The P.polylepis bloom in 1988 in the Kattegatt and Skagerack was very toxic for several different phyla and a chemical analysis showed that the involved toxin had hemolytic properties ( Stabell et al., 1993). Unfortunately, the P. polylepis bloom in the Baltic Sea in 2008 was not chemically tested for toxins. Hajdu et al., (unpubl) could not find any toxic effects of the P. polylepis bloom on other plankton species. However, the result of their study does not exclude the possibility that female eiders were affected by the P polylepis bloom through a toxic pathway because mussels may accumulate toxic substances making the mussels themselves toxic or detrimental for mussel feeding organisms. Thus, although a link between the P. polylepis bloom and breeding eiders via a toxin is possible, direct evidence is lacking.