Effect of ocean warming and acidification on the e

Authors: T Foster J P Gilmour C M Chua J L Falter M T McCulloch

Publish Date: 2015/09/03

Volume: 34, Issue: 4, Pages: 1217-1226

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Abstract

This study investigated the impacts of acidified seawater pCO2 ~ 900 μatm and elevated water temperature +3 °C on the early life history stages of Acropora spicifera from the subtropical Houtman Abrolhos Islands 28°S in Western Australia Settlement rates were unaffected by high temperature 27 °C ~250 μatm high pCO2 24 °C ~900 μatm or a combination of both high temperature and high pCO2 treatments 27 °C ~900 μatm There were also no significant differences in rates of postsettlement survival after 4 weeks of exposure between any of the treatments with survival ranging from 60 to 70  regardless of treatment Similarly calcification as determined by the skeletal weight of recruits was unaffected by an increase in water temperature under both ambient and high pCO2 conditions In contrast high pCO2 significantly reduced early skeletal development with mean skeletal weight in the high pCO2 and combined treatments reduced by 60 and 48  respectively compared to control weights Elevated temperature appeared to have a partially mitigative effect on calcification under high pCO2 however this effect was not significant Our results show that rates of settlement postsettlement survival and calcification in subtropical corals are relatively resilient to increases in temperature This is in marked contrast to the sensitivity to temperature reported for the majority of tropical larvae and recruits in the literature The subtropical corals in this study appear able to withstand an increase in temperature of 3 °C above ambient indicating that they may have a wider thermal tolerance range and may not be adversely affected by initial increases in water temperature from subtropical 24 to 27 °C However the reduction in skeletal weight with high pCO2 indicates that early skeletal formation will be highly vulnerable to the changes in ocean pCO2 expected to occur over the twentyfirst century with implications for their longerterm growth and resilienceThis work was funded by the ARC Centre of Excellence for Coral Reef Studies CE140100020 The authors would like to thank the Batavia Coast Maritime Institute in Geraldton for technical support A Negri A Heyward AIMS and M Holcomb for sharing their expertise in coral culturing V Beltran AIMS for providing cultured zooxanthellae and P Clode and three anonymous reviewers for helpful comments on the manuscript We would like to extend a special thank you to the many hours of volunteer work contributed by L and T Foster J Melvin C Wood K Antipas Z Snedden and particularly the Basile family whose logistical and technical support made work at the Abrolhos Islands possible

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