Ecophysiological and cellular stress responses in the cosmopolitan brown macroalga Ectocarpus as biomonitoring tools for assessing desalination brine impacts

Abstract

Seawater desalination via reverse osmosis (SWRO) is highlighted as one of the most feasible solutions for obtaining freshwater. However, brine produced by SWRO is generally discharged to the subtidal area potentially causing detrimental effects on benthic organisms. In this study, we evaluated for the first time, ecophysiological and cellular responses of brown macroalgae as diagnosis tools to assess environmental impacts of desalination, through transplantation experiments with the cosmopolitan brown alga Ectocarpus. Transplants located at 10 and 30 m from the discharge point of a desalination plant located in Antofagasta, Chile, showed impaired photosynthetic parameters (ETR, Fv/Fm, αETR and ETRmax) and oxidative stress responses like accumulation of H2O2 and enhanced lipid peroxidation. Also, increased salinity produced high accumulation of ascorbate but a decrease in glutathione content. Also, genes encoding for enzymes related to salinity tolerance, SOS2, and oxidative stress, SOD, APX, PRX and GR, were highly up-regulated in transplanted Ectocarpus, especially at 10 m from the brine discharge. Altogether, our results demonstrate that Ectocarpus is a sensitive species to brine impacts, and that the transplantation method combined with its physiological and molecular responses are reliable tools to incorporate in environmental monitoring plans to address for desalination brine impacts on coastal ecosystems.