Relationship between cyanobacterial bloom composition and anatoxin-a and microcystin occurrence in the eutrophic dam reservoir [SE Poland]

Long-lasting cyanobacterial blooms were observed over summer periods 2001–2003 in the highly eutrophic dam reservoir (Zemborzycki Reservoir near Lublin, SE Poland) loaded with nitrogen and phosphorus by the river Bystrzyca. Chlorophyll a content and water transparence reached in summer periods 2002–2003 average values 115–129 µg l⁻¹ and 0.5 m, respectively. The blooms consisted of eight taxa of Cyanobacteria occurring in different proportions: Aphanizomenon flos-aquae, Anabaena circinalis, Anabaena spiroides, Anabaena flos-aquae, Planktothrix agardhii, Microcystis aeruginosa, Microcystis viridis, Microcystis wesenbergii. At decreased average water temperature and increased concentration of dissolved ammonium-nitrogen in summer 2003, compared with two earlier years, a replacement of dominant Aph. flos-aquae to P. agardhii was observed. The total abundance of potential microcystin producers was positively correlated with the content of these hepatotoxins in the reservoir water. First time in Poland, mass occurrence of Anabaena strains producing anatoxin-a was observed. Anatoxin-a concentration in the reservoir water was positively correlated with total abundance of 3 taxa of Anabaena. It was no such correlation with Aph. flos-aquae.