Journal Article

Historical thermal regimes define limits to coral acclimatization

van Oppen, Madeleine J. H., Willis, Bette L., Howells, Emily J., Berkelmans, Ray, Bay, Line K.

2013

Overview

Knowledge of the degree to which corals undergo physiological acclimatization or genetic adaptation in response to changes in their thermal environment is crucial to the success of coral reef conservation strategies. The potential of corals to acclimatize to temperatures exceeding historical thermal regimes was investigated by reciprocal transplantation of Acropora millepora colonies between the warm central and cool southern regions of the Great Barrier Reef (GBR) for a duration of 14 months. Colony fragments retained at native sites remained healthy, whereas transplanted fragments, although healthy over initial months when temperatures remained within native thermal regimes, subsequently bleached and suffered mortality during seasonal temperature extremes. Corals hosting Symbiodinium D transplanted to the southern GBR bleached in winter and the majority suffered whole (40%; n = 20 colonies) or partial (50%) mortality at temperatures 1.1°C below their 15-year native minimum. In contrast, corals hosting Symbiodinium C2 transplanted to the central GBR bleached in summer and suffered whole (50%; n = 10 colonies) or partial (42%) mortality at temperatures 2.5°C above their 15-year native maximum. During summer bleaching, the dominant Symbiodinium type changed from C2 to D within corals transplanted to the central GBR. Corals transplanted to the cooler, southern GBR grew 74-80% slower than corals at their native site, and only 50% of surviving colonies reproduced, at least partially because of cold water bleaching of transplants. Despite the absence of any visual signs of stress, corals transplanted to the warmer, central GBR grew 52-59% more slowly than corals at their native site before the summer bleaching (i.e., from autumn to spring). Allocation of energy to initial acclimatization or reproduction may explain this pattern, as the majority (65%) of transplants reproduced one month earlier than portions of the same colonies retained at the southern native site. All parameters investigated (bleaching, mortality, Symbiodinium type fidelity, reproductive timing) demonstrated strong interactions between genotype and environment, indicating that the acclimatization potential of A. millepora populations may be limited by adaptation of the holobiont to native thermal regimes.

• Publisher: Ecological Society of America
• Subject: acclimation / Acclimatization / Acropora millepora / Animal and plant ecology / Animal, plant and microbial ecology / Animals / Anthozoa - physiology / Applied ecology / assisted migration / autumn / Biological and medical sciences / Bleaching / Cnidaria. Ctenaria / cold / Conservation, protection and management of environment and wildlife / coral / coral bleaching / coral mortality / Coral Reefs / Corals / energy / Environmental degradation: ecosystems survey and restoration / Fundamental and applied biological sciences. Psychology / General aspects / Genotype & phenotype / genotype-environment interaction / Great Barrier Reef / Great Barrier Reef, Australia / Heat tolerance / Hot Temperature / Invertebrates / local adaptation / Marine ecology / Millepora / Mortality / Reefs / reproduction / sea temperature rise / Summer / Symbiodinium / Symbiosis / Temperature / thermal tolerance / Time Factors / Transplantation / winter / zooxanthellae