Functional and morphological groups in the phytoplankton of large reservoirs used for aquaculture in Bulgaria

Functional and morphological concepts for the classification of phytoplankton are increasingly used in environmental studies of freshwater ecosystems. The present study focuses mainly on the application of the three approaches (FGs, MFGs, MBFGs) for morpho-functional classifications used for detecting changes in phytoplankton communities in five Bulgarian large reservoirs that have long been used for aquaculture. Totally 113 taxa of planktonic algae were identified. The representatives of Cyanoprokaryota (H1, M; 5a, 5b, 5e; III, VII), Chlorophyta (J; 3b, 9b; IV), Streptophyta (P, N; 8a; IV) and Bacillariophyceae (P, MP, D; 6b; VI) had the largest contribution to the abundance of algae in the studied reservoirs. Fourty-two dominant species from eighteen functional groups (FGs), fifteen morpho-functional groups (MFGs) and seven morphologically based functional groups (MBFGs) were found. The functional groups with most species were: H1, J, N, Lo, P M, most common among MFGs were: 5a, 5b, 5e, 6b, 8a and 9b, and among MBFGs: III, IV, VI and VII. The large gelatinous colonial (M; 5b; VII) and filamentous (H1; 5a, 5e, III) cyanoprokaryotes, some of which are potentially toxic species indicative of eutrophication, were among the most common taxa in three of the studied reservoirs. According to the presented study, the three morpho-functional environmental concepts provide an important tool for understanding the seasonal changes in phytoplankton communities, as well as for assessing the environmental status of heavily modified freshwater reservoirs.