AB 14:289-298 (2012)  -  DOI: https://doi.org/10.3354/ab00405

ABSTRACT: Stress often induces metabolically expensive countermeasures. Bivalve shell production is costly and can thus be indirectly impacted by environmental stress. Suboptimal salinity and temperature may constitute stressors that allocate energy away from shell production to cellular processes such as osmoregulation or to the repair of cellular damage. In the course of climate change, water temperatures of the Baltic Sea are predicted to increase, and salinity is predicted to regionally decrease. These shifts may lead to increased stress for temperate marine species adapted to relatively cool water temperatures and high salinity conditions. To better understand the importance of climate change-related stress, we assessed the isolated and interactive effects of salinity and temperature on shell increment (cumulative growth: shell), cellular oxidative stress (accumulation of oxidized lipids and proteins: lipofuscin), instantaneous physiological condition (condition index: CI), and mortality of young Mytilus edulis and Arctica islandica from the western Baltic Sea. Temperature and salinity interactively affected shell increment, lipofuscin accumulation, and mortality of M. edulis as well as shell increment of A. islandica. Shell increment of M. edulis was less affected by hyposalinity than shell increment of A. islandica. In both species the CI decreased and lipofuscin accumulation increased with increasing temperature. Lipofuscin accumulation negatively correlated with shell increment in M. edulis. We conclude that Baltic Sea populations of ecologically relevant bivalve species may experience severe stress by the predicted regional scenario of warming and desalination if evolutionary adaptation does not happen at a similar rate.

KEY WORDS: Mytilus edulis · Arctica islandica · Growth · Condition · Cellular stress · Mortality