Toxicological Assessment of Petroleum Product WAFs in Crassostrea gigas: Evidence for Sub-chronic Tolerance and Rapid PAC Depuration.

With increasing petroleum transport through coastal waters of the northeastern Pacific, understanding the ecological hazards of these mixtures is essential, yet the sublethal impacts on benthic filter feeders remain poorly characterized. The sub-chronic (7-d exposure) effects of crude oil (CO), marine diesel (MD), and diluted bitumen (DB) water-accommodated fractions (WAFs) on the scope for growth (oxygen consumption, food absorption efficiency, and clearance rate), as well as gonadal and digestive gland histopathology in Pacific oysters (Crassostrea gigas) were examined. Initial total polycyclic aromatic compound (TPAC) concentrations in WAFs were ranked CO > MD > DB, which also accumulated within oyster tissues in the same order. Sub-chronic exposures to different WAF dilutions of three petroleum products did not alter any measured endpoints in Pacific oysters. PACs accumulated in oyster tissues had a rapid depuration after the exposure period due to the potential biotransformation of parent hydrocarbons, which could elucidate the lack of significant adverse effects. These results indicate that adult C. gigas maintained physiological and tissue-level integrity under transient, declining petroleum exposure conditions, providing context for interpreting potential impacts of short-term nearshore spill scenarios.