A case study of the phytoplankton used as a biological water quality element in a shallow temperate lake

Phytoplankton dynamics of Karagol Lake, Balikesir, Turkey were studied from summer 2015 to spring 2016 in order to assess the ecological status of the lake using the phytoplankton assemblage index (Q). The fuctional groups, J (Desmodesmus communis), X1 (Selenastrum bibraianum), L-O (Ceratium hirundinella), P (Staurastrum pingue) and H1 (Anabaena crassa) dominated phytoplankton in summer, W2 (Trachelomonas volvocina), X1 (S. bibraianum) and L-O (C. hirundinella) in fall, MP (Hantzschia amphioxys), D (Synedra acus), J (D. communis) and P (Fragilaria crotonensis) in winter, H1 (A. crassa), J (D. communis), W2 (T. volvocina) and P (S. pingue) in spring. The phytoplankton functional groups of Karagol Lake were typical to well-mixed eutrophic shallow lakes. The canonical correspondence analysis (CCA) explained 95.4 % of the cumulative percentage of the variance in the phytoplankton functional groups and their relationships with environmental variables. The Q index showed that the ecological status of Karagol Lake varied seasonally from bad to moderate. In winter 2015, the lake had a moderate ecological status and in spring 2016 it had a bad ecological status. The results of this study showed that the Q index satisfactorily reflected the changes in phytoplankton composition and functional group approach displayed itself as sensitive and responsive to environmental changes of shallow lakes, regardless of their geographic region.