Opposite responses by an intertidal predator to increasing aquatic and aerial temperatures

Predicting the effects of climate change on ecosystems requires an understanding of how temperature alters organismal physiology and behavior. Because predation can shape patterns of abundance and diversity across a community, it is critical to understand the effect of temperature on predator behavior. Climate change in intertidal systems will comprise changes in both air and water temperatures, yet most previous marine intertidal studies have focused on either air or water temperature alone. In a 20 d laboratory study, we examined the effect of changing emersed and submersed body temperatures on the feeding and growth rates of Nucella ostrina, a common northeastern Pacific intertidal gastropod that feeds primarily on the barnacle Balanus glandula. Our results revealed a large increase in both predation and growth rates with higher submersion temperatures (13.5°C compared with 11°C). In contrast, we observed a large decrease in the feeding and growth of N. ostrina exposed to the highest emersed body temperature (28°C) when compared with intermediate (20°C) and cooler (12°C) aerial temperatures. Thus, while B. glandula may suffer greater predation-related mortality in warmer water temperatures, it may actually experience a release from predation if air temperatures warm. Our study points to the importance of considering temperatures reached during both submersion and emersion separately, and examining behavioral responses in light of physiologically relevant temperatures and thermal regimes.