Salinity is changing in aquatic systems due to anthropogenic activities (like irrigation or dam management) and climate change. Although there are studies on the effects of salinity variations on individual species, little is known about the effects on overall ecosystems, these impacts being more uncertain in transitional waters such as estuaries or fiords. The few works that do address this topic have considered these impacts using ecotoxicity models. However, these models state that an increase in the concentration of a pollutant generates an increase in the impacts, disregarding the effects of water freshening. The present research work introduces a general framework to address the impacts of salinity variations, including emission-related positive effects. We validated this framework by applying it to an estuarine area in Galicia (northwestern Spain), where sharp drops in the salt concentration have caused mass mortalities of shellfish in recent decades. This research work addresses for the first time the potential effects on the environment derived from a decrease in the concentration of essential substances, where the effects of an emission can also generate positive impacts. Moreover, it is expected that the framework can also be applied to model the environmental impacts of other essential substances in life cycle assessment (LCA), such as metals and macronutrients.
Keywords: biodiversity; climate change; ecotoxicity; life cycle impact assessment (LCIA); salinity; species-sensitivity distribution; transitional waters.