Surface seawater pH is currently 0.1 units lower than pre-industrial values and is projected to decrease by up to 0.4 units by the end of the century. This acidification has the potential to cause significant perturbations to the physiology of ocean organisms, particularly those such as corals that build their skeletons/shells from calcium carbonate. Reduced ocean pH could also have an impact on the coral microbial community, and thus may affect coral physiology and health. Most of the studies to date have examined the impact of ocean acidification on corals and/or associated microbiota under controlled laboratory conditions. Here we report the first study that examines the changes in coral microbial communities in response to a natural pH gradient (mean pHT 7.3-8.1) caused by volcanic CO2 vents off Ischia, Gulf of Naples, Italy. Two Mediterranean coral species, Balanophyllia europaea and Cladocora caespitosa, were examined. The microbial community diversity and the physiological parameters of the endosymbiotic dinoflagellates (Symbiodinium spp.) were monitored. We found that pH did not have a significant impact on the composition of associated microbial communities in both coral species. In contrast to some earlier studies, we found that corals present at the lower pH sites exhibited only minor physiological changes and no microbial pathogens were detected. Together, these results provide new insights into the impact of ocean acidification on the coral holobiont.
Bibliographical noteFunding Information:
The work was partially supported by the US-Israel Binational Science Foundation grant no. 2006318 to EB and ACB and by the Israel Science Foundation 09/328 to MF. This is a contribution of the European Project ‘Mediterranean Sea Acidification under a changing climate’ (MedSeA; grant agreement 265103). Thanks are due to all collaborators from StazioneZoologica ‘A. Dohrn’ for their help during the fieldwork. RR-M was granted by the Journal Experimental Biology travel fellowship. The work contributes to the EU ‘Mediterranean Sea Acidification under a changing climate’ project (MedSeA; grant agreement 265103). We thank Ayalana Reiss for her critical review of the manuscript and Dr Maya Offek for her help with statistical analyses. This research is part of the requirements for a Ph.D. thesis for Dalit Meron at Bar Ilan University.
- microbial community
- ocean acidification