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  • 1
    Electronic Resource
    Electronic Resource
    Responses of phytoplankton to fish predation and nutrient loading in shallow lakes: a pan-European mesocosm experiment (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. The impacts of nutrients (phosphorus and nitrogen) and planktivorous fish on phytoplankton composition and biomass were studied in six shallow, macrophyte-dominated lakes across Europe using mesocosm experiments.2. Phytoplankton biomass was more influenced by nutrients than by densities of planktivorous fish. Nutrient addition resulted in increased algal biomass at all locations. In some experiments, a decrease was noted at the highest nutrient loadings, corresponding to added concentrations of 1 mg L−1 P and 10 mg L−1 N.3. Chlorophyll a was a more precise parameter to quantify phytoplankton biomass than algal biovolume, with lower within-treatment variability.4. Higher densities of planktivorous fish shifted phytoplankton composition toward smaller algae (GALD 〈 50 μm). High nutrient loadings selected in favour of chlorophytes and cyanobacteria, while biovolumes of diatoms and dinophytes decreased. High temperatures also may increase the contribution of cyanobacteria to total phytoplankton biovolume in shallow lakes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.2004.01307.x
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  • 2
    Electronic Resource
    Electronic Resource
    Life history consequences for Daphnia pulex feeding on nutrient-limited phytoplankton (1997)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 38 (1997), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. The growth and feeding of Daphnia pulex De Geer on different algal species was examined. The green algae Chlamydomonas reinhardtii Dangeard and Scenedesmus acutus Meyen, the diatom Synedra tenuissima Kützing, the cryptophyte Cryptomonas pyrenoidifera Geitler and the cyanobacterium Microcystis aeruginosa Kützing were cultured in non-limiting and in N- or P-limiting medium and used as food for D. pulex.2. Growth limitations were reflected in the elemental and biochemical composition and the morphological characteristics of the algal resources.3. The clearance rates of D. pulex feeding on nutrient-limited algae were reduced. This was not observed when nutrient-limited mutant Chlamydomonas cells without cell walls were used as food, indicating that the cell wall may play an important part.4. In comparison with animals grown on nutrient-sufficient cells, nutrient-limited algae resulted in smaller body length, reduced brood sizes, reduced size at maturity, increased age at first reproduction and, consequently, in reduced Daphnia population growth rates.5. Daphnia population growth rates (r) were negatively correlated with the C : P ratio and the carbohydrate content of the food. Moreover, significant correlations between r and clearance rates were found.6. The observed differences in the grazing and the life history parameters of Daphnia feeding on non-limited and nutrient-limited algae may be the result of both reduced nutritional value and reduced digestibility of nutrient-limited algae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.1997.00242.x
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  • 3
    Electronic Resource
    Electronic Resource
    Natural community bioassays to determine the abiotic factors that control phytoplankton growth and succession (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 20 (1988), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. The successional patterns of the dominant phytoplankton species in Lake Maarsseveen (The Netherlands) were very similar in 1980 and 1981. In December/January the diatoms Stephanodiscus hantzschii Grun., Stephanodiscus astraea (Ehr.) Grun. and Asterionella formosa Hass. dominated the algal community (A. formosa had several further population increases during the year). Fragilaria crotonensis Kitt. came to dominance in March/April, followed by the chrysophyte Dinobryon divergens Imhof and the diatom Cyclotella comta (Ehr.) Kütz in May/June. A second appearance of D. divergens was observed in July/August, followed in 1980 by F. crotonensis and a third small increase of D. divergens. In both years S. astraea and S. hantzschii started to grow again in November/December. Cryptophyceae and Chlorophyta were present throughout the year, but did not show a distinct succession.2. Natural community bioassays, performed under natural light and temperature conditions in a newly developed outdoor bioassay apparatus, showed that phosphate was the major nutrient limiting the growth rate of the phytoplankton. From January till June, during the decline in phosphorus concentration, the diatoms became successively phosphate limited in the sequence: S. hantzschii, S. astraea, F. crotonensis, A. formosa and C. comta. Light limitation was probably the major cause of the relatively late start of F. crotonensis in early spring.3. D. divergens, increasing after the diatoms from June till September, was stimulated by the addition of a chelator (EDTA). The chelator might stimulate the formation of trace metal species favouring their uptake (e.g. iron).4. The patterns of succession of the diatoms observed from January till June and from July till December were to a large extent symmetrical. The controlling factors followed opposite trends: declining phosphorus concentrations with increasing irradiance from winter till spring and increasing phosphorus concentrations with decreasing irradiance from summer till late winter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1988.tb00443.x
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  • 4
    Electronic Resource
    Electronic Resource
    Continental-scale patterns of nutrient and fish effects on shallow lakes: introduction to a pan-European mesocosm experiment (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. Shallow lake ecosystems are normally dominated by submerged and emergent plants. Biological stabilising mechanisms help preserve this dominance. The systems may switch to dominance by phytoplankton, however, with loss of submerged plants. This process usually takes place against a background of increasing nutrient loadings but also requires additional switch mechanisms, which damage the plants or interfere with their stabilising mechanisms.2. The extent to which the details or even major features of this general model may change with geographical location are not clear. Manipulation of the fish community (biomanipulation) has often been used to clear the water of algae and restore the aquatic plants in northerly locations, but it is again not clear whether this is equally appropriate at lower latitudes.3. Eleven parallel experiments (collectively the International Mesocosm Experiment, IME) were carried out in six lakes in Finland, Sweden, England, the Netherlands and Spain in 1998 and 1999 to investigate the between-year and large-scale spatial variation in relationships between nutrient loading and zooplanktivorous fish on submerged plant and plankton communities in shallow lakes.4. Comparability of experiments in different locations was achieved to a high degree. Cross-laboratory comparisons of chemical analyses revealed some systematic differences between laboratories. These are unlikely to lead to major misinterpretations.5. Nutrient addition, overall, had its greatest effect on water chemistry then substantial effects on phytoplankton and zooplankton. Fish addition had its major effect on zooplankton and did not systematically change the water chemistry. There was no trend in the relative importance of fish effects with latitude, but nutrient addition affected more variables with decreasing latitude.6. The relative importance of top-down and bottom-up influences on the plankton differed in different locations and between years at the same location. The outcome of the experiments in different years was more predictable with decreasing latitude and this was attributed to more variable weather at higher latitudes that created more variable starting conditions for the experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.2004.01302.x
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  • 5
    Electronic Resource
    Electronic Resource
    Continental-scale patterns of nutrient and fish effects on shallow lakes: synthesis of a pan-European mesocosm experiment (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. Results are analysed from 11 experiments in which effects of fish addition and nutrient loading on shallow lakes were studied in mesocosms. The experiments, five in 1998, six in 1999, were carried out in six lakes, distributed from Finland to southern Spain, according to a standard protocol.2. Effects of the treatments on 29 standard chemical, phytoplankton and zooplankton variables are examined to assess the relative importance of bottom-up (nutrient enrichment) and top-down (fish predation) effects. For each year, the experiments in different locations are treated as replicates in a meta-analysis. Results of individual experiments are then compared in terms of the patterns of significant influences of nutrient addition and fish predation with these overall results (the baseline), and between years in the same location.3. The overall meta-analysis gave consistent results across the 2 years, with nutrient loading influencing all of the chemical variables, and on average 31% of primary producer and 39% of zooplankton variables. In contrast, fish influenced none of the chemical variables, 11% of the primary producer and 44% of the zooplankton variables. Nutrient effects on the system were thus about three times greater than fish effects, although fish effects were not inconsiderable.4. The relative importance of nutrients and fish in individual experiments often differed between years at the same location and effects deviated to varying degrees from the baseline. These deviations were treated as measures of consistency (predictability) of conclusions in repeat experiments. Consistency increased southwards and this is interpreted as a consequence of more variable annual weather northwards.5. The influence of nutrient loading was greater southwards and this was probably manifested through naturally greater annual macrophyte abundance in warmer locations in consequence of the longer plant growing-season. There was no trend in the relative importance of fish effects with latitude but this may partly be an artefact of the simple fish community used. These findings suggest that nutrient control should be a greater priority than biomanipulation in the restoration of eutrophicated shallow lakes in warm temperate regions.6. Starting conditions affected the outcome of experiments. High initial concentrations of total phosphorus and planktonic chlorophyll a concentration (created by local conditions prior to the experiment) led to de-emphasis of the importance of nutrient loading in the experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.2004.01304.x
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  • 6
    Electronic Resource
    Electronic Resource
    Selective grazing by adults and larvae of the zebra mussel (Dreissena polymorpha): application of flow cytometry to natural seston (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. Selective grazing of adults and larvae of the zebra mussel (Dreissena polymorpha) on phytoplankton and detritus from both laboratory cultures and natural seston was quantified using flow cytometry.2. Mean clearance rate of adult zebra mussels was higher on a mixture of the green alga Scenedesmus and the cyanobacterium Microcystis than when Scenedesmus was offered as single food, suggesting selective feeding by the mussels.3. Feeding on lake seston both adults and larvae showed a higher clearance rate on phytoplankton than on detritus particles, suggesting that zebra mussels select for phytoplankton. Furthermore, it was noted that adults preferred seston particles in the 0–1 and 30–100 μm size ranges.4. In our study, zebra mussels did not discriminate against cyanobacteria, and our results indicate that they may even ingest them preferentially.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2426.2003.01173.x
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  • 7
    Electronic Resource
    Electronic Resource
    Changes in food quality of the green alga Scenedesmus induced by Daphnia infochemicals: biochemical composition and morphology (1997)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 38 (1997), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. The effects of Daphnia infochemicals on the morphology and biochemical composition of Scenedesmus were studied and subsequently their influence on Daphnia life history. Three species of Scenedesmus (S. acutus, S. obliquus and S. subspicatus) were tested for Daphnia-induced colony formation. Life history experiments were performed with Daphnia cucullata and D. magna feeding on unicellular or colonial S. acutus.2. Colony formation was promoted when S. acutus and S. obliquus were exposed to filtered water from a D. magna culture. S. subspicatus did not form colonies when exposed to culture water, but showed some colony formation when exposed to live D. magna.3. No clear differences were found in total lipid, protein or carbohydrate content between the unicellular and colonial ecomorphs of the three Scenedesmus species. However, fatty acid (FA) concentration and composition were changed. Total FA as a percentage of frozen dry weight (DW) were increased in colonies. The ratio of monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA) and the ratio of ω3 : ω6 fatty acids decreased in colonies.4. A short-term grazing experiment with three size classes of Scenedesmus revealed lower clearance rates for small Daphnia when feeding on large colonial Scenedesmus.5. Life history parameters of both Daphnia species were influenced by food type. The intrinsic rate of population increase (r) was significantly lower for daphnids feeding on colonies.6. The negative influence of colonial Scenedesmus on population growth of Daphnia seems to be determined by algal morphology rather than biochemical composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.1997.00225.x
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  • 8
    Electronic Resource
    Electronic Resource
    Comparing grazing by Dreissena polymorpha on phytoplankton in the presence of toxic and non-toxic cyanobacteria (2002)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 47 (2002), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY 1. The feeding behaviour of the zebra mussel (Dreissena polymorpha) was studied in the laboratory on different combinations of food, including a green alga (Chlamydomonas reinhardtii) and toxic and non-toxic strains of the cyanobacterium Microcystis aeruginosa.2. The highest clearance rate of phytoplankton by zebra mussels was found when the mussels were feeding on a mixture of Chlamydomonas and non-toxic Microcystis, the lowest on a mixture of Chlamydomonas and toxic Microcystis.3. The differences found in the clearance rates between food combinations can be partly explained by the production of pseudofaeces containing live phytoplankton cells. Zebra mussels expelled significantly more live phytoplankton cells in the presence of toxic Microcystis than in the presence of non-toxic Microcystis. The pseudofaeces contained predominantly live Chlamydomonas cells. Proportionately much less live Microcystis cells were encountered in the pseudofaeces.4. Consequently, grazing of zebra mussels on a combination of Chlamydomonas and Microcystis may finally result in a dominance of Chlamydomonas over Microcystis. The presence of toxic Microcystis may even strengthen this shift.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2002.00933.x
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  • 9
    Electronic Resource
    Electronic Resource
    Restoration by biomanipulation in a small hypertrophic lake: first-year results (1990)
    Springer
    Hydrobiologia 191 (1990), S. 285-295 
    Details
    ISSN: 1573-5117
    Keywords: biomanipulation ; lake restoration ; phytoplankton ; zooplankton ; grazing ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Biomanipulation was carried out in order to improve the water quality of the small hypertrophic Lake Zwemlust (1.5 ha; mean depth 1.5 m). In March 1987 the lake was drained to facilitate the elimination of fish. Fish populations were dominated by planktivorous and benthivorous species (total stock c. 1500 kg) and were collected by seine- and electro-fishing. The lake was subsequently re-stocked with 1500 northern pike fingerlings (Esox lucius L.) and a low density of adult rudd (Scardinius erythrophthalmus). The offspring of the rudd served as food for the predator pike. Stacks of Salix twigs, roots of Nuphar lutea and plantlets of Chara globularis were brought in as refuge and spawning grounds for the pike, as well as shelter for the zooplankton. The impact of this biomanipulation on the light penetration, phytoplankton density, macrophytes, zooplankton and fish communities and on nutrient concentrations was monitored from March 1987 onwards. This paper presents the results in the first year after biomanipulation. The abundance of phytoplankton in the first summer (1987) after this biomanipulation was very low, and consequently accompanied by increase of Secchi-disc transparency and drastic decline of chlorophyll a concentration. The submerged vegetation remained scarce, with only 5 % of the bottom covered by macrophytes at the end of the season. Zooplankters became more abundant and there was a shift from rotifers to cladocerans, comprised mainly of Daphnia and Bosmina species, the former including at least 3 species. The offspring of the stocked rudd was present in the lake from the end of August 1987. Only 19% of the stocked pike survived the first year. Bioassays and experiments with zooplankton community grazing showed that the grazing pressure imposed by the zooplankton community was able to keep chlorophyll a concentrations and algal abundance to low levels, even in the presence of very high concentrations of inorganic N and P. The total nutrient level increased after biomanipulation, probably due to increased release from the sediment by bioturbation, the biomass of chironomids being high. At the end of 1987 Lake Zwemlust was still in an unstable stage. A new fish population dominated by piscivores, intended to control the planktivorous and benthivorous fish, and the submerged macrophytes did not yet stabilize.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026064
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  • 10
    Electronic Resource
    Electronic Resource
    Long-term responses to fish-stock reduction in small shallow lakes: interpretation of five-year results of four biomanipulation cases in The Netherlands and Denmark (1994)
    Springer
    Hydrobiologia 275-276 (1994), S. 457-466 
    Details
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of fish stock reduction have been studies in 3 Dutch lakes (Lake Zwemlust, Lake Bleiswijkse Zoom and Lake Noorddiep) and 1 Danish lake (Lake Væng) during 4–5 years. A general response id described. The fish stock reduction led in general to a low fish stock, low chlorophyii-a, high transparency and high abunuance of macrophytes. Large Daphnia became abundant, but their density decreased, due to food limitation and predation by fish. The total nitrogen concentration became low due to N-uptake by macrophytes and enhanced denitrification. In Lake Bleiswijkse Zoom the water transparency deteriorated and the clear water state was not stable. The fish stock increased and the production of young fish in summer was high. lear water occurred only in spring. Large daphnids were absent in summer and the macrophytes decreased. In Lake Zwemlust, Lake Væng and Lake Noorddiep the water remained clear during the first five years. In summer of the sixth year (1992) transparency decreased in Lake Zwemlust (with high P-concentration of 1.0 mg P l-1). Also in Lake Væng (with a low nutrient concentration of 0.15 mg P.⋆-1) a short term turbid stage (1.5 month) occurred in summer 1992 after a sudden collapse of the macrophytes. Deterioration of the water quality seems to start in summer and seems related to a collapse in macrophytes. At a low planktivorous fishstock (e.g. Lake Væng)thhe duration of the turbid state is shorter. than in presence of a high planktivorous fish biomass (e.g. Lake Zwemlust, and later years of Lake Bleiswijkse Zoom).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026734
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