Do fluctuating temperature environments elevate coral thermal tolerance?
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In reef corals, much research has focused on the capacity of corals to acclimatize and/or adapt to different thermal environments, but the majority of work has focused on distinctions in mean temperature. Across small spatial scales, distinctions in daily temperature variation are common, but the role of such environmental variation in setting coral thermal tolerances has received little attention. Here, we take advantage of back-reef pools in American Samoa that differ in thermal variation to investigate the effects of thermally fluctuating environments on coral thermal tolerance. We experimentally heat-stressed Acropora hyacinthus from a thermally moderate lagoon pool (temp range 26.5–33.3°C) and from a more thermally variable pool that naturally experiences 2–3 h high temperature events during summer low tides (temp range 25.0–35°C). We compared mortality and photosystem II photochemical efficiency of colony fragments exposed to ambient temperatures (median: 28.0°C) or elevated temperatures (median: 31.5°C). In the heated treatment, moderate pool corals showed nearly 50% mortality whether they hosted heat-sensitive (49.2 ± 6.5% SE; C2) or heat-resistant (47.0 ± 11.2% SE; D) symbionts. However, variable pool corals, all of which hosted heat-resistant symbionts, survived well, showing low mortalities (16.6 ± 8.8% SE) statistically indistinguishable from controls held at ambient temperatures (5.1–8.3 ± 3.3–8.3% SE). Similarly, moderate pool corals hosting heat-sensitive algae showed rapid rates of decline in algal photosystem II photochemical efficiency in the elevated temperature treatment (slope = −0.04 day−1 ± 0.007 SE); moderate pool corals hosting heat-resistant algae showed intermediate levels of decline (slope = −0.039 day−1 ± 0.007 SE); and variable pool corals hosting heat-resistant algae showed the least decline (slope = −0.028 day−1 ± 0.004 SE). High gene flow among pools suggests that these differences probably reflect coral acclimatization not local genetic adaptation. Our results suggest that previous exposure to an environmentally variable microhabitat adds substantially to coral–algal thermal tolerance, beyond that provided by heat-resistant symbionts alone.
KeywordsCoral Climate change Acropora Symbiodinium Thermal tolerance
The authors would like to acknowledge the assistance of C. Birkeland, Dan Barshis, Lance Smith, and Cheryl Squair at University of Hawaii, Peter Craig and Fale Tuilagi (US National Park Service, American Samoa); Seabird McKeon at the University of Florida; and Kirsten Oleson and Jason Ladner of Stanford University for their support in American Samoa; the Hawaiian Undersea Research Lab; and the National Park of American Samoa. An NSF Predoctoral fellowship program, the Woods Institute for the Environment at Stanford University, NOAA and the National Science Foundation provided funding.
- Brown BE, Dunne RP, Goodson MS, Douglas AE (2002) Experience shapes the susceptibility of a reef coral to bleaching. Coral Reefs 21:119–126Google Scholar
- Coles S (1975) A comparison of effects of elevated temperature versus temperature fluctuations on reef corals at Kahe Point, Oahu. Pac Sci 29:15–18Google Scholar
- Coles S, Jokiel P, Lewis C (1976) Thermal tolerance in tropical versus subtropical Pacific reef corals Pac Sci 30:159–166Google Scholar
- Endler JA (1986) Natural selection in the wild. Princeton University Press, PrincetonGoogle Scholar
- Excoffier L, Laval G, Schneider S (2005) Arlequin (version 3.0): an integrated software package for population genetics data analysis. Evol Bioinformatics Online 1:47Google Scholar
- Feder M (1996) Ecological and evolutionary physiology of stress proteins and the stress response: the Drosophila melanogaster model. In: Johnston IA, Bennett AF (eds) Animals and temperature: Phenotypic and evolutionary adaptation. Cambridge University Press, Cambridge, pp 79–102CrossRefGoogle Scholar
- Gates RD, Edmunds PJ (1999) The physiological mechanisms of acclimatization in tropical reef corals. Am Zool 39:30–43Google Scholar
- Goreau TJ, Hayes RL (1994) Coral bleaching and ocean hotspots. Ambio 23:176–180Google Scholar
- Hoegh-Guldberg O, Mumby PJ, Hooten AJ, Steneck RS, Greenfield P, Gomez E, Harvell CD, Sale PF, Edwards AJ, Caldeira K, Knowlton N, Eakin CM, Iglesias-Prieto R, Muthiga N, Bradbury RH, Dubi A, Hatziolos ME (2007) Coral reefs under rapid climate change and ocean acidification. Science 318:1737–1742PubMedCrossRefGoogle Scholar
- Hughes TP, Baird AH, Bellwood DR, Card M, Connolly SR, Folke C, Grosberg R, Hoegh-Guldberg O, Jackson JBC, Kleypas J, Lough JM, Marshall P, Nystrom M, Palumbi SR, Pandolfi JM, Rosen B, Roughgarden J (2003) Climate change, human impacts, and the resilience of coral reefs. Science 301:929–933PubMedCrossRefGoogle Scholar
- Hutchison VH, Ferrance MR (1970) Thermal tolerances of Rana pipiens acclimated to daily temperature cycles. Herpetologica 26:1–8Google Scholar
- LaJeunesse TC, Smith R, Walther M, Pinzón J, Pettay DT, McGinley M, Aschaffenburg M, Medina-Rosas P, Cupul-Magaña AL, Pérez AL, Reyes-Bonilla H, Warner ME (2010) Host–symbiont recombination versus natural selection in the response of coral–dinoflagellate symbioses to environmental disturbance. Proc R Soc Biol Sci Ser B 277:2925–2934CrossRefGoogle Scholar
- Liu G, Strong AE, Skirving WJ, Arzayus LF (2006) Overview of NOAA Coral Reef Watch Program’s Near-Real-Time Satellite Global Coral Bleaching Monitoring Activities. Proceedings 10th International Coral Reef Symp: 1783–1793Google Scholar
- Mayer A (1914) The effects of temperature upon tropical marine animals. Pap Tortugas Lab Carnegie Inst Wash VI:1–24Google Scholar
- McClanahan TR, Muthiga NA, Mangi S (2001) Coral and algal changes after the 1998 coral bleaching: Interaction with reef management and herbivores on Kenyan reefs. Coral Reefs 19:380–391Google Scholar
- Schaefer J, Ryan A (2006) Developmental plasticity in the thermal tolerance of zebrafish Danio rerio J Fish Biol 722–734Google Scholar
- Suggett DJ, Smith DJ (2010) Interpreting the sign of coral bleaching as friend vs. foe. Global Change Biol published online: Dec 16 2009. doi: 10.1111/j.1365-2486.2009.02155.x