The Effect of Climate Change and Predator Presence on the Metabolic Rate of Red Abalone (Haliotis rufescens)

Climate change threatens to disrupt marine ecosystems, prompting concern for their long-term health. Understanding the effect of environmental conditions and predator presence on an organisms energetic costs can provide insight to the fitness of species. Until now, the metabolic response of red abalone (Haliotis rufescens) to a combination of temperature, pH, and predator presence have not been quantified. Abalone were exposed to a fully factorial design crossing two temperatures (mean = 14.2°C and 16.2°C), two levels of pH (mean = 7.52 or 7.82), and predator presence or absence for 5-7 days. The effects of these variables were tested on three size classes: small (17-21 mm), medium (22-30 mm), and large (35-41 mm) abalone. Post exposure, the metabolic rate of abalone from each treatment combination was estimated using closed chamber respirometry. ANOVA analyses were used to determine the individual and interactive effects of temperature, pH, and the presence of predators on abalone metabolism. The effect of predators and pH were insignificant on red abalone metabolic rate across all size classes. Similarly, the effect of temperature was also insignificant in the medium and large groups, though elevated temperature may drive increased metabolism in small abalone. In addition to prior studies, our results add to the literature suggesting H. rufescens might be particularly vulnerable in their early life-history stages to climate change and may experience a bottleneck up to ~20 mm.