Effects of chronic exposure to dispersed oil on selected reproductive processes in adult blue mussels (Mytilus edulis) and the consequences for the early life stages of their larvae

► Adults Mytilus edulis were exposed to oil–water dispersion during gametogenesis. ► Reproductive endpoints in 0.25mg/l exposed females were affected after 1month. ► Parental exposure to 0.25mgoil/l caused growth and development impairment. ► These effects were more severe in larval stages maintained at 0.25mg oil/l. ► Combining adult reproductive endpoints to larval development should be recommended. Mussels (Mytilus edulis) were continuously exposed to dispersed crude oil (0.015–0.25mg/l) for 7months covering the whole gamete development cycle. After 1month exposure to 0.25mgoil/l, the level of alkali-labile phosphates (ALP) and the volume density of atretic oocytes in female gonads were higher than those in the gonads of control females, indicating that oil affected the level of vitellogenin-like proteins and gamete development. Spawning of mussels was induced after 7months oil exposure. Parental oil exposure did not affect subsequent fertilization success in clean seawater but this was reduced in 0.25mgoil/l. Parental exposure to 0.25mgoil/l caused both slow development and a higher percentage of abnormalities in D-shell larvae 2days post-fertilization; reduced growth 7days post-fertilization. These effects were greatly enhanced when larval stages were maintained at 0.25mgoil/l. Similar studies are warranted for risk assessment prognosis.