Impact of hypersaline brines on benthic meio- and macrofaunal assemblages: A comparison from two desalination plants of the Mediterranean Sea

Abstract

Growing water demands and decreasing water supplies are exacerbating water scarcity, which is one of the challenges for sustainable development. Desalination is expanding worldwide, particularly in the Mediterranean region and plants discharge at sea large amounts of hypersaline brines, which might have consequences on marine life. We report the results of the effects of brine discharge on sediments' biogeochemistry and benthic fauna (meiofaunal and macrofaunal abundance, diversity, taxonomic composition) of two desalination plants of the Mediterranean Sea, characterized by different desalination capacity and different environmental conditions. Brine discharge causes accumulation of organic matter and alteration of its biochemical composition in sediments downstream of the discharge point and along the direction of the main current, but only within few meters. The responses of faunal assemblages depend on the characteristics of the plants, the brine discharged and the consequent changes in the amount and quality of trophic resources. We conclude that direct and indirect impacts of desalination on benthic fauna, although of local interest, can reach a larger spatial scale depending on the amount of the brine produced and the hydrodynamic conditions. Therefore, future plants to be truly eco-sustainable should assess case-by-case the potential impacts of brine discharge on marine habitats.