In hot water: sustained ocean warming reduces survival of a low-latitude coral reef fish

Rodgers, G.G., Donelson, J.M., McCormick, M.I., and Munday, P.L. (2018) In hot water: sustained ocean warming reduces survival of a low-latitude coral reef fish. Marine Biology, 165. 73.

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Tropical species are predicted to be particularly vulnerable to the impacts of climate change given the relatively narrow thermal range they naturally experience. Within the tropics, average temperature and thermal variation can differ among populations and consequently low-latitude populations may respond differently to increased temperatures than higher latitude tropical populations. In this study, we investigate the long-term effects of climate change relevant temperature increases on commonly measured condition metrics for a low-latitude population of damselfish (Acanthochromis polyacanthus). Adult fish were randomly assigned to one of the three seasonally cycling treatments: (1) current average ocean temperatures for the collection locations, (2) 1.5 °C, or (3) 3 °C higher than current average temperatures. Treatments were maintained for approximately 10 months. At the end of the experimental period, Fulton’s K and hepatosomatic index were calculated for fish from each treatment group and critical thermal limit (CTMax) was measured for a subset of fish at control temperatures. Fish mortality was recorded throughout the experimental period, as well as at the end of the experimental period after the introduction of a secondary exercise stressor. No significant effect of temperature was observed on fish condition (Fulton’s K and hepatosomatic index); however, significant mortality was observed for fish maintained at 3 °C higher than current average temperatures. When a secondary exercise stressor was introduced, significant mortality was also observed at 1.5 °C higher than current average temperatures. Acute exposure to higher temperatures (CTMax) suggested a much higher thermal tolerance for this population than long-term mortality, producing a thermal limit of 37.1 °C compared with a chronic thermal limit of 33 °C. Our results show that some basic measures of fish condition may not be capable of detecting lethal and sub-lethal effects of increased temperature. The results of this study are consistent with the hypothesis that low-latitude species are already living close to their thermal maximum.

Item ID: 54293
Item Type: Article (Research - C1)
ISSN: 1432-1793
Funders: Australian Research Council (ARC), Australian Research Council (ARC) Centre of Excellence for Coral Reef Studies (CE), James Cook University (JCU)
Projects and Grants: JCU Higher Degree Research Enhancement Funding Scheme
Research Data:
Date Deposited: 25 Jun 2018 05:31
FoR Codes: 31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 50%
31 BIOLOGICAL SCIENCES > 3199 Other biological sciences > 319902 Global change biology @ 50%
SEO Codes: 96 ENVIRONMENT > 9603 Climate and Climate Change > 960307 Effects of Climate Change and Variability on Australia (excl. Social Impacts) @ 100%
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