In shifting seas: Effects of warming waters and hyposalinity on the physiology of juvenile commercial bivalves

Variations in temperature and salinity are among the most important climate stressors affecting estuarine ecosystems. Shellfish beds are unique, highly productive habitats that are particularly vulnerable to these stressors. The changing conditions can impair bivalve physiological performance and alter community structure, with substantial ecological and socio-economic impacts for coastal communities. Changes that affect juvenile stages are of particular concern, as they may compromise population dynamics and long-term persistence. We evaluated the sublethal effects of short-term seawater warming and hyposalinity events, each acting independently, under typical conditions in the study area. In two laboratory experiments, juveniles of four commercially important bivalve species— Ruditapes decussatus , Ruditapes philippinarum , Venerupis corrugata , and Cerastoderma edule —were exposed to a range of temperature and salinity levels, while key components of the scope for growth, including clearance, respiration and excretion rates, were measured. Temperature responses were species- and size-dependent, whereas hyposalinity thresholds closely matched those reported for adults, suggesting that species-specific tolerance limits are conserved across life stages. Notably, the effects of reduced salinity were stronger than those of elevated temperature. The findings emphasize the heightened vulnerability of V. corrugata juveniles to warming and reduced salinity, indicating that climate-driven fluctuations in temperature and salinity could disproportionately affect certain bivalve species under global change.