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Title: Ecophysiology of mesophotic reef‐building corals in Hawai‘i is influenced by symbiont–host associations, photoacclimatization, trophic plasticity, and adaptation
Abstract

Mesophotic reef corals remain largely unexplored in terms of the genetic adaptations and physiological mechanisms to acquire, allocate, and use energy for survival and reproduction. In the Hawaiian Archipelago, theLeptoserisspecies complex form the most spatially extensive mesophotic coral ecosystem known and provide habitat for a unique community. To study how the ecophysiology ofLeptoserisspecies relates to symbiont–host specialization and understand the mechanisms responsible for coral energy acquisition in extreme low light environments, we examinedSymbiodinium(endosymbiotic dinoflagellate) photobiological characteristics and the lipids and isotopic signatures fromSymbiodiniumand coral hosts over a depth‐dependent light gradient (55–7μmol photons m−2s−1, 60–132 m). Clear performance differences demonstrate different photoadaptation and photoacclimatization across this genus. Our results also show that flexibility in photoacclimatization depends primarily onSymbiodiniumtype. Colonies harboringSymbiodiniumsp.COI‐2showed significant increases in photosynthetic pigment content with increasing depth, whereas colonies harboringSymbiodiniumspp.COI‐1andCOI‐3showed variability in pigment composition, yield measurements for photosystem II, as well as size and density ofSymbiodiniumcells. Despite remarkable differences in photosynthetic adaptive strategies, there were no significant differences among lipids ofLeptoserisspecies with depth. Finally, isotopic signatures of both host andSymbiodiniumchanged with depth, indicating that coral colonies acquired energy from different sources depending on depth. This study highlights the complexity in physiological adaptations within this symbiosis and the different strategies used by closely related mesophotic species to diversify energy acquisition and to successfully establish and compete in extreme light‐limited environments.

 
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NSF-PAR ID:
10460416
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Limnology and Oceanography
Volume:
64
Issue:
5
ISSN:
0024-3590
Page Range / eLocation ID:
p. 1980-1995
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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