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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 6, issue 8 | Copyright

Special issue: The ocean in the high-CO2 world II

Biogeosciences, 6, 1811-1823, 2009
https://doi.org/10.5194/bg-6-1811-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

  27 Aug 2009

27 Aug 2009

Net Loss of CaCO3 from a subtropical calcifying community due to seawater acidification: mesocosm-scale experimental evidence

A. J. Andersson1, I. B. Kuffner2, F. T. Mackenzie3, P. L. Jokiel4, K. S. Rodgers4, and A. Tan3 A. J. Andersson et al.
  • 1Bermuda Institute of Ocean Sciences, St. George's, Bermuda, UK
  • 2US Geological Survey, Florida Integrated Science Center, St. Petersburg, FL, USA
  • 3Department of Oceanography, University of Hawaii, Honolulu, HI, USA
  • 4Hawaii Institute of Marine Biology, Kaneohe, HI, USA

Abstract. Acidification of seawater owing to oceanic uptake of atmospheric CO2 originating from human activities such as burning of fossil fuels and land-use changes has raised serious concerns regarding its adverse effects on corals and calcifying communities. Here we demonstrate a net loss of calcium carbonate (CaCO3) material as a result of decreased calcification and increased carbonate dissolution from replicated subtropical coral reef communities (n=3) incubated in continuous-flow mesocosms subject to future seawater conditions. The calcifying community was dominated by the coral Montipora capitata. Daily average community calcification or Net Ecosystem Calcification (NEC=CaCO3 production – dissolution) was positive at 3.3 mmol CaCO3 m−2 h−1 under ambient seawater pCO2 conditions as opposed to negative at −0.04 mmol CaCO3 m−2 h−1 under seawater conditions of double the ambient pCO2. These experimental results provide support for the conclusion that some net calcifying communities could become subject to net dissolution in response to anthropogenic ocean acidification within this century. Nevertheless, individual corals remained healthy, actively calcified (albeit slower than at present rates), and deposited significant amounts of CaCO3 under the prevailing experimental seawater conditions of elevated pCO2.

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