Coccolithophores and calcite saturation state in the Baltic and Black Seas

• Main Authors: Tyrrell, T., Schneider, B., Charalampopoulou, A., Riebesell, U.
• Other Authors: National Oceanography Centre Southampton (NOC), University of Southampton, Leibniz-Institut für Ostseeforschung Warnemünde (IOW), Leibniz Association, Leibniz-Institut für Meereswissenschaften (IFM-GEOMAR)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO]; [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph]; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Ocean acidification
• Online Access: https://hal.science/hal-00297924; https://hal.science/hal-00297924/document; https://hal.science/hal-00297924/file/bgd-4-3581-2007.pdf

International audience 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 CaCO 3 . Data for the Black Sea are more limited, but it appears to remain strongly supersaturated year-round. 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.