Physiological response to salinity variation in the European native oyster Ostrea edulis from a hyperhaline lagoon

This study investigates the acute (48h) and acclimated (1 month) physiological responses of the European native oyster, Ostrea edulis, individuals inhabiting an hyperhaline lagoon to varying salinities (20, 30, 40, 50, and 60 PSU). Significant differences were identified across all physiological measurements (clearance rate, ingestion rate, absorption efficiency, absorption rate, oxygen consumption and scope for growth) for both salinity and time factors, except for the interaction effects on absorption efficiency and scope for growth. The study revealed the capability of the flat oyster to adjust their energetic physiology to a wide range of salinities, from 20 to 50 PSU. Time-dependent changes were observed, with significant physiological adjustments between T1 and T2, particularly at 20 PSU, where deleterious effects were observed in the acute exposition but acclimation was observed after one month. On the contrary, individuals at 50 PSU showed a similar response to 30 and 40 PSU for the acute exposition, but a lower fitness in the long-term. For 60 PSU, physiological decline was observed during the experiment, highlighting a potential salinity threshold for the species' survival. Overall, this study demonstrates the complex interactions between salinity, exposure time, and physiological and biometric responses in the flat oyster, highlighting the importance of assessing both acute and long-term responses to environmental changes. The findings contribute to a better understanding of the adaptability and resilience of this species in the face of fluctuating salinity levels, which is crucial for ecological and restoration practices. • Oysters' physiology develops properly in a wide range of salinities (20–50 PSU). • Acute exposition at 20 PSU showed a constraint on adaptation to the osmotic shock. • In the long-term, 60 PSU would be a limit survival threshold for the species. • The salt pans could be a favorable environment for the recovery of Ostrea edulis .