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Change in algal symbiont communities after bleaching, not prior heat exposure, increases heat tolerance of reef corals.
Glob Chang Biol. 2015 Jan; 21(1):236-49.GC

Abstract

Mutualistic organisms can be particularly susceptible to climate change stress, as their survivorship is often limited by the most vulnerable partner. However, symbiotic plasticity can also help organisms in changing environments by expanding their realized niche space. Coral-algal (Symbiodinium spp.) symbiosis exemplifies this dichotomy: the partnership is highly susceptible to 'bleaching' (stress-induced symbiosis breakdown), but stress-tolerant symbionts can also sometimes mitigate bleaching. Here, we investigate the role of diverse and mutable symbiotic partnerships in increasing corals' ability to thrive in high temperature conditions. We conducted repeat bleaching and recovery experiments on the coral Montastraea cavernosa, and used quantitative PCR and chlorophyll fluorometry to assess the structure and function of Symbiodinium communities within coral hosts. During an initial heat exposure (32 °C for 10 days), corals hosting only stress-sensitive symbionts (Symbiodinium C3) bleached, but recovered (at either 24 °C or 29 °C) with predominantly (>90%) stress-tolerant symbionts (Symbiodinium D1a), which were not detected before bleaching (either due to absence or extreme low abundance). When a second heat stress (also 32 °C for 10 days) was applied 3 months later, corals that previously bleached and were now dominated by D1a Symbiodinium experienced less photodamage and symbiont loss compared to control corals that had not been previously bleached, and were therefore still dominated by Symbiodinium C3. Additional corals that were initially bleached without heat by a herbicide (DCMU, at 24 °C) also recovered predominantly with D1a symbionts, and similarly lost fewer symbionts during subsequent thermal stress. Increased thermotolerance was also not observed in C3-dominated corals that were acclimated for 3 months to warmer temperatures (29 °C) before heat stress. These findings indicate that increased thermotolerance post-bleaching resulted from symbiont community composition changes, not prior heat exposure. Moreover, initially undetectable D1a symbionts became dominant only after bleaching, and were critical to corals' resilience after stress and resistance to future stress.

Authors+Show Affiliations

Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Cswy, Miami, FL, 33149, USA.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

25099991

Citation

Silverstein, Rachel N., et al. "Change in Algal Symbiont Communities After Bleaching, Not Prior Heat Exposure, Increases Heat Tolerance of Reef Corals." Global Change Biology, vol. 21, no. 1, 2015, pp. 236-49.
Silverstein RN, Cunning R, Baker AC. Change in algal symbiont communities after bleaching, not prior heat exposure, increases heat tolerance of reef corals. Glob Chang Biol. 2015;21(1):236-49.
Silverstein, R. N., Cunning, R., & Baker, A. C. (2015). Change in algal symbiont communities after bleaching, not prior heat exposure, increases heat tolerance of reef corals. Global Change Biology, 21(1), 236-49. https://doi.org/10.1111/gcb.12706
Silverstein RN, Cunning R, Baker AC. Change in Algal Symbiont Communities After Bleaching, Not Prior Heat Exposure, Increases Heat Tolerance of Reef Corals. Glob Chang Biol. 2015;21(1):236-49. PubMed PMID: 25099991.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Change in algal symbiont communities after bleaching, not prior heat exposure, increases heat tolerance of reef corals. AU - Silverstein,Rachel N, AU - Cunning,Ross, AU - Baker,Andrew C, Y1 - 2014/09/09/ PY - 2014/05/07/received PY - 2014/06/13/accepted PY - 2014/8/8/entrez PY - 2014/8/8/pubmed PY - 2015/8/11/medline KW - Symbiodinium KW - bleaching KW - climate change KW - community disturbance KW - coral-algal symbiosis KW - functional redundancy KW - heat tolerance KW - resilience SP - 236 EP - 49 JF - Global change biology JO - Glob Chang Biol VL - 21 IS - 1 N2 - Mutualistic organisms can be particularly susceptible to climate change stress, as their survivorship is often limited by the most vulnerable partner. However, symbiotic plasticity can also help organisms in changing environments by expanding their realized niche space. Coral-algal (Symbiodinium spp.) symbiosis exemplifies this dichotomy: the partnership is highly susceptible to 'bleaching' (stress-induced symbiosis breakdown), but stress-tolerant symbionts can also sometimes mitigate bleaching. Here, we investigate the role of diverse and mutable symbiotic partnerships in increasing corals' ability to thrive in high temperature conditions. We conducted repeat bleaching and recovery experiments on the coral Montastraea cavernosa, and used quantitative PCR and chlorophyll fluorometry to assess the structure and function of Symbiodinium communities within coral hosts. During an initial heat exposure (32 °C for 10 days), corals hosting only stress-sensitive symbionts (Symbiodinium C3) bleached, but recovered (at either 24 °C or 29 °C) with predominantly (>90%) stress-tolerant symbionts (Symbiodinium D1a), which were not detected before bleaching (either due to absence or extreme low abundance). When a second heat stress (also 32 °C for 10 days) was applied 3 months later, corals that previously bleached and were now dominated by D1a Symbiodinium experienced less photodamage and symbiont loss compared to control corals that had not been previously bleached, and were therefore still dominated by Symbiodinium C3. Additional corals that were initially bleached without heat by a herbicide (DCMU, at 24 °C) also recovered predominantly with D1a symbionts, and similarly lost fewer symbionts during subsequent thermal stress. Increased thermotolerance was also not observed in C3-dominated corals that were acclimated for 3 months to warmer temperatures (29 °C) before heat stress. These findings indicate that increased thermotolerance post-bleaching resulted from symbiont community composition changes, not prior heat exposure. Moreover, initially undetectable D1a symbionts became dominant only after bleaching, and were critical to corals' resilience after stress and resistance to future stress. SN - 1365-2486 UR - https://www.unboundmedicine.com/medline/citation/25099991/Change_in_algal_symbiont_communities_after_bleaching_not_prior_heat_exposure_increases_heat_tolerance_of_reef_corals_ L2 - https://doi.org/10.1111/gcb.12706 DB - PRIME DP - Unbound Medicine ER -