Lang, Bethan J., Donelson, Jennifer M., Caballes, Ciemon F., Doll, Peter C., and Pratchett, Morgan S. (2021) Metabolic responses of Pacific Crown-of-Thorns sea stars (Acanthaster sp.) to acute warming. Biological Bulletin, 241 (3).

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Abstract

Climate change and population irruptions of crown-of-thorns sea stars (Acanthaster sp.) are two of the most pervasive threats to coral reefs. Yet there has been little consideration regarding the synergies between ocean warming and the coral-feeding sub-adult and adult stages of this asteroid. Here we explored the thermosensitivity of the aforementioned life stages by assessing physiological responses to acute warming. Thermal sensitivity was assessed based on the maximal activity of enzymes involved in aerobic (citrate synthase) and anaerobic (lactate dehydrogenase) metabolic pathways, as well as the stan-dard metabolic rate of sub-adult and adult sea stars. In both life stages, citrate synthase activity declined with increasing temperature from 15C to 40C, with negligible activity occurring >35C. On the other hand, lactate dehydrogenase activity increased with temperature from 20C to 45C, indicating a greater reliance on anaerobic metabolism in a warmer environment. The standard metabolic rate of sub-adult sea stars in-creased with temperature throughout the testing range (24C to 36C). Adult sea stars exhibited evidence of thermal stress, with metabolic depression occurring from 33C. Here, we demonstrate that crown-of-thorns sea stars are sensitive to warming but that adults, and especially sub-adults, may have some resilience to short-term marine heatwaves in the near future.

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