The Chemistry and Toxicity of Sediment Affected by Oil from the North Cape Spilled into Rhode Island Sound

On 19 January 1996, the barge North Cape spilled more than three million liters of No. 2 fuel oil into Rhode Island Sound near Matunuck, Rhode Island. The toxicity and chemistry of this oil in two subtidal sediments were followed for more than 9 months. Maximum concentrations of polycyclic aromatic hydrocarbons (PAHs) in the sediments reached 730 μg/g dry weight (DW). Water samples taken immediately after the spill were phototoxic to embryos of the bivalve Mulinia lateralis. Total PAHs and toxicity to the amphipod Ampelisca abdita were high immediately after the spill, decreasing to background values (10 μg/g DW and <20% mortality, respectively) after 6 months. Changes in toxicity to A. abdita related closely to changes of PAH concentrations in sediments. Weathering and degradation of the oil were followed by using ratios of PAHs, and alkanes as indicators. To distinguish effects of local boat traffic from spill effects, these ratios plus distributions of PAHs in sediments from a nearby marina were used.