| Summary: | An experimental subsurface release of chemically dispersed oil at Cape Hatt, northern Baffin Island, resulted in short-term relatively high oil concentrations in the waters of two adjacent bays, whereas untreated oil released onto the surface of a third bay could not be detected in the water below a depth of 1 m. The only immediate response in epibenthos observed by divers was narcosis in urchins and starfish following the dispersed oil release. Analysis of data from in situ counts in the three test bays and in a fourth (reference) bay during the open water seasons of 1980-83 showed that densities of the starfish Leptasterias polaris were not affected by either oil release and that effects on urchin densities were minor or transitory: Strongylocentrotus droebachiensis apparently made immediate and transitory attempts to avoid dispersed oil in the water and possibly tried to avoid untreated and dispersed oil in sediments two years after oiling. Analysis of airlift samples collected at 3 and 7 m depths in the four bays during 1980-83 showed no major effects of either oil release on densities of epibenthic crustaceans; taxa examined included all crustaceans, all cumaceans, one species of cumacean, all amphipods and eight individual amphipod taxa. The overall trend was toward increases in epibenthic crustacean densities over the study period. Effects that may have been attributable to oil were found in only 2 of 22 analyses of density data for individual taxa. In those cases, effects were minor: untreated oil in sediments apparently altered the depth distribution of Anonyx juveniles, and dispersed oil in the water column apparently had a delayed adverse effect on reproduction in the amphipod family Stenothoidae. Densities of Pontoporeia femorata were not affected by oil, but inspection of size-frequency data indicated a possible delayed adverse effect on its reproduction.Key words: arctic epibenthos, amphipods, echinoderms, oil effects, dispersed oil effects, experimental oil releases, Baffin Island, macrobenthos Mots clés: épibenthos arctique, amphipodes, échinodennes, effets dus au pétrole, effets dus au pétrole dispersé, déversements expérimentaux de pétrole, île Baffin, macrobenthos
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