The French Mussel Watch: More than two decades of chemical contamination survey in Mediterranean coastal waters

Active biomonitoring of chemical contamination (e.g., Cd, Hg, Pb, DDT, PCB, PAH) in French Mediterranean coastal waters has been performed for more than two decades. This study aimed at presenting the current contamination in 2021 and the temporal evolution of concentrations from 2000. Based on a relative spatial comparison, low concentrations were measured in 2021 at most sites (>83 %). Also, several stations with moderate to high levels were highlighted in the vicinity of major urban industrial centers (e.g., Marseille, Toulon) and near river mouths (e.g., Rhone, Var). Over the last 20 years, no major trend was revealed, mostly, especially for the relative high-level sites. This likely constant contamination over time, plus slight increases of metallic elements at a few sites, still raise questions on the efforts that remain to be made. The decreasing trends of organic compounds, in particular PAH, provide evidence of the efficiency of some management actions.

Automated summary

Active biomonitoring of chemical contamination in French Mediterranean coastal waters has been conducted for over two decades. This study presents the current contamination levels in 2021 and the temporal changes from 2000. The results show that most sites had low concentrations in 2021 (>83%), but moderate to high levels were detected near urban industrial centers and river mouths. There was no major trend in contamination over the past 20 years, raising questions about future efforts needed. However, decreasing trends in organic compounds indicate the effectiveness of some management actions.