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Title: Mesophotic corals in Hawai‘i maintain autotrophy to survive low-light conditions

In mesophotic coral ecosystems, reef-building corals and their photosynthetic symbionts can survive with less than 1% of surface irradiance. How depth-specialist corals rely upon autotrophically and heterotrophically derived energy sources across the mesophotic zone remains unclear. We analysed the stable carbon (δ13C) and nitrogen (δ15N) isotope values of aLeptoseriscommunity from the ‘Au‘au Channel, Maui, Hawai‘i (65–125 m) including four coral host species living symbiotically with three algal haplotypes. We characterized the isotope values of hosts and symbionts across species and depth to compare trophic strategies. Symbiontδ13C was consistently 0.5‰ higher than hostδ13C at all depths. Mean colony host and symbiontδ15N differed by up to 3.7‰ at shallow depths and converged at deeper depths. These results suggest that both heterotrophy and autotrophy remained integral to colony survival across depth. The increasing similarity between host and symbiontδ15N at deeper depths suggests that nitrogen is more efficiently shared between mesophotic coral hosts and their algal symbionts to sustain autotrophy. Isotopic trends across depth did not generally vary by host species or algal haplotype, suggesting that photosynthesis remains essential toLeptoserissurvival and growth despite low light availability in the mesophotic zone.

 
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Award ID(s):
2044840 1655682
NSF-PAR ID:
10520531
Author(s) / Creator(s):
; ; ; ; ; ;
Publisher / Repository:
The Royal Society Publishing
Date Published:
Journal Name:
Proceedings of the Royal Society B: Biological Sciences
Volume:
291
Issue:
2017
ISSN:
0962-8452
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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