MEPS prepress abstract  -  DOI: https://doi.org/10.3354/meps13047

Restoring the flat oyster Ostrea angasi in the face of a changing climate

Roberta R. C. Pereira, Elliot Scanes, Laura Parker, Maria Byrne, Pauline M. Ross*

*Email: pauline.ross@sydney.edu.au

ABSTRACT: Across the globe, restoration efforts are stemming the loss of native oyster reefs and their ecosystem services. These efforts will need to consider climate change in order to be sustainable. South-eastern Australia is the focus of restoring the once abundant oyster Ostrea angasi. This region is also a climate-change “hot spot” where the ocean is warming rapidly, with the potential to be exacerbated by marine heat waves and coastal acidification. In this study, the impact of near-future (~2050) elevated temperature and pCO2 on O. angasi was determined and considered in context with concerns for the long-term sustainability of oyster reef restoration efforts. Oysters were exposed to ambient and elevated pCO2 concentrations (408 ± 19.8 and 1070 ± 53.4 µatm [mean ± S.E.]) and ambient and elevated temperatures (22.78 ± 0.17 and 25.73 ± 0.21 °C [mean ± S.E.]) for ten weeks in outdoor flowthrough mesocosms. Shell growth, condition index, standard metabolic rate (SMR), extracellular pH and survival were measured. Elevated temperature caused high mortality (36%) and decreased the condition of oysters (33%). Elevated pCO2 increased SMR almost four-fold and lowered the extracellular pH of O. angasi by a mean 0.29 pH units. In combination, elevated pCO2 and temperature ameliorated effects on SMR and survivorship pf of oysters. O. angasi appears to be living near the limits of its thermal tolerance. Restoration projects need to account for the temperature sensitivity of this species and its changing habitat to “climate proof” long-term restoration efforts.