Coccolithophores and calcite saturation state in the Baltic and Black Seas

Tyrrell, T., Schneider, B., Charalampopoulou, A. and Riebesell, U. (2008) Coccolithophores and calcite saturation state in the Baltic and Black Seas. Biogeosciences, 5 (2), 485-494.

Abstract

The Baltic and Black Seas are both brackish, that
is to say both have salinities intermediate between freshwater
and seawater. The coccolithophore Emiliania huxleyi is
abundant in one, the Black Sea, but absent from the other,
the Baltic Sea. Here we present summertime coccolithophore
measurements confirming this difference, as well as data on
the calcium carbonate saturation state of the Baltic Sea. We
find that the Baltic Sea becomes undersaturated (or nearly
so) in winter, with respect to both the aragonite and calcite
mineral forms of CaCO3. Data for the Black Sea are more
limited, but it appears to remain strongly supersaturated yearround.
The absence of E. huxleyi from the Baltic Sea could
therefore potentially be explained by dissolution of their coccoliths
in winter, suggesting that minimum annual (wintertime)
saturation states could be most important in determining
future ocean acidification impacts. In addition to this potential
importance of winter saturation state, alternative explanations
are also possible, either related to differences in
salinity or else to differences in silicate concentrations.

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Contributors

Author: T. Tyrrell

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