A Preliminary Comparison of Meiobenthic Cladoceran Assemblages in Natural and Constructed Wetlands in Central Florida

In Florida, phosphate mining companies that destroy natural wetlands are required to construct mitigation wetlands. Comparisons of plant communities are frequently used to determine the degree to which constructed wetlands mimic natural wetlands, but efforts to address similarity based on fauna are rare. Studies in lake littoral zones suggest that meiobenthic cladocerans possess characteristics that may make their use in wetland comparisons advantageous. In this study, meiobenthic cladocerans were sampled from 8 natural freshwater wetlands and 11 freshwater wetlands constructed on phosphate-mined lands. The pulsed nature of the cladoceran communities limits their value as a quantitative measure of the similarity of natural and constructed wetlands. Qualitative analyses based on the presence or absence of species suggest that cladoceran assemblages of some constructed wetlands mimic those of some natural wetlands, but the range of assemblages found in constructed wetlands is narrower than that found in natural wetlands. © 1993 Society of Wetland Scientists

Distribution of Planktonic Ciliates in Highly Coloured Subtropical Lakes: Comparison with Clearwater Ciliate Communities and the Contribution of Myxotrophic Taxa to Total Autotrophic Biomass

SUMMARY 1. The planktonic ciliate communities of eleven organically coloured north and central Florida lakes representing a variety of trophic conditions were examined during 1979–80. The total abundance and biomass of ciliates were not significantly different from comparable clearwater lakes and only minor taxonomic replacements were noted at the order level. 2. Timing of population peaks of oligotrophic lakes was dissimilar to clearwater lakes of the same trophic state, but seasonality in meso‐trophic and eutrophic lakes resembled patterns described for comparable clearwater lakes. 3. Various ciliate components were strongly correlated with chlorophyll a concentrations, but only moderately correlated to dominant phytoplankton groups. No significant correlations were found between ciliate components and bacterial abundance. 4. Myxotrophic taxa numerically dominated oligotrophic systems, particularly during midsummer, and accounted for a large percentage of the total ciliate biomass. Estimates of the ciliate contribution to total autotrophic biomass indicate that these zoochlorellae‐bearing protozoa may account for much of the autotrophic biomass during midsummer periods in coloured lakes, and thus may lead to an overestimation of phytoplankton standing crops available to zooplankton grazers if chlorophyll a is used as a surrogate measure of algal biomass

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

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. [KEYWORDS: alternative stable states ; community structure ; eutrophication ; fish ; large-scale variation ; nutrients]