The brackish water cyanobacterium Nodularia spumigena regularly forms waterblooms in the Baltic Sea. Many N. spumigena strains can produce
nodularin, a hepatotoxic
penta-
peptide, which has caused several animal
poisonings in the Baltic Sea area. To improve our understanding of
nodularin bioaccumulation in aquatic organisms this study measured
nodularin in flounder and cod caught from the Baltic Sea. Flounders were collected from the western Gulf of Finland in July 1996, September 1997, and September 1998, and from the Gulf of Bothnia in August 1997 and September 1998. Flounders were also collected from the coastal areas of Sweden in the Baltic Proper during September 1998. Cod were caught from the southern Baltic Sea in August 1998. Livers and muscles of the 1997 fish were isolated, extracted, and analysed for
nodularin using high-performance liquid chromatography (HPLC) and
enzyme-linked
immunosorbent assay (ELISA) and
protein phosphatase 1 (PP1) inhibition assay. Approximately 30-70 ng of
nodularin/g dry weight (maximum value 140 ng/g) were found in the liver tissue samples by ELISA and PP1 inhibition. These concentrations were below the detection limit of HPLC. PP1 assay showed inhibition also in muscle samples, but this may due to other compounds present in the muscle extracts rather than NODLN or due to matrix interference. The recovery of
nodularin from liver tissue with ELISA and PP1 assays was about 30%.
Nodularin concentrations in samples are not corrected for recovery. Although the concentrations of
nodularin found in this study are low further studies of
nodularin are needed to assess possible bioaccumulation in brackish water food webs.