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Responses of phytoplankton to fish predation and nutrient loading in shallow lakes: a pan-European mesocosm experiment (2004)

Van De Bund, W. J. ; Romo, S. ; Villena, M. J. ; [et al.]

Oxford, UK : Blackwell Publishing

Freshwater biology 49 (2004), S. 0

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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

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Life history consequences for Daphnia pulex feeding on nutrient-limited phytoplankton (1997)

LÜRLING, M. ; VAN DONK, E.

Oxford, UK : Blackwell Science Ltd

Freshwater biology 38 (1997), S. 0

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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

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Continental-scale patterns of nutrient and fish effects on shallow lakes: introduction to a pan-European mesocosm experiment (2004)

Stephen, D. ; Balayla, D. M. ; Bécares, E. ; [et al.]

Oxford, UK : Blackwell Science Ltd

Freshwater biology 49 (2004), S. 0

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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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Continental-scale patterns of nutrient and fish effects on shallow lakes: synthesis of a pan-European mesocosm experiment (2004)

Moss, B. ; Stephen, D. ; Balayla, D. M. ; [et al.]

Oxford, UK : Blackwell Science Ltd

Freshwater biology 49 (2004), S. 0

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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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5

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Selective grazing by adults and larvae of the zebra mussel (Dreissena polymorpha): application of flow cytometry to natural seston (2004)

Dionisio Pires, L. M. ; Jonker, R. R. ; Van Donk, E. ; [et al.]

Oxford, UK : Blackwell Science Ltd

Freshwater biology 49 (2004), S. 0

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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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6

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Changes in food quality of the green alga Scenedesmus induced by Daphnia infochemicals: biochemical composition and morphology (1997)

LÜRLING, M. ; DE LANGE, H.J. ; VAN DONK, E.

Oxford, UK : Blackwell Science Ltd

Freshwater biology 38 (1997), S. 0

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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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7

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Comparing grazing by Dreissena polymorpha on phytoplankton in the presence of toxic and non-toxic cyanobacteria (2002)

Dionisio Pires, L. M. ; Van Donk, E.

Oxford, UK : Blackwell Science Ltd

Freshwater biology 47 (2002), S. 0

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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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8

Electronic Resource

Field Research for the Authorisation of Pesticides (2000)

Van Dijk, H. F. G. ; Brussaard, L. ; Stein, A. ; [et al.]

Springer

Ecotoxicology 9 (2000), S. 377-381

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ISSN: 1573-3017

Keywords: authorisation ; field research ; model ecosystems ; monitoring ; pesticides

Source: Springer Online Journal Archives 1860-2000

Topics: Energy, Environment Protection, Nuclear Power Engineering

Notes: Abstract On request of the Dutch government a committee of the Health Council of the Netherlands has reviewed the role that results of field research in its broadest sense (i.e., including multi-species toxicity tests in the laboratory, research on model ecosystems et cetera) can play in ecotoxicological risk assessment for the authorisation of pesticides. The Committee believes that field research can provide valuable additional data about the exposure of non-target organisms and the resultant effects at population, community and ecosystem level. However, it frequently is unclear how these data might be used in reaching a decision about authorisation. To solve this problem, it is necessary to specify what is understood by “unacceptable damage”. Both more clearly formulated protection goals of the government and a better understanding of the ecological significance of effects are needed to clarify this. Furthermore, the Committee points out that the statistical power of field trials must be sufficient to allow for the detection of changes that might be regarded as ecologically relevant. Finally, it recommends keeping a finger on the pulse in relation to authorised pesticides by monitoring their presence in environmental compartments and by investigating their role in suddenly occurring mortality among conspicuous animal species, such as birds, fish and honeybees. This kind of research forms a safety net for substances that have been wrongly authorised.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1008920401180

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