The project was conducted in a period (2008–2010) when blue-green algae blooms were not as pronounced as in earlier years (SMHI 2008); as a matter of fact, the ferry route crossed Selleckchem Dabrafenib the Baltic Proper in a region not so subject to intensive blooms. Nevertheless, the discrete samples analysed between 7 and 28 July 2008 showed abundant Cyanophyceae.

Their biomass varied from 660.0 mm3 m− 3 (max.) at station GK6 on 14 July to 99.33 mm3 m− 3 (min.) at station GK3 on 21 July, i.e. respective contributions to the total phytoplankton biomass of 83.0% and 41.0%. The toxic Nodularia spumigena was found in the majority of discrete samples from this period. The largest proportions of N. spumigena, 84.4% in the Cyanophyceae biomass and 66.7% in the total phytoplankton biomass, was recorded at station GK4 on 14 July. A high biomass of N. spumigena (18.0 mm3 m− 3; 61.6% of the Cyanophyceae and 35.5% of the total biomass) was recorded at station GK1 on 14 July, when the maximum concentration of nodularin was also recorded ( Figure 6). The data on the proportion PD0325901 cell line of cyanobacteria in the total summer phytoplankton biomass tally with the observations of increasing trends in the proportion of cyanobacteria

in the Baltic phytoplankton (Wasmund and Uhlig, 2003 and Olli et al., 2011). The ecological consequences of plankton blooms and their most harmful effects are linked to the occurrence of a high biomass of heterocystous species, which supply an additional

load of nitrogen to the Baltic Sea ecosystem. N. spumigena is a cyanobacterium that forms vast blooms in the Baltic Sea during the summer ( Kahru et al., 1994, Wrzołek, 1996, Wasmund, 1997 and Finni Idoxuridine et al., 2001). This phenomenon is both important and dangerous, as N. spumigena is capable of producing a potent toxin – nodularin (NOD) ( Reinhart et al. 1988). A non-ribosomal cyclic pentapeptide of unusual structure, nodularin alters the liver’s structure and function by inhibiting the activity of eukaryotic protein phosphatases (PP1 and PP2A) ( Carmichael 1992). Incidents of poisoning involving domestic animals, cattle and birds are well documented ( Edler et al., 1985 and Sivonen and Jones, 1999). The concentrations of nodularin measured in discrete samples in 2008 (Figure 6 and Figure 7) were comparable to those recorded in the Gulf of Gdańsk and the Baltic Sea in recent years; e.g. during the N. spumigena bloom in summer 2007, Kankaanpää et al. (2009) reported a NOD concentration of 2.45 μg dm− 3. The average NOD concentration in the Baltic Sea, determined by Mazur-Marzec et al. (2006), did not usually exceed 1 μg dm−3. However, in coastal waters, including bathing areas, the concentration of the toxin can temporarily exceed 20 000 μg dm− 3 ( Mazur-Marzec et al. 2006).