Letter

Nature 454, 96-99 (3 July 2008) | doi:10.1038/nature07051; Received 13 March 2008; Accepted 1 May 2008; Published online 8 June 2008

Volcanic carbon dioxide vents show ecosystem effects of ocean acidification

Jason M. Hall-Spencer1, Riccardo Rodolfo-Metalpa1, Sophie Martin2, Emma Ransome1, Maoz Fine3,4, Suzanne M. Turner5, Sonia J. Rowley1, Dario Tedesco6,7 & Maria-Cristina Buia8

  1. Marine Institute, Marine Biology and Ecology Research Centre, University of Plymouth, Plymouth PL4 8AA, UK
  2. CNRS-Université de Paris 6, Villefranche-sur-Mer 06234, France
  3. Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
  4. The Interuniversity Institute for Marine Science, Eilat 88103, Israel
  5. School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK
  6. Department of Environmental Sciences, 2nd University of Naples, Caserta 81100, Italy
  7. Istituto di Geologia Ambientale e Geoingegneria, CNR, Rome 00138, Italy
  8. Laboratorio di Ecologia del Benthos, Stazione Zoologica Anton Dohrn, Naples 80077, Italy

Correspondence to: Jason M. Hall-Spencer1 Correspondence and requests for materials should be addressed to J.M.H.-S. (Email: jhall-spencer@plymouth.ac.uk).

The atmospheric partial pressure of carbon dioxide (p CO2) will almost certainly be double that of pre-industrial levels by 2100 and will be considerably higher than at any time during the past few million years1. The oceans are a principal sink for anthropogenic CO2 where it is estimated to have caused a 30% increase in the concentration of H+ in ocean surface waters since the early 1900s and may lead to a drop in seawater pH of up to 0.5 units by 2100 (refs 2, 3). Our understanding of how increased ocean acidity may affect marine ecosystems is at present very limited as almost all studies have been in vitro, short-term, rapid perturbation experiments on isolated elements of the ecosystem4, 5. Here we show the effects of acidification on benthic ecosystems at shallow coastal sites where volcanic CO2 vents lower the pH of the water column. Along gradients of normal pH (8.1–8.2) to lowered pH (mean 7.8–7.9, minimum 7.4–7.5), typical rocky shore communities with abundant calcareous organisms shifted to communities lacking scleractinian corals with significant reductions in sea urchin and coralline algal abundance. To our knowledge, this is the first ecosystem-scale validation of predictions that these important groups of organisms are susceptible to elevated amounts of p CO2. Sea-grass production was highest in an area at mean pH 7.6 (1,827 muatm p CO2) where coralline algal biomass was significantly reduced and gastropod shells were dissolving due to periods of carbonate sub-saturation. The species populating the vent sites comprise a suite of organisms that are resilient to naturally high concentrations of p CO2 and indicate that ocean acidification may benefit highly invasive non-native algal species. Our results provide the first in situ insights into how shallow water marine communities might change when susceptible organisms are removed owing to ocean acidification.

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