THE BRAER OIL-SPILL - HYDROCARBON CONCENTRATIONS IN INTERTIDAL ORGANISMS

The concentrations of non-specific narcotic toxins such as the aromati c hydrocarbons toluene, naphthalene and phenanthrene were determined i n specimens of limpets (Patella vulgata) and razor shells (Ensis spp.) collected from Shetland at the time of the Braer oil spin (84 000 t o f Gullfaks production crude) and 3, 6 and 15 months after the spill. T he analytical methods involved the use of deuterated analogues of the toxins to account for losses of analytes during recovery by steam dist illation and determination by cryogenic GC-MS selected ion monitoring of molecular ions, Although the organisms were impacted by oil, the co ncentrations of total determinants in dead razor shells collected just after tbe oil spill were below the tissue effective concentrations fo r 50% reduction in filtering activity (TEC(50)) for mussels (the most valid toxicological data available for comparative purposes). A portio n of the unresolved monoaromatic hydrocarbons of Gullfaks crude would probably add to the burden of toxins, but this was not measured in thi s study, The distribution of aromatic hydrocarbons in the organisms (p henanthrenes > naphthalenes > toluene) was the reverse of that in the oil and correlates with the expected bioconcentration behaviour of hyd rophobic organics whereby less water soluble compounds with higher oct anol-water partition coefficients are concentrated. Concentrations of naphthalene to methylphenanthrenes in limpets collected in January at the time of the spill from sites close to the wreck were wen below the TEC(50) values for mussels but comparison with the lower concentratio ns in limpets from a more remote site in Shetland indicated that the o il had impacted organisms near to tbe spill, consistent with intertida l survey data. Comparison with limited literature data for limpets and more extensive data for mussels also supported this conclusion, as di d the identification of the oil residues in the limpets by biomarker f ingerprinting. As with the razor shells, bioconcentration of the more hydrophobic compounds was observed. Concentrations in Shetland limpets generally decreased with increasing distance from the spill site. Con centrations of aromatic hydrocarbons decreased with time after the spi ll, such that by July concentrations were at what can reasonably be as sumed to be background levels, comparable to the concentrations found at all times in the more remote site, Concentrations in a limited numb er of samples collected 15 months after the spill, following a further winter of storms in which sediment-sorbed oil could have been reintro duced to the limpets, showed no Increase. Copyright (C) 1996 Elsevier Science Ltd