Influence of the Rhone River intrusion on microplastic distribution in the Bay of Marseille

Abstract

We present the spatiotemporal distribution of microplastics (MP) in surface waters and sediments between 2020 and 2022 in the Bay of Marseille. Microplastics were extracted with an improved, ecological protocol from 27 surface water and 16 sediment samples. The hydrodynamical circulation model MARS3D-RHOMA was used with in-situ data to test the influence of meteorological and hydrodynamic forcing on the concentration of MPs during the study period. The reported concentrations are analogous to abundances previously found in the Bay of Marseille, as well as in similar coastal systems. Average MP concentrations are 5.79 ± 12.71 MP.m−3 in surface water and 855 ± 413 MP.kg−1 dw in sediments. Simulations revealed hydrodynamic features associated with several episodes of Rhone intrusion in the Bay of Marseille. The observed MP concentrations and distribution in February 2020 suggest that the Rhone River’s plume entered the Bay of Marseille.