Summary of Abstract Submission

Abstract Submission No. IO50-03-0010PresentationPoster


Till Röthig*1, Riaan van der Merwe1, Michael A. Ochsenkühn1, Anna Roik1, Christian R. Voolstra1

1 King Abdullah University of Science and Technology (KAUST), Saudi Arabia


Scleractinian corals are assumed to be stenohaline osmoconformers. Yet, studies showed various corals to differ in their ability to cope with different salinities, depending on exposure time, magnitude, and rate of salinity change. Physiological reactions to hypo- and hypersaline treatments include mucus production, decreased photosynthetical performance, changes in respiration rates, bleaching, and mortality. While some species are able to tolerate salinities up to 50 PSU we know little about the mechanisms involved. Studies have primarily addressed algal symbionts and/or the coral host, but the associated bacterial communities were overlooked. To further investigate the response of the coral holobiont (i.e. coral host, algal symbiont, and associated bacteria) of Fungia granulosa to strongly increased salinity levels resulting from seawater reverse osmosis desalination plant discharge, we conducted a combination of short- (4h) and long-term (29d) experiments. After 4-hour incubations we measured significant changes in photosynthetic efficiency, net photosynthesis, and calcification rates. However, we could not find major changes in the associated bacterial community. In contrast, in a 29-day transplantation experiment we found no (photo)physiological changes but a major restructuring of the bacterial communities as a response to elevated salinities. We conclude that corals display distinct short- and long-term responses to increased salinity levels across holobiont compartments, and that bacteria may facilitate the long-term acclimation of the coral holobiont to increased salinity.