In the Baltic Sea, cyanobacterial community is mainly composed of filamentous nitrogen-fixing forms, including the toxic Nodularia spumigena, and single-celled picocyanobacteria (Pcy), represented by Synechococcus spp. The main aim of the work was to test the hypothesis that the picocyanobacteria dependend on the presence of the nitrogen-fixing cyanobacteria. In addition, the contamination of blue mussels and fish with nodularin (NOD), the N. spumigena toxin, was examined. In years 2008-2011, the samples for the study were collected in the Southern Baltic Proper using FerryBox system and, occasionally, during research cruises. The analyses showed no correlation between the growth of the nitrogen-fixing cyanobacteria and Synechococcus. Compared with the previously published data, a shift in the composition of Pcy phenotypes was observed. This shift might be an indication of the proceeding changes induced by the reduced nutrient loading and/or climate change. Analyses of NOD revealed differences in the cyanotoxin concentrations between mussels of different shell size. The highest concentration of NOD was detected in the liver of round goby. However, temporarily, also the fish muscles were significantly contaminated with the toxin.

In this work, the authors examined the presence of cyanobacteria and cyanotoxins in 21 samples collected from fresh water bodies located in 5 provinces in Poland: Lublin (2), Podlasie (1), Pomerania (6), Warmia-Masuria (1) and Wielkopolska (11). In addition, to determine the general pattern of geographical distribution, frequency of cyanobacteria occurrence, and cyanotoxins production, the published data from 238 fresh water bodies in Poland were reviewed. On the basis of these collected results, we concluded that Planktothrix, Aphanizomenon, Microcystis and Dolichospermum were dominant. The general pattern in geographical distribution of the identified cyanobacterial genera was typical of other eutrophic waters in Europe. The production of cyanotoxins was revealed in 18 (86%) of the 21 samples analyzed in the present work and in 74 (75%) of the 98 total water bodies for which the presence of toxins had been examined. Among the 24 detected microcystin variants, [Asp 3 ]MC-RR was most common. These results can be verified when more data from the less explored water bodies in the southern and eastern parts of Poland are available.

Thus far, the negative effects of Nodularia spumigena blooms on aquatic organisms have been mainly attributed to the production of the hepatotoxic nodularin (NOD). In the current work, the accumulation of other N. spumigena metabolites in blue mussels and crustaceans, and their effect on Thamnocephalus platyurus and Artemia franciscana, were examined. The liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses provided evidence that both blue mussels collected after a cyanobacterial bloom in the Baltic Sea and the crustaceans exposed under laboratory conditions to N. spumigena extract accumulated the cyclic anabaenopeptins (APs). In the crustaceans, the linear peptides, spumigins (SPUs) and aeruginosins (AERs), were additionally detected. Exposure of T. platyurus and A. franciscana to N. spumigena extract confirmed the negative effect of nodularin on the organisms. However, high numbers of dead crustaceans were also recorded in the nodularin-free fraction, which contained protease inhibitors classified to spumigins and aeruginosins. These findings indicate that cyanobacterial toxicity to aquatic organisms is a complex phenomenon and the induced effects can be attributed to diverse metabolites, not only to the known hepatotoxins.

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