The aim of this study was to determine the response of planktonic cyanobacteria and periphyton assemblages (periphytic algae in the separator pipes, epilithon and epiphyton) to lamella separator-treated stormwaters in urban Lake Jeziorak Mały in 1997–2003 and 2005. Relationships between periphyton and phytoplankton assemblage and water chemistry variables were analyzed by calculating the Spearman’s rank correlation coefficient, and then with canonical correspondence analysis (CCA). The basic factors favouring the cyanobacterial growth were water temperature and iron, while high chloride concentration limited their development. Cyanobacterial abundance recorded at the separators was half that of the pelagic zone because of a lower water temperature and higher Cl concentration, indicating high algal sensitivity to the considerable velocity and disturbances caused by stormwater effluents. Higher silicon and calcium concentrations at the separators and orthophosphates at sites with stones and gravel showed connection with the growth of diatoms, especially Fragilaria leptostauron var. martyi, Diatoma vulgaris and Navicula gregaria. The richness of the dominant cyanobacteria, Aphanizomenon gracile and Limnothrix redekei, was related with the water temperature, conductivity, pH, and TN. Similarities in the periphyton dynamics in separator pipes and epilithon between the years covered by the study suggest significant influence of separator-treated stormwater on these assemblages, in contrast to epiphyton and phytoplankton in the pelagial zone, where these waters had limited influence.

20.1.2015