the estuary. The results also showed that a lateral variation was due to the local pollution as indicated by intense organic matter degradation and high rates of oxygen consumption. The seasonal variation related to temperature and the variation associated with the semidiurnal tidal cycle were also apparent. These, however, contributed less than the spatial variation to the total variability in the measured parameters of the Tagus estuary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02084231
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  • 16
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    Seasonal variation of phytoplankton community in Thale Sap Songkhla, a lagoonal lake in southern Thailand (1997)
    Springer
    Aquatic ecology 30 (1997), S. 297-307 
    Details
    ISSN: 1573-5125
    Keywords: phytoplankton ; temporal variation ; abundance ; diversity ; salinity ; total nitrogen ; total phosphorus ; lagoonal lake ; Thailand
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phytoplankton in Thale Sap Songkhla was investigated at 2–3 month intervals from August 1991 to October 1993. The abundance of phytoplankton ranged from 1.4×106 to 1.3×109 cells m−3. A total of 6 divisions with 103 genera were identified as Bacillariophyta: 49 genera, Chlorophyta: 21 genera, Pyrrhophyta: 15 genera, Cyanophyta: 12 genera, Chrysophyta: 3 genera and Euglenophyta: 3 genera. Although phytoplankton abundance was distinctly greater in the first year of study (August 1991–June 1992) than in the second year (August 1992–October 1993), their patterns are similar: 2 peaks yearly. The peaks of phytoplankton occurred in the heavy rainy season (northeast monsoon) and the light rainy season (southwest monsoon). The main bloom was found during December–January, with a predominance of blue-green algae (e.g. Aphanizomenon andPhormidium) and green algae (e.g. Eudorina). Their species composition also increased, an effect of the large amount of rainfall resulting in low salinity during the northeast monsoon. The minor bloom was produced by diatoms during June–July when water salinity was moderate to seawater. Both phytoplankton numbers and species composition were high. However, unpredictably heavy rainfall during the southwest monsoon period may reduce diatom production due to rapid immediate replacement by blue-green species. Besides salinity concentration, a low total nitrogen: total phosphorus (TN: TP) ratio tended to support the growth of blue-green algae. The diversity of phytoplankton was lowest in the heavy rainy period.
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    URL: http://dx.doi.org/10.1007/BF02085873
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  • 17
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    A review of the feedbacks between bivalve grazing and ecosystem processes (1997)
    Springer
    Aquatic ecology 31 (1997), S. 349-359 
    Details
    ISSN: 1573-5125
    Keywords: suspension-feeding bivalves ; phytoplankton ; nutrient cycling ; primary production ; carrying capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper gives an overview of interactions betweenbivalve grazing and ecosystem processes, that mayaffect the carrying capacity of ecosystems for bivalvesuspension feeders. These interactions consist of anumber of positive and negative feedbacks.Bivalve grazing can result in local food depletion,which may negatively influence bivalve growth. On alarger scale, it may induce a top-down control ofphytoplankton biomasss, and structural shifts inphytoplankton composition. In the case of harmfulalgal blooms, phytoplankton may negatively affectbivalve grazing rates.The processing of large amounts of particulate mattermay change nutrient cycling on the scale of estuaries,and can result in changes in the inorganic nutrientpool available for phytoplankton, through regenerationand reduced storage of nutrients in algal biomass.This can reduce nutrient limitation of thephytoplankton and stimulate algal growth rates.Observations from mesocosm studies suggest that apositive feedback from bivalve grazing onphytoplankton growth may also change the physiologicalstate of the algae and improve food quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009924624259
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  • 18
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    Water treatment of land-based fish farm effluents by outdoor culture of marine diatoms (1996)
    Springer
    Journal of applied phycology 8 (1996), S. 193-200 
    Details
    ISSN: 1573-5176
    Keywords: water treatment ; mariculture ; effluents ; phytoplankton ; diatoms ; Skeletonema ; Chaetoceros ; mass culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The feasibility of using fish farm effluents was evaluated as a source of inorganic nutrients for mass production of marine diatoms. Batch cultures were conducted from May to July 1995 in 16-L outdoor rectangular tanks, homogenized by gentle aeration (0.2 L air L−1 h−1). The effluents from the two fish farms studied were both characterized by high concentrations of inorganic materials (NH4-N, PO4-;P, Si(OH)4-Si) and were shown to support production of marine diatoms. Moreover, periodic measurements of inorganic matter levels in the cultures showed that clearance was efficacious (90% in 3–5 days). Water purification efficiency and culture productivity were further increased through appropriate nutrient balancing. When effluents were limited in silicate, addition of Na2SiO3 induced a significant increase in both diatom biomass and nutrient removal efficiency. In this case, up to 720 000 cell mL−1 were produced dominated bySkeletonema costatum. By contrast, in effluents loaded with silicate, adjustment of the N:P:Si ratio by NH4-N and PO4-P supplementation then gave increased biomass production. In this case, the maximum cell density found was 450 000 cell mL−1, dominated byChaetoceros spp.
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    URL: http://dx.doi.org/10.1007/BF02184971
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  • 19
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    Effects of different N- and P-loading on primary and secondary production in an experimental marine ecosystem (1999)
    Springer
    Aquatic ecology 33 (1999), S. 65-81 
    Details
    ISSN: 1573-5125
    Keywords: eutrophication ; mesocosm ; phytoplankton ; zooplankton ; macrobenthos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of nutrient loading on phytoplankton, zooplankton and macrozoobenthos in experimental ecosystems was studied in a 7-month experiment. The mesocosms were designed to mimic the major physical characteristics (irradiance, temperature, mixing) of the Dutch coastal zone in the river Rhine plume. Three different nutrient loading scenarios were used, representing present and future conditions. The level of the spring phytoplankton bloom was determined by phosphorus loading, whereas during summer the nitrogen loading determined phytoplankton biomass. The differences in nutrient loading did not result in shifts in phytoplankton species composition. With exception of the early phase of the spring bloom, diatoms dominated phytoplankton biomass in all nutrient treatments. This was ascribed to microzooplankton grazing on smaller algal species. Microzooplankton biomass showed a positive correlation with primary production, and also significant differences between nutrient treatments. Copepod development was limited, probably due to competition with microzooplankton and predation by benthic fauna. Macrobenthos biomass correlated with primary production, and was lower in the lowest nutrient treatment.
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    Monitoring of algae in Dutch rivers: does it meet its goals? (1998)
    Springer
    Journal of applied phycology 10 (1998), S. 171-181 
    Details
    ISSN: 1573-5176
    Keywords: Cyanobacteria ; diatoms ; eutrophication/kwd〉 ; green algae ; monitoring ; phytoplankton ; rivers ; water management ; The Netherlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Observations on phytoplankton in the lower reaches of the rivers Rhine and Meuse were carried out in the framework of the national monitoring programme of the main water systems in The Netherlands. Seasonal changes in density and species composition were analysed to detect the major variables and to discuss whether this monitoring meets its goals. Phytoplankton reached peak densities of 140 and 65 µg L-1 Chl a in the Rhine and Meuse, respectively. Overall density was correlated with seasonal variation in water discharge rather than with nutrient concentrations, that are high in both rivers. The position of sampling sites in relation to the downstream development of the plankton was very important, especially in the regulated Meuse. Despite hydrographic and chemical differences between the two rivers, many species, predominantly diatoms and green algae, were shared. The occurrence of the diatom Skeletonema subsalsum in the Rhine and the green algae Neodesmus danubialis, Micractinium pusillum and Pseudotetrastrum punctatum in the Meuse (1992, but not 1996) was interpreted as a feature related, respectively, to the high salinity of the Rhine and specific riverine conditions of the Meuse. In general the potamoplankton was characterised as an opportunistic assemblage exploiting the high nutrient contents and disturbed hydrography of both rivers. Nevertheless, the phytoplankton contributed to the characterisation of the present river communities, ones that differ rather strongly in historic records. Although year to year variation in phytoplankton density is mainly related to variation in water discharge, phytoplankton biomass did increase as a result of eutrophication over a period of decades. The widespread nature of many of today's potamoplankton species in the two rivers render these organisms less useful for indicating short-term changes in water quality. However the importance of phytoplankton in trophic relationships merits its inclusion in the monitoring of riverine ecosystems.
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    URL: http://dx.doi.org/10.1023/A:1008049000764
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    Zooplankton-phytoplankton interactions: the case for refining methods, measurements and models (1997)
    Springer
    Aquatic ecology 31 (1997), S. 59-71 
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    ISSN: 1573-5125
    Keywords: Daphnia ; phytoplankton ; sampling-variance ; birth-rate ; grazing ; sedimentation ; autocorrelation analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Many of the classic experiments on the interactions between animals and their food supply were performed using laboratory cultures of Daphnia but comparable predator-prey cycles have seldom been recorded in the field. In this paper, we report the results of a field experiment designed to examine the effect of seasonal variations in the supply of edible algae on the population dynamics of Daphnia hyalina var lacustris. The experiment was performed in a large (45 m diameter) enclosure that was fertilised at regular intervals to sustain phytoplankton production. The results demonstrate that predator prey interactions of the kind recorded in culture can be detected in the field if large numbers of samples are collected and the results analysed using appropriate methods. Analyses using the numbers of Daphnia collected at a single station and chlorophyll a as a measure of food availability produced inconclusive results. Similarly, Daphnia birth rates calculated using the total number of individuals provided a poor measure of the animals reproductive response to changes in the supply of food. The clearest evidence of systematic plant-herbivore interactions was obtained when improved estimates of Daphnia numbers and adult birth rates were combined with estimates of edible rather than total algal biomass. Daphnia birth rates were then positively correlated with the estimated amount of ingestible carbon (r = 0.77) and the proportion of gravid adults decreased dramatically when the concentration of food fell below 0.10 mg C l-1. Measurements and models of phytoplankton loss rates were then used to assess the impact of Daphnia grazing on the growth and decline of three species of edible algae. The results demonstrated that most species were able to sustain positive growth rates despite short-term increases in the population filtration rate. For much of the summer, the Daphnia appeared to behave as ‘non-interactive’ grazers and had very little effect on the growth rate of their main phytoplankton food. Their grazing activity did, however, arrest the growth of a late summer population of Chlorella when the Daphnia were estimated to be filtering all the water contained in the enclosure in less than a day.
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    URL: http://dx.doi.org/10.1023/A:1009920214357
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    Antibiotic effect of linolenic acid fromChlorococcum strain HS-101 andDunaliella primolecta on methicillin-resistantStaphylococcus aureus (1995)
    Springer
    Journal of applied phycology 7 (1995), S. 121-127 
    Details
    ISSN: 1573-5176
    Keywords: algae ; antibiotics ; methicillin resistance ; fatty acids ; linolenic acid ; phytoplankton ; Chlorococcum ; Dunaliella primolecta ; Staphylococcus aureus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methanol extracts fromChlorococcum strain HS-101 andDunaliella primolecta strongly inhibited the growth of a strain of methicillin-resistantStaphylococcus aureus (MRSA), which is causing serious problems in Japanese hospitals. So that the anti-MRSA substance(s) could be purified and identified, the growth medium was improved for antibiotic production. When the two strains were cultured in their improved media, antibiotic production byChlorococcum strain HS-101 was 1.8-fold that in the standard BG-11 medium, and production byD. primolecta was 2.3-fold. The activity pattern of fractions eluted by silica-gel or gel-permeation chromatography suggested that both strains produced two antibiotic substances. Identification of the purified substances by NMR and GC-MS showed that one of the active substances in both strains wasα-linolenic acid. Ten fatty acids from other sources were tested, and it was found that unsaturated fatty acids had antibiotic activity against MRSA, with the highest activity that of γ-linolenic acid.
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    URL: http://dx.doi.org/10.1007/BF00693057
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    Eukaryotic microbiota in the surface waters and sea ice of the Southern Ocean: aspects of physiology, ecology and biodiversity in a ‘two-phase’ ecosystem (1996)
    Springer
    Biodiversity and conservation 5 (1996), S. 1473-1504 
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    ISSN: 1572-9710
    Keywords: Southern Ocean ; protozoa ; phytoplankton ; euphotic zone ; physical environment ; sea ice ; ecosystem ; food web
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: The Southern Ocean provides a habitat for microplankton which is strongly influenced by physical factors. Of these, one of the most important and striking is the formation of sea ice. Organisms in the ice form a unique community with specific properties and adaptations. Material and organisms are exchanged between the water column and the ice during the annual cycle, and ice is an important factor in modifying biogeochemical processes and exchange between ocean and atmosphere. The coupled system, in which a range of organisms alternate between a fluid and a solid medium, provides an interesting exercise in community ecology, and has implications for the assessment of biodiversity in understanding large-scale change.
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    URL: http://dx.doi.org/10.1007/BF00051988
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    Interactions of light, temperature and inorganic nitrogen in controlling planktonic nitrogen utilisation in the Tagus estuary (1999)
    Springer
    Aquatic ecology 33 (1999), S. 251-261 
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    ISSN: 1573-5125
    Keywords: irradiance ; nitrogen uptake ; phytoplankton ; Tagus estuary ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of light, temperature and ammonium on inorganic nitrogen uptake by phytoplankton was investigated from June 1994 through December 1995 at three sites in the Tagus estuary (Portugal), during high tide of neap tides. Ammonium concentrations higher than 10 μM reduced nitrate uptake down to 24% but never prevented it. Below this threshold concentration, nitrate uptake was neither inhibited nor changed. Uptake of both nitrate and ammonium as a function of light intensity exhibited a saturation response. Uptake reduction occurred in the near bottom phytoplankton populations, particularly for nitrate. The ammonium uptake system was less limited by light than the nitrate uptake system, indicating the importance of ammonium as a nitrogen source for the phytoplankton which is likely to experience high changes in light in the well-mixed water column of this estuarine environment. Ammonium uptake was exponentially related to temperature in the upper estuary whereas in the mid and lower estuary this relationship was linear. The effect of temperature on nitrate uptake was linear but far less marked than for ammonium uptake.
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    URL: http://dx.doi.org/10.1023/A:1009993300873
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    Distribution of filter-feeding caddisflies (Trichoptera) and plankton drift in a Swedish lake-outlet stream (1999)
    Springer
    Aquatic ecology 33 (1999), S. 377-386 
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    ISSN: 1573-5125
    Keywords: phytoplankton ; POC ; stream ecology ; trophic interaction ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The objectives of this investigation were to relate the longitudinal distribution of filter-feeding caddisflies to quality and quantity of seston, and to document factors facilitating coexistence among filter-feeding species, in a 4th-order lake-outlet stream in central Sweden. A sharp decline in abundance and biomass of filtering caddisflies was evident within 1 km from the lake outlet following negative power functions. In contrast to particulate organic carbon, significant reductions of both phytoplankton and zooplankton biomass, especially some large species, were recorded between the lake-outlet and 1.9 km downstream. Differences in longitudinal and temporal distribution provide evidence of resource partitioning between filtering species included.
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    URL: http://dx.doi.org/10.1023/A:1009926509349
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    The edibility of Staurastrum chaetoceras and Cosmarium abbreviatum (desmidiaceae) for Daphnia galeata/hyalina and the role of desmids in the aquatic food web (1997)
    Springer
    Aquatic ecology 31 (1997), S. 73-78 
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    ISSN: 1573-5125
    Keywords: phytoplankton ; green algae ; extracellular mucous envelope ; grazing ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A laboratory clone of Daphnia galeata/hyalina was fed with two different planktic desmid taxa: Staurastrum chaetoceras and Cosmarium abbreviatum var. planctonicum, being about equal in cell size. Whereas Staurastrum chaetoceras was readily ingested and assimilated to a high degree, Cosmarium was hardly incorporated. This could be partly due to the presence of an extracellular mucilaginous envelope in the latter species. When decapsulated by mild sonification, Cosmarium cells were significantly better ingested but digestion was still inferior to that of Staurastrum, presumably because of the more compact cell shape of Cosmarium. From literature it appears that small-sized planktic desmid species occasionally may constitute a main food source for zooplankton, especially in eutrophic lakes. Most likely however, desmids, particularly large-sized species, play a much more important role in the food chain in the benthic compartment of shallow, oligotrophic water bodies where they serve as a food source for various macro-invertebrate taxa.
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    URL: http://dx.doi.org/10.1023/A:1009987217642
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    The interactive effects of UV-B radiation and a herbicide on uptake and allocation of carbon in two strains of the green algaScenedesmus (1997)
    Springer
    Aquatic ecology 31 (1997), S. 261-272 
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    ISSN: 1573-5125
    Keywords: sherbicide tolerance ; photosynthesis ; phytoplankton ; simetryn ; triazine ; herbicides ; ultraviolet radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the effects of UV B radiation on14C-uptake rates and carbon assimilation into the major end-products of photosynthesis of the green algaScenedesmus in the presence and absence of the triazine herbicide simetryn. Experiments were conducted using both a herbicide-susceptible and herbicide-tolerant strains ofScenedesmus. Three different UV-B dose rates were used as well as a light control. The lowest dose rate was almost the same level as in subsurface of ponds and lakes, while the other two were slightly lower and higher than natural sunlight on the surface of ponds and lakes, respectively. Total uptake rates of14C were not reduced by the UV B irradiation alone even at the highest dose rate. However, in the presence of the herbicide, uptake rates were clearly reduced by the highest dose rate of UV-B concomitant with increasing herbicide concentrations in the herbicide-susceptible strain. On the other hand, the proportion of lipid fraction was slightly reduced by all the UV-B treatments in the herbicide-susceptible strain even in the absence of the herbicide. In the herbicide-tolerant strain, uptake rates were not affected by UV-B radiation or by the herbicide. These facts indicated that UV-B effects could be smaller than predicted. It may be important to examine combined effects of UV-B and other anthropogenic and/or natural stresses for assessing actual UV-B effects in the field.
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    URL: http://dx.doi.org/10.1007/BF02493513
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    Effects of temperature and light on the composition of brackish-water rock pool ecosystems (1998)
    Springer
    Aquatic ecology 32 (1998), S. 323-334 
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    ISSN: 1573-5125
    Keywords: microcosm ; ecosystem-level ; productivity gradient ; zooplankton ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract I examined the effect of temperature and light on ecosystem composition was examined in a two factorial design using microcosms set up from natural rockpool communities. Furthermore I tested if the effect of temperature on different ecosystem components was dependent on the initial community composition by using communities from seven different rockpools that differed considerably in standing stocks of phytoplankton, zooplankton, zooplankton species composition, sediment mass and nutrient concentrations. Increased light caused phytoplankton biomass to decrease while zooplankton biomass and sediment dry weight was positively correlated to increased light levels. The effect of temperature on phytoplankon was largely determined by community type. Zooplankton biomass decreased with increasing temperature between 10 °C and 25 °C and this trend was not significantly different between different community types. A negative effect on zooplankton biomass was found at 7 °C in one community. I propose, that the stronger temperature sensitivity of metabolical cost for herbivorous organisms compared to algae productivity might explain the decrease in zooplankton biomass at high temperatures. I discuss how edibility of algae and grazer characteristics may influence the response of ecosystem composition to temperature.
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    A weighted-averaging regression and calibration model for inferring lakewater salinity using chrysophycean stomatocysts from lakes in western Canada (1995)
    Springer
    International journal of salt lake research 4 (1995), S. 1-23 
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    ISSN: 1573-8590
    Keywords: British Columbia ; chrysophytes ; paleolimnology ; saline lakes ; stomatocysts ; weighted-averaging model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract Chrysophycean stomatocysts were identified and enumerated from the surface sediments of 60 lakes located on the Interior Plateau of British Columbia. The lakes span a salinity gradient from freshwater to hypersaline (0.0–92.4 g L−1), with the majority being fresh to hyposaline. One hundred and ten stomatocyst morphotypes, almost all of which were previously described, were identified from the lake sediments. The first axis of direct gradient analysis, which was highly significant, was essentially a salinity axis (i.e. [Ca], [Mg], [K], [Na], [SO4], [DIC], and [Cl]). Most cysts were found to have fairly broad tolerances, with the narrowest tolerances occurring among morphotypes with the lowest salinity optima. Weighted-averaging regression and calibration techniques were used to develop an inference model to measure the relationship between measured average lakewater salinity and stomatocyst inferred salinity (apparent r2=0.80). Simple weighted-averaging produced a model with a lower bootstrapped RMSE of prediction than weighted-averaging with tolerance downweighting. These data indicate that chrysophyte stomatocysts are useful quantitative indicators of past lakewater salinity (in the freshwater to hyposaline range) in B.C. lakes, and can be used to strengthen the interpretations from diatom-inference models already developed from the same region.
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    URL: http://dx.doi.org/10.1007/BF01992411
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    Phytoplankton structure, composition and production in saline water-bodies in the Lower Amu Dar'ya (1997)
    Springer
    International journal of salt lake research 6 (1997), S. 217-231 
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    ISSN: 1573-8590
    Keywords: saline water-bodies ; phytoplankton ; biomass ; production ; chlorophyll ; P/B ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract Phytoplankton and its production in water-bodies of the lower Amu Dar'yawere investigated in 1984–1989. The structure and functional nature ofthe phytoplankton in the water-bodies studied were analogous to those ofthe littoral zone of eutrophic lakes, considering hydrological andhydrochemical conditions. The very high average annual P/B ratios(453–582) are considered as regional features, namely high lightintensity and prolonged light period, the salinity usual for salinewaters under anthropogenic influence, the frequent and discrete incomeof nutrients in drainage water and from sediments.
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    URL: http://dx.doi.org/10.1023/A:1009047219000
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    Seasonal fluctuations in the plankton community in a hypersaline temporary lake (Honda, southern Spain) (1997)
    Springer
    International journal of salt lake research 6 (1997), S. 353-371 
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    ISSN: 1573-8590
    Keywords: hypersaline lakes ; multivariate methods ; phytoplankton ; seasonality ; shallow lakes ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract Honda saline lake is located in an endorheic basin in the south of Spain. The lake is very shallow, with frequent seasonal drought and a high degree of unpredictability. It was sampled monthly during a relatively dry year (1994–1995, 5 months permanence). To establish a relationship between environmental variables (temperature, depth, salinity and conductivity), variables related to biological activity (organic matter, total solids suspension, and pH) and the planktonic community in the sampled months, various uni- and multivariate statistical methods were carried out. Dunaliella salina, D. viridis, and ciliates sp. 2 is the principal species group used to average out the dissimilarity between the samples. Multivariate analysis showed that salinity (as TDS), conductivity and pH made major and significant contributions to the explanation of the variance in the sample data.
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    Seasonal fluctuations in the plankton community in a hypersaline temporary lake (Honda, southern Spain) (1997)
    Springer
    International journal of salt lake research 6 (1997), S. 353-371 
    Details
    ISSN: 1573-8590
    Keywords: hypersaline lakes ; multivariate methods ; phytoplankton ; seasonality ; shallow lakes ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract Honda saline lake is located in an endorheic basin in the south of Spain. The lake is very shallow, with frequent seasonal drought and a high degree of unpredictability. It was sampled monthly during a relatively dry year (1994–1995, 5 months permanence). To establish a relationship between environmental variables (temperature, depth, salinity and conductivity), variables related to biological activity (organic matter, total solids suspension, and pH) and the planktonic community in the sampled months, various uni-and miltivariate statistical methods were carried out.Dunaliella salina, D. viridis, and ciliates sp. 2 is the principal species group used to average out the dissimilarity between the samples. Muttivariate analysis showed that salinity (as TDS), conductivity and pH made major and significant contributions to the explanation of the variance in the sample data.
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    Artemia parthenogenetica in Lake Hayward, Western Australia. II. Feeding biology in a shallow, seasonally stratified, hypersaline lake (1998)
    Springer
    International journal of salt lake research 7 (1998), S. 13-24 
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    ISSN: 1573-8590
    Keywords: Artemia ; bacteria ; benthic microbial communities ; ecology ; feeding biology ; grazing ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract Primary production in Lake Hayward, Western Australia, is dominated by benthic microbial communities, with limited planktonic primary production. This study investigated the question of how Artemia, commonly regarded as simple, obligate, non-selective filter feeders, were able to survive in this system. Bacteria (heterotrophic and autotrophic, filamentous and unicellular) were the major components in the diet of the Artemia in Lake Hayward. These bacteria were derived from bacterial aggregates in the water column and also from benthic mat material (both still attached to the substrate and from pieces floating in the water column). Benthic diatoms were a substantial dietary component of animals living in the unstratified shallow regions. Photosynthetic eukaryotic nanoplankton comprised a minor component of the diet of this Artemia population. Gut contents of a large number of animals and the results of a simple laboratory test indicated that these animals utilise substrate-bound food resources. The results of the present study raises the question of the ecological significance of surface grazing by brine shrimps in other shallow, benthos dominated saline systems.
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    Littoral benthos of the saline crater lakes of the basin of Oriental, Mexico (1998)
    Springer
    International journal of salt lake research 7 (1998), S. 87-108 
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    ISSN: 1573-8590
    Keywords: benthos ; crater lakes ; littoral ; macroinvertebrates ; Mexico ; Puebla ; saline lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract Two saline crater lakes in the basin of Oriental, Puebla-Tlaxcala-Veracruz, were investigated for littoral benthic macroinvertebrates. Fifty taxa were identified with the oligochaetes, amphipods, chironomids and leeches the dominant organisms. These four taxa made up to 99 per cent in both number and biomass. Limnodrilus hoffmeisteri, Hyalella azteca, Tanypus (Apelopia) sp. and Stictochironomus sp. were the most abundant organisms. Unlike other saline lakes which have a littoral benthos dominated by chironomids, Alchichica and Atexcac were dominated by oligochaetes (70–73 per cent). The gastropod, Physa sp., was found up to a salinity of 8 g L-1; in other studies, it has been found in lower salinities. L. hoffmeisteri is also a typical inhabitant of freshwater lakes, particularly of deep waters. It was dominant in the shallow, saline waters of the two lakes studied. Salinity did not affect species richness. Alchichica, the most saline of the six crater lakes of Puebla (salinity, 7.4 g L-1), had 30 per cent more species than the freshwater lakes, and double the species number of Atexcac. It seems the main factor controlling species richness and the density and biomass of organisms in Alchichica and Atexcac is the presence of aquatic vegetation. It does this by increasing habitat heterogeneity and providing food and protection against predators.
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    Littoral benthos of the saline crater lakes of the basin of Oriental, Mexico (1998)
    Springer
    International journal of salt lake research 7 (1998), S. 87-108 
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    ISSN: 1573-8590
    Keywords: benthos ; crater lakes ; littoral ; macroinvertebrates ; Mexico ; Puebla ; saline lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract Two saline crater lakes in the basin of Oriental, Puebla-Tlaxcala-Veracruz, were investigated for littoral benthic macroinvertebrates. Fifty taxa were identified with the oligochaetes, amphipods, chironomids and leeches the dominant organisms. These four taxa made up to 99 per cent in both number and biomass.Limnodrilus hoffmeisteri, Hyalella azteca, Tanypus (Apelopia) sp. andStictochironomus sp. were the most abundant organisms. Unlike other saline lakes which have a littoral benthos dominated by chironomids, Alchichica and Atexcac were dominated by oligochaetes (70–73 per cent). The gastropod,Physa sp., was found up to a salinity of 8 g L−1; in other studies, it has been found in lower salinities.L. hoffmeisteri is also a typical inhabitant of freshwater lakes, particularly of deep waters. It was dominant in the shallow, saline waters of the two lakes studied. Salinity did not affect species richness. Alchichica, the most saline of the six crater lakes of Puebla (salinity, 7.4 g L−1), had 30 per cent more species than the freshwater lakes, and double the species number of Atexcac. It seems the main factor controlling species richness and the density and biomass of organisms in Alchichica and Atexcac is the presence of aquatic vegetation. It does this by increasing habitat heterogeneity and providing food and protection against predators.
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    Anthropogenic perturbations to the trophic structure in a permanent hypersaline shallow lake: La Salada de Chiprana (north-eastern Spain) (1998)
    Springer
    International journal of salt lake research 7 (1998), S. 187-210 
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    ISSN: 1573-8590
    Keywords: microbial mats ; mixis ; nutrient loading ; periphyton ; saline lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract The changes in the trophic state in the Salada de Chiprana (north-eastern Spain) over two quite different seasonal cycles (1989, 1994/95) were studied. During the former cycle, the lake was permanently stratified, and was biogenically meromictic, and in the latter, showed no apparent stratification. The main variables related to the physico-chemical changes observed can be attributed to the effect caused by the increase in the nutrient loading. The large amounts of nutrients (total-N and total-P) and organic matter are due to the use of the lake as a reservoir for water discharged from irrigation. Two remarkable effects of the change are the permanent mixing of the water column and the immobilization of phosphorus in the form of ionic species and solid phases that are not available to the biota especially primary producers (phytoplankton, periphyton, microbial mats). The results of the present study emphasize the fragility of (hyper) saline ecosystems to anthropogenic disturbances such as increases in freshwater inflow and nutrient inputs. Likewise, the study reveals the failure of conservation criteria that have been used to manage this lake, especially those which refer to the control of freshwater, nutrient-rich influents.
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    Potential salinity limitations on nitrogen fixation in sediments from Mono Lake, California (1998)
    Springer
    International journal of salt lake research 7 (1998), S. 261-274 
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    ISSN: 1573-8590
    Keywords: cyanobacteria ; lake management ; Mono Lake ; nitrogen fixation ; salinity ; saline lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract Mono Lake is a hypersaline alkaline lake in the high altitude Great Basin desert of eastern California. Algal productivity of the lake is nitrogen-limited, and a contributing source is derived from benthic nitrogen fixation. Lake level and salinity have fluctuated with natural climatic variations but have also been affected by the diversion of tributary streams. This research examines the influence of varied salinity and lake level on the potential for benthic nitrogen fixation in Mono Lake. A sediment-surface microbial mat community was exposed directly, and in acclimated cultures, to a range of Mono Lake salinities under anaerobic incubations and the activity of nitrogenase assayed by acetylene reduction. Activity was stimulated in light, but also occurred in darkness. Over an experimental salinity range from 50 to 150 g L−1 TDS, nitrogenase activity was reduced by 90 per cent, with the activity persisting at the highest salinity being attributable to dark fixation alone. Between a salinity of 50 g L−1, occurring in Mono Lake over 50 years ago, and 100 g L−1, nitrogenase activity was reduced by nearly half. Changes in the area of the littoral zone at varied lake levels also affect the total amount of potential benthic nitrogen fixation in the lake. An accounting of yearly inputs of nitrogen to Mono Lake suggests N2-fixation could contribute as much as 76–81 percent of the total. Inhibition of nitrogen fixation rates by increased salinity could limit the long-term nutrient supply and benthic primary productivity of this ecosystem.
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    Particulate lipid class composition of three marine phytoplankters Chaetoceros gracilis, Isochrysis galbana (Tahiti) and Dunaliella tertiolecta grown in batch culture (1995)
    Springer
    Hydrobiologia 306 (1995), S. 1-6 
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    ISSN: 1573-5117
    Keywords: Chaetoceros gracilis ; Dunaliella tertiolecta ; Isochrysis galbana ; phytoplankton ; lipids ; algal culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The green algae D. tertiolecta, the flagellate I. galbana and the diatom C. gracilis were grown in batch cultures. The organisms were analysed for lipid class composition at the logarithmic and stationary growth phases using the Chromarod-Iatroscan thin layer chromatography with flame ionization detection (TLC-FID) system. There were major differences in lipid class production among the organisms investigated, but few differences in lipid class distribution between log phase and stationary phase cultures of D. tertiolecta and I. galbana. C. gracilis displayed the general trend exhibited in diatom metabolism, which can be characterized by an increase in triacylglycerol synthesis in situations of stress.
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    Effects of arsenate and copper on the algal communities in polluted lakes in the northern parts of Sweden assayed by PICT (Pollution-Induced Community Tolerance) (1995)
    Springer
    Hydrobiologia 306 (1995), S. 109-124 
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    ISSN: 1573-5117
    Keywords: ecotoxicology ; phytoplankton ; carbon dioxide fixation ; arsenate ; copper
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The tolerance for arsenate and copper in the carbon dioxide fixation activity of phytoplankton communities coming from lakes around the smelter at Rönnskär at the Swedish east-coast were measured during three years (1989–1991). The smelter have for several decades discharged arsenic and heavy metals into the air, and their concentrations in the lakes were clearly correlated with the distance from the smelter. The tolerance of communities from the three most polluted lakes were higher than communities from reference lakes with background concentrations of arsenic and copper. In accordance with the PICT concept it is indicated that those communities have been affected by these substances. These communities also had lower diversity than the others, but no clear correlation could be done with phytoplankton species number, or between phytoplankton biomass and pollution levels.
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    Reduced digestibility of UV-B stressed and nutrient-limited algae by Daphnia magna (1995)
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    Hydrobiologia 307 (1995), S. 147-151 
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    ISSN: 1573-5117
    Keywords: Daphnia ; digestibility ; grazing ; nutrient limitation ; phytoplankton ; UV-B
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Daphnia magna was fed the green alga Selenastrum capricornutum, cultured under four different growth conditions: (1) phosphorus limitation, (2) nitrogen limitation, (3) UV-B irradiation, and (4) no nutrient limitation, no UV-B irradiation. Contrary to non-limited algal cells, nutrient-limited cells were not efficiently assimilated. Especially, P-limited cells passed through the gut mostly intact, while N-limited cells were partly assimilated. Also, algae exposed to moderate doses of UV-B radiation (0.3 mW cm−2 of UV312) were less efficiently assimilated after being grazed. Digestibility of the algae decreased with increased UV-B exposure time. Nutrient-limited and UV-B stressed algal cells increased in volume and became granular in appearance. These changes in the algal cells, combined with changed cell wall properties, most probably reduced their digestibility.
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    Feeding selectivity of Corbicula fluminea (Bivalvia) on natural phytoplankton (1995)
    Springer
    Hydrobiologia 312 (1995), S. 171-182 
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    ISSN: 1573-5117
    Keywords: grazing selectivity ; freshwater ; molluscs ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytoplankton in water samples from the lower delta of the Paraná river (Argentina) and in the gut contents of a local populaton of the Asiatic clam Corbicula fluminea was identified and counted monthly between April 1992 and March 1993. Relative abundances of algal species were generally similar in the medium and in the stomachs of clams, suggesting the absence of feeding selectivity on the basis of taxonomic group or size-class. Diatoms made up a slightly but consistently larger (yet not significantly different) proportion of the diet of C. fluminea than of the plankton; this pattern is attributed to enhanced preservation of algal siliceous frustules, rather than to feeding selectivity. It is suggested that non-selective feeding by the bivalve is a response to the overall scarcity of food and, probably, to food collection by a combination of deposit and filter feeding.
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    Limnological survey of Lake Amvrakia, western Greece (1996)
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    Hydrobiologia 318 (1996), S. 207-218 
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    ISSN: 1573-5117
    Keywords: warm sulphate lakes ; physical limnology ; phytoplankton ; Greece
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Limnological characteristics of lake Amvrakia, a deep warm monomictic and sulphate lake in western Greece, are presented. A set of physical and chemical variables were monitored for one year cycle (October 1988–September 1989). Phytoplankton community structure and biomass are given for the entire depth of the water column. The trophic status of the lake is compared to that of other temperate and tropical lakes.
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    Low activity of alkaline phosphatase in two eutrophic reservoirs (1995)
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    Hydrobiologia 297 (1995), S. 11-16 
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    ISSN: 1573-5117
    Keywords: phosphate ; alkaline phosphatase ; P-cycling ; phytoplankton ; reservoirs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied recycling of phosphate by enzymatic hydrolysis in two temperate very eutrophic reservoirs. To assess the potential importance of phosphate regeneration by alkaline phosphatase, we determined the activity of this enzyme in lake water concomitantly with the determinations of the concentrations of phosphomonoesters, soluble reactive phosphate, total soluble phosphate and total phosphate. Contrary to our expectations for such productive waters where algal blooms are frequent, during the study period this process of phosphate regeneration was not significant, probably because the product of hydrolysis (contained in the soluble reactive phosphate fraction) was always abundant. We conclude that, in spite of what has been observed repeatedly in natural lakes with similar trophic characteristics, the readily available fraction of phosphate in these reservoirs is large and for that reason alkaline phosphatase production is low. Therefore hydrolysis by this enzyme is not significant for growth. What seems intriguing is the small amount of phosphomonoesters found in the water; with no phosphatase activity this phosphate fraction should always be high, unless hydrolysis takes place either during phosphomonoester release or later due to their instability.
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    Effect of young-of-the-year walleye (Percidae: Stizostedion vitreum) on plankton dynamics and water quality in ponds (1995)
    Springer
    Hydrobiologia 297 (1995), S. 217-227 
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    ISSN: 1573-5117
    Keywords: fish ; zooplankton ; phytoplankton ; bacteria ; nutrients ; trophic interaction ; biomanipulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To understand the impact of young-of-the-year (YOY) fish on food web dynamics and water quality, we stocked larval walleye (9 mm TL) (Stizostedion vitreum) in six experimental ponds using two fish densities (10 and 50 fish m−3) with three replicates. At high fish density, the average abundances of cladocerans and copepods and the Secchi depth were lower whereas abundances of rotifers and algae, gross primary productivity (GPP), pH and total phosphorus concentration were higher than at low fish density. Fish impact on bacterial abundance, dissolved oxygen, nitrogen and phosphorus concentrations, however, was not significant. The within treatment measurements of all variables except GPP were significantly different over time. Our results indicate that YOY walleye predation at high density can affect plankton community by reducing large zooplankton biomass and water clarity, and increasing phytoplankton abundance. The impact of YOY piscivorous fish on plankton should be considered when biomanipulation is applied for improvement of water quality.
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    A comparison of natural and human determinants of phytoplankton communities in the Kentucky River basin, USA (1995)
    Springer
    Hydrobiologia 297 (1995), S. 201-216 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; cell densities ; chl a ; taxonomic composition ; rivers ; Kentucky ; stream size ; land use ; nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Physical, chemical, and biological characteristics of the Kentucky River and its tributaries were assessed for one year to compare effects of seasonal, spatial, and human environmental factors on phytoplankton. Phytoplankton cell densities were highest in the fall and summer and lowest in the winter. Cell densities averaged 1162 (± 289 SE) cells m1−1. Cell densities were positively correlated to water temperature and negatively correlated to dissolved oxygen concentration and to factors associated with high-flow conditions (such as, suspended sediment concentrations). Chrysophytes, diatoms, and blue-green algae dominated winter, spring, and summer assemblages, respectively. Ordination analyses (DCCA) indicated that variation in taxonomic composition of assemblages was associated with stream size as well as season. Spatial variation in phytoplankton assemblages and effects of humans was investigated by sampling 55 sites in low flow conditions during August. Phytoplankton density increased with stream size. Assemblages shifted in composition from those dominated by benthic diatoms upstream to downstream communities dominated by blue-green algae and small flagellates. Human impacts were assumed to cause higher algal densities in stream basins with high proportions of agricultural or urban land use than in basins with forested/mined land use. While density and composition of phytoplankton were positively correlated to agricultural land use, they were poorly correlated to nutrient concentrations. Phytoplankton diversity changed with water quality: decreasing with nutrient enrichment and increasing with conditions that probably changed species composition or inhibited algal growth. Human impacts on phytoplankton in running water ecosystems were as great or greater than effects by natural seasonal and spatial factors. Our results indicated that phytoplankton could be useful indicators of water quality and ecosystem integrity in large river systems.
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    Can suspension feeding by bivalves regulate phytoplankton biomass in Lake Waccamaw, North Carolina? (1996)
    Springer
    Hydrobiologia 325 (1996), S. 193-200 
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    ISSN: 1573-5117
    Keywords: bivalves ; feeding ; lake ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Suspension feeding by bivalves has been hypothesized to control phytoplankton biomass in shallow aquatic ecosystems. Lake Waccamaw, North Carolina, USA is a shallow lake with a diverse bivalve assemblage and low to moderate phytoplankton biomass levels. Filtration and ingestion rates of two relatively abundant species in the lake, the endemic unionid, Elliptio waccamawensis, and an introduced species, Corbicula fluminea, were measured in experiments using natural phytoplankton for durations of 1 to 6 days. Measured filtration and ingestion rates averaged 1.78 and 1.121 ind.−1 d−1, much too low to control phytoplankton at the observed phytoplankton biomass levels and growth rates. Measured ingestion rates averaged 4.80 and 1.50 µg chlorophyll a ind.−1 d−1, too low to support individuals of either species. The abundance of benthic microalgae in Lake Waccamaw reaches 200 mg chlorophyll a m−2 in the littoral zone and averages almost an order of magnitude higher than depth-integrated phytoplankton chlorophyll a. Total microalgal biomass in the lake is therefore not controlled by suspension feeding by bivalves.
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    Multivariate analysis of phytoplankton and related environmental factors, in a shallow hypertrophic lake (1995)
    Springer
    Hydrobiologia 299 (1995), S. 93-101 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; lake ; shallowness ; hypertrophy ; ricefields area ; long-term study ; redundancy analysis ; Spain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Data on some relevant environmental variables and phytoplankton species composition, collected from the hypertrophic shallow lake Albufera of Valencia (Spain) during 1980–88, were examined using Redundancy Analysis (RDA). The hydrological cycle of the lake is manipulated for rice cultivation in the area. Seasonality and the particular hydrological cycle of the lake were the principal factors influencing long-term phytoplankton dynamics. Annual or horizontal differences were less important than the seasonal factor. However, a trend of phosphate increase and underwater illumination decrease was observed between 1980 and 1988. These changes might be related to some species year-to-year variations, although in general interannual phytoplankton changes were scarce. Spatial phytoplankton differences were much smaller than physical and chemical differences, which were mainly related to loading and residence times at the different sampling zones. Shallowness, hypertrophy and the regular hydrological cycle of the Albufera for rice yield, seem to contribute to the maintenance of an almost stable and homogeneous algal community, mainly composed of filamentous cyanophytes. RDA analysis has proved to be an efficient method in yielding valuable information on phytoplankton-environment interactions and trends over a long series of data. It seems also a feasible technique to monitor the results of lake management and restoration in the future.
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    Primary production of Lake Peipsi-Pihkva (1996)
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    Hydrobiologia 338 (1996), S. 77-89 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; primary production ; daily dynamics ; seasonal dynamics ; long-term changes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Primary production (PP) in Lake Peipsi-Pihkva, the tripartite border waterbody between Estonia and Russia, was first measured in 1965–1966. Since 1970 there exists a continuous timeseries of monthly PP measurements from May to October. Detailed investigations of the seasonal and daily dynamics as well as the vertical distribution of PP were carried out in 1985–1987. The long-term average values of integral PP (PPint) in Lakes Peipsi and Pihkva were equal (0.8 g C m−2 d−1), although the values per cubic metre (PPmax) differed more than twofold and characterized L. Pihkva as a eutrophic lake and L. Peipsi as a transition type between meso- and eutrophic lakes. The years from 1973 to 1980, 1987 and 1991 were of low productivity, while in 1971, 1983, 1988 and 1990 PP peaks occurred in both lakes. In the seasonal pattern PPint had peaks in May and July. In June, after the spring bloom, PP as well as the chlorophyll a (Chl) and ATP content were low. The high Chl peak in autumn was probably built up by the degradation products of chlorophyll, as neither PP nor ATP increased. Seasonal changes in integral PP in L. Peipsi could be well described (R 2 = 0.91) by an empirical model relating PPint to PPmax, Secchi depth (S) and total solar radiation (Q). In mixed conditions prevailing in both lakes, PP was inhibited in the surface layer and its maximum was located at a depth of 0.25...0.5 S. The threshold total solar radiation level for the onset of inhibition was between 1200 and 2000 kJ m−2 h−1 in May and July, and decreased to 〈 500 kJ m−2 h−1 in October. As a rule, inhibition started in the morning at a higher irradiance than necessary for keeping it up during evening hours. When compared with PPmax, photosynthesis in the surface layer at noon was suppressed by 56% in May, by 45% in July and by 40% in October.
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    31P-NMR study of natural phytoplankton samples (1995)
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    Hydrobiologia 300-301 (1995), S. 391-398 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; phosphorus ; 31P-NMR ; in situ sample fixation ; maximum entropy method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new fixation method was developed for the Nuclear Magnetic Resonance (NMR) study of natural phytoplankton samples collected in situ. To test NMR reliability, a Chlorella continuous culture was used in a phosphorus deficiency recovery experiment. The method was then applied to natural metalimnetic cyanobacterial plankton. The maximum Entropy Method was used to enhance the generally poor signal to noise ratio resulting from the low amount of available material and NMR sensitivity. Suggestions are made on how to improve reliability.
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    Limnological survey of the warm monomictic lake Trichonis (central western Greece); II. Seasonal phytoplankton periodicity – a community approach (1997)
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    Hydrobiologia 344 (1997), S. 141-153 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; distribution patterns ; speciesseasonality ; diversity ; multivariate analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytoplankton assemblages of the warm monomictic lakeTrichoniswere studied during the period April 1985 to February 1986.Speciescomposition and biomass data are presented along withinformationon the seasonal periodicity of dominant taxa of microalgae.Multivariate methods were used to analyze community structureandannual succession. Population succession patterns correspondtochanges in environmental variables. According to thegeneralizedphytoplankton sequences Trichonis is classified as anoligotrophiclake.
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    Long term study on the influence of eutrophication, restoration and biomanipulation on the structure and development of phytoplankton communities in Feldberger Haussee (Baltic Lake District, Germany) (1996)
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    Hydrobiologia 330 (1996), S. 89-110 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; biodiversity ; Cyanophyta ; Chlorophyta ; eutrophication ; biomanipulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Feldberger Haussee provides a classic example of eutrophication history of hardwater lakes in the Baltic Lake District (Germany) and of changes in their algal flora during the 20th century. The lake originally was regarded as slightly eutrophic. A process of drastic eutrophication from the 1950s until the end of the 1970s caused mass developments of blue-green and green algae. A restoration program was started in the 1980s to improve the water quality of the lake using both diversion of sewage outside the catchment area, and biomanipulation by altering the fish community. This restoration program led to positive changes in the lake ecosystem. Direct effects of biomanipulation resulted in an increase of herbivorous zooplankton, a decrease of phytoplankton biomass, and an increase of water transparency. The recovery of Feldberger Haussee also may have been indirectly enhanced by an increase in nutrient sedimentation as a consequence of intensified calcite precipitation, decrease in phosphorus remobilization due to a pH-decrease, increased NIP-ratio, and recolonization of the littoral zone by macrophytes. This paper concentrates on the long term development of the phytoplankton community as a response to changes in the food web structure as well as to alterations in the chemical environment of the algae. Both are reflected in four major stages passed by the algal assemblage between 1980 and 1994: (1) From 1980-summer 1985 dense green algal populations were found indicating similar conditions as in the 1970s during the period of maximum eutrophication. (2) A diverse phytoplankton community during summer 1985–1989 showed the first effects of a recovery. (3) From 1990–1992 the phytoplankton was characterized by ungrazeable filamentous blue-green algae first of all as a response to increased herbivory of zooplankton on edible species and to increasing N/P-ratios. (4) Finally, the algal species diversity increased in 1993 and 1994 whereas the phytoplankton biomass decreased showing the success of the combined restoration measures.
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    Short-term changes in the Barra Bonita reservoir (São Paulo, Brazil): emphasis on the phytoplankton communities (1996)
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    Hydrobiologia 330 (1996), S. 163-175 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; diversity ; mixing ; stratification ; stability ; disturbance hypothesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigated the biomass, primary productivity, species diversity and their controlling factors in the deeper region of the Barra Bonita reservoir (22°29′S and 48°34′W) in the State of São Paulo, Brazil. To accomplish this, short term changes (days and month) were measured during two periods of the year, winter 1993 and summer 1994. The response of the phytoplankton communities to the variability of the system, taking into account the Intermediate Disturbance Hypothesis (IDH), indicated that the frequency and intensity of the disturbances have a critical influence on the establishment of the communities. In Barra Bonita Reservoir the conditions for mixing in the winter were probably important for maintaining high diversity. On the other hand, in summer, the concentrations of suspended material, the high temperatures, and the greater stability of the water column, were probably responsible for permitting the establishment of Microcystis aeruginosa.
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    Thermal stratification, nutrient dynamics, and phytoplankton productivity during the onset of spring phytoplankton growth in Lake Baikal, Russia (1996)
    Springer
    Hydrobiologia 331 (1996), S. 9-24 
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    ISSN: 1573-5117
    Keywords: Lake Baikal ; phytoplankton ; primary productivity ; thermal stratification ; nutrient limitation ; nitrogen and phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Baikal, Russian Siberia, was sampled in July 1990 during the period of spring mixing and initiation of thermal stratification. Vertical profiles of temperature, dissolved nutrients (nitrate and soluble reactive phosphorus), phytoplankton biomass, and primary productivity were determined in an eleven-station transect encompassing the entire 636 km length of the lake. Pronounced horizontal variability in hydrodynamic conditions was observed, with the southern region of the lake being strongly thermally stratified while the middle and north basins were largely isothermal through July. The extent of depletion of surface water nutrients, and the magnitude of phytoplankton biomass and productivity, were found to be strongly correlated with the degree of thermal stratification. Horizontal differences likely reflected the contribution of two important factors: variation in the timing of ice-out in different parts of the lake (driving large-scale patterns of thermal stratification and other limnological properties) and localized effects of river inflows that may contribute to the preliminary stabilization of the water column in the face of intense turbulent spring mixing (driving meso-scale patterns). Examination of the relationships between surface water inorganic N and P depletion suggested that during the spring and early summer, phytoplankton growth in unstratified portions of the lake was largely unconstrained by nutrient supplies. As summer progressed, the importance of co-limitation by both N and P became more apparent. Uptake and regeneration rates, measured directly using the stable isotope 15N, revealed that phytoplankton in stratified portions of the lake relied primarily on NH4 as their N source. Rates of NH4 regeneration were in approximate equilibrium with uptake; both processes were dominated by organisms 〈2 µm. This pattern is similar to that observed for oligotrophic marine systems. Our study underscores the importance of hydrodynamic conditions in influencing patterns of biological productivity and nutrient dynamics that occur in Lake Baikal during its brief growing season.
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    Modelling phytoplankton dynamics in lakes and reservoirs: the problem of in-situ growth rates (1997)
    Springer
    Hydrobiologia 349 (1997), S. 5-17 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; dynamics ; growthmodelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Supposing the ability to elect in situspecies-specific replication rates of phytoplankton tobe an essential step towards the development of soundecological models of phytoplankton populations inlakes and reservoirs, we promote the case for takingmaximum specific growth rates under ideal cultureconditions as base, rather than derivations ofspecific growth rate assembled from models ofphotosynthetic carbon fixation and nutrient uptake. Itis argued that these yield capacities for growth butcan greatly exaggerate in-situ replication rates. Theuse of published regressions of robust properties oforganismic assembly is recommended and some relevantmodel algorithms are outlined.
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    The role of phytoplankton in the removal of arsenic by sedimentation from surface waters (1996)
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    Hydrobiologia 324 (1996), S. 117-123 
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    ISSN: 1573-5117
    Keywords: arsenic ; sedimentation ; phytoplankton ; partition coefficient ; particle concentration effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of phytoplankton in the removal of arsenic (As) by particle adsorption and sedimentation was investigated in Moira Lake, Canada. Sampling water and suspended particles over one year illustrated significant variation in As partitioning between particulate and aqueous phases, but failed to establish a correlation between the partition coefficient, K d, and indicators of phytoplankton biomass. A highly significant inverse logarithmic relationship was noted between K d and the concentration of suspended particles (log K d = 5.1 − 1.4 log SS; p = 0.0001) in an apparent demonstration of the particle concentration effect (O' Connor & Connolly, 1980). Particle deposition, measured by means of sediment traps, appeared to include a substantial component of resuspended surficial sediment making sediment trap results unreliable for quantifying the removal of substances from the water column. The As concentration of particles from deep traps deployed during late summer and early fall exceeded the As concentrations of suspended particles and surficial sediment, and may indicate that a highly contaminated nepheloid layer acts as a temporary sink for As.
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    Xanthophyll-cycle and photosynthetic adaptation to environment in macro- and microalgae (1996)
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    Hydrobiologia 326-327 (1996), S. 407-413 
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    ISSN: 1573-5117
    Keywords: diatoxanthin ; Gracilaria ; photoinhibition ; phytoplankton ; seaweed ; xanthophyll-cycle ; zeaxanthin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microalgae and macrophytes adapt their pigment content to the environment because excessive light could limit their photosynthetic rate by inducing photoinhibition. Carotenoids participate in the photoadaptative response especially through the operation of xanthophyll cycles (violaxanthin-zeaxanthin or diadinoxanthin-diatoxanthin). An increasing gradient of diatoxanthin in phytoplankton chromophytes is found from the inshore to the offshore waters, less turbid in relation to the different light penetration in seawater. In addition, a nyctemeral cycle is noted, with a suppression of diatoxanthin at night and its accumulation with the increase of the light. Similarly the vertical distribution, on the French Brittany coasts, of several Gracilaria and Gracilariopsis species corresponds to increasing zeaxanthin amounts in the seaweeds living at the upper zones, which are more resistant to photoinhibition as shown by fluorescence and oxygen evolution analysis. An operating xanthophyll cycle should be regarded as a regulatory mechanism involved in stress response for the dissipation of excessive excitation energy through deepoxidated xanthophylls such as zeaxanthin or diatoxanthin.
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    Size-fractionated productivity and nutrient dynamics of phytoplankton in subtropical coastal environments (1997)
    Springer
    Hydrobiologia 352 (1997), S. 97-106 
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    ISSN: 1573-5117
    Keywords: size-fractionation ; phosphate uptake ; productivity ; phytoplankton ; coastal environment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It is now well established that the size distribution of phytoplankton plays an important role in primary production processes and nutrient dynamics of coastal environment. In situ observations showed that nanophytoplankton (3–20 µm) contributed 72.08% and58.18% of phytoplankton biomass and 58.32% and 41.14% of primary productivity to Xiamen Western Waters and the northern Taiwan Strait, respectively; picophytoplankton (0.2–3 µm) dominated the biomass (64.70%) and productivity (66.09%) in the southern Taiwan Strait. Furthermore, nanophytoplankton accounted for 75% of phosphate uptake with the highest rate constant (8.3×10-5 s-1) and uptake rate in unit water volume (5.4×10-5 mmol dm-3s-1); picophytoplankton had the highest uptake rate in unit biomass (5.4×10-5 mmol mg-1s-1) and photosynthetic index (3.8 mgC mgChl a-1h-1). All the results highlighted the remarkable characteristics of small size ranged (0.2–20 µm) phytoplankton in subtropical coastal environments: main contributor to phytoplankton biomass and production, high efficiency on organic carbon production and nutrient recycling. The far reaching environmental and ecological implications were discussed.
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    On a new species of Fabaeformiscandona KRSTIC, 1972 (Crustacea, Ostracoda) from China, with a preliminary checklist of Recent Chinese non-marine ostracods (1997)
    Springer
    Hydrobiologia 357 (1997), S. 117-128 
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    ISSN: 1573-5117
    Keywords: taxonomy ; Ostracoda ; China ; ancient lakes ; saline lakes ; biogeography ; checklist ; Fabaeformiscandona danielopoli n.sp.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fabaeformiscandona danielopoli n.sp. isdescribed from the Chinese Lake Erhai, a freshwaterlagoon of the ancient saline lake Qinghai. The speciesbelongs to the acuminata-group of the genus andis characterized by the shape of both male and femalevalves and by the morphology of the female genitallobe and of lobe ‘a’ in the hemipenis. The new speciesis quite rare in its type locality and might beendemic to the ancient Qinghai basin. A checklist ofRecent non-marine Chinese ostracods is offered inappendix.
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    Seasonal variation in the composition and rate of change of the phytoplankton community in a deep subalpine lake (Lake Garda, Northern Italy). An application of nonmetric multidimensional scaling and cluster analysis (1996)
    Springer
    Hydrobiologia 337 (1996), S. 49-68 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; seasonality ; community change rate ; nonmetric multidimensional scaling ; cluster analysis ; Lake Garda
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seasonal variations and spatial homogeneity of the phytoplankton community were followed, from spring 1991 to spring 1992, in four pelagic stations of a large deep subalpine lake (Lake Garda, Northern Italy). Both cluster analysis and nonmetric multidimensional scaling (NMDS) applied to Bray & Curtis' dissimilarity matrices computed on density and biovolume data were employed; the Bray & Curtis index, calculated between pairs of chronologically contiguous samples, was also used as a measure of the community change rate over the temporal succession. In the tree diagrams obtained both from density and biovolume data, six groups of different size have been identified, with ordered sequences of samples within them. Superimposition of the results of cluster analysis on the NMDS configurations has allowed interpretations of the trajectories of the samples as a chronological and cyclical succession of compositionally homogeneous groups. A clear relationship between the community change rate and stability of the water column has been assessed. The specific composition of the six groups has been discussed in relation to environmental variables and in terms of adaptive strategies. During winter (winter-spring group) the turbulence of the water and the availability of nutrients favour the development of colonial Bacillariophyceae (Fragilaria crotonensis Kitton, Tabellaria fenestrata (Lyngb.) Kütz., Aulacoseira spp.), Cyanophyceae (Planktothrix agardhii (Gom.) Anagn. et Kom. and Planktolyngbya limnetica (Lemur.) Kom.-Legn. et Cronb.) and Cryptophyceae. In late spring group, with the stabilisation of the water column and silicon depletion, the diatoms give way to small, opportunistic species (Ankyra judayi (G. M. Smith) Fott, Cyclotella spp., Chroomonas acuta Utermhöl) and larger species (Ceratium hirundinella (O. F. Müll.) Dujardin). The three summer groups are characterised by a development of Chlorophyceae (chiefly Chlorococcales), Cyanophyceae (mainly Chroococcales), Cyclotella spp. and Dinophyceae. With the autumn destratification the summer community undergoes a rearrangement principally in favour of Cyanophyceae and Cryptophyceae.
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    Microbial activity under the ice cover of the shallow Neusiedler See (Austria, Central Europe) (1997)
    Springer
    Hydrobiologia 357 (1997), S. 173-184 
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    ISSN: 1573-5117
    Keywords: ice cover ; shallow lake ; bacterioplankton ; phytoplankton ; growth efficiency ; dissolved organic matter ; humic matter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In an attempt to assess bacterioplankton production and growth yieldunder low temperature conditions and to compare bacterioplankton withphytoplankton production in the ice-covered water column of the shallowNeusiedler See, outdoor measurements under near in situ conditions wereperformed during the winter of 1995/96. During the investigation period,mean chlorophyll (Chl) a concentration was 21.03 ± 14.95 µg Chla l-1. Phytoplankton primary production integrated over thewater column ranged from 1.35 to production integrated over the water columnranged from 1.35 to 4.23 mg C m-2 d-1 (mean± SD = 2.46 ± 1.06 mg C m-2d-1). Bacterial abundance varied from 20 to 40×105 ml-1 for most of the investigationperiod and increased by the end of March concomitantly with the increase intemperature from 1.3 to 6.3 °C within 5 days. Mean bacterial productionwas 15.3 ± 12.8 µg C l-1 d-1(range: 3.0 to 41.7 µg C l-1 d-1) and meanbacterial growth rate 0.23 ± 0.16 d-1 following closelythe pattern in bacterial production. DOC concentration declined linearlyfrom 20.7 mg C l-1 to 16.45 mg C l-1 over the 4months period of ice cover. The contribution of humic substances to thetotal DOC pool declined from 43.6% at the end of November to37.3% at the end of March. Calculated on an area basis, phytoplanktonproduction amounted to only 16% of bacterial production which makesit unlikely that phytoplankton supply substrate for bacterioplankton growthin significant quantities when the lake is ice covered. From the observeddecline in DOC over the investigation period and assuming only negligibleinput of DOC from other sources we calculated an average DOC uptake by thebacterioplankton community of 47.5 µg C l-1d-1 resulting in a bacterial growth efficiency of 15.9%for the ice covered conditions. Based on the growth efficiency we estimatethat pelagic primary production amounts to 2.8% of the bacterialcarbon demand. This might indicate that the bacterioplankton in NeusiedlerSee sustain their high growth rates at low temperatures (〈2°C formost of the investigation period) by using probably the DOC originating fromthe previous season. This DOM stems most likely from the decay of the reedPhragmites australis and its epiphytes and, probably of minor importance,from phytoplankton leachates.
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    Microbial food web in a large shallow lake (Lake Balaton, Hungary) (1996)
    Springer
    Hydrobiologia 339 (1996), S. 57-65 
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    ISSN: 1573-5117
    Keywords: shallow lake ; phytoplankton ; bacterioplankton ; heterotrophic nanoflagellates ; pelagic carbon flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seasonal variations of phyto-, bacterio- and colourless flagellate plankton were followed across a year in the large shallow Lake Balaton (Hungary). Yearly average chlorophyll-a concentration was 11 µg 1−1, while the corresponding values of bacterioplankton and heterotrophic nanoflagellate (HNF) plankton biomass (fresh weight) were 0.24 mg 1−1 and 0.35 mg 1−1, respectively. About half of planktonic primary production was channelled through bacterioplankton on the yearly basis. However, there was no significant correlation between phytoplankton biomass and bacterial abundance. Bacterial specific growth rates were in the range of 0.009 and 0.09 h−1, and ended to follow the seasonal changes in water temperature. In some periods of the year, predator-prey relationships between the HNF and bacterial abundance were obvious. The estimated HNF grazing on bacteria varied between 3% and 227% of the daily bacterial production. On an annual basis, 87% of bacterial cell production was grazed by HNF plankton.
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    The influence of macrophytes on a phytoplankton community in experimental conditions (1995)
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    Hydrobiologia 306 (1995), S. 21-32 
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    ISSN: 1573-5117
    Keywords: macrophytes ; phytoplankton ; cyanobacteria ; allelopathy ; dialysis bags ; extracts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The impact of submerged macrophytes or their extracts on planktonic algae was studied under experimental conditions. Live Ceratophyllum demersum L., its extract, and extracts of four other plant species induced modifications in the phytoplankton dominance structure. These modifications were: a decline in the number of Oscillatoria limnetica Lemm., which was the most numerous cyanobacterian species, and a decline in biomass and percentage contribution of all cyanobacteria to total algal biomass. This was accompanied by an increase in biomass and percentage contribution of green algae, especially Chlorella sp. and Chlamydomonas sp. Also, there was an increase in biomass and percentage contribution of nanoplankton (under 50 µm) to total phytoplankton biomass. The isolation of planktonic algae from direct influence of C. demersum by means of dialysis membranes caused an increase in number, biomass and percentage contribution of cyanobacteria. Release of organic compounds of over 3000 daltons by macrophytes apparently contributed to a decline of cyanobacteria by changing the phytoplankton dominance structure.
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    Effects of environmental factors on the phytoplankton community in the Gulf of Finland – unattended high frequency measurements and multivariate analyses (1997)
    Springer
    Hydrobiologia 363 (1997), S. 127-139 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; Baltic Sea ; Gulf of Finland ; high frequencymeasurements ; multivariate analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Relationships between phytoplankton species composition andenvironmental factors were studied in open areas of the central and easternGulf of Finland in late summer 1993. The data was collected using unattendedwater sampling, as well as spatially and temporally frequent measurements onin vivo fluorescence of chlorophyll a, temperature and salinity on board apassenger ferry, which plied between Helsinki and St. Petersburg. Therelative abundances of phytoplankton species, concentrations of nutrients(Tot-N, NO2-N+NO3-N, NH4-N,Tot-P, PO4-P, Si) and chlorophyll a were analysed from thewater samples. The collected data set enabled the use of various statisticalmethods in order to explain the phytoplankton community structure in thestudy area. The multivariate analyses were carried out using SAS softwareprocedures (GLM, CLUSTER, CANCORR). Variability in the phytoplanktoncommunity (biomass, species composition) was high, and this paper clearlydemonstrates that valuable information regarding pelagial biologicaldynamics, connected to extreme values, will be lost if the data isincorrectly simplified.
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    Relations between planktivorous fish abundance, zooplankton and phytoplankton in three lakes of differing productivity (1997)
    Springer
    Hydrobiologia 363 (1997), S. 81-95 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; zooplankton ; planktivorous fish ; phosphorus ; biomanipulation ; trophic interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Water chemistry, phytoplankton, zooplankton and fish populations werestudied over several years in three shallow, non-stratified lakes withdiffering nutrient loadings and fish communities in southwest Finland. LakePyhäjärvi was weakly mesotrophic in 1980–1996, LakeKöyliönjärvi was highly eutrophic in 1991–1996, andLake Littoistenjärvi was mesotrophic in 1993–1996 and eutrophicin 1992. In Lake Pyhäjärvi, natural year-class fluctuations ofvendace and smelt (range of combined biomass 5–28 kgha™1) caused significant variation in planktivory. The verydense fish stocks of Lake Köyliönjärvi (mainly roach, breamand smelt) were decimated from 〉175 kg ha™1 in 1991 toabout 50 kg ha−1 in 1996 by removal fishing. The roach stockof Lake Littoistenjärvi declined from about 71 kg ha−1 toabout 28 kg ha−1 during 1993–1996. In LakePyhäjärvi, strong stocks of planktivorous fish were accompaniedwith depressed crustacean zooplankton biomass, reduced role of calanoids andcladocerans, a low proportion of larger cladocerans (length 〉 0.5 mm),and a high chlorophyll level. In the lakes Littoistenjärvi andKöyliönjärvi, zooplankton was dependent on both fish andphytoplankton: in spite of dense fish stocks, a high crustacean biomassdeveloped in a phytoplankton peak year, but it was dominated by very smallcladocerans. In Lake Pyhäjärvi, late summer chlorophyllconcentration was predictable from total phosphorus in water and cladoceranbiomass (r2 = 0.68), both factors explaining roughlysimilar fraction of total variation. In combined data from all three lakes,chlorophyll was almost solely dependent on total phosphorus, while thecladocerans were regulated both from below by productivity and from above byfish. Our data from Pyhäjärvi lend support to consumer regulationof late summer phytoplankton; low chlorophyll values prevailed whenplanktivorous fish biomass was below 15 kg ha−1. In largeeutrophic lakes it may be difficult to reduce fish stocks to such a lowlevel: in Lake Köyliönjärvi, after six years of removalfishing, fish biomass still remained higher, and changes in plankton wereaccordingly small. Unexpectedly, in 1993–1996, phytoplankton biomassin Littoistenjärvi remained low in spite of low crustacean zooplanktonbiomass; submerged macrophytes probably regulated the water quality.
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    Group-specific phytoplankton biomass/dissolved carbohydrate relationships in the Gulf of Trieste (Northern Adriatic) (1997)
    Springer
    Hydrobiologia 363 (1997), S. 191-205 
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    ISSN: 1573-5117
    Keywords: carbohydrates ; dissolved organic carbon ; photosynthetic pigments ; phytoplankton ; coastal waters ; northern Adriatic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Distribution of carbohydrates (CHO) and photosynthetic pigments werestudied in the Gulf of Trieste, northern Adriatic Sea, during the period ofsummer stratification with a special emphasis on determining the impact ofthe taxonomic composition and concentration of phytoplankton biomass on thecarbohydrate levels in the water column. Dissolved total carbohydrates(DTCHO), dissolved monosaccharides (DMCHO) as well as particulatecarbohydrates (PTCHO) were determined using the colorimetric MBTH-method,while pigment biomarkers of the phytoplankton biomass were determined byreversed-phase HPLC. Concentrations of the total CHO (dissolved+particulate) varied in a wide range from 173 µg Cl™1 to 1552 µg C l™1. The percentage ofPTCHO in the total CHO concentration was relatively low(4–25%), indicating that the main pool of CHO was in thedissolved phase. The contribution of DTCHO to the total dissolved organiccarbon (DOC) in late summeontribution r was highly variable(10–65%) with an average value of 20 ± 14%, whilein early summer this percentage was somewhat lower and less variable (range11–23%; average 17± 3%). Analyses of biomarkerpigments revealed a very high diversity and a rather heterogenous verticaland spatial distribution of the phytoplankton biomass during the period ofsummer stratification. In September 1994, the predominant taxonomic groupsof phytoplankton were prymnesiophytes, diatoms, silicoflagellates,cyanobacteria and, especially in the bottom layer, dinoflagellates. Arelatively good correlation (r2 =0.51) found betweenDTCHO and chl a suggested that DTCHO were mainly of phytoplankton origin.Furthermore, a concomitant increase of DTCHO with peridinin and fucoxanthinindicated that dinoflagellates and diatoms had a decisive impact on CHOlevels in the water column. By contrast, early summer phytoplankton (June),which was dominated by prymnesiophytes, exhibited a comparatively lowerimpact on the CHO distribution.
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    Trends and relations among basic phytoplankton characteristics in the course of the long-term oligotrophication of Lake Maggiore (Italy) (1998)
    Springer
    Hydrobiologia 369-370 (1998), S. 243-257 
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    ISSN: 1573-5117
    Keywords: long-term studies ; phytoplankton ; lake recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Maggiore underwent a process of eutrophication in the course of the 1960s and 1970s which caused the lake status to change from oligotrophy to meso-eutrophy, sewage phosphorus being the main responsible factor. Starting from the late 1970s the P load has been gradually reduced, so that total phosphorus in-lake concentration is now below 10 µg l-1 at winter mixing, compared to a maximum value of 30 µg l-1 in 1978. Nearly two decades after the start of this reversal in trophic conditions, long-term analyses become fruitful, not least because of a scarcity of published long-term data on lake re-oligotrophication, and consequently of agreed predictions on specific points. This paper presents such an analysis, regarding some phytoplankton characteristics (numbers, biovolume, cell size, chlorophyll a, species richness and composition) and their mutual relations in the time series 1981-1995, as well as recent primary production compared with early observations. Notwithstanding phosphorus reduction, the phytoplankton remained quite stable for many years. Only after 1987, when TP concentration fell to about 15 µg l-1 at mixing, definite changes in species diversity and composition appeared. At the same time, average cell size decreased abruptly and persistently, together with chlorophyll and total biovolume while cell numbers were unchanged or rising. Annual primary production was halved in comparison to a past reference period and the efficiency of the photosynthetic process was apparently enhanced.
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    What factors influence the species composition of phytoplankton in lakes of different trophic status? (1998)
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    Hydrobiologia 369-370 (1998), S. 11-26 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; lake typology ; trophic status
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The paper articulates some present concepts relating to the selection of phytoplankton along trophic gradients. Concerns over lake eutrophication have heightened the importance of nutrients but it is not obvious that interspecific differences in the nutrient requirements of algae genuinely segregate species except under chronic deficiencies. The selectivity supposedly generated by altered resource ratios is re-examined. It is argued that ratios explain very little of the distribution of species with respect to trophy. However, changing nutrient loading does have consequential impacts on the availability of other requirements including light and carbon dioxide. It is argued that the trophic spectrum is not a single dimension of a single factor but, rather, a template of factors covarying in consequence of the larger levels of biomass that are supported, and which weight in favour of the growth and survival prospects of particular kinds of planktonic algae. The trophic spectrum is a probabalistic outcome of several dimensions of variability.
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    Chrysophytes and chlamydomonads: pioneer colonists in extremely acidic mining lakes (pH 〈3) in Lusatia (Germany) (1998)
    Springer
    Hydrobiologia 369-370 (1998), S. 315-327 
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    ISSN: 1573-5117
    Keywords: acidic mining lakes ; phytoplankton ; Chlamydomonas ; Ochromonas ; water chemistry ; limiting factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Twenty-three extremely acidic (pH between 2.5 and 3.5) mining lakes in Lusatia (Germany) were analysed in order to classify their hydrochemistries and to assist the understanding of phytoplankton colonization of these extreme environments. Neither morphometric nor physical parameters influence phytoplankton composition but determine the extent to which the nutrient supply supports the mass development of Chrysophyceae and Chlorophyceae in certain layers of the water (hypo- or epilimnetic chlorophyll maxima and short mass developments). Conventional trophic classification is not readily applicable to these lakes but a chemical classification on the basis of hydrogen, total iron and acidity is proposed. Species of Ochromonas and Chlamydomonas dominate the phytoplankton in fourteen of the most acid lakes; dinoflagellates occurre additionally in four; a more diverse algal assemblage with diatoms and cryptophytes is found in lakes with moderately acidic (pH 5.7–7.0) or alkaline conditions (pH 7.0–9.4). The lake chemistry is the main determinant for the planktonic composition of the water bodies whereas the trophic state mainly determines the level of algal biomass.
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    Phytoplankton communities in relation to trophic status in lakes from Hope Bay (Antarctic Peninsula) (1998)
    Springer
    Hydrobiologia 369-370 (1998), S. 73-87 
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    ISSN: 1573-5117
    Keywords: Antarctica ; lakes ; phytoplankton ; trophic status ; typology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nine lakes and ponds of Hope Bay (Antarctic Peninsula), with different trophic status were surveyed during four summer periods between 1991 and 1996. Some limnological features and the structure of their algal assemblages were strongly influenced by the eutrophication caused by sea-birds activity in their areas. Such differences among lakes were evidenced by the results of Principal Component Analyses, based on both physico-chemical and phytoplankton data. Oligotrophic lakes showed a scarce phytoplankton, commonly dominated by small flagellated Chrysophyceae, and a well developed phytobenthos. Water bodies enriched by ornithogenic nutrients revealed an abundant phytoplankton usually dominated by Chlorophyceae (Volvocales) and planktonic Cyanobacteria. A study on one particular lake showed that summer changes in the phytoplankton community were mainly affected by physical phenomena such as variation in light intensity, and thawing, mixing and freezing processes.
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    The most typical phytoplankton taxa in four types of boreal lakes (1998)
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    Hydrobiologia 369-370 (1998), S. 89-97 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; boreal lakes ; acidic ; oligotrophic ; dystrophic ; eutrophic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The monitoring of phytoplankton quantities and species composition in Finnish lakes started in the early 1960s. In addition, a substantial number of physical and chemical variables have been measured and recorded from the monitored lakes. The purpose of the present evaluation is to differentiate the phytoplankton taxa of the lakes being classified as acidic, oligotrophic, dystrophic and eutrophic. At present, these four lake types are differentiated on the bases of concentration of total phosphorus (µg l-1), water colour (mg l-1 Pt), and Secchi-disc transparency. A total of 38 lakes with 163 samples from the years 1984 to 1994 were selected for this study. Cyanoprokaryota Merismopedia warmingiana (M. tenuissima) was abundant in clear and dystrophic acidic lakes whereas Dinobryon divergens (Chrysophyceae) was dominant only in the clear lake types. Oocystis rhomboidea (Chlorophyceae) was also an important species, especially in the dark acidic lakes. In oligotrophic lakes, the phytoplankton biomass was low because of the combined effect of low organism numbers and small cell size of the occurring species. Additional chrysophyceans like Uroglena americana, unidentified Ochromonadales and Dinobryon divergens were especially abundant, as well as Merismopedia warmingiana. In the dystrophic lakes flagellated taxa, such as Cryptomonas spp., Uroglena americana, Ochromonadales and Pseudopedinella spp. dominated. In eutrophic lakes, the cyanoprokaryotes Microcystis aeruginosa, M. viridis and M. wesenbergii, as well as Anabaena flos-aquae and Aphanizomenon flos-aquae dominated both cell numbers and biomass. Some identification problems are also discussed.
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    Seasonality of phytoplankton as an indicator of trophic status of the large perialpine ‘Lago di Garda’ (1998)
    Springer
    Hydrobiologia 369-370 (1998), S. 153-162 
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    ISSN: 1573-5117
    Keywords: seasonality ; phytoplankton ; Lake Garda ; eutrophication ; trophic index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The seasonality of phytoplankton and its vertical distribution in Lake Garda, Italy, was studied on the basis of monthly sampling during 1994. Chlorophyll a concentration, phytoplankton biovolumes and species composition are used for the trophic characterization of the lake, supplemented by water chemistry data (nutrients and total phosphorus) and Secchi depth. Horizontal differences in trophic status are investigated by comparing data from three sampling stations, whereas the long term changes in trophic status are based on a comparison of the recent findings with earlier studies of the phytoplankton.
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    Development of the phytoplankton of the shallow Srebarna Lake (north-eastern Bulgaria) across a trophic gradient (1998)
    Springer
    Hydrobiologia 369-370 (1998), S. 259-267 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; shallow lake ; trophic gradient ; eutrophication ; restoration ; biosphere reserve ; Danube
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Results of an analysis of phytoplankton samples, collected between 1982 and 1995 from Srebarna Lake, a biosphere reserve, in north-eastern Bulgaria, are presented. The lake is polymictic, and strongly eutrophied. It has undergone an anthropogenically-forced succession. In 1994, a restoration of the lake was commenced when a canal connecting it to the Danube River was built. Special attention is paid to the shifts in the qualitative composition of the phytoplankton (240 species), in the number of dominant species and assemblage structure, as well as to the changes in structural parameters and phytoplankton abundance during lake enrichment. The generalised changes involved a shift from a chlorococcal dominated-phytoplankton, rich in phytoplankton groups, to a chroococcal and oscillatoralean one, poor in algal groups. With recovery, from hypertrophy to eutrophy, more algal groups contributed to the phytoplankton, and dominance of chlorococcal genera resumed. An increase in total phytoplankton abundance with advancing eutrophication and a decrease during early oligotrophication were detected. The values of structural parameters were related to nutrient input and changed after restoration. However, the stages of phytoplankton development along the trophic gradient and back were not exactly reversed.
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    Temporal variation in plankton assemblages and physicochemistry of Devils Lake, North Dakota (1998)
    Springer
    Hydrobiologia 377 (1998), S. 57-71 
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    ISSN: 1573-5117
    Keywords: saline lakes ; climate ; nitrogen limitation ; phytoplankton ; zooplankton ; community structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seasonal and annual variation in biomass and structure of algal assemblages of hyposaline Devils Lake were examined in relation to turbidity, ambient concentrations of major ions, trace elements and nutrients, and the standing crop of herbivores. Lake level declined during the early years of study, but rose markedly in subsequent years as historically large volumes of water flowed into this hydrologically-closed basin. Winter algal assemblages were dominated (in biomass) most years by small, non-motile chlorophytes ( Choricystis minor, Kirchneriella lunaris or Dunaliella sp.), or Euglena sp. in the most saline sub-basin. Spring assemblages were dominated by diatoms (Stephanodiscus cf. minutulus, Surirella peisonis, Cyclotella meneghiniana and Entomoneis paludosa were especially prominent) or chlorophytes ( C. minor) until the lake level rose. C. minor abundances then declined in spring assemblages and diatoms ( Stephanodiscus cf. agassizensis and S. niagarae; E. paludosa in the more saline sub-basins) dominated. The potential for nitrogen-deficient conditions for phytoplankton growth was evidenced most summers and early autumns by consistently high concentrations of reactive-P relative to inorganic-N and blooms of the N-fixing cyanophyte Aphanizomenon flos-aquae; Microcystis aeruginosa typically was a co-dominant (〉30% of biomass) in these assemblages. Pulses of diatoms ( S. cf. agassizensis and C. meneghiniana) occurred in summers following unusually prolonged periods of calm weather or large water inflows. Physical (irradiance, turbulence) and chemical (major nutrients) variables were the primary factors associated with phytoplankton growth. Transparency and major nutrient concentrations accounted for more of the annual variation in phytoplankton structure than did salinity. Seasonal abundance patterns of the dominant zooplankton (the copepod Diaptomus sicilis; the cladocerans Ceriodaphnia quadrangula, Chydorus sphaericus, Daphnia pulex and Diaphanosoma birgei; and the rotifers Brachionus spp., Filinia longiseta, Keratella cochlearis and K. quadrata) also indicated variation in algal populations related to grazing.
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    Effect of larval fish and nutrient enrichment on plankton dynamics in experimental ponds (1996)
    Springer
    Hydrobiologia 321 (1996), S. 109-118 
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    ISSN: 1573-5117
    Keywords: larval fish ; nutrients ; zooplankton ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The hypotheses that larval fish density may potentially affect phytoplankton abundance through regulating zooplankton community structure, and that fish effect may also depend on nutrient levels were tested experimentally in ponds with three densities of larval walleye, Stizostedion vitreum (0, 25, and 50 fish m−3), and two fertilizer types (inorganic vs organic fertilizer). A significant negative relationship between larval fish density and large zooplankton abundance was observed despite fertilizer types. Larval walleye significantly reduced the abundances of Daphnia, Bosmina, and Diaptomus but enhanced the abundance of various rotifer species (Brachionus, Polyarthra, and Keratella). When fish predation was excluded, Daphnia became dominant, but Daphnia grazing did not significantly suppress blue-green algae. Clearly, larval fish can be an important regulator for zooplankton community. Algal composition and abundance were affected more by fertilizer type than by fish density. Inorganic fertilizer with a high N:P ratio (20:1) enhanced blue-green algal blooms, while organic fertilizer with a lower N:P ratio (10:1) suppressed the abundance of blue-green algae. This result may be attributed to the high density of blue-green algae at the beginning of the experiment and the fertilizer type. Our data suggest that continuous release of nutrients from suspended organic fertilizer at a low rate may discourage the development of blue-green algae. Nutrient inputs at a low N:P ratio do not necessarily result in the dominance of blue-green algae.
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    URL: http://dx.doi.org/10.1007/BF00023168
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    Littoral zone of Lake Ladoga: ecological state evaluation (1996)
    Springer
    Hydrobiologia 322 (1996), S. 39-47 
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    ISSN: 1573-5117
    Keywords: Lake Lagoda ; littoral zone ; monitoring ; pollution ; macrophytes ; periphyton ; phytoplankton ; zooplankton ; macrobenthos ; meibenthos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The littoral zone of a lake is an important ecotone between terrestrial and aquatic systems. From the point of view of the lake ecosystem, much of the mineral, organic and toxic substances entering the lake from the drainage basin are transformed in the littoral zone by physical processes and biochemical pathways. The littoral zone of Lake Ladoga can be divided into three main regions: the shallow southern region, the fairly steep western and eastern shorelines, and the northern archipelago. In these regions, the communities of aquatic macrophytes, periphyton, phyto- and zooplankton and meio- and macrobenthos have been extensively studied. This paper presents numerical data on these communities, with special reference to comparisons between areas subjected to different degrees of anthropogenic loading. Most of the communities are characterized by high species diversity and spatial heterogeneity, especially among the macrophyte associations in which intensive production and decomposition takes place. Water dynamics and water exchange rate are the main abiotic factors in the formation of littoral communities. The characteristics of plant associations and bottom substrate, rather than pollution, appear as the most important factors structuring meio- and macrobenthic invertebrate communities in the littoral.
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    Relations among heterotrophic bacteria, chlorophyll-a, total phytoplankton, total zooplankton and physical and chemical features in the Paranoá reservoir, Brasília, Brazil (1996)
    Springer
    Hydrobiologia 337 (1996), S. 171-181 
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    ISSN: 1573-5117
    Keywords: tropical reservoir ; phytoplankton ; zooplankton ; eutrophication ; physical and chemical features ; heterotrophic bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The plankton community, chlorophyll-a, heterotrophic bacteria and physical and chemical features of the Paranoá Reservoir were studied at monthly intervals at seven stations from March 1988 to March 1989. Thermal structure had a circulation period from May to July and stratification during the other months. The phytoplankton consisted of 76 taxa, was dominated by the cyanophyte Cylindrospermopsis raciborskii and attained concentrations ranging from 7,759,000 up to 98,160,000 org. l−1. The zooplankton consisted of 36 taxa and was present in densities between 8 and 8,056 org. l−1. In stations, or seasons with highly eutrophic conditions, there was a decrease in total phytoplankton and an increase in bacteria and total zooplankton. The results had spatial and temporal variations. Spatial variation demonstrated the existence of water quality deterioration at two or three sampling points. Temporal variation showed the influences of water column stability and the dry versus rainy seasons on nutrient concentrations and the planktonic community.
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    Diel changes in the alkaline phosphatase activity of bacteria and phytoplankton in the hypereutrophic Villerest reservoir (Roanne, France) (1995)
    Springer
    Hydrobiologia 300-301 (1995), S. 49-56 
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    ISSN: 1573-5117
    Keywords: reservoir ; phytoplankton ; bacteria ; alkaline phosphatase activity ; diel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The diel changes of the size fractioned alkaline phosphatase activity (APA) were studied in relation to several abiotic and biotic factors in Villerest reservoir (located on the Loire river, near the city of Roanne, France), bihourly during two days in July 1992. The APA measured in this work exceeded considerably those reported in the literature, suggesting that dissolved mineral phosphorus was not available to microorganisms. At 1 m, the APA was primarily due to bacteria which actively assimilated organic P compounds released by photosynthetic algal metabolism. At 5, 10 and 20 m, the APA was predominantly algal. The high concentrations in SRP (soluble reactive phosphorus) would indicate that orthophosphates were not bioavailable. The reverse (i. e availability to phytoplankton) would have resulted in undetectable levels of P-PO inf4 sup3− due to the massive proliferation of algae in Villerest reservoir.
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    Vertical and seasonal variations of inorganic carbon allocation into macromolecules by phytoplankton population in a brown-colored and a clear-water lake (1995)
    Springer
    Hydrobiologia 300-301 (1995), S. 57-70 
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    ISSN: 1573-5117
    Keywords: Lakes ; phytoplankton ; inorganic carbon incorporation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aim of this study was to asses vertical and seasonal variations of inorganic carbon allocation into macromolecules by phytoplankton population in an humic and acidic lake (Lake Vassivière) and in a clearwater lake (Lake Pavin). Biochemical fractionation was done by consecutive differential extractions in order to separate proteins, polysaccharides, lipids and low molecular weight compounds (LMW) by virtue of their relative solubilities in different extraction solvents. Independent of depth and season, the principal photosynthetic end products were polysaccharides followed by proteins, LMW and lipids. However, inorganic carbon allocation into macromolecules varied, in these two lakes, with depth and with the taxonomic composition of phytoplankton. Carbon allocation into polysaccharides decreased with increasing depth, especially in the brown-colored humic lake, and Diatoms, showed high C incorporation into polysaccharides.
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    Diel changes in the biochemical composition of the particulate matter coupled with several parameters in the hypereutrophic Villerest reservoir (Roanne, France) (1995)
    Springer
    Hydrobiologia 300-301 (1995), S. 85-91 
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    ISSN: 1573-5117
    Keywords: reservoirs ; phytoplankton ; biochemical composition ; diel changes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The diel changes of the biochemical composition of particulate matter was studied in Villerest reservoir (located on the Loire river, near the city of Roanne, France) during July 92. Several biomass and metabolic indicators (proteins, carbohydrates, lipids, chlorophyll a and primary production) were assessed bihourly over 2 days. Since the P/C is largely recognized as a good integrator of the metabolic functions of the cells, we examined its distribution pattern concomitantly with aforementioned parameters. The results demonstrated enhanced P/C ratios clearly indicating that nutrients were sufficiently available for growth. In addition, this index showed a diel significant variation with levels higher in the night than in the day. Moreover, these results suggest that phytoplankton species during the night used the day-synthesized carbohydrates to insure the cell metabolic functioning.
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    Zooplankton–phytoplankton interactions in lakes Võrtsjärv, Peipsi (Estonia) and Yaskhan (Turkmenia) (1997)
    Springer
    Hydrobiologia 342-343 (1997), S. 175-184 
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    ISSN: 1573-5117
    Keywords: zooplankton ; phytoplankton ; interactions ; grazing ; nutrient regeneration ; shallow eutrophic lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Zooplankton-phytoplankton interactions have been studied inthreeshallow lakes of different trophic state. In stronglyeutrophic,large and very shallow Lake Võrtsjärv the grazing doesnotplay a leading role in controlling phytoplankton productionand itsstanding stock. Small-size zooplankton can not eat filamentousblue-greens. The nutrient regeneration by zooplankton has aweakimpact on phytoplankton, the latter being limited rather byunderwater light than by nutrient availability. In largemoderatelyeutrophic Lake Peipsi the presence of concentrated zooplanktoninthe experimental vessel mostly stimulated steady-statephytoplankton growth and negative grazing values weremeasured.Most probably the nutrients (N, P), excreted by zooplankton ingrazing chamber stimulated the growth of larger phytoplanktonwhichdominated because of heavy grazing pressure on edible forms.InLake Peipsi phytoplankton seems to be nutrient-limited andheavilycontrolled by zooplankton community. In eutrophic,macrophyte-dominated Lake Yaskhan zooplankton in grazingchamberalso mainly stimulated the growth of phytoplankton communitywhichseemed to be nutrient-limited because of strong competitionwithmacrophytes.
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    Effects of macrophyte growth forms on invertebrate communities in saline lakes of the Wyoming High Plains (1996)
    Springer
    Hydrobiologia 323 (1996), S. 83-96 
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    ISSN: 1573-5117
    Keywords: macroinvertebrate communities ; macrophyte growth forms ; salinity ; saline lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In saline lakes, areal cover and both species and structural diversity of macrophytes often decline as salinity increases. To assess effects of the loss of certain macrophyte growth forms, we characterized benthic and epiphytic invertebrates in three growth forms (thin-stemmed emergents, erect aquatics, and low macroalgae) in oligosaline lakes (0.8–4.2 mS cm−1) of the Wyoming High Plains, USA. We also measured the biomass and taxonomic composition of epiphytic and benthic invertebrates in two erect aquatics with very similar structure that are found in both oligosaline (Potamogeton pectinatus) and mesosaline (9.3–23.5 mS cm−1) (Ruppia maritima) lakes. Although total biomass of epiphytic invertebrates varied among oligosaline lakes, the relative distribution of biomass among growth forms was similar. For epiphytic invertebrates, biomass per unit area of lake was lowest in emergents and equivalent in erect aquatics and low macroalgae; biomass per unit volume of macrophyte habitat was greatest in low macroalgae. For benthic invertebrates, biomass was less beneath low macroalgae than other growth forms. Taxonomic composition did not differ appreciably between growth forms for either benthic or epiphytic invertebrates, except that epiphytic gastropods were more abundant in erect aquatics. Total biomass of epiphytic and benthic invertebrates for the same growth form (erect aquatic) did not differ between oligosaline (Potamogeton pectinatus) and mesosaline (Ruppia maritima) lakes, but taxonomic composition did change. In the oligosaline to mesosaline range, direct toxic effects of salinity appeared important for some major taxa such as gastropods and amphipods. However, indirect effects of salinity, such as loss of macrophyte cover and typically higher nutrient levels at greater salinities, probably have larger impacts on total invertebrate biomass lake-wide.
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    Modelling the daily integral of photosynthesis by phytoplankton: its dependence on the mean depth of the population (1997)
    Springer
    Hydrobiologia 349 (1997), S. 65-74 
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    ISSN: 1573-5117
    Keywords: daily integral of photosynthesis ; phytoplankton ; vertical distribution ; waterblooms ; cyanobacteria ; Aphanizomenon ; Baltic Sea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Detailed descriptions have been made of theunder-water light field based on continuousmeasurements of surface photon irradiance,calculations of losses by surface reflection andmeasurements of the vertical light attenuation. Thesemeasurements have been combined with measurements ofthe vertical distribution of phytoplankton chlorophylland the photosynthesis/irradiance curve to produce ameasurement of the daily integral of photosynthesis bynumerical integration using a PC spreadsheet; theaccuracy of the integrations is evaluated. The resultshave been compared with models that assume a uniformvertical distribution of phytoplankton. Suchassumptions produced underestimates of the dailyintegral of photosynthesis by 50–109% for apopulation of Aphanizomenon flos-aquae inthe Baltic Sea owing to the overestimate ofrespiratory losses. Buoyant cyanobacterial populationsfloat up during brief episodes of calm; this increasesthe insolation they receive and their resultantphotosynthetic activity may increase several times.These advantages of buoyancy, provided by gasvesicles, are a major factor in determining thesuccess of waterbloom-forming cyanobacteria. A modelis produced of the relationship between the mean depthof the Aphanizomenon phytoplankton populationand the daily integral of photosynthesis at differentinsolations; this may provide the basis forimprovement of models applicable to otherphytoplankton populations. The integration spreadsheetis available athttp://www.bio.bris.ac.uk/research/walsby/integral.htm.
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    Nutrients, light and primary production by phytoplankton and microphytobenthos in the eutrophic, turbid Westerschelde estuary (The Netherlands) (1995)
    Springer
    Hydrobiologia 311 (1995), S. 9-19 
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    ISSN: 1573-5117
    Keywords: Westerschelde estuary ; phytoplankton ; primary production ; turbidity ; microphytobenthos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Abiotic factors and primary production by phytoplankton and microphytobenthos was studied in the turbid Westeschelde estuary. Because of the high turbidity and high nutrient concentrations primary production by phytoplankton is light-limited. In the inner and central parts of the estuary maximum rates of primary production were therefore measured during the summer, whereas in the more marine part spring and autumn bloom were observed. Organic loading is high, causing near anaerobic conditions upstream in the river Schelde. Because of this there were no important phytoplankton grazers in this part of the estuary and hence the grazing pressure on phytoplankton was minimal. As this reduced losses, biomass is maximal in the river Schelde, despite the very low growth rates. On a number of occasions, primary production by benthic micro-algae on intertidal flats was studied. Comparison of their rates of primary production to phytoplankton production in the same period led to the conclusion that the contribution to total primary production by benthic algae was small. The main reason for this is that the photosynthetic activity declines rapidly after the flats emerged from the water. It is argued that CO2-limitation could only be partially responsible for the noticed decrease in activity.
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    Importance of water-level fluctuation on population dynamics of cladocerans in a hypertrophic reservoir (Lake Arancio, south-west Sicily, Italy) (1997)
    Springer
    Hydrobiologia 360 (1997), S. 223-232 
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    ISSN: 1573-5117
    Keywords: Zooplankton ; man-made lakes ; phytoplankton ; fish predation ; water-level fluctuations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During a period of three years (1990–1991 and 1993),we studied the population dynamics of planktoniccladocerans in a hypertrophic reservoir. Weeklysampling revealed that the five most common speciesfollowed a trend which reflects the peculiarhydrological characteristics of the reservoir andtheir key position in the pelagic food web. Inparticular, 1991 was characterized by a strong waterinflow which probably interfered with the reproductiveactivities of the dominant fish population (Rutilus rubilio) and reduced the concentration ofinedible planktonic algae allowing the development ofsmall Chlorococcales. This event was associated withhigher population densities of Daphnia hyalinacompared to the other years of the survey. In spring1991, an extended clear-water phase was observed andSecchi disk depth increased to 6 m, whereas in theother years it did not surpass 1 m. In addition, theD. hyalina population persisted throughout thesummer in 1991, whereas it started to decline at theend of June in the other years. This development ofD. hyalina probably influenced the populationdynamics of the other cladoceran species in thereservoir, and in particular reduced the summer growthof Diaphanosoma lacustris and delayed theoccurrence of Bosmina longirostris. Stomachanalysis indicated that D. hyalina is thepreferred food item of juvenile (less than two monthsold) R. rubilio. Overall, the hydrology of thereservoir was observed to interact with the trophicprocesses in the pelagic environment of the ecosystemin at least two different ways: via bottom-upprocesses, influencing phytoplankton dynamics, and viatop-down processes, regulating the predationefficiency of the planktivores.
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    Responses of the phytoplankton to a deliberate attempt to raise the trophic status of an acidic, oligotrophic mountain lake (1998)
    Springer
    Hydrobiologia 369-370 (1998), S. 127-131 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; trophic status ; phosphorus ; eutrophication ; species composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The paper reports the impact of a sharp artificial enrichment of the available phosphorus in a small, acidic and oligotrophic corrie lake and its effects upon the phytoplankton supported. Annual average chlorophyll increased tenfold within two years, from ∼ 1.2 to 12.6 µg chl a l-1, but the species represented by large populations are the same as previously. Chrysophyte species, however, make up a smaller fraction of the total crop.
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    Long-term changes in hydrography, nutrients and phytoplankton in Tolo Harbour, Hong Kong (1997)
    Springer
    Hydrobiologia 352 (1997), S. 107-115 
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    ISSN: 1573-5117
    Keywords: coastal waters ; nutrients ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper presents the results of a long-term survey of the hydrography, nutrients and phytoplankton in Tolo Harbour carried out between 1982 and 1992. Some nutrients such as total inorganic nitrogen, ammonia and total phosphorus increased during the 10 year period, but chlorophyll a, which indicated algal biomass, did not show an increasing trend. The phytoplankton of Tolo Harbour consisted largely of diatoms. Dinoflagellates and minor algal groups such as cryptomonads and small flagellates constituted a smaller fraction of the phytoplankton population. Densities of diatoms and minor algal groups increased in some stations, but the density of dinoflagellates remained relatively unchanged during the study period. Most nutrient variables were negatively correlated with densities of diatom and total phytoplankton, and positively correlated with densities of minor algal groups. While dinoflagellate densities were positively correlated with total nitrogen in some stations, no correlation existed between dinoflagellate density and most of the nutrient variables. Our results show that there is a gradual change in phytoplankton community in Tolo Harbour,most notably in the nutrient-rich inner harbour waters, with the smaller algae assuming increasing abundance. Thus there was a net increase in density of total phytoplankton even though chlorophyll a concentrations did not increase. No evidence was found in this study to show that increased nutrient loading would inevitably lead to increase in densities of dinoflagellates in Tolo Harbour. Instead, dinoflagellate densities showed stronger correlations with physical variables such as temperature, pH and salinity.
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    A comparison of marine planktonic and sediment core diatoms in Hong Kong with emphasis on Pseudo-nitzschia (1997)
    Springer
    Hydrobiologia 352 (1997), S. 147-156 
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    ISSN: 1573-5117
    Keywords: Thanatocoenoses ; Hong Kong ; sediment cores ; diatoms ; phytoplankton ; dissolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Potentially toxic diatoms belonging to the genus Pseudo-nitzschia were observed for the first time in plankton samples from Hong Kong collected in 1996. To determine whether potentially toxic diatoms had become more common during the last six decades, three gravity cores were taken from the anaerobic sediments of Kowloon Bay in Victoria Harbour. Anaerobic sediments are thought to be ideal for palaeoecological reconstructions because their vertical stratigraphy is undisturbed by bioturbidation. Analysis of the Kowloon Bay sediment cores indicated that very few individual diatoms belonged to the genus Pseudo-nitzschia, even though Pseudo-nitzschia was found in abundance in many of the plankton samples taken from a nearby site. The relative absence of Pseudo-nitzschia frustules was interpreted as indicating that these thin walled, poorly silicified, planktonic diatoms failed to preserve in the saline (32–34‰), slightly alkaline (pH 7.6–7.8), anaerobic sediments of Kowloon Bay. Dissolution of thinly silicified diatoms rather than predation was believed to be the reason for their virtual absence in the core. The anaerobic conditions near the bottom of Kowloon Bay and the shallowness of the Bay, 12 m, makes predation an unlikely explanation. Diatom abundance declined in the sediment cores below a depth of 15 cm (ca 1955). This was attributed to the decrease in nutrient loading to Victoria Harbour prior to 1955 rather than enhance diatom dissolution in the deeper sediments. Benthic diatoms became proportionately more abundant below the15 cm core depth.
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    Interrelationships between crustacean zooplankton and phytoplankton: Results from 15 years of field observations at the mesotrophic Saidenbach Reservoir (Germany) (1995)
    Springer
    Hydrobiologia 307 (1995), S. 231-238 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; crustacean plankton ; long-term observation ; interrelationships ; Secchi depth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fifteen years of data (1975–1990) on the phyto- and crustacean plankton in the meso/eutrophic Saidenbach Reservoir were analysed to reveal correlations between these groups or members of them. The weekly or fortnightly samples were collected from different depths and times, and were integrated to form seasonal averages. For the dominant organisms, summer means of abundance were plotted against one another. Among the Crustacea, Daphnia galeata exerts a strong influence on nanoplankton resulting in an increased Secchi depth in years with a high standing stock of Daphnia. No such correlations were found for Eudiaptomus and the Cyclopoida, which are not able to remove such small particles. The abundance of Daphnia showed no obvious effects on Cyanophyta, colony forming Chlorophyta and Asterionella formosa. This implies that in the Saidenbach Reservoir, factors other than crustacean grazing are of crucial importance for the population dynamics of the latter algal groups. It is shown, that the influence of the Crustacea on the phytoplankton is evident not only for short periods, i.e. in clear-water stages, or in biomanipulated lakes, but also can be observed under ‘non-manipulated’ conditions for longer time periods.
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    The influence of photon flux density (PFD) on short term 14C incorporation into proteins, carbohydrates and lipids in freshwater algae (1995)
    Springer
    Hydrobiologia 308 (1995), S. 51-59 
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    ISSN: 1573-5117
    Keywords: photon flux density ; intracellular metabolic pools ; proteins ; carbohydrates ; lipids ; polysaccharides ; photosynthesis ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of photon flux density (PFD) on the partitioning of photosynthetically fixed 14CO2-C into major intracellular end products was investigated for three species of freshwater planktonic algae (Nitzschia palea, Monoraphidium minutum and Synechococcus elongatus belonging to three different classes. This study was designed to investigate the phenomenon of polysaccharide synthesis associated with the saturation of protein synthesis and to test if this process is common to all three phytoplankton species. Protein synthesis was saturated at low PFD in all three species of algae studied. However, fixed carbon was differentially stored, namely in lipids in Nitzschia palea (Bacillariophyceae), in polysaccharides in Monoraphidium minutum (Chlorophyceae), and in low molecular weight metabolites (LMW) in Synechococcus elongatus (Cyanophyceae). The results of this transient state study indicate that the metabolic pathways of algae can easily be controlled by different irradiance. Furthermore, it appears that the difference in the patterns of synthesis is taxonomy dependent.
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    URL: http://dx.doi.org/10.1007/BF00037787
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    Effects of nutrient addition on phytoplankton in Lake Nakanuma, Japan (1995)
    Springer
    Hydrobiologia 308 (1995), S. 109-116 
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    ISSN: 1573-5117
    Keywords: amino acids ; carbon uptake ; neutral sugars ; nitrogen uptake ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We measured the uptake of carbon and inorganic nitrogen in nutrient-enriched water samples during 15-days incubation in summer in Lake Nakanuma, Japan. We calculated daily variations in neutral sugars and amino acids of the phytoplankton and estimated the efficiency of the increases in sugars and amino acids relative to photosynthetic activities. Only a small portion of carbon incorporated via photosynthesis was used for synthesis of sugars and amino acids during the incubation periods. The percentage increase in neutral sugars plus amino acids compared to photosynthetic rates ranged from 3.7 to 26.9% with an average of 12.8%. These findings suggest that large amounts of photosynthates were not used for the synthesis of cell components of phytoplankton and were lost through processes such as excretion and respiration.
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    URL: http://dx.doi.org/10.1007/BF00007395
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    Plankton and hydrochemistry of Lake Futalaufquen (Patagonia, Argentina) during the growing season (1995)
    Springer
    Hydrobiologia 316 (1995), S. 63-73 
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    ISSN: 1573-5117
    Keywords: Patagonia ; oligotrophy ; nitrogen limitation ; phytoplankton ; zooplancton ; spatial heterogeneity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plankton communities and hydrochemistry of an oligotrophic lake occupying a glacial valley in Argentinian Patagonia (42 °49′S; 71 °43′W) were studied. Monthly samples at three stations integrated from 0 to 50 m and stratified samples at the site of maximum depth, were taken during the growing season. Transparency was always controlled by glacial silt, and not by phytoplankton. Lake water belongs to the calcium-bicarbonate type, with low conductivity (24 µS cm−1), and poor buffering capacity. Forty-five phytoplankton taxa were found. Mean phytoplankton density was 49 cells ml−1 and mean biomass 69 µg l−1. N:P relationships, inorganic nitrogen exhaustion in the photic layer, and correlations between nutrients and phytoplankton density suggests nitrogen as the main limiting factor. Fifteen zooplankton species were found. Mean zooplankton density was 12.2 ind. l−1 and mean biomass 22.9 µg l−1. Diatoms and Boeckellidae were the dominant planktonic groups. Morphometry and hydrological factors were responsible for horizontal heterogeneity in phytoplankton and chemical variables.
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    URL: http://dx.doi.org/10.1007/BF00019376
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    An experimental demonstration of trophic interactions affecting water quality of Rice Lake, Ontario (Canada) (1996)
    Springer
    Hydrobiologia 319 (1996), S. 73-85 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; zooplankton ; phosphorus ; aquatic mesocosms ; trophic interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Eight cylindrical enclosures (3 m diameter, 2.7 m long, V = 20m3) were installed in eutrophic Rice Lake (Ontario, Canada) in late spring of 1987. Fish (yearling yellow perch (Perca flavescens) and macrophytes (Potamogeton crispus) presence and absence were set at the beginning of the experiment to yield four combinations of duplicate treatments. The purpose of the experiment was to determine if the phytoplankton, zooplankton, macrophytes and fish species resident in the lake interact to influence water quality (major ions, phosphorus, algal densities and water clarity). The presence of fish was associated with: (1) decreased biomass of total zooplankton, (2) decreased number of species in the zooplankton, (3) decreased average size of several zooplankton taxa, (4) higher total phosphorus concentrations, (5) higher phytoplankton and chlorophyll a concentrations, (6) lower water clarity, (7) lower potassium levels during macrophyte die-back, (8) lower pH and higher conductivity in the presence of macrophytes. Biomass of large Daphnia species (but not total zooplankton) was highly correlated with the algal response (r 2 = 0.995) and was associated with reduced biomass of several algal taxa including some large forms (Mougeotia, Oedogonium) and several colonial blue-green algae. However, no significant control of late summer growth of the bloom-forming blue-green alga Anabaena planctonica Brun. was achieved by the Daphnia presence-fish absence treatment. Release of phosphorus to the water column during the die-back of P. crispus was not an important phenomenon.
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    URL: http://dx.doi.org/10.1007/BF00020973
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    The influence of a dissolved inorganic nitrogen gradient on phytoplankton community dynamics in a chain of lakes (1996)
    Springer
    Hydrobiologia 319 (1996), S. 225-235 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; nitrogen limitation ; productivity ; diversity ; community structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a chain of lakes along which nutrient availability varies in a gradient, we performed factorial nutrient enrichment experiments to determine if nitrogen limitation was the principal factor controlling the differences in phytoplankton biomass, photosynthetic productivity, diversity, and species composition among two of the lakes in the chain. In the least productive lake, East Graham Lake, P and C enrichments (in the absence of N enrichment) had no effect on biomass and diversity, whereas within two weeks the N enrichments (alone or in any combination with P and/or C) increased the biomass and decreased the diversity of East Graham Lake phytoplankton to levels similar or identical to those in more productive Shoe Lake. Short-term 14C photosynthetic rates in East Graham Lake water also responded only to N in the third week. However, photosynthesis was stimulated by P in the first week, and a few species did increase in numbers with P enrichment, suggesting that some degree of P limitation remains in addition to the strong N limitation in East Graham Lake. A number of species responded individually to the enrichments in a manner similar to that of the overall community, and a strong overlapping of discriminant analysis scores for N-enriched East Graham Lake with those of Shoe Lake was consistent with our prediction that the community structure of N-enriched East Graham Lake water would shift toward that of Shoe Lake. However, many species did not respond consistently with these results, and the nutrients tested were clearly not a major factor in the differences in abundance of those species among the two lakes. The results support the argument that overall biomass production and diversity of the phytoplankton community in a lake can be a relatively simple function of a single most-limiting nutrient. However, many of the species responses also confirm that, while nutrient availability is an important factor in the control of the species composition of the community, other factors are likely to prevent reliable predictions of all species effects on the basis of nutrient availability alone.
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    URL: http://dx.doi.org/10.1007/BF00013735
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    Hydrological cycle and interannual variability of the aquatic community in a temporary saline lake (Fuente de Piedra, Southern Spain) (1997)
    Springer
    Hydrobiologia 345 (1997), S. 131-141 
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    ISSN: 1573-5117
    Keywords: saline lakes ; shallow lakes ; seasonality ; interannual variability ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fuente de Piedra is a shallow, temporary saline lake whoseseasonal behavior is strongly dependent on the annual hydrologicalbudget. In this study, we outline the characteristics of Fuente dePiedra Lake for two years that had different hydrological budgets.The high precipitations in 1989–90 caused the lake not to dry asusual, and decreased both salinity and the amplitude of changes.There were also differences in nutrient dynamics, with generallylower concentrations of soluble reactive phosphorus and ammonium,whereas in the more humid year nitrate showed a distinct maximum inwinter. Winter bloom chlorophyll a concentrations were alsomuch higher in 1989–90 (〉600 μg l-1) but there wasalso a winter productive phase that was presumably poorly coupledwith consumption processes that predominate in spring. Planktonicassemblages were different between years. Highly halotolerantphytoplankton species (Dunaliella salina and D. viridis) became scarcer, and especially two previouslyunrecorded diatoms (Cyclotella sp. and Chaetoceros sp.)became dominant in the bloom time in the wet year. The speciesrichness of the zooplankton increased in the wet year, with newspecies appearing that were not collected during 1987–88(Branchinectella media, Daphnia mediterranea, Macrothrix sp.,Arctodiaptomus salinus, Cyclops sp., Sigara sp...).There was also a much higher development of macrophytes (Ruppiadrepanensis, Althenia orientalis, Lamprothamnium papulosum)and bird populations, especially flamingoes (Phoenicopterusruber). Important interannual variations in this sort of system pointto the need for long term studies to observe the whole range ofstates that define the lake as an entity.
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    URL: http://dx.doi.org/10.1023/A:1002983723725
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    Phytoplankton periodicity and sequences of dominance in an Amazonian flood-plain lake (Lago Batata, Pará, Brasil): responses to gradual environmental change (1997)
    Springer
    Hydrobiologia 346 (1997), S. 169-181 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; succession ; flood-plain lake ; Amazon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The composition of the phytoplankton of Lago Batata,a flood-plain lake connected to Rio Trombetas,undergoes a conspicuous annual cycle which is relatedto the hydrology (depth of water, rate of fluvialflushing) and the hydrography (stability, frequency ofmixing of the water) of the lake. From a sparsenanoplankton at high-water and high flushing, the lakepasses to desmid-diatom dominance and finally tofilamentous cyanobacteria when the lake is barely 2 mdeep. As it refills, the lake again becomes desmid-dominated; then, when the turbidity is least and thestratification most stable, Botryococcus becomesa major component. Eventually flushing becomes toorapid for any but the relatively fastest-growingspecies. These changes are gradual and, at the scaleof algal generation times, cannot be explained assharp or sudden disturbances. Neither do they have theproperties of ecological successions but ratherrepresent compositional responses to a progressiveenvironmental modification analogous to the floristicphenomenon of gradual climate change.
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    URL: http://dx.doi.org/10.1023/A:1002926318409
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    Phytoplankton community response to reservoir aging, 1968–92 (1997)
    Springer
    Hydrobiologia 346 (1997), S. 183-192 
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    ISSN: 1573-5117
    Keywords: reservoir aging ; phytoplankton ; turbidity ; sedimentation ; eutrophication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of reservoir aging on the phytoplankton community of amidwestern U.S. reservoir constructed in 1965 (Pawnee Reservoir) werestudied by comparing algal biovolume and species composition from April 1992through November 1992 to surveys conducted in 1968–73 and 1990. Meansummer total phosphorus, nitrate-nitrogen, Secchi disk depth, totalsuspended solids, chlorophyll a, and phytoplankton species composition datacharacterized Pawnee Reservoir during 1968–69 as a high nutrient,relatively clear water environment. Phytoplankton biomass was relativelylow, consisting mainly of cyanophytes and non-flagellated chlorophytes.During 1970–73, water clarity was poor, total suspended solids werehigh, and total phosphorus was lower, but was still greater than 100 µgl−1. The 1970–73 phytoplankton biomass was high and wasdominated by cyanophytes. Mean summer total phosphorus remained 〉100µg l−1, water clarity remained poor, but phytoplanktonbiomass decreased significantly during 1990–92. The dramatic drop inchlorophyll a and low mean volatile suspended solids indicated thatinorganic suspended sediments, rather than phytoplankton, accounted for themajority of the turbidity in 1990-92. In addition to lower phytoplanktonbiomass, community composition shifted away from buoyancy-regulatingcyanophytes toward flagellated chlorophytes. These data suggest that asreservoirs located in agricultural watersheds age, (1) inorganic suspendedsediments have a significant effect on the light environment as well asphytoplankton biomass and species composition, (2) the control ofphytoplankton biomass and species composition shifts away from nutrients tolight and suspended sediments, and (3) there is a 1–2 year lag in theresponse of phytoplankton biomass to maximum nutrient loading during thetrophic upsurge period. Thus, sedimentation has been shown to be a primarydeterminant of plankton and benthic macroinvertebrate community compositionas Pawnee Reservoir aged.
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    URL: http://dx.doi.org/10.1023/A:1002978302479
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    Spatial patterns and relationships between phytoplankton, zooplankton and water quality in the Saimaa lake system, Finland (1996)
    Springer
    Hydrobiologia 322 (1996), S. 267-276 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; zooplankton ; trophic gradient ; grazing ; multivariate analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The interactions between phytoplankton and zooplankton were studied in two large lakes in the Saimaa lake system, Finland. Both are subjected to substantial waste water loading, and exhibit a clear trophic gradient between the loaded and unloaded areas. The phytoplankton and zooplankton were compared in terms of composition, abundance and biomass at 34–39 stations located in different parts of the lakes. At least four mechanisms were thought to affect the composition of plankton communities: (1) the amount of nutrients (trophic gradient), (2) grazing of algae by herbivores, (3) the effect of the algal species composition on feeding by zooplankters (large, colonial algae in the more loaded parts of the lakes) and (4) the regeneration and reorganization of nutrients.
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    URL: http://dx.doi.org/10.1007/BF00031839
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    The trophic state of Lake Ladoga as indicated by late summer phytoplankton (1996)
    Springer
    Hydrobiologia 322 (1996), S. 9-16 
    Details
    ISSN: 1573-5117
    Keywords: phytoplankton ; trophic state ; intercalibration ; Lake Ladoga
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract As a part of the joint Russian-Finnish evaluation of human impact on Lake Ladoga, we studied the phytoplankton of the lake in order to find biological indicators for eutrophication. A second aim of the investigation was intercalibration of sampling and phytoplankton counting techniques between the Russian and Finnish laboratories. Phytoplankton samples were collected from 27 sampling stations in the lake and from the rivers Volkhov and Neva in 9–13 August 1993. In surface water samples the phytoplankton fresh weight biomass varied in the range 218–3575 mg m−33. Highest biomass values were encountered in Sortavala Bay, and lowest ones in the western central part of the lake. Phytoplankton species composition varied considerably in the lake; blue-green and green algae predominated near-shore areas and Cryptophyceae in the offshore stations. Canonical correspondance analysis revealed close grouping of eutrophy indicating communities, dominated mainly by greens and blue-greens, in the most nutrient-rich parts of Lake Ladoga, the Volkhov and Svir Bays. Samples from the vicinity of the inflows of Vuoksi and Burnaya Rivers and off Pitkaranta formed a separate group, dominated by diatoms, most of which were typical to mesotrophic or eutrophy lakes. As judged by phytoplankton biomass values and chlorophyll a concentrations, Lake Ladoga may generally be classified as mesotrophic. Eutrophicated areas are found in the northern archipelago of the lake and in the areas influenced by large rivers.
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    URL: http://dx.doi.org/10.1007/BF00031799
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    Does the intermediate disturbance hypothesis comply with thermodynamics? (1996)
    Springer
    Hydrobiologia 323 (1996), S. 9-21 
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    ISSN: 1573-5117
    Keywords: ecological thermodynamics ; exergy ; ecosystem development ; phytoplankton ; models ; dynamic structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A unique data set from Keszthely Bay, Lake Balaton has been applied to develop a dynamic structural model able to describe the observed changes in phytoplankton biomass and diversity. We tested whether the model reacts according to the Intermediate Disturbance Hypothesis and according to the hypothesis that ecosystem reactions attempt to maximize the thermodynamic function exergy under prevailing conditions. If the answer to these tests are confirmatory, it can be considered a support for IDH and for the use of the exergy maximization principle as a general principle to explain ecosystem reactions.
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    URL: http://dx.doi.org/10.1007/BF00020543
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    Determination of the trophic state by qualitative and quantitative phytoplankton analysis in two gravel pit lakes (1996)
    Springer
    Hydrobiologia 323 (1996), S. 97-105 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; trophic state ; gravel pit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phytoplankton of two gravel pits with comparable nutrient concentrations but different chlorophyll-a concentrations and phytoplankton biovolume was investigated qualitatively and quantitatively over a period of two years. This study deals with the phytoplankton-rich ‘Rotter See’ and the phytoplankton-poor ‘Paulsmaar’, both South of Cologne. The trophic state of both lakes was determined comparatively according to Ryding & Rast (1989) and the categories used by Brettum (1989). The results were compared with each other. The trophic lake index according to Hörnström (1981) was modified slightly and subsequently determined for both lakes. A combination of qualitative and quantitative phytoplankton analysis made a proposal of a rehabilitation for the Rotter See possible.
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    URL: http://dx.doi.org/10.1007/BF00017587
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