Biological effects of mechanically and chemically dispersed oil on the Icelandic scallop (Chlamys islandica)

• Short- and long-term effects of dispersed oil were assessed on Icelandic scallops.
• Dynamic exposure conditions simulating sub-Arctic coastal oil spills were utilized.
• Potential short-term effects may be delayed in Arctic species.
• Generally equal effects were observed for chemically and mechanically dispersed oil.

This study aimed to simulate conditions in which dispersant (Dasic NS) might be used to combat an oil spill in coastal sub-Arctic water of limited depth and water exchange in order to produce input data for Net Environmental Benefit Analysis (NEBA) of Arctic and sub-Arctic coastal areas. Concentration dependent differences in acute responses and long-term effects of a 48 h acute exposure to dispersed oil, with and without the application of a chemical dispersant, were assessed on the Arctic filter feeding bivalve Chlamys islandica. Icelandic scallops were exposed for 48 h to a range of spiked concentrations of mechanically and chemically dispersed oil. Short-term effects were assessed in terms of lysosomal membrane stability, superoxide dismutase, catalase, gluthatione S-transferases, glutathione peroxidases, glutathione reductase, glutathione, total oxyradical scavenging capacity, lipid peroxidation and peroxisomal proliferation. Post-exposure survival, growth and reproductive investment were followed for 2 months to evaluate any long-term consequence. Generally, similar effects were observed in scallops exposed to mechanically and chemically dispersed oil. Limited short-term effects were observed after 48 h, suggesting that a different timing would be required for measuring the possible onset of such effects. There was a concentration dependent increase in cumulative post-exposure mortality, but long-term effects on gonadosomatic index, somatic growth/condition factor did not differ among treatments.