Impact of ocean acidification on the metabolism of calcifying planktonic organisms

Atmospheric pCO2 is predicted to double by the end of the century, and this increase is expected to lead to both global warming and ocean acidification, both being enhanced in polar oceans. Because of the freshening and increased carbon uptake in response to sea ice retreat, pH should decrease by more than 50% by 2050 in the Arctic. Marine calcifying organisms are particularly important in high latitudes as a food source for different species and for carbon fluxes, and will likely be directly affected as shells and other structures of calcium carbonates dissolve with lower pH. It is unclear though how those organisms will react, adapt and survive within this carbonate undersaturation scenario. Marine calcifying organisms include strictly planktonic as well as meroplanktonic organisms. Meroplankton spend only part of their life in a planktonic stage and include benthic larvae. In order to understand the effect of decreasing pH on the metabolism of calcifying organisms, perturbation experiments were performed on two meroplanktonic organisms: benthic gastropods and clams larvae, and one strictly planktonic organism: pteropods. During these experiments, oxygen was monitored every 4-8 hours in order to measure the organisms’ respiration at regular sea water pH (8.1) and at the lower pH predicted for the next 100 years (7.7). The increase of respiration at lower pH reflects a change in the organisms’ metabolism probably due to stress. By affecting calcifying organism metabolism, ocean acidification is likely to lead to changes in food web structure, carbon fluxes and benthic communities.

Morata, N. & Manno, C., 2010. Impact of ocean acidification on the metabolism of calcifying planktonic organisms. State of the Arctic meeting, 16-19 March 2010 (poster abstract). Abstract.

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