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  • 1
    Electronic Resource
    Electronic Resource
    Some factors affecting distribution of diatom assemblages in Pyrenean springs (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 24 (1990), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 〈list xml:id="l1" style="custom"〉1 The composition and abundance of diatom assemblages were studied together with physiographical and physicochemical variables in twenty-eight springs in the Central Pyrenees during the period 1987–88.2 Characteristic groupings of diatom taxa are revealed by Principal Components Analysis. One group, made up of assemblages of the taxa Navicula cincta, Caloncis spp. and Niizschia elliptica, is characteristic of springs with waters of high ionic strength. Certain diatom taxa are characteristic of hard water springs, either in quiet waters (Denticula tenuis, Achnanthes minutissima, Eunotia spp.) or fast flowing ones (Fragilaria spp., Diatoma hiemale). Other taxa are representative of relatively quiet, softwater springs: Anomoeoneis bracfiysira, Tabellaria flocculosa, Aulacoseira distans and Fragilaria vaucheriae.3 Five different spring types were identified, with respect to diatom assemblages, using discriminant analysis. The first consisted of high mountain springs with cold, fast waters and low ionic strength. The second group, distributed throughout the Pyrenees, had similar environmental characteristics to the first group but with intermediate water velocity and slightly higher mineral content. The third contained springs in calcareous regions of the Pyrenees, mainly slow-flowing and with hard waters. The fourth was composed of softwater springs, whilst the fifth consisted of two springs which were subject to stressful conditions (limitation of light, abundance of nitrates or high salinity).4 Ionic strength and current velocity appeared to be the dominant environmental factors affecting diatom distribution in Pyrenean springs. These factors also seem to determine diatom communities in some other geographical areas. In some springs, however, peculiar environmental factors (dim light, salinity, and high temperature) affect the structure of diatom assemblages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1990.tb00727.x
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  • 2
    Electronic Resource
    Electronic Resource
    Nutrient enrichment effects on biofilm metabolism in a Mediterranean stream (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 33 (1995), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Biofilm biomass and metabolism were analysed in La Solana, a calcareous, undisturbed second-order stream. Measurements were carried out in two Mediterranean climatic extremes, summer and winter. Two on-site experimental channels were used to study changes following nutrient addition to one of them.2. Algal biomass (chlorophyll a), NDPP (net daily primary production), GDPP (gross daily primary production) and R (respiration) increased in the enriched channel, and these increases were greater in summer.3. Photosynthetic capacity (Pmaxchl) decreased during summer, possibly due to enhanced self-shading accompanying the increase in biomass.4. In winter, Pmaxchl increased and reached values similar to those in the summer control channel. Because grazing was low, the higher values of Pmaxchl were attributed to partial substitution of the cyanobacterial assemblage by a green-algae dominated assemblage with higher photosynthetic capacity as well as the low increase in biomass preventing any significant self-shading.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1995.tb00399.x
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  • 3
    Electronic Resource
    Electronic Resource
    Flow extremes and benthic organic matter shape the metabolism of a headwater Mediterranean stream (2004)
    Oxford, UK : Blackwell Publishing
    Freshwater biology 49 (2004), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Single-station diel oxygen curves were used to monitor the oxygen metabolism of an intermittent, forested third-order stream (Fuirosos) in the Mediterranean area, over a period of 22 months. Ecosystem respiration (ER) and gross primary production (GPP) were estimated and related to organic matter inputs and photosynthetically active radiation (PAR) in order to understand the effect of the riparian forest on stream metabolism.2. Annual ER was 1690 g O2 m−2 year−1 and annual GPP was 275 g O2 m−2 year−1. Fuirosos was therefore a heterotrophic stream, with P : R ratios averaging 0.16.3. GPP rates were relatively low, ranging from 0.05 to 1.9 g O2 m−2 day−1. The maximum values of GPP occurred during a few weeks in spring, and ended when the riparian canopy was fully closed. The phenology of the riparian vegetation was an important determinant of light availability, and consequently, of GPP.4. On a daily scale, light and temperature were the most important factors governing the shape of photosynthesis–irradiance (P–I) curves. Several patterns could be generalised in the P–I relationships. Hysteresis-type curves were characteristic of late autumn and winter. Light saturation responses (that occurred at irradiances higher than 90 μE m−2 s−1) were characteristic of early spring. Linear responses occurred during late spring, summer and early autumn when there was no evidence of light saturation.5. Rates of ER were high when compared with analogous streams, ranging from 0.4 to 32 g O2 m−2 day−1. ER was highest in autumn 2001, when organic matter accumulations on the streambed were extremely high. By contrast, the higher discharge in autumn 2002 prevented these accumulations and caused lower ER. The Mediterranean climate, and in its effect the hydrological regime, were mainly responsible for the temporal variation in benthic organic matter, and consequently of ER.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.2004.01239.x
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  • 4
    Electronic Resource
    Electronic Resource
    Phosphate limitation influences the sensitivity to copper in periphytic algae (2004)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 49 (2004), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. To assess the influence of nutrient limitation on copper toxicity, periphitic communities from an oligotrophic stream were exposed to copper for six to 12 days with and without the supply of nutrients (mainly P).2. In contrast to the hypothesis that nutrient cycling in mature biofilms would protect them from Cu toxicity, low and high biomass biofilms did not differ in their physiological response to copper after 6 days of exposure.3. A clear influence of P-limitation on copper toxicity was observed. Periphytic communities that were previously fertilised for 18 days were three times more tolerant than control communities indicating that P-limitation enhanced Cu toxicity and tolerance induction were probably related to the higher P-availability. In addition, a compensation of Cu toxicity after P-addition was observed in the long-term (after 12 days).4. We conclude that periphyton from oligotrophic streams is more sensitive to copper than periphyton from fertilised streams, and that therefore a higher effect of chronic copper exposure is expected to occur in oligotrophic P-limited fluvial systems.5. Extrapolation of our results to the area of study (Catalonia, north-east of Spain) indicates that while the levels of Cu commonly found in the zone may negatively affect the periphyton from oligotrophic streams, because of the interaction between Cu and P, they are not able to control the growth of nuisance algae which is common under high nutrient conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.2004.01196.x
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of primary producers on the heterotrophic metabolism of a stream biofilm (1999)
    Oxford, UK : Blackwell Science, Ltd
    Freshwater biology 41 (1999), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. ,The influence of benthic algae on heterotrophic metabolism in a forested Mediterranean stream was investigated. Bacterial density and ectoenzymatic activities, as well as algal biomass (chlorophyll-a) and metabolism (the rate of 14C incorporation), were measured during colonization over 60 days of artificial substrata (clay tiles) under light and dark conditions.2. ,Chlorophyll-a and the rate of 14C incorporation were significantly higher in light-grown than in dark-grown biofilms. Bacterial density and ectoenzymatic activity (especially β-glucosidase) were also significantly higher in light-grown biofilms.3. ,Regressions of chlorophyll-a and 14C incorporation values on the ectoenzymatic activities were significant. The slopes of regression lines obtained for dark-grown biofilms were significantly higher than those obtained for light -grown biofilms.4. ,The differences in the slope (of the regression lines) between dark and light-grown biofilms suggest that the response of the heterotrophs is faster in biofilms with low algal biomass accrual and slows down when algal biomass is increased.5. ,It is concluded that algal accumulation in the epilithic biofilm influences the use of organic matter by the heterotrophic community by increasing the amount of organic substrate available for bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.1999.00413.x
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  • 6
    Electronic Resource
    Electronic Resource
    Variability of heterotrophic activity in Mediterranean stream biofilms: A multivariate analysis of physical-chemical and biological factors (2000)
    Springer
    Aquatic sciences 62 (2000), S. 205-215 
    Details
    ISSN: 1420-9055
    Keywords: Key words: Benthic biofilms, extracellular enzymes, heterotrophic activity, ionic content, chlorophyll a, ETS, bacteria, Mediterranean streams.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract: Environmental factors responsible for inter-site and temporal variations in extracellular enzymatic activities in benthic biofilms were studied in three Mediterranean streams. Results from canonical correlation analysis suggest that ionic content of the water and chlorophyll a content of biofilms (algal biomass) were the main factors accounting for the variability in extracellular enzyme activity of the biofilms in these streams. Water temperature was not an important factor accounting for differences among streams, while nutrient concentration played a role only in special situations such as periods when flow stops. Episodes of flow cessation and high discharge greatly affected the extracellular enzymatic activities. Biofilms differed in their efficiency in the use of polysaccharides (defined as the activity of $ \beta $ -glucosidase and $ \beta $ -xylosidase per bacterial cell). Biofilms at the site showing high nutrient concentrations (Ter River) were the least efficient, while those occurring at lower nutrient concentrations (La Solana and sandy sediments of Riera Major) were the most efficient. The highest efficiency was associated with stromatolitic communities in La Solana. The epilithic biofilms of Riera Major showed a lower efficiency than biofilms on sand in the same stream, suggesting that biofilm type may be another factor inducing variation in biofilm activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00001332
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  • 7
    Electronic Resource
    Electronic Resource
    Epilithic ectoenzyme activity in a nutrient-rich Mediterranean river (1999)
    Springer
    Aquatic sciences 61 (1999), S. 122-132 
    Details
    ISSN: 1420-9055
    Keywords: Key words: Ectoenzymatic activity, epilithon, Mediterranean river, seasonality, discharge, organic matter.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract: The epilithic biofilms of a fourth-order river, the Ter, was characterized by high algal biomass and activity and bacterial density. The epilithon was the most important site for the cycling of organic matter, while the water column had rather low activities. In spite of being a nutrient-rich system, the ectoenzymatic activities were not significantly higher in the River Ter than in other streams of lower nutrient content. Biomass and activities followed a markedly seasonal pattern, mainly showing a peak in spring and autumn. Discharge and nutrients were the most important factors for the regulation of the biofilm metabolism. Drastic decrease in mid-summer were related to the extremely dry conditions during that period. The activity of epilithic ectoenzymes was higher during high discharge periods, which were coupled with higher DOC content in the stream water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000270050057
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  • 8
    Electronic Resource
    Electronic Resource
    An assessment of recent trophic changes in Windermere South Basin (England) based on diatom remains and fossil pigments (1995)
    Springer
    Journal of paleolimnology 14 (1995), S. 151-163 
    Details
    ISSN: 1573-0417
    Keywords: chlorophyll ; diatoms ; myxoxanthophyll ; oscillaxanthin ; sediments ; eutrophication ; England ; paleolimnology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Cyanobacterial carotenoids and diatom remains have been analyzed in recent sediments from the Windermere South Basin (WSB) to study the trophic evolution experienced by the lake. Dates in the top 30 cm were specifically established through radionuclide (210Pb and137Cs) analyses. Diatom stratigraphy shows dominance of the centric diatomsCyclotella comensis andC. radiosa and several benthic taxa in the early postglacial. This indicates oligotrophy in the WSB during that period. This assemblage was replaced by another dominated by the diatomAsterionella formosa in the 1870's, as has been established from the210Pb dating. From that date onwards, the lake underwent a progression towards eutrophy, indicated by the progressive increase inAulacoseira subarctica (c. 1930's),Fragilaria crotonensis (c. 1943), and more recently, of the centricsStephanodiscus parvus (c. 1971) andCyclotella meneghiniana (1988). Carotenoid stratigraphy reveals the differences between different sections of the core. Oscillaxanthin and myxoxanthophyll had very low records in the early and medium parts of the core, but increased fromc. 1950's, showing peaks atc. 1967, 1979 and 1987. Some of these peaks indicated a differential abundance ofOscillatoria, and are matched to those observed directly during the ongoing monitoring of the phytoplankton of the lake. The coincidence between the historic appearance of diatoms associated with nutrient-rich waters and the enhanced carotenoid occurrence suggest a common response to phosphorus enrichment, and that the progressive change towards eutrophy has been accentuated during the last twenty-five years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00735479
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of removal of riparian vegetation on algae and heterotrophs in a Mediterranean stream (1997)
    Springer
    Journal of aquatic ecosystem stress and recovery 6 (1997), S. 129-140 
    Details
    ISSN: 1573-5141
    Keywords: riparian removal ; Mediterranean ; algae ; bacteria ; ectoenzymatic activities ; macroinvertebrates ; biomass ; productivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of removal of a riparian strip on aquaticautotrophic (algae) and heterotrophic (bacteria,macroinvertebrates) organisms was monitored in aMediterranean stream during the canopy growing period.Community composition, biomass and metabolicactivities were compared with those recorded during apre-riparian removal period and in a forested stretchdownstream. Higher irradiance was associated with Cladophora increase in the logged section. Algalbiomass increased up to ten times, and productivitywas up to four times higher than in the pre-removalperiod and the forested section. Bacterialcommunities showed higher ectoenzymatic activities(β-glucosidase, β-xylosidase) in thelogged section than in forested conditions. Moreoverthe coincidence between the maxima ofβ-glucosidase and chlorophyll-a suggeststhat bacterial activity was enhanced by the higheravailability of high-quality algal material. Themacroinvertebrate community had higher density andbiomass in the logged section than in the forestedsection and in the pre-removal period. Scrapers andfilterers become dominant after riparian removal,while shredders, predators and collectors did not showsignificant changes either between sites or periods.Responses of environmental variables and bioticcommunities indicate that the changes occurring in thestream due to riparian removal could be consideredbottom-up controlled, as increased illumination wasthe main mechanism responsible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009938511352
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  • 10
    Electronic Resource
    Electronic Resource
    Stromatolitic communities in Mediterranean streams: adaptations to a changing environment (2000)
    Springer
    Biodiversity and conservation 9 (2000), S. 379-392 
    Details
    ISSN: 1572-9710
    Keywords: climate change ; cyanobacteria ; ectoenzymes ; Mediterranean ; nutrient limitation ; photosynthesis ; stromatolite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A stromatolitic microbial mat extensively covers La Solana streambed, a calcareous Mediterranean stream. This stromatolite shows remarkable biological and physiological diversity. It is mainly composed by cyanobacteria, with Rivularia and Schizothrix as the most abundant taxa. The stromatolite is photosynthetically adaptated to the high irradiances reaching the streambed. Photosynthetically active chlorophyll is present even in the lowest layers of the stromatolite, indicating the presence of well-preserved cyanobacteria in that part. Diffusion of gases and nutrients within the stromatolite can be possible because of the high porosity of the crust. It has been experimentally established that the stromatolite recovers heterotrophic and autotrophic activities in a few hours, after being desiccated for long periods. Recovery after desiccation is indicative of the high resilience of this community to environmental extremes, which are common in Mediterranean climatic regimes. The stromatolitic community is adapted to nutrient limitation, both to low availability of inorganic phosphorus and nitrogen (that constrain growth of primary producers), and to low dissolved organic carbon (mainly affecting heterotrophs). Stromatolitic heterotrophs mainly rely on the organic carbon stored in the crust as the main organic carbon source. These strategies are the direct response of the stromatolite to oligotrophy, and justify the restricted occurrence in stream systems affected by organic pollution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008954801397
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