Baltic Sea coccolithophores - an overview of insights into their taxonomy and ecology from the last 40 years

It is an established fact that coccolithophores are of little importance with respect to biomass and diversity in the Baltic proper. The likely biogeochemical and environmental reasons for this have recently been critically analyzed and reviewed. The main conclusion is that the calcium carbonate saturation of the Baltic Sea is the main controlling feature, and that in particular an undersaturation during wintertime remains the critical bottleneck for coccolithophores to prevail in the Baltic proper. While there is no reason to question these observations, it is still relevant to put on record the actual findings of coccolithophores from the Baltic proper. Examinations of Baltic Sea material from the Bothnian Sea, the Bothnian Bay and the Gulf of Finland prepared for transmission electron microscopy has thus revealed a consistent presence of a low diversity community of lightly calcified coccolithophores (i.e. Balaniger virgulosa HOL and HET, Papposphaera arctica HOL cfr. and Papposphaera iugifera). When including here also material examined from the Danish transitional waters connecting the North Sea and the Baltic proper, it is possible to generally support the presence in the western Baltic, the Sounds and the Kattegat of a contingent of coccolithophores that appear to be either persistently present within the area or episodically occurring as determined by larger scale hydrographical events within the North Sea/Baltic Sea confluence area.