Multiple stressors effects on the physiological performance of Mytilus trossulus

Mytilus galloprovincialis and M. trossulus co-occur and hybridize along set biogeographical ranges of temperature and salinity along the Pacific coast, USA. However, the role of physiological traits in mussel distribution remains poorly understood. We investigated metabolic rate, antioxidant activity (superoxide dismutase, catalase), oxidative damage (malondialdehyde content, MDA), and clearance rate of M. trossulus under multiple stressors: 7 days of hyposalinity (20, 28, 34 ppt), followed by an acute heat shock (17, 20, 25 °C). We found a significant effect of temperature on metabolic rate, an interaction effect on antioxidant activity, and MDA, and independent temperature and salinity effects on clearance rate. Additionally, we compared thermal performance and Hsp70 relative protein abundance between M. trossulus and M. galloprovincialis. M. galloprovincialis displayed approximately 10 °C higher thermal optimum and upper critical limits, consistent with observed Hsp70 abundance levels. Therefore, our study suggests species-specific physiological responses to multiple stressors may connect thermal limits and observed spatial demography of these congeners.