Cyanobacterial hepatotoxins, microcystins and nodularins, in fresh and brackish waters of the Pomeranian Province, northern Poland

Microcystins (MCs) and structurally related nodularins (NODs) are hepatotoxic cyclic peptides produced by bloom-forming cyanobacteria. These toxins have been implicated in the deaths of wild and domestic animals as well as in incidents of human illness. Cyanobacterial toxins occurring in the fresh and brackish waters of the Pomeranian Province, northern Poland were characterized in this study. Water samples collected from seven lakes in August and September 2005 were analysed by high performance liquid chromatography (HPLC), enzyme linked immunosorbent assay (ELISA) and protein phosphatase inhibition assay (PPIA). Cyanobacterial toxins present in field samples and in an isolated strain of Planktothrix agardhii were also characterized by liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). In most of the fresh water samples MC-LR, MC-RR and MC-YR dominated. In the lakes where P. agardhii was most abundant demethylated microcystin variants tentatively identified as [D-Asp³]MC-LR, [D-Asp³]MC-YR and [D-Asp³]MC-RR, were found. Total concentrations of the toxins measured by HPLC ranged from 0.1 μg 1^-1 to 305.4 μg 1^-1. Nodularia spumigena bloom samples were collected from brackish waters of the Gulf of Gdańsk, southern Baltic, and LC-ISP-MS/MS of extract from these revealed the presence of two geometrical isomers of linear nodularin and nodularin variant with aspartic acid methyl ester [MeAsp¹(OMe)]NOD.