Symbiosis and host morphological variation: Symbiodiniaceae photosynthesis in the octocoral Briareum asbestinum at ambient and elevated temperatures

Ramsby, Blake D., and Goulet, Tamar L. (2019) Symbiosis and host morphological variation: Symbiodiniaceae photosynthesis in the octocoral Briareum asbestinum at ambient and elevated temperatures. Coral Reefs, 38. pp. 359-371.

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Intra-species morphological variation may occur in sessile organisms, such as corals, living in different habitats. Conversely, the octocoral Briareum asbestinum exhibits both encrusting and upright branching morphologies at the same shallow water habitat, enabling studying physiological differences uncoupled from habitat variation due to depth or reef location. We investigated the mutualism between endosymbiotic dinoflagellate algae, Breviolum spp. (previously clade B Symbiodinium), and these B. asbestinum morphologies at ambient and elevated temperatures. Based on msh1 gene sequences, the host morphologies were genetically similar although they differed in protein content, polyp expansion behavior, and associated Breviolum (B19 for encrusting and B21 for branching B. asbestinum). Due to colony orientation, polyps in encrusting B. asbestinum experienced irradiance levels nearly three times higher than polyps in the branching morph, which probably contributed to the lower photochemical and light absorption efficiencies of the Breviolum in encrusting fragments. The light-limited portion of photosynthesis-irradiance curves and the intracellular chlorophyll concentrations, however, indicated that Breviolum in both morphologies were acclimated to similar internal irradiances. Encrusting B. asbestinum exhibited higher Breviolum density, areal chlorophyll a, and greater photosynthetic rates cm(-2) compared to branching B. asbestinum. Notably, elevated temperature did not cause bleaching in either morphology, as Breviolum and chlorophyll densities did not differ significantly from ambient temperature, although the two morphologies adjusted some of the measured parameters, indicating coping with the stressor. In the face of continued ocean warming, the high thermal tolerance of octocorals may reinforce the shift of Caribbean reefs from scleractinian coral to octocoral dominance.

Item ID: 58283
Item Type: Article (Research - C1)
ISSN: 1432-0975
Keywords: Caribbean, Coral, Climate change, Zooxanthellae, Symbiodinium, Breviolum
Copyright Information: © Springer-Verlag GmbH Germany, part of Springer Nature 2019
Funders: The Explorers Club (EC), National Science Foundation (NSF)
Projects and Grants: NSF Grant No. IOS 0747205
Date Deposited: 15 May 2019 07:45
FoR Codes: 41 ENVIRONMENTAL SCIENCES > 4104 Environmental management > 410407 Wildlife and habitat management @ 50%
41 ENVIRONMENTAL SCIENCES > 4101 Climate change impacts and adaptation > 410102 Ecological impacts of climate change and ecological adaptation @ 50%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 100%
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