Phytoplankton taxonomic groups in relation to physicochemical parameters. A case study from Greek lakes

Abstract

The composition, abundance and biomass of phytoplankton are long considered as indicative of the eutrophication pressure in lakes. In addition, cyanobacteria-formed algal blooms are mostly linked to poor water quality. The objectives of the present study were a) to explore phytoplankton groups and physicochemical parameters of lakes in a Mediterranean setting and b) to investigate the response of phytoplankton taxonomic groups to phosphorus loading in those lakes. We analyzed data from the National Monitoring Network from 2019-2021 for 16 freshwater lakes in Greece. Water transparency, ionic composition and Total Phosphorus (TP) were correlated with major phytoplankton groups (chlorophytes, dinoflagellates, cryptophytes, bacillariophyceae and cyanobacteria). Based on both phytoplankton and physicochemical parameters, two groups of lakes were formed in cluster analysis, corresponding a) to deep warm monomictic and b) shallow and very shallow polymictic lakes. With regard to the impact from phosphorus loading, in both groups of lakes, a considerable increase of cyanobacteria biomass along a TP gradient was observed. Chlorophytes showed a statistically significant response in relation to TP in shallow and very shallow lakes. The results highlight the importance of phytoplankton in monitoring and evaluation of the status of aquatic ecosystems as phytoplankton biomass and community structure respond to changes in environmental parameters.