It is an established fact that coccolithophores are of little importance in the Baltic proper. The likely biogeochemical and environmental reasons for this have been critically analyzed and reviewed by Tyrell et al. (2008), and their main conclusion is that calcium carbonate saturation in the Baltic Sea is the primary controlling factor for coccolithophores and in particular an undersaturation during wintertime remains the critical impediment for coccolithophore development in the Baltic proper. While there is no reason to question these observations, it is still relevant to record the actual occurrences of coccolithophores from the Baltic proper. Repeated examinations of Baltic Sea material from Bothnian Bay and the Gulf of Finland by means of transmission electron microscopy has revealed a consistent presence of a small community of lightly calcified coccolithophores (i.e., Balaniger virgulosa HOL and HET, Turrisphaera sp., and Papposphaera sp.). If material examined from the Danish transitional waters that connect the North Sea and the Baltic proper is also considered, it is possible not only to define a demarcation line for Emiliania huxleyi, which runs into the Arkona Basin east of the island of Bornholm, but also to document the presence in the western Baltic, the Sounds, and the Kattegat of a small contingent of coccolithophores that appear to be persistently present within the area.
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