COLONIZATION OF AMPHIPODS AND POLYCHAETES TO SEDIMENTS EXPERIMENTALLY EXPOSED TO OIL HYDROCARBONS

Field experiments using colonization trays with or without cover, and larger enclosures were used to investigate the effects of the water soluble fractions of oil hydrocarbons (Ekofisk Crude oil) on recruitment of zoobenthos to shallow soft bottoms. The experiments were performed in situ at 8 m depth off Bergen, Norway. The main macrofaunal immigrants (July-December 1980) were amphipods (mainly Corophium bonelli) and polychaetes (mainly capitellids, cirratulids, orbinids, and spionids). Covered trays had lower colonization by polychaetes than open trays, but addition of low levels of oil hydrocarbons did not affect polychaete density. C. bonelli showed similar rates of colonization to open and covered trays, but the latter showed that exposure to oil had a negative effect on population density, especially on juveniles. The reduced density in the oil exposure treatment may have been due to reduced survival of the marsupial embryos, or increased swimming activity (escape reactions to the oil). Natural predation on the amphipods in the uncovered trays was high enough to mask any negative effect of exposure to oil. © 1990.