Very Low Concentrations of Maritime Exhaust Gas Cleaning System Effluent Impair Fertilization and Larval Development in the Green Sea Urchin Strongylocentrotus droebachiensis

Exhaust gas cleaning systems (EGCS) are increasingly used to meet IMO sulfur regulations while permitting the continued use of heavy fuel oil. EGCS effluents are acidic and contain metals, polycyclic aromatic compounds, and other contaminants that are known to affect marine organisms. Whole effluent toxicity tests were conducted on fertilization and larval development of the green sea urchin Strongylocentrotus droebachiensisusing a 0–10% dilution series of open-loop EGCS effluent. Fertilization success was significantly reduced at the lowest concentration tested (0.0001%). Larval abnormalities increased with effluent concentration, reaching 100% at 10% effluent, where larvae failed to develop skeletons and reach the pluteus stage. Larval growth rates declined with increasing exposure and ceased at a 10% effluent. Exposure to the lowest test concentration caused an estimated additional mortality of 4.6% day–1, indicating a high risk of population-level impacts. As carbonate chemistry remained unchanged below 0.1% effluent, the toxicity was attributed primarily to contaminants. These findings indicate that EGCS effluents pose a significant threat to marine life.