Temperature and salinity stress alter metabolism and epiphyte grazin in Phyllaplysia taylori

Phyllaplysia taylori, a sea hare found in eelgrass beds along the Pacific coast, is an integral part of eelgrass ecosystems. Temperatures and salinities in San Francisco Bay are highly variable and expected to shift with continued climate change. Phyllaplysia taylori exposure to elevated temperatures and reduced salinities was hypothesized to reduce survival and increase metabolic and epiphyte grazing rates, indicating the energetic costs of temperature and salinity stress. Low survival was observed at the lowest exposure salinities, and metabolic and grazing rates indicated higher levels of stress and increased energy requirements at low salinities. An orthogonal experimental design was used to determine the interactive effects of temperature and salinity stress. The highest metabolic and feeding rates were measured at a combination of higher temperature and lower salinity, and the lowest metabolic and feeding rates were at a combination of lower temperature and higher salinity. An effect of P. taylori body size and sexual maturity on metabolic and grazing rates was also observed, with higher metabolic rates occurring in smaller pre-reproductive individuals, and higher feeding rates occurring in larger reproductive individuals. The results of this study will help inform eelgrass ecological studies throughout San Francisco Bay by indicating the impacts of shifting temperature and salinity on modulating the relationship between P. taylori and eelgrass performance in response to environmental change.