Natural recovery reduces impact of the 1970 ARROW oil spill

Abstract

In 1970 the tanker ARROW ran aground releasing 2,000 m3 of Bunker C crude oil along 300 km of Nova Scotia's coastline, of which only 10% was subjected to cleanup, the rest was left to degrade naturally. Sediment and interstitial water collected in 1993 and 1997 from Black Duck Cove in Chedabucto Bay, a representative untreated site, showed that the remaining residual oil has undergone substantial biodegradation. The environmental significance of this intrinsic remediation process was assessed with a battery of microscale biotests: CYP1A and mixed function oxygenase induction in winter flounder, Amphipod Survival, Echinoid Fertilization, Grass Shrimp Embryo-Larval Toxicity, Microtox® Solid-Phase and 100% Tests. While much oil remains in the sediment (426-12, 744 ppm), results of the biotests show that it is of low toxicity and habitat recovery is evident from the level of benthic diversity.