A cross-ocean comparison of responses to settlement cues in reef-building corals

This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by PeerJ. The published article can be found at: https://peerj.com/.Caribbean coral reefs have deteriorated substantially over the past 30 years, which\ud is broadly attributable to the effects of global climate change. In the same time,\ud Indo-Pacific reefs maintain higher coral cover and typically recover rapidly after\ud disturbances. This difference in reef resilience is largely due to much higher\ud coral recruitment rates in the Pacific. We hypothesized that the lack of Caribbean\ud recruitment might be explained by diminishing quality of settlement cues and/or\ud impaired sensitivity of Caribbean coral larvae to those cues, relative to the\ud Pacific. To evaluate this hypothesis, we assembled a collection of bulk samples\ud of reef encrusting communities, mostly consisting of crustose coralline algae\ud (CCA), from various reefs around the world and tested them as settlement cues\ud for several coral species originating from different ocean provinces. Cue samples\ud were meta-barcoded to evaluate their taxonomic diversity. We observed no\ud systematic differences either in cue potency or in strength of larval responses\ud depending on the ocean province, and no preference of coral larvae towards\ud cues from the same ocean. Instead, we detected significant differences in cue\ud preferences among coral species, even for corals originating from the same reef.\ud We conclude that the region-wide disruption of the settlement process is unlikely to\ud be the major cause of Caribbean reef loss. However, due to their high sensitivity to the\ud effects of climate change, shifts in the composition of CCA-associated communities,\ud combined with pronounced differences in cue preferences among coral species, could\ud substantially influence future coral community structure