Diet changes thermal acclimation capacity, but not acclimation rate in a marine ectotherm (Girella nigricans) during warming

Abstract

Global climate change is increasing thermal variability in coastal marine environments and the frequency, intensity, and duration of marine heatwaves. At the same time, nutritional resources are being altered by anthropogenic environmental changes. Marine ectotherms often cope with changes in temperature through physiological acclimation, which can take several weeks to occur and is a nutritionally demanding process. Here, we tested the hypothesis that different ecologically relevant diets (omnivorous, herbivorous, carnivorous) can impact thermal acclimation rate and capacity, using a temperate omnivorous fish as a model (opaleye;Girella nigricans). We measured acute thermal performance curves for maximum heart rate because cardiac function has been observed to set upper thermal limits in ectotherms. Opaleye acclimated rapidly after warming, but their thermal limits and acclimation rate were not affected by diet. However, the fish's acclimation capacity for maximum heart rate was sensitive to diet, with fish in the herbivorous treatment displaying the smallest change in heart rate throughout acclimation. Mechanistically, ventricle fatty acid composition differed with diet treatment and was significantly related to cardiac performance in ways consistent with homoviscous adaptation. Our results suggest that diet is an important, but often overlooked, determinant of thermal performance in ectotherms on environmentally relevant timescales.

Diet changes thermal acclimation capacity, but not acclimation rate, in a marine ectotherm (Girella nigricans) during warming

“…Data accessibility. The data and code that support the findings of this study are openly available in Dryad at https://doi.org/10.25349/ D9Q905 [63].…”

Despite plasticity, heatwaves are costly for a coral reef fish

“…In the case of a heatwave, which is prompt and temporary, the cardiac response is ideally rapid and reversible. By measuring the cardiac thermal limits of fish acclimated to different temperatures for one week, we captured the acclimation abilities of hawkfish to a relevant marine-heatwave timescale, where full thermal acclimation may not have yet occurred 51 .…”

“…Despite having been acclimatized to a similar mean temperature of 28 °C, wild-caught fish had a lower peak f Hmax , T ARR , and T PEAK than laboratory fish acclimated to 28 °C. This may be related to differences in thermal variation 65 , diet 51 , or other holding effects. Alternatively, fish may have had residual effects from the clove oil used to capture fish 3–8 h earlier in the day, though this is known to reduce T PEAK and f Hmax and not T ARR 28 .…”

Diet effects on ectotherm thermal performance

“…Diet and temperature can influence both thermal limits and biological rates, including growth, metabolism, cardiac function, locomotion, digestion and more (e.g. Hardison et al ., 2021; Papadopoulou et al ., 2022; Hardison, Schwieterman & Eliason, 2023; Brankatschk et al ., 2018; Lee et al ., 2015; Rho & Lee, 2017; Clissold, Coggan & Simpson, 2013).…”

“…TPCs provide valuable data that can be used to inform models and management efforts for ectotherms. However, there are several limitations involved in extrapolating individual performance curves to larger ecological processes, including that factors like diet, which are often not considered, can alter the shape of TPCs throughout the time course of acclimation (Carreira et al ., 2020; Hardison et al ., 2021, 2023; Huey & Buckley, 2022, Sinclair et al ., 2016, Fig. 2B).…”