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  • Articles  (30)
  • phytoplankton
  • saline lakes
  • Springer  (30)
  • 1995-1999  (30)
  • Geography  (24)
  • Chemistry and Pharmacology  (6)
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  • Articles  (30)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 23 (1997), S. 2299-2312 
    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.
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  • 2
    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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  • 3
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    Springer
    International journal of salt lake research 6 (1997), S. 217-231 
    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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  • 4
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    International journal of salt lake research 6 (1997), S. 353-371 
    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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  • 5
    Electronic Resource
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    Springer
    International journal of salt lake research 6 (1997), S. 353-371 
    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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  • 6
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    International journal of salt lake research 7 (1998), S. 13-24 
    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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  • 7
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    International journal of salt lake research 7 (1998), S. 87-108 
    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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  • 8
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    Springer
    International journal of salt lake research 7 (1998), S. 87-108 
    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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  • 9
    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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  • 10
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    International journal of salt lake research 7 (1998), S. 261-274 
    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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  • 11
    ISSN: 1573-8590
    Keywords: conductivity ; relative abundance ; saline lakes ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract Zooplankton collected from vertical net tows were related to the environmental variables from 98 lakes from the Interior Plateau of British Columbia. Canonical correspondence analysis showed that both salinity and ionic composition (pH and Mg) of the lake-water made major and significant contributions to the first two ordination axes (λ=0.42 and 0.11 respectively,P〈0.05). BothArtemia franciscana andMoina hutchinsoni had their highest relative abundance in meso-hypersaline waters. However,Artemia franciscana preferred waters that were higher in Mg and Ca, whileMoina hutchinsoni was found in waters that were lower in Mg and Ca. Similarly, at intermediate salinities,Daphnia pulex and the calanoid copepods preferred waters slightly lower in Mg and Ca, whereasCeriodaphnia laticaudata andSimocephalus spp. were relatively more common in waters higher in Mg and Ca. Because the freshest lakes studied varied much less in ionic composition, the zooplankton in these lakes did not show a preference to ionic composition. As expected, multi-generic groups, such as the calanoid copepods, cyclopoid copepods and nauplii, had wider tolerances to conductivity than groups identified to lower taxonomic levels. Significant weighted-averaging regression and calibration models of conductivity were developed based on zooplankton species composition from the study lakes (r 2=0.56,P〈0.05). Samples composed largely of multi-generic taxa yielded the worst estimates of salinity in the reconstruction model. This study suggests that zooplankton community composition may be developed into a useful proxy for paleosalinity reconstruction.
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  • 12
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    International journal of salt lake research 6 (1997), S. 5-16 
    ISSN: 1573-8590
    Keywords: Aral Sea ; Central Asia ; EC (electrical conductivity) ; Lake Balkhash ; Lake Kamyslybas ; phytoplankton ; saline lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract The Aral Sea, Lake Balkhash, and Lake Kamyslybas are closed lakes inCentral Asia. They range from oligosaline to metasaline. The salinity of theAral Sea has increased by more than 30 g L−1 sincewidespread irrigation began in its catchment area. Few studies of thephytoplankton have been conducted on these lakes since extensive irrigationstarted. The investigation reported here compares the flora of phytoplanktonin these saline lakes. In the Small Aral Sea, phytoplankton densitygradually decreased with increasing electrical conductivity (EC) (∼salinity), but there was no such relation in Lake Balkhash and LakeKamyslybas. In the Aral Sea, Dinophyceae and Bacillariophyceae werefrequently observed in most areas of high EC value, and Cyanophyceae weremost conspicuous in the area of medium and lower EC values. In LakeBalkhash, Cyanophyceae were most conspicuous, but Chlorophyceae were alsonoticeable. Most Cyanophyceae in Aral Sea formed filaments with heterocysts.The distinct characteristic of the phytoplankton of the Lake Balkhash wasthat all dominant species form colonies covered with a gelatinous film.Siliceousplankton diversity gradually decreased with increasing EC values inthe Aral Sea and Lake Balkhash.
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  • 13
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    International journal of salt lake research 6 (1997), S. 217-231 
    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'ya were investigated in 1984–1989. The structure and functional nature of the phytoplankton in the water-bodies studied were analogous to those of the littoral zone of eutrophic lakes, considering hydrological and hydrochemical conditions. The very high average annual P/B ratios (453–582) are considered as regional features, namely high light intensity and prolonged light period, the salinity usual for saline waters under anthropogenic influence, the frequent and discrete income of nutrients in drainage water and from sediments.
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  • 14
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    International journal of salt lake research 7 (1998), S. 261-274 
    ISSN: 1573-8590
    Keywords: cyanobacteria ; lake management ; Mono Lake〉/kwd〉 ; 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 crnt, 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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  • 15
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    International journal of salt lake research 8 (1999), S. 7-18 
    ISSN: 1573-8590
    Keywords: coastal waters ; production ; decomposition ; phytoplankton ; Aral Sea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract The species composition, population density, biomass and main functional characteristics of the phytoplankton community near Cape Tastubec, northern Aral Sea in September 1993 were investigated. The characteristics investigated were daily primary production, decomposition, and photosynthetic intensity. The data indicate that certain changes in the structure and function of the phytoplankton have recently taken place.
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  • 16
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    International journal of salt lake research 8 (1999), S. 7-18 
    ISSN: 1573-8590
    Keywords: coastal waters ; production ; decomposition ; phytoplankton ; Aral Sea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract The species composition, population density, biomass and main functional characteristics of the phytoplankton community near Cape Tastubec, northern Aral Sea in September 1993 were investigated. The characteristics investigated were daily primary production, decomposition, and photosynthetic intensity. The data indicate that certain changes in the structure and function of the phytoplankton have recently taken place.
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  • 17
    ISSN: 1573-8590
    Keywords: bacterioplankton ; blue-green algae ; meromictic salt lake ; phytoplankton ; vertical structure ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract The specific composition, vertical distribution and daily migration of plankton in a meromictic salt lake, Lake Shira, have been investigated. The main structural components of the ecosystem are bacteria, algae and crustaceans. Since the late 1970s, blue-green algae are reported as dominant. Nowadays the phytoplankton is dominated by Lyngbya contorta, Microcystis ichtyoblabe (Cyanophyta), Cyclotella tuberculata (Bacillariophyta) and Dictyosphaerium tetrachotomum (Chlorophyta). The zooplankton of Lake Shira comprises Arctodiaptomus salinus (Copepoda), Brachionus plicatilis and Hexarthra oxiuris (Rotatoria). Investigation revealed a stratified vertical distribution of all dominant species except Cyclotella with a maximum at a depth of 12--15 m during the summer growth period. Zooplanktons differ in the pattern of distribution and daily migration, but most zooplankton tend to concentrate near the surface. The possible reasons for the vertical distribution of the plankton are discussed.
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  • 18
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    International journal of salt lake research 5 (1996), S. 287-313 
    ISSN: 1573-8590
    Keywords: claypans ; hydrology ; intermittent wetlands ; littoral invertebrates ; physicochemical features ; saline lakes ; tadpoles ; waterbirds ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract Bloodwood Station, 130 km NW of Bourke, NSW, has a diverse array of intermittently flooded wetlands raging from salinas to fresh waters, either clear, opaque or very turbid, and from relatively large (820 ha) to quite small (〈1 ha). A study during 1995 followed the filling of 22 wetlands after heavy rain in January to subsequent drying or recession, and looked at the relationship between physicochemical features, aquatic plants, zooplankton, littoral invertebrates, tadpoles, and waterbirds. Wetlands were delineated into two major groups: saline and fresh, with the latter subdivided into five types — clear fresh waters, artificial tanks, vegetated pans, turbid pans, and miscellaneous. The saline lakes developed extensive beds of macrophytes some months after filling which attracted large number of waterbirds. Later, abundant Zooplankton were feed for many Pink-eared Duck. Most of the fresh waters developed large initial populations of phyllopodous crustaceans, Zooplankton and tadpoles, but these waters attracted few waterbirds. Clearer fresh waters later grew macrophytes which attracted many waterbirds, but the turbid claypans remained unattractive to waterbirds during their existence, despite harbouring a host of invertebrates. The vegetated pans, artificial tanks and miscellaneous sites attracted only a few waterbirds, but the tanks along with the persistent clear fresh waters become important as feeding and resting sites as other wetlands dried towards the year end. Few waterbirds bred on these wetlands during 1995. However, many were important as major feeding sites and formed part of a mosaic of intermittent wetlands for Australia's inland waterbirds.
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  • 19
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    International journal of salt lake research 5 (1996), S. 253-260 
    ISSN: 1573-8590
    Keywords: saline lakes ; chlorophyll ; size-fractions ; phytoplankton ; shallow lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract The size-fractionated distribution of chlorophylla was studied in a temporary hypersaline lake situated in the south of Spain during an annual hydrological cycle characterized by low levels of rainfall. The contribution of each size class to the total chlorophylla concentration indicates that ultraplankton (size class 〈5μm) was the most important fraction of phytoplankton biomass during this year.
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  • 20
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    International journal of salt lake research 6 (1997), S. 5-16 
    ISSN: 1573-8590
    Keywords: Aral Sea ; Central Asia ; EC (electrical conductivity) ; Lake Balkhash ; Lake Kamyslybas ; phytoplankton ; saline lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract The Aral Sea, Lake Balkhash, and Lake Kamyslybas are closed lakes in Central Asia. They range from oligosaline to metasaline. The salinity of the Aral Sea has increased by more than 30 g L−1 since widespread irrigation began in its catchment area. Few studies of the phytoplankton have been conducted on these lakes since extensive irrigation started. The investigation reported here compares the flora of phytoplankton in these saline lakes. In the Small Aral Sea, phytoplankton density gradually decreased with increasing electrical conductivity (EC) (∼ salinity), but there was no such relation in Lake Balkhash and Lake Kamyslybas. In the Aral Sea, Dinophyceae and Bacillariophyceae were frequently observed in most areas of high EC value, and Cyanophyceae were most conspicuous in the area of medium and lower EC values. In Lake Balkhash, Cyanophyceae were most conspicuous, but Chlorophyceae were also noticeable. Most Cyanophyceae in Aral Sea formed filaments with heterocysts. The distinct characteristic of the phytoplankton of the Lake Balkhash was that all dominant species form colonies covered with a gelatinous film. Siliceousplankton diversity gradually decreased with increasing EC values in the Aral Sea and Lake Balkhash.
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  • 21
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    International journal of salt lake research 7 (1998), S. 45-80 
    ISSN: 1573-8590
    Keywords: aquatic flora and fauna ; circum-lacustrine vegetation ; cormophytes ; microphytobenthos ; pelogenous/non-pelogenous lakes ; phytoplankton ; Romania ; saline lakes ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract An inventory of the aquatic and circum-lacustrine flora and aquatic fauna of 23 karst- and anthroposaline lakes formed on Miocene rock salt bodies in Romania was undertaken. Simultaneous field determinations of water and sediment pH, total dissolved solids, Secchi transparency and lake maximum depth were also made. Environmental conditions for phytoplankton, microphytobenthos, macrophyte and cormophyte species were defined. Relations between the numbers of plankton, microbenthos, macrophyte and cormophyte species differentiated pelogenous (usually, therapeutic) and non-pelogenous lakes. High densities and occurrence frequencies characterized the most representative species. For three of these species, Amphora veneta, Artemia sp. and Potamogeton pectinatus, ecological conditions were noted. In the circum-lacustrine vegetation, glycophytes were more important than halophytes.
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  • 22
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    International journal of salt lake research 7 (1998), S. 13-24 
    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 howArtemia, 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 theArtemia 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 thisArtemia 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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  • 23
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    Electronic Resource
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    International journal of salt lake research 7 (1998), S. 45-80 
    ISSN: 1573-8590
    Keywords: aquatic flora and fauna ; circum-lacustrine vegetation ; cormophytes ; microphytobenthos ; pelogenous/non-pelogenous lakes ; phytoplankton ; Romania ; saline lakes ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract An inventory of the aquatic and circum-lacustrine flora and aquatic fauna of 23 karst- and anthroposaline lakes formed on Miocene rock salt bodies in Romania was undertaken. Simultaneous field determinations of water and sediment pH, total dissolved solids, Secchi transparency and lake maximum depth were also made. Environmental conditions for phytoplankton, microphytobenthos, macrophyte and cormophyte species were defined. Relations between the numbers of plankton, microbenthos, macrophyte and cormophyte species differentiated pelogenous (usually, therapeutic) and non-pelogenous lakes. High densities and occurrence frequencies characterized the most representative species. For three of these species,Amphora veneta, Artemia sp. andPotamogeton pectinatus, ecological conditions were noted. In the circum-lacustrine vegetation, glycophytes were more important than halophytes.
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  • 24
    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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  • 25
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    International journal of salt lake research 8 (1999), S. 211-232 
    ISSN: 1573-8590
    Keywords: bacterioplankton ; blue-green algae ; meromictic salt lake ; phytoplankton ; vertical structure ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geography
    Notes: Abstract The specific composition, vertical distribution and daily migration of plankton in a meromictic salt lake, Lake Shira, have been investigated. The main structural components of the ecosystem are bacteria, algae and crustaceans. Since the late 1970s, blue-green algae are reported as dominant. Nowadays the phytoplankton is dominated byLyngbya contorta, Microcystis ichtyoblabe (Cyanophyta),Cyclotella tuberculata (Bacillariophyta) andDictyosphaerium tetrachotomum (Chlorophyta). The zooplankton of Lake Shira comprisesArctodiaptomus salinus (Copepoda),Brachionus plicatilis andHexarthra oxiuris (Rotatoria). Investigation revealed a stratified vertical distribution of all dominant species exceptCyclotella with a maximum at a depth of 12–15 m during the summer growth period. Zooplanktons differ in the pattern of distribution and daily migration, but most zooplankton tend to concentrate near the surface. The possible reasons for the vertical distribution of the plankton are discussed.
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  • 26
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    Biogeochemistry 40 (1998), S. 235-247 
    ISSN: 1573-515X
    Keywords: fish ; invertebrates ; ligands ; mercury ; methylmercury ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract To understand the accumulation of inorganic mercury and methylmercury at the base of the estuarine food chain, phytoplankton (Thalassiosira weissflogii) uptake and mercury speciation experiments were conducted. Complexation of methylmercury as methylmercury-bisulfide decreased the phytoplankton uptake rate while the uptake rate of the methylmercury-cysteine and -thiourea complexes increased with increasing complexation by these ligands. Furthermore, our results indicated that while different ligands influenced inorganic mercury/methylmercury uptake by phytoplankton cells, the ligand complex had no major influence on either where the mercury was sequestered within the phytoplankton cell nor the assimilation efficiency of the mercury by copepods. The assimilation efficiency of inorganic mercury/methylmercury by copepods and amphipods feeding on algal cells was compared and both organisms assimilated methylmercury much more efficiently; the relative assimilation efficiency of methylmercury to inorganic mercury was 2.0 for copepods and 2.8 for amphipods. The relative assimilation is somewhat concentration dependent as experiments showed that as exposure concentration increased, a greater percentage of methylmercury was found in the cytoplasm of phytoplankton cells, resulting in a higher concentration in the copepods feeding on these cells. Additionally, food quality influenced assimilation by invertebrates. During decay of a T. weissflogii culture, which served as food for the invertebrates, copepods were increasingly less able to assimilate the methylmercury from the food, while even at advanced stages of decay, amphipods were able to assimilate mercury from their food to a high degree. Finally, fish feeding on copepods assimilated methylmercury more efficiently than inorganic mercury owing to the larger fraction of methylmercury found in the soft tissues of the copepods.
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  • 27
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    Journal of chemical ecology 22 (1996), S. 2221-2231 
    ISSN: 1573-1561
    Keywords: Exudation ; Nuphar lutea ; Nymphaeaceae ; yellow water lily ; macrophytes ; phytoplankton ; zooplankton ; phenols ; resorcinol ; allelochemicals ; nitrate ; light
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Resorcinol (1,3-dihydroxybenzene) was identified as one of the major constituents of the exudate ofNuphar lutea seedlings, which were raised from seeds and cultivated under axenic conditions. The compound is released from the plants in considerable amounts (up to 15 nmol/seedling/day). Highest rates of resorcinol exudation were measured when the seedlings were incubated under physiological conditions (macronutrient and light supply) that resembled those of natural stands of the plant. An inverse correlation exists between nitrate and/or light supply and resorcinol production. Because of its generally toxic properties, resorcinol is suggested to play a role as an allelochemical in interactions between macrophytes and other organisms of the aquatic ecosystem. A first approach of resorcinol application to zooplankton and phytoplankton organisms resulted in deleterious effects against aDaphnia species. Two Cryptophyceae species reduced resorcinol concentration to zero, showing a concomitant increase of the size of starch granule enclosures. Cyanophyceae and Chlorophyceae seemed not to be affected.
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  • 28
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    Biogeochemistry 35 (1996), S. 235-260 
    ISSN: 1573-515X
    Keywords: benthic mineralization ; continental shelf ; denitrification ; global N cycle ; nitrogen ; North Atlantic ; nutrients ; onwelling ; phytoplankton ; sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A model of coupled nitrification/denitrification was developed for continental shelf sediments to estimate the spatial distribution of denitrification throughout shelf regions in the North Atlantic basin. Using data from a wide range of continental shelf regions, we found a linear relationship between denitrification and sediment oxygen uptake. This relationship was applied to specific continental shelf regions by combining it with a second regression relating sediment oxygen uptake to primary production in the overlying water. The combined equation was: denitrification (mmol N m−2 d−1)=0.019* phytoplankton production (mmol C m−2 d−1). This relationship suggests that approximately 13% of the N incorporated into phytoplankton in shelf waters is eventually denitrified in the sediments via coupled nitrification/denitrification, assuming a C:N ratio of 6.625:1 for phytoplankton. The model calculated denitrification rates compare favorably with rates reported for several shelf regions in the North Atlantic. The model-predicted average denitrification rate for continental shelf sediments in the North Atlantic Basin is 0.69 mmol N m− 2 d−1. Denitrification rates (per unit area) predicted by the model are highest for the continental shelf region in the western North Atlantic between Cape Hatteras and South Florida and lowest for Hudson Bay, the Baffin Island region, and Greenland. Within latitudinal belts, average denitrification rates were lowest in the high latitudes, intermediate in the tropics and highest in the mid-latitudes. Although denitrification rates per unit area are lowest in the high latitudes, the total N removal by denitrification (53 × 1010 mol N y−1) is similar to that in the mid-latitudes (60 × 1010 mol N y−1) due to the large area of continental shelf in the high latitudes. The Gulf of St. Lawrence/Grand Banks area and the North Sea are responsible for seventy-five percent of the denitrification in the high latitude region. N removal by denitrification in the western North Atlantic (96 × 1010 mol N y−1) is two times greater than in the eastern North Atlantic (47 × 1010 mol N y−1). This is primarily due to differences in the area of continental shelf in the two regions, as the average denitrification rate per unit area is similar in the western and eastern North Atlantic. We calculate that a total of 143 × 1010 mol N y−1 is removed via coupled nitrification/denitrification on the North Atlantic continental shelf. This estimate is expected to underestimate total sediment denitrification because it does not include direct denitrification of nitrate from the overlying water. The rate of coupled nitrification/denitrification calculated is greater than the nitrogen inputs from atmospheric deposition and river sources combined, and suggests that onwelling of nutrient rich slope water is a major source of N for denitrification in shelf regions. For the two regions where N inputs to a shelf region from onwelling have been measured, onwelling appears to be able to balance the denitrification loss.
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  • 29
    ISSN: 1573-515X
    Keywords: phytoplankton ; nutrients ; heavy metals ; colloids ; ultrafiltration ; river
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The impact of the spring phytoplanktonic blooms on the partition of nutrients and metals between the dissolved and particulate phases was studied over two years in the river Marne, upstream of its confluence with the river Seine. Particular attention was devoted to copper and manganese, determined in the dissolved phase (〈 0.22 μm), subdivided into the colloidal phase and the 'truly dissolved' phase (〈 10 KDaltons) obtained by tangential ultrafiltration. During the algal growth peaks, a sharp reduction of nutrients was observed in the dissolved phase: in 1994, consumption of 70% of silica, 50% of ammonium and 40% of soluble phosphorus present before the phytoplanktonic bloom. The water concentration peaks of suspended matter (SM) and of particulate metals, phosphorus and carbon coincide with those of chlorophyll. The highly significant correlations between pH and chlorophyll (r = 0.92, P 〈 0.001), pH and SM (r = 0.97, P 〈 0.001) and chlorophyll and SM (r = 0.93, P 〈 0.001) confirmed the phytoplanktonic nature of SM and the determining role of pH in the partition of metals, its increase being responsible for the coprecipitation of metal. As a corollary to the increase in the particulate phase, a decrease of 55% was observed for copper and manganese in the 'truly dissolved' phase compared to the concentrations outside bloom periods. The importance of the colloidal fraction was also shown. During the strong algal growth periods, the proportion of 'colloidal metal' in the dissolved phase (〈 0.22 μm) reached 60% and the increase in the colloidal fraction was 4 times stronger for copper than for manganese. While manganese seemed to be more associated with macroparticles, copper was more associated with fine colloidal biological particles intrinsic to the phytoplankton.
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  • 30
    ISSN: 1573-515X
    Keywords: phytoplankton ; nutrients ; heavy metals ; colloids ; Ultrafiltration ; river
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The impact of the spring phytoplanktonic blooms on the partition of nutrients and metals between the dissolved and particulate phases was studied over two years in the river Marne, upstream of its confluence with the river Seine. Particular attention was devoted to copper and manganese, determined in the dissolved phase (〈 0.22μm), subdivided into the colloidal phase and the ‘truly dissolved’ phase (〈 10 KDaltons) obtained by tangential Ultrafiltration. During the algal growth peaks, a sharp reduction of nutrients was observed in the dissolved phase: in 1994, consumption of 70% of silica, 50% of ammonium and 40% of soluble phosphorus present before the phytoplanktonic bloom. The water concentration peaks of suspended matter (SM) and of particulate metals, phosphorus and carbon coincide with those of chlorophyll. The highly significant correlations between pH and chlorophyll (r=0.92,P 〈 0.001), pH and SM (r=0.97,P 〈 0.001) and chlorophyll and SM (r=0.93,P 〈 0.001) confirmed the phytoplanktonic nature of SM and the determining role of pH in the partition of metals, its increase being responsible for the coprecipitation of metal. As a corollary to the increase in the particulate phase, a decrease of 55% was observed for copper and manganese in the ‘truly dissolved’ phase compared to the concentrations outside bloom periods. The importance of the colloidal fraction was also shown. During the strong algal growth periods, the proportion of ‘colloidal metal’ in the dissolved phase (〈 0.22μm) reached 60% and the increase in the colloidal fraction was 4 times stronger for copper than for manganese. While manganese seemed to be more associated with macroparticles, copper was more associated with fine colloidal biological particles intrinsic to the phytoplankton.
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