Mussels show capacity for persistence under, and recovery from, marine heatwaves

The ability of marine organisms to persist under, and recover from, periods of stressful conditions will shape their occurrence in future oceans characterized by exacerbated marine heatwaves (MHWs). Organism persistence and recovery may, in turn, be shaped by traits of the organisms themselves including, for example, body size. In the present study, we tested the responses (survival, heart rate, Arrhenius breakpoint temperature - ABT, clearance rate, respiration rate, and condition index) of large (5 cm) and small (3 cm) Perna viridis mussels after exposure to a three-week marine heatwave (MHW; + 4 degrees C) and a oneweek recovery period. Exposure to elevated temperatures did not affect the survival of large or small mussels, however, at the end of the MHW both size classes exhibited increased heart rate under elevated temperatures, small mussels exhibited increased ABT, and large mussels exhibited significantly increased clearance rate. Following one week of recovery at control temperature, the altered responses had returned to be similar to those of mussels held under control conditions. The results obtained here indicate that both sizes of mussels can readily recover from exposure to short-term elevated temperatures imposed by MHWs, enabling the continued persistence of P. viridis mussels in future oceans.