Data for: Seasonal variability in resilience of a coral reef fish to marine heatwaves and hypoxia

Climate change projections indicate more frequent and severe tropical
marine heatwaves (MHWs) and accompanying hypoxia year-round. However, most
studies have focused on peak summer peak conditions under the assumption
that annual maximum temperatures will induce the greatest physiological
consequences. This study challenges this idea by characterizing seasonal
MHWs (i.e., mean, maximum, and cumulative intensities, durations, heating
rates, and mean annual occurrence) and comparing metabolic traits (i.e.,
standard metabolic rate (SMR), Q10 of SMR, maximum metabolic rate (MMR),
aerobic scope, and critical oxygen tension (Pcrit)) of winter- and
summer-acclimatized convict tang (Acanthurus triostegus) to the combined
effects of MHWs and hypoxia. Fish were exposed to one of six MHW
treatments with seasonally varying maximum intensities (winter: 24.5,
26.5, 28.5°C; summer: 28.5, 30.5, 32.5°C), representing past and future
MHWs under IPCC projections (i.e., +0, +2, +4°C). Surprisingly, MHW
characteristics did not significantly differ between seasons, yet SMR was
more sensitive to winter MHWs (mean Q10 = 2.92) than summer MHWs (mean Q10
= 1.81), despite higher absolute summer temperatures. Concurrently, MMR
increased similarly among winter +2°C and +4°C treatments (i.e., 26.5,
28.5°C) and all summer MHW treatments, suggesting a ceiling for maximal
MMR increase. Aerobic scope did not significantly differ between seasons
nor among MHW treatments. While mean Pcrit did not significantly vary
between seasons, warming of +4°C during winter (i.e., 28.5°C)
significantly increased Pcrit relative to the winter control group.
Contrary to the idea of increased sensitivity to MHWs during the warmest
time of year, our results reveal heightened sensitivity to the deleterious
effects of winter MHWs, and that seasonal acclimatization to warmer summer
conditions may bolster metabolic resilience to warming and hypoxia.
Consequently, physiological sensitivity to MHWs and hypoxia may extend
across larger parts of the year than previously expected, emphasizing the
importance of evaluating climate change impacts during cooler seasons when
essential fitness-related traits such as reproduction occur in many
species.