Implementation of a portable module for assessing the eutrophication risk: initial evaluation in the upwelling-driven bay of Ria de Arousa (NW-Iberian Peninsula)

This study presents the implementation of a portable module designed for autonomous analysis sea-surface inorganic nutrients onboard vessels opportunity, as an additional tool assessing levels eutrophication risk. The was carried out during August-mid-September 2019 in Ria de Arousa and outer shelf area (NW-Iberian coastal upwelling system). During this period, distributions measured concentrations nitrate phosphate were compared according to three Oceanographic Environments (OEs). OEs defined interplay between upwelling/downwelling events river discharge on system. nutrient measurements agreed well with OEs, showing that is useful opportune can serve complement available monitoring networks. An initial evaluation risk indicated low (following Environmental European Agency criteria) most points summer, except some vulnerable areas under certain OEs. Nutrient are sensitive periods Sustained Upwelling events, reaching medium (7.14 - 9.05 µmol L-1 0.39 0.64 phosphate) inner parts Arousa. These characterized by abrupt bathymetric changes channel intensify processes, increasing concentrations. High (1.53 L-1) detected close coastline Relaxation periods. Under these conditions, continental flows, previously retained upwelling, able expand. location samples difference concentration indicate likely source wastewater outflows. Our results highlight need deeper studies synergy processes water discharges its modulation nutrients.