The importance of aquatic plants in maintaining zooplankton diversity and abundance: An experimental approach

The influence of different species and ecological forms of higher aquatic plants on the abundance, biomass and species diversity of zooplankton was investigated in experimental ecosystems (microcosms). It was shown that in the absence of fish and macroinvertebrate predators, the abundance and diversity of zooplankton in the plants beds increased. Not only phytophilous, littoral, and small planktonic crustaceans, but also some large obligate planktonic crustaceans, reached a high abundance among the plants. Plants belonging to different ecological groups stimulated an increase in the abundance of different groups of zooplankton. In the beds of submerged plants, the number of Cladocera increased to a greater extent than Copepoda or Rotifera. The abundance of Copepoda, both Cyclopoida and Calanoida, grew in the beds of helophytes. The relative number of predators in the community increased among the plants. The species structure and quantitative parameters of zooplankton had their own characteristics in monospecies and mixed phytocenoses of the same plant species. The index of species diversity of zooplankton acquired the highest values in the mixed phytocenosis. Higher aquatic plants increase spatial heterogeneity, which stimulates the development of facultative planktonic and benthic species. The formation of phytogenic detritus and the lifetime release of organic substances by plants into the water causes the development of bacteria and protozoa, which expands the quality and size range of food organisms for zooplankton. Therefore, zooplankton becomes more diverse in terms of the set of trophic groups.

Heavy Metals Mixture Phytotoxic Impact upon Elodea canadensis Macrophite uner the Experimental Ecosystems Conditions

Phytotoxic effect of the heavy metal mixture polluted water has been investigated. The experimental microcosm water contained heavy metals (Zn, Сu, Pb, Cd, Fe+2, Fe+3, Cr+6, Ni). Metal concentrations have been selected to simulate water pollution with machine-building waste (slimes). Such an experiment has been carried out in vitro for the first time. Elodea canadensis macrophite as one of the most adopted and wide-spread species was incubated into the microcosms. No phytotoxic effect was recorded in the microcosms with plants and admixture of heavy metals over the first three days. The death of plants was detected 168 hours (7 days) after the start of incubation. Microcosms with plants without adding of the metals did not alter after the start of incubation. On the second day after incubation and orange sediment precipitated in the microcosms without macrophytes but with the heavy metals adding. The investigation results supplement the vision concerning polyfunctional role of hydrocoles in the elements migration within aquatic ecosystems. The obtained data indicated the prospective and promising character of further research of Elodea canadensis in terms of phytomefitation and search for the upper boundary of tolerance to heavy metals.