INTERACTIONS BETWEEN OCEAN ACIDIFICATION AND WARMING ON THE MORTALITY AND DISSOLUTION OF CORALLINE ALGAE 1

• Published in: Journal of Phycology
• Main Authors: Diaz‐Pulido, Guillermo, Anthony, Kenneth R. N., Kline, David I., Dove, Sophie, Hoegh‐Guldberg, Ove
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2011
• Subjects: Ocean acidification
• Online Access: http://dx.doi.org/10.1111/j.1529-8817.2011.01084.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1529-8817.2011.01084.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1529-8817.2011.01084.x

Coralline algae are among the most sensitive calcifying organisms to ocean acidification as a result of increased atmospheric carbon dioxide ( p CO 2 ). Little is known, however, about the combined impacts of increased p CO 2 , ocean acidification, and sea surface temperature on tissue mortality and skeletal dissolution of coralline algae. To address this issue, we conducted factorial manipulative experiments of elevated CO 2 and temperature and examined the consequences on tissue survival and skeletal dissolution of the crustose coralline alga (CCA) Porolithon (= Hydrolithon ) onkodes (Heydr.) Foslie (Corallinaceae, Rhodophyta) on the southern Great Barrier Reef (GBR), Australia. We observed that warming amplified the negative effects of high p CO 2 on the health of the algae: rates of advanced partial mortality of CCA increased from <1% to 9% under high CO 2 (from 400 to 1,100 ppm) and exacerbated to 15% under warming conditions (from 26°C to 29°C). Furthermore, the effect of p CO 2 on skeletal dissolution strongly depended on temperature. Dissolution of P. onkodes only occurred in the high‐ p CO 2 treatment and was greater in the warm treatment. Enhanced skeletal dissolution was also associated with a significant increase in the abundance of endolithic algae. Our results demonstrate that P. onkodes is particularly sensitive to ocean acidification under warm conditions, suggesting that previous experiments focused on ocean acidification alone have underestimated the impact of future conditions on coralline algae. Given the central role that coralline algae play within coral reefs, these conclusions have serious ramifications for the integrity of coral‐reef ecosystems.