In 1970 the Arrow oil spill off Cape Breton contaminated 305 kilometres of shoreline. Aerial and land surveys have demonstrated that natural weathering has occurred throughout this period, but it was relatively slow, especially in sheltered areas like Black Duck Cove lagoon. This study analyzed the microbial hydrocarbon degradation potential in the lagoon sediments using direct and culture-based techniques. Mineralization of hydrocarbon substrates (hexadecane, octacosane and naphthalene) indicated the presence of an active degradative microbial community, however, genes from known bacterial hydrocarbon degradation pathways (alkB, ndoB, phnAc) were not detected by direct extraction of sediment DNA and PCR amplification. Sediment enrichment cultures had increased mineralization rates for naphthalene and hexadecane, and a hexadecane-degrading pure culture, Rhodococcus sp. BDC14, with a typical alkB gene was isolated. PCR analysis of total community DNA extracted directly from the enrichments indicated the presence of the Alcanivorax borkumensis alkB1 genotype. The results demonstrated that there were notable differences between culture-based and direct molecular analytical techniques in characterizing the contaminated sediments.

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