Aquatic Plants during Decomposition as an Environment-Forming Factor for Zooplankton: An Experiment in Microcosms

摘要

Aquatic vascular plants at different stages of their life cycle exhibit different physiological and metabolic activity, resulting in a change in habitat conditions for hydrobionts. The hydrochemical parameters of the environment, the concentrations of phytoplankton pigments, and the abundance of bacteria and zooplankton have been studied in experimental ecosystems (microcosms), including aquatic plants going through varying degrees of decomposition. In microcosms with hornwort Ceratophyllum demersum L., which lost half of the biomass, but continued vegetation, the concentration of P-tot, Mg2+, and BOD5 increase and Na+ and Ca2+ decrease. In systems with dying arrowhead Sagittaria sagittifolia L., the concentration of K+ increases to the greatest extent and P-tot, Cl-, and BOD5 to a lesser extent; the concentrations of SO42- and O-2 dissolved in water decrease. In the presence of plants, higher concentrations of phytoplankton pigments are observed compared to the control. The quantitative parameters of bacterioplankton do not differ. The abundance and biomass of zooplankton in general and of the dominant species Daphnia longispina in microcosms with plants exceed these control parameters. Hornworts, which lose half of their biomass but continue vegetation, have a stronger stimulating effect on the abundance of zooplankton than arrowheads, which finish vegetation