Starvation reduces thermal limits of the widespread copepod Acartia tonsa

Abstract

Organismal thermal limits affect a wide range of biogeographical and ecological processes. Copepods are some of the most abundant animals on the planet and play key roles in aquatic habitats. Despite their abundance and ecological importance, there is limited data on the factors that affect copepod thermal limits, impeding our ability to predict how aquatic ecosystems will be affected by anthropogenic climate change. In a warming ocean, one factor that may have particularly important effects on thermal limits is the availability of food. A recently proposed feedback loop known as “metabolic meltdown” suggests that starvation and exposure to high temperatures interact to drastically reduce organismal thermal limits, increasing vulnerability to warming. To investigate one component of this feedback loop, we examined how starvation affects thermal limits (critical thermal maxima: CTmax) of Acartia tonsa, a widespread estuarine copepod. We found that there was no effect of short‐duration exposure to starvation (up to 2 days). However, after 3 days, there was a significant decrease in the CTmax of starved copepods relative to the fed controls. Our results provide empirical evidence that extended periods of starvation reduce thermal limits, potentially initiating “metabolic meltdown” in this key species of coastal copepod. This suggests that changes in food availability may increase the vulnerability of copepods to increasing temperatures, amplifying the effects of climate change on coastal systems.

Hot and scared: how do heatwaves and predation risk impact resource acquisition and allocation?

“…Heatwave events are expected to become more frequent and intense [1], and warmer temperatures obligate increased energy expenditure for most animals [2]. Thus, animals' reliance on food is linked to heatwaves-increased food consumption can offset the metabolic costs of elevated temperatures and promote heat tolerance [3][4][5]. However, foraging entails predation risks for many animals [6,7], and elevated temperatures can increase predation through improved capture efficiency and shifts in the functional response [8][9][10].…”