Presence, levels, and distribution of organic and elemental pollutants in Zooplankton from the Northwestern Mediterranean sea

Abstract Persistent organic pollutants (POPs), such as the legacy contaminants polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDTs), as well as trace elements (TEs) pose a significant risk to marine ecosystems due to their toxicity, persistence, and bioaccumulative nature. Despite regulatory bans, PCBs and DDTs continue to be detected in the marine environment, while TEs levels remain conspicuous as a result of both natural and anthropogenic sources. In this study, we investigated the presence, concentrations, and spatial distribution of 32 PCB congeners, 6 DDT compounds, and 16 TEs in zooplankton collected from 40 sites across the Northwestern Mediterranean Sea. Results revealed widespread contamination, with PCBs detected in all samples (53.2 ± 63.0 ng g-1 dw) and DDTs present in over half the samples (5.1 ± 6.0 ng g-1 dw). Hotspots of POPs contamination were identified near Marseille, and in the wider Gulf of Lion, Barcelona, and the Ebro River mouth. All TEs were detected in zooplankton, with high concentrations of essential TEs, but also elevated levels of toxic elements such as Hg, Pb, and Cd in certain locations such as Barcelona, the Gulf of Lion, Balearic Islands, and southwestern Corsica. Spatial patterns of contamination were strongly linked to urban, industrial, riverine, and historical mining inputs. These results underline the important role of zooplankton as bioindicators for assessing pollutant transfer at the base of the marine food web. They also highlight the urgent need for integrated, long-term monitoring strategies to better understand contaminant dynamics and mitigate ecological risks in the Mediterranean Sea.