VEGETATION RESPONSE AND SEDIMENT POLYCYCLIC AROMATIC HYDROCARBON ATTENUATION IN A CAREXMARSH IN HOWE SOUND, BRITISH COLUMBIA, CANADA FOLLOWING A SPILL OF BUNKER C Fuel Oil

Abstract

ABSTRACT A spill of Bunker C fuel oil in Howe Sound, British Columbia, Canada in August 2006 affected approximately 10.5 acres (4.2 hectares) of marsh habitat unique to the Pacific Northwest. A cleanup approach to reduce impacts from response actions was balanced with a desire to remove all residual oil. Cleanup techniques that were used include flushing, cutting, raking, passive sorbent collection, natural recovery, and manual excavation (sediment removal). Evaluation of the habitat response relative to oiling conditions and treatments was undertaken by examining vegetation indices in treatment and control areas and temporal changes in sediment concentrations of poly cyclic aromatic hydrocarbons (PAHs). One year post-spill results suggest that the amount or degree of oiling on the dominant vegetation, Carex lyngbyei and ?leocharis palustris, had little or no apparent effect, or was insignificant in comparison to the impact of the treatment. Vegetation cutting alone had no positive or negative effect on vegetation recovery indices. Treatments which were aggressive in physically disturbing the sediments and root systems of the marsh (heavy trampling, heavy scraping, excavation and/or excessive trampling) retarded vegetation recovery in oiled and unoiled habitats and prolonged oil persistence in comparison to non aggressive treatment, vegetation cutting alone or natural recovery. Mechanical damage was the best predictor of ?AH persistence.