Rotatoria–Cladocera–Copepoda relations in the long-term monitoring of water quality in lakes with trophic variation (E. Poland)

Abstract

On the basis of long-term research (since the 1960s), changes were determined in zooplankton in five lakes located in the Łeczna-Wlodawa Lake District (E. Poland). During this time period, the region changed from being economically neglected and difficult to explore to being under intense human impact, with hydrological changes and deformations in the earth’s surface also taking place. This alteration was connected with substantial changes in abiotic variables in the lakes that were studied; these were accompanied by changes in species number, density and structure of zooplankton dominance as well as the ROT:CLA:COP ratio. The most highlighted changes in the zooplanktonic communities were a (1) decrease in zooplankton species richness in lakes showing strongest changes in water chemistry, (2) replacement of large cladocerans by smaller cladocerans with an increase in trophic status and inverse operation in the process of deeutrophication, (3) decrease in Rotatoria density in favour of Cladocera and Copepoda in the ROT:CLA:COP ratios along with the process of eutrophication, and inverse operation in the process of deeutrophication. The study showed that species of Brachionus, Filinia and Polyarthra as well as Bosmina longirostris are indicative of a long-term rise in water temperature; Trichocerca prefer elevated conductivity; the occurrence of Chydoridae species and some Daphnidae, including Ceriodaphnia quadrangula and Simocephalusvetulus coincides with a rising gradient in dissolved oxygen; Daphnia longispina and Monospilus dispar prefer waters with elevated N–NH4; Cyclops kolensis and Cyclops strenuus correlate with a rising gradient in P–PO4; and Eucyclops serrulatus, Eudiaptomus graciloides, and Macrocyclops albidus are indicative of elevated pH levels.