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      Reduced calcification of marine plankton in response to increased atmospheric CO2.

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          Abstract

          The formation of calcareous skeletons by marine planktonic organisms and their subsequent sinking to depth generates a continuous rain of calcium carbonate to the deep ocean and underlying sediments. This is important in regulating marine carbon cycling and ocean-atmosphere CO2 exchange. The present rise in atmospheric CO2 levels causes significant changes in surface ocean pH and carbonate chemistry. Such changes have been shown to slow down calcification in corals and coralline macroalgae, but the majority of marine calcification occurs in planktonic organisms. Here we report reduced calcite production at increased CO2 concentrations in monospecific cultures of two dominant marine calcifying phytoplankton species, the coccolithophorids Emiliania huxleyi and Gephyrocapsa oceanica. This was accompanied by an increased proportion of malformed coccoliths and incomplete coccospheres. Diminished calcification led to a reduction in the ratio of calcite precipitation to organic matter production. Similar results were obtained in incubations of natural plankton assemblages from the north Pacific ocean when exposed to experimentally elevated CO2 levels. We suggest that the progressive increase in atmospheric CO2 concentrations may therefore slow down the production of calcium carbonate in the surface ocean. As the process of calcification releases CO2 to the atmosphere, the response observed here could potentially act as a negative feedback on atmospheric CO2 levels.

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          Author and article information

          Journal
          Nature
          Nature
          Springer Science and Business Media LLC
          0028-0836
          0028-0836
          Sep 21 2000
          : 407
          : 6802
          Affiliations
          [1 ] Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany. uriebesell@awi-bremerhaven.de
          Article
          10.1038/35030078
          11014189
          eb35df6b-3014-4a05-9c8c-2870872452c1
          History

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