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Marine Ecology Progress Series

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MEPS 526:41-53 (2015)  -  DOI:

Shifts in sponge-microbe mutualisms across an experimental irradiance gradient

Christopher J. Freeman1,2,*, David M. Baker3, Cole G. Easson2, Robert W. Thacker2

1Smithsonian Marine Station, Fort Pierce, Florida, 34949 USA
2Department of Biology, University of Alabama at Birmingham, Birmingham, Alabama, 35294 USA
3The Swire Institute of Marine Science, School of Biological Sciences & Department of Earth Science, University of Hong Kong, Hong Kong, PR China
*Corresponding author:

ABSTRACT: To investigate how the interactions between the closely related sponge species Aplysina cauliformis and Aplysina fulva and their symbiotic microbial communities vary under changing environmental conditions, we conducted a manipulative shading experiment with treatments spanning a gradient of 6 irradiances. In A. cauliformis, there was a tight coupling of symbiont and host metabolism across treatments, and changes in growth rate were correlated more with shifts in symbiont δ13C and δ15N values than with shade treatment. In contrast, symbiont and host C metabolism were weakly coupled in A. fulva, and the growth of this species was not correlated with shifts in symbiont δ13C and δ15N values. In addition, although photosymbiont metabolism was an important driver of shifts in holobiont C and N metabolism of both host species, host and photosymbiont C metabolism were only correlated in A. cauliformis. Thus, although both species host stable, abundant, and similar photosymbiont communities, each host forms a unique mutualism with its symbionts. These 2 host species may be on different evolutionary trajectories, potentially allowing each to exploit novel niche space in coral reef ecosystems. This study provides data in support of the hypothesis that these symbioses represent a dynamic balance of costs and benefits and provides evidence that, because these costs and benefits are highly speciesspecific, not all species will respond similarly to environmental fluctuations.

KEY WORDS: Stable isotopes · Metabolism · Mutualism · Porifera · Symbiosis

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Cite this article as: Freeman CJ, Baker DM, Easson CG, Thacker RW (2015) Shifts in sponge-microbe mutualisms across an experimental irradiance gradient. Mar Ecol Prog Ser 526:41-53.

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