Toxic cyanobacteria blooms in the Lithuanian part of the Curonian Lagoon

The phenomenon of cyanobacteria (blue-green algae) blooms in the Baltic and the surrounding freshwater bodies has been known for several decades.The presence of cyanobacterial toxic metabolites in the Curonian Lagoon has been investigated and demonstrated for the first time in this work (2006–07). Microcystis aeruginosa was the most common and widely distributed species in the 2006 blooms. Nodularia spumigena was present in the northern part of the Curonian Lagoon, following the intrusion of brackish water from the Baltic Sea; this is the first time that this nodularin-(NOD)-producing cyanobacterium has been recorded in the lagoon.W ith the aid of high-performance liquid chromatography (HPLC), four microcystins (MC-LR, MC-RR, MC-LY, MC-YR) and nodularin were detected in 2006.T he presence of these cyanobacterial hepatotoxic cyclic peptides was additionally confirmed by enzyme-linked immunosorbent assay (ELISA) and protein phosphatase inhibition assay (PP1).Micr ocystin-LR, the most frequent of them, was present in every sample at quite high concentrations (from <0.1 to 134.2 μg dm−3).I n 2007, no cyanobacterial bloom was recorded and cyanotoxins were detected in only 4% of the investigated samples.A comparably high concentration of nodularin was detected in the northern part of the Curonian Lagoon.I n one sample dimethylated MC-RR was also detected (concentration 7.5 μg dm−3).