Interactions between phytoplankton and zooplankton in the hypertrophic Swarzedzkie Lake in western Poland

Abstract

The hypertrophic Swarzedzkie Lake, Poland, is characterized by high species diversity, abundance and biomass of both phytoplankton and zooplankton (up to 99.5 mg WW L −1 and 817.75 μg DW L −1 , respectively). The community grazing rate calculated with the use of two empirical models, and based on herbivorous crustaceans, peaked in spring and early autumn up to 150.6% of water filtered per day, and was the lowest during winter. Simple statistics revealed a positive correlation between zooplankton biomass and chlorophyll a concentration (r = 0.404, P = 0.033) and between zooplankton abundance and phytoplankton biomass (r = 0.42, P = 0.028). Canonical statistics indicated, however, that the relationship exists only with size groups and/or living forms of a few taxonomical groups of phytoplankton. Redundancy analysis (RDA) confirmed a positive influence of the community grazing rate on micro- and nanoplanktonic Cryptophyceae, but not on the microplanktonic Cyanobacteria, as was suggested by canonical correlation analysis. RDA also indicated a weak negative influence on nanoplanktonic Euglenophyceae and Chlorophyceae exerted by filtering crustaceans. Some taxonomically diverse flagellated nanoplanktonic algae were grazing sensitive, whereas microplanktonic cryptophytes and coenobial green algae were significantly grazing resistant.