Influence of Tiber River plume on phytoplankton primary production

River plumes have a significant impact on phytoplankton primary production by carrying high nutrient loads, suspended particles and dissolved organic matter into the seawater.
Dynamic processes mainly modulate nutrient availability as well as light attenuation along the water column thus influencing marine phytoplankton distribution along the plume gradient, also according to the seasonal variability of the river flow.
A series of oceanographic cruises have been conducted since 2020 to examine how physical processes influence phytoplankton dynamics within the entire physiographic unit, which extends between Capo d'Anzio and Capo Linaro. A high phytoplankton abundance was observed both at the surface and bottom depths up to a bathymetry of 40-60 meters. At the surface, it was directly related to the Tiber River plume, while at the bottom it seemed to be linked to sediment resuspension phenomena. Going offshore, the distribution of phytoplankton along the water column assumed the Typical Tropical Structure (TTS) trend with a well-formed Deep Chlorophyll Maximum (DCM) around 60 to 90 meters depth.
In light of these findings, to deepen our understanding of these phenomena, a detailed campaign along the river mouth was carried out in May 2022 in collaboration with the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS to collect hydrological (temperature, conductivity - salinity, density-, dissolved oxygen) and biogeochemical (PAR, downwelling and upwelling irradiance, nutrients, phytoplankton photosynthetic efficiency, composition and biomass, TSM, CDOM) data.