Temperature determines physiological rates and predation in Galápagos rocky reefs

Water temperature plays a critical role in determining physiological rates in marine ectotherms and influences the strength of ecological interactions. We investigated the effects of temperature on multiple traits of the whelk Hexaplex princeps — a common predator in the rocky reefs of the Galápagos, a region characterized by significant temperature fluctuations. We measured metabolic rate, activity levels, prey handling time, and feeding rates across a temperature gradient. First, we conducted respirometry assays to measure the temperature dependence of metabolism. Next, we performed mesocosm experiments to assess how temperature affects predator activity, prey handling time, and feeding rates. Third, we conducted a field experiment to measure predation’s response to seasonal temperature changes. The results from our mesocosms experiment showed a large variation in thermal performance across traits. Nevertheless, all traits exhibit low performance at our coldest experimental temperature with a peak at intermediate temperature, suggesting a unimodal response. Similarly, we observed higher feeding rates in the field at medium temperatures. Our results highlight the importance of temperature in moderating physiological rates and interactions between species, and the challenges of predicting complex ecological processes from individual traits (e.g. metabolic rate, movement, prey handling time). As ocean temperatures continue to rise, understanding how temperature shapes physiological responses across organisms is essential for predicting the future dynamics of marine communities.