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Title: Role of host genetics and heat‐tolerant algal symbionts in sustaining populations of the endangered coral Orbicella faveolata in the Florida Keys with ocean warming
Abstract

Identifying which factors lead to coral bleaching resistance is a priority given the global decline of coral reefs with ocean warming. During the second year of back‐to‐back bleaching events in the Florida Keys in 2014 and 2015, we characterized key environmental and biological factors associated with bleaching resilience in the threatened reef‐building coralOrbicella faveolata. Ten reefs (five inshore, five offshore, 179 corals total) were sampled during bleaching (September 2015) and recovery (May 2016). Corals were genotyped with 2bRADand profiled for algal symbiont abundance and type.O. faveolataat the inshore sites, despite higher temperatures, demonstrated significantly higher bleaching resistance and better recovery compared to offshore. The thermotolerantDurusdinium trenchii(formerlySymbiondinium trenchii) was the dominant endosymbiont type region‐wide during initial (78.0% of corals sampled) and final (77.2%) sampling; >90% of the nonbleached corals were dominated byD. trenchii. 2bRADhost genotyping found no genetic structure among reefs, but inshore sites showed a high level of clonality. While none of the measured environmental parameters were correlated with bleaching, 71% of variation in bleaching resistance and 73% of variation in the proportion ofD. trenchiiwas attributable to differences between genets, highlighting the leading role of genetics in shaping natural bleaching patterns. Notably,D. trenchiiwas rarely dominant inO. faveolatafrom the Florida Keys in previous studies, even during bleaching. The region‐wide high abundance ofD. trenchiiwas likely driven by repeated bleaching associated with the two warmest years on record for the Florida Keys (2014 and 2015). On inshore reefs in the Upper Florida Keys,O. faveolatawas most abundant, had the highest bleaching resistance, and contained the most corals dominated byD. trenchii, illustrating a causal link between heat tolerance and ecosystem resilience with global change.

 
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Award ID(s):
1737312
NSF-PAR ID:
10450070
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley-Blackwell
Date Published:
Journal Name:
Global Change Biology
Volume:
25
Issue:
3
ISSN:
1354-1013
Page Range / eLocation ID:
p. 1016-1031
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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