Responses of a seagrass community dominated by Cymodocea nodosa to sunscreens exposure

Seagrass ecosystems have been recognized for their significant ecological and economic value. However, increasing anthropogenic disturbances, such as marine pollution, have led to a progressively declining of seagrasses on a global scale. Despite in the last years the number of publications about the effects of UV filters used in sunscreens on marine species has increased substantially, studies of these products on marine plants are still scarce, although it could be another cause of seagrass decline. In this study, the effect of a commercial sunscreen mixture (40g/mL, 80g/mL, no cream) on a community dominated by the seagrass Cymodocea nodosa was evaluated in a 28-day laboratory experiment. Subsequently, physiological (i.e. carbohydrates), morphological (i.e. biomass) and community (i.e. carbon metabolisms and sediment properties) responses were analyzed. Cymodocea nodosa community was heterotrophic under sunscreen treatment, independently of concentration, showing a decrease in gross primary production, probably due to a lower photosynthetic efficiency. Moreover, the sunscreen presence increased sucrose content in leaves and in rhizomes as metabolic adaptations to the sunscreen addition. Regarding biometry, the increase in leaves length was considered a defence or adaptation to the harmful effects of sunscreen. On the other hand, OC, OM and chlorophyll content in sediments increased under sunscreen treatments, probably due to higher decomposition rate of seagrass biomass by toxic compounds of sunscreens. Overall, this study show that sunscreen products are a significant source of organic and inorganic chemicals with potential ecological consequences on seagrasses, highlighting the need to improve our knowledge on the in situ concentrations of chemicals released from sunscreen products as well as their combined effects with other environmental variables (e.g. temperature) on this valuable ecosystem.