How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

How Blue Mussels Tolerate Seawater of High CO2 Partial Pressure
Thomsen, J., Casties, I., Pansch, C., Kortzinger, A. and Melzner, F. 2013. Food availability outweighs ocean acidification effects in juvenile Mytilus edulis: laboratory and field experiments. Global Change Biology 19: 1017-1027.

The authors write that shallow temperate estuaries such as those of the Western Baltic Sea "are characterized by higher and more fluctuating seawater pCO2," citing Thomsen et al. (2010), Haynert et al. (2012) and Melzner et al. (2012), which phenomenon "is strongly amplified by high primary production caused by eutrophication from sewage discharge and agriculture," as described by HELCOM (2009).

What was done
"In a coupled field and laboratory study," in the words of Thomsen et al., "we examined the annual pCO2 variability in this habitat and the combined effects of elevated pCO2 and food availability on juvenile M. edulis growth and calcification."

What was learned
The five German researchers report that at the field location where they worked (Kiel Fjord), maximum pCO2 values experienced during the summer were about 2500 µatm at the surface of the fjord and more than 3000 µatm at its bottom. They also say that in the laboratory experiment that they conducted, "mussel growth and calcification were found to chiefly depend on food supply, with only minor impacts of pCO2 up to 3350 µatm." In fact, in the field experiment they conducted, they observed "seven times higher growth and calcification rates of M. edulis at a high pCO2 inner fjord field station (mean pCO2 ca. 1000 µatm) in comparison to a low pCO2 outer fjord station (ca. 600 µatm)." And they note that this high inner fjord productivity "was enabled by higher particulate organic carbon concentrations," as a result of the fjord's "being "highly impacted by eutrophication, which causes bottom water hypoxia and consequently high seawater pCO2."

What it means
In the concluding paragraph of their paper, Thomsen et al. state that their study demonstrates "a high inherent resilience of calcifying benthic communities in an estuarine, eutrophic habitat to elevated seawater pCO2," where "food supply, and not pCO2, appears to be the primary factor driving biomass and biogenic CaCO3 production, as well as community structure."

Haynert, K., Schonfeld, J., Polovodova-Asteman, I. and Thomsen, J. 2012. The benthic foraminiferal community in a naturally CO2-rich coastal habitat of the southwestern Baltic Sea. Biogeosciences 9: 4421-4440.

HELCOM. 2009. Eutrophication in the Baltic Sea - an integrated thematic assessment of the effects of nutrient enrichment and eutrophication in the Baltic Sea region. Baltic Sea Environmental Proceedings, 115B.

Melzner, F., Thomsen, J., Koeve, W., Oschlies, A., Gutowska, M., Bange, H. W., Hansen, H. P. and Körtzinger, A. 2012. Future ocean acidification will be amplified by hypoxia in coastal habitats. Marine Biology: 10.1007/s00227-012-1954-1.

Thomsen, J., Gutowska, M.A., Saphorster, J., Heinemann, A., Trubenbach, K., Fietzke, J., Hiebenthal, C., Eisenhauer, A., Kortzinger, A., Wahl, M. and Melzner, F. 2010. Calcifying invertebrates succeed in a naturally CO2-rich coastal habitat but are threatened by high levels of future acidification. Biogeosciences 7: 3879-3891.

Reviewed 21 August 2013