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Marine Ecology Progress Series

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MEPS 479:85-97 (2013)  -  DOI:

Long-term monitoring of algal symbiont communities in corals reveals stability is taxon dependent and driven by site-specific thermal regime

Andrew C. Baker1,2,*, Tim R. McClanahan2, Craig J. Starger3,4, Roxane K. Boonstra1

1Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Cswy., Miami, Florida 33149, USA
2Marine Program, Wildlife Conservation Society, 2300 Southern Boulevard, Bronx, New York 10460, USA
3Division of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, 10th Street NW and Constitution Avenue NW, Washington, DC 20530, USA
4Science and Technology Policy Fellowships, Center of Science, Policy and Society Programs, American Association for the Advancement of Science, 1200 New York Avenue NW, Washington, DC 20005, USA

ABSTRACT: Survival trajectories for coral reefs under climate change may depend in part on shifts in the composition of their algal symbiont communities (Symbiodinium spp.). Shifts favoring thermotolerant symbionts have been recorded in response to mass bleaching events but rarely tracked through time. A 10 yr monitoring study of Symbiodinium in a variety of Kenyan corals assessed their variability through time, across coral taxa and between sites, and their relationship to environmental conditions. Coral genera varied significantly in their propensity to host thermotolerant symbionts of Symbiodinium clade D, with some genera becoming dominated by clade D at annual maximum temperatures of 32°C but others showing clade D only rarely at 35°C. High annual maximum temperatures, high standard deviation, positive skewness and positive kurtosis characterized sites where clade D was common. In corals whose symbiont communities were thermally labile (e.g. Pocillopora) an increase in maximum annual temperature from 30 to 35°C resulted in 3- to 4-fold increases in dominance by clade D. There was no directional change in symbiont communities over the study period, but there was evidence for a ~6 yr decline in the incidence of mixed (C + D) communities following the 1998 bleaching event. These data illustrate how acute and chronic thermal stress caused by oceanographic and tidal oscillations interact to produce highly dynamic symbiotic communities. The clade D niche is a function of the environment and host taxon and, through a variety of mechanisms, is expected to expand with climate warming. Corals from warm and variable conditions represent conservation priorities because they establish a niche for these symbionts in contemporary reef environments.

KEY WORDS: Acclimatization · Adaptation · Adaptive bleaching hypothesis · Community change · Indian Ocean · Symbiosis

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Cite this article as: Baker AC, McClanahan TR, Starger CJ, Boonstra RK (2013) Long-term monitoring of algal symbiont communities in corals reveals stability is taxon dependent and driven by site-specific thermal regime. Mar Ecol Prog Ser 479:85-97.

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