Mytilus edulis and Psammechinus miliaris as bioindicators of ecotoxicological risk by maritime exhaust gas scrubber water

Approximately 15 % of the global anthropogenic emissions of sulfur oxides (SOx) come from shipping. To meet sulfur emission regulations for marine vessels, many shipping companies have chosen to use exhaust gas cleaning systems (EGCS), commonly known as scrubbers. The resulting washwater from scrubbers contains various pollutants such as polycyclic aromatic hydrocarbons (PAHs), trace metals, and nitrates, is then directly discharged into the surrounding surface water, transferring potential atmospheric pollutants to the marine environment. The aim of this study was to investigate the impact of EGCS discharge water on blue mussels (Mytilus edulis) and sea-urchin (Psammechinus miliaris) embryos and larvae. Chronic toxicity tests were performed using a fertilization test and a larval development bioassay exposed to scrubber water dilutions (0.001, 0.01, 0.1, 1, 2, 5, 10, 20, 40 and 100 % of the original sample). Negative effects on fertilization success and larvae development in both species at very low concentrations were observed (EC₁₀ < 1 %) indicating the severe impact of EGCS discharges on these species. EGCS effluents showed different effects depending on the species and life stages. Sea urchin embryos were more sensitive than the blue mussel embryos. However, blue mussel larvae were much more sensitive than sea urchin larvae. These results emphasize the potential toxic effects of direct exposure -not dietary- to scrubber water discharges on marine invertebrate. EGCS discharge limits are urgent to prevent further potentially irreversible damage to the marine environment.