Description of the first natural ocean acidification analogue in the Caribbean

Chair: Ulf Riebesell

Helen E. Graham1, Tina Kutti2, Sebastien Riviere3  Jason M Hall-Spencer4, Samuel P.S. Rastrick2

 

1) Uni Research Environment, Postboks 7810, 5020 Bergen, Norway.

2) Institute of Marine Research, PO Box 1870 Nordness, 5870 Bergen, Norway

3) The Government of the Commonwealth of Dominica Ministry of Agriculture and Fisheries, Fisheries Division, Government Headquarters, Roseau, 00109-8000, Commonwealth of Dominica

4) Marine Biology and Ecology Research Centre, School of Marine Science & Engineering, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK

 

Volcanic CO2 vent sites are well established as analogues for future predicted ocean acidification, providing an opportunity to simultaneously investigate changes in naturally assembled community structure and capacity for physiological adaptation/acclimatisation of key species. However to date no such site has been described in the Caribbean.

Consequently we investigated changes in species distribution and biodiversity associated with the release of volcanic CO2  from the swallow water vents at Anse Bateaux (“Champagne”), Dominica. pH at the site ranges from about 6.9 close to the venting gas to 8.2 at >30m form the vents. Salinity is constant across the site at about 33. The effect of the vents on temperature is localised to just a few cm around an individual vent and the overall temperature was stable across the gradient varying between 27.8 and 28.5 °C. Total alkalinity also appears to be stable. Benthic invertebrate and alga species were surveyed the using non-invasive photo-quadrats Preliminary data suggests that the reef community which is usually dominated by a number of corals, calcifying alga, and urchins at a pH of 8.2 changes at a pH of about

7.7 to become dominated by tube sponges (Aplysina spp.) with fewer urchins and

calcifying corals/alga. On the vent site were the pH is about 6.9 the community is dominated by brown non-calcifying alga and anemones (not found away from the vent), small calcifying alga and brain corals are found but in much lower numbers. As the common yellow tube sponge appears to be able to out compete many of the other  corals  and  sponges  at  pCO2   levels  predicted  in  the  next  hundred  years, possible  due  to  it  photosynthetic  symbionts,  we  suggest  that  in  the  future  the common yellow tube sponge may increase in numbers as the numbers of other corals and sponges decrease in Dominican waters.