title: INTERACTIONS BETWEEN OCEAN ACIDIFICATION AND WARMING ON THE MORTALITY AND DISSOLUTION OF CORALLINE ALGAE(1).
abstract: Coralline algae are among the most sensitive calcifying organisms to ocean acidification as a result of increased atmospheric carbon dioxide (pCO2 ). Little is known, however, about the combined impacts of increased pCO2 , 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 CO2 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 pCO2 on the health of the algae: rates of advanced partial mortality of CCA increased from <1% to 9% under high CO2 (from 400 to 1,100 ppm) and exacerbated to 15% under warming conditions (from 26°C to 29°C). Furthermore, the effect of pCO2 on skeletal dissolution strongly depended on temperature. Dissolution of P. onkodes only occurred in the high-pCO2 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.
authors.affiliation: Griffith School of Environment and Australian Rivers Institute - Coast & Estuaries, Nathan Campus, Griffith University, 170 Kessels Road, Brisbane, Nathan, Queensland 4111, Australia Global Change Institute and Australian Research Council Centre of Excellence for Coral Reef Studies, The University of Queensland, Brisbane, St Lucia, Queensland 4072, AustraliaGlobal Change Institute and Australian Research Council Centre of Excellence for Coral Reef Studies, The University of Queensland, Brisbane, St Lucia, Queensland 4072, Australia.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Diaz-Pulido
authors.affiliation: Griffith School of Environment and Australian Rivers Institute - Coast & Estuaries, Nathan Campus, Griffith University, 170 Kessels Road, Brisbane, Nathan, Queensland 4111, Australia Global Change Institute and Australian Research Council Centre of Excellence for Coral Reef Studies, The University of Queensland, Brisbane, St Lucia, Queensland 4072, AustraliaGlobal Change Institute and Australian Research Council Centre of Excellence for Coral Reef Studies, The University of Queensland, Brisbane, St Lucia, Queensland 4072, Australia.
authors.forename: Kenneth R N
authors.initials: KR
authors.lastname: Anthony
authors.affiliation: Griffith School of Environment and Australian Rivers Institute - Coast & Estuaries, Nathan Campus, Griffith University, 170 Kessels Road, Brisbane, Nathan, Queensland 4111, Australia Global Change Institute and Australian Research Council Centre of Excellence for Coral Reef Studies, The University of Queensland, Brisbane, St Lucia, Queensland 4072, AustraliaGlobal Change Institute and Australian Research Council Centre of Excellence for Coral Reef Studies, The University of Queensland, Brisbane, St Lucia, Queensland 4072, Australia.
authors.forename: David I
authors.initials: DI
authors.lastname: Kline
authors.affiliation: Griffith School of Environment and Australian Rivers Institute - Coast & Estuaries, Nathan Campus, Griffith University, 170 Kessels Road, Brisbane, Nathan, Queensland 4111, Australia Global Change Institute and Australian Research Council Centre of Excellence for Coral Reef Studies, The University of Queensland, Brisbane, St Lucia, Queensland 4072, AustraliaGlobal Change Institute and Australian Research Council Centre of Excellence for Coral Reef Studies, The University of Queensland, Brisbane, St Lucia, Queensland 4072, Australia.
authors.forename: Sophie
authors.initials: S
authors.lastname: Dove
authors.affiliation: Griffith School of Environment and Australian Rivers Institute - Coast & Estuaries, Nathan Campus, Griffith University, 170 Kessels Road, Brisbane, Nathan, Queensland 4111, Australia Global Change Institute and Australian Research Council Centre of Excellence for Coral Reef Studies, The University of Queensland, Brisbane, St Lucia, Queensland 4072, AustraliaGlobal Change Institute and Australian Research Council Centre of Excellence for Coral Reef Studies, The University of Queensland, Brisbane, St Lucia, Queensland 4072, Australia.
authors.forename: Ove
authors.initials: O
authors.lastname: Hoegh-Guldberg
keywords: calcification; carbon dioxide; carbonate dissolution; climate change; coral reefs; coralline algae; global warming; greenhouse effect; ocean acidification; temperature effects