Bivalve mortality and burrowing behavior under compound stress of salinity and temperature: Data from a mesocosm experiment

The frequency of extreme weather events, such as heatwaves and flash floods, is increasing due to global climate change. While many studies have investigated the potential impact of high temperature and salinity fluctuations on benthic animals in tidal flats, few have explored how these stressors affect the relationship between native and introduced species, including the potential establishment of introduced species in response to extreme short-term events. This study investigates the compound effects of heatwaves and salinity changes on the survival and burrowing behaviors of native and introduced bivalve species. Specifically, the introduced species Ruditapes philippinarum and the native species Cerastoderma edule were cultivated in four salinity settings under five temperature blocks using a mesocosm experiment. The results show that R. philippinarum exhibits lower mortality than C. edule under temperatures exceeding 35 °C, especially those in lower salinity levels of 10 and 20 PSU. Interestingly, the burrowing behaviors of the two species did not differ significantly, indicating that they share similar ecological functions under future climate change. However, if heatwaves coincide with other stressors, like strong freshwater inputs, as shown in this study, a potential widening of the establishment window for introduced species may occur in future climate change scenarios. These findings provide valuable insights into how compound extreme weather events may drive species shift on tidal flats, with important implications for understanding population dynamics under future climate change.