LAUSR

A multi-index approach (larval lenghthening and malformations, developmental disruption, and genotoxicity) was applied using sea-urchin embryos as test-organisms. PAH levels measured in the under-ice weathered aqueous fraction (UIWAF) were lower than in the low-energy water accommodated fraction (LEWAF) and similar amongst UIWAFs of different oils. UIWAFs and LEWAFs caused toxic effects, more markedly in UIWAFs, that could not be attributed to measured individual PAHs or to their mixture. Conversely, UIWAF was less genotoxic than LEWAF, most likely because naphthalene concentrations were also lower. In agreement, NAN LEWAF, the most genotoxic, exhibited the highest naphthalene levels. Dispersant addition produced less consistent changes in PAH levels and embryo toxicity in UIWAFs than in LEWAFs, and did not modify LEWAF genotoxicity. Overall, under ice weathering resulted in lowered waterborne PAHs and genotoxicity but augmented embryo toxicity, not modified by dispersant application.