The Effects of Multiple Environmental Stressors on the Respiration Rate of Mytilus galloprovincialis

Intertidal organisms are subject to environmental variations that may influence their physiological performance. As processes such as respiration depend on gas exchange between organisms and their environment, they are potentially affected by water temperature and velocity. In this study, we compare the effects of multiple environmental stressors (temperature and flow velocity) on the respiration rate in two mytilids, the Mediterranean mussel, Mytilus galloprovincialis and the temperate bay mussel M. trossulus. Thermal performance curves (5, 11, 17, 23, and 29 °C) for respiration rate were quantified at five different flow velocities (2, 4, 6, 10, 20 cm s-1) in a fully crossed design. Well-defined thermal performance curves were present at moderate to high water velocities, whereas, at the lowest velocity (2 cm s-1) respiration rates remained low across all temperatures. Although Mediterranean mussels displayed higher thermal optima than Bay mussels under moderate flow speeds (4-6 cm s-1), those differences were absent at higher flow velocities (>10 cm s-1). These results highlight the importance of considering hydrodynamic conditions when estimating thermal tolerance in marine mussels