A field demonstration of the efficacy of bioremediation to treat oiled shorelines following the Sea Empress incident.

Bioremediation was investigated as a method of treating a mixture of Fortie s Crude Oil and Heavy Fuel Oil stranded on Bullwell Bay, Milford Haven, UK after the grounding of the Sea Empress in 1996. A randomised block design i n triplicate was used to test the efficacy of two bioremediation treatments : a weekly application of mineral nutrients dissolved in seawater and a sin gle application of a slow-release fertilizer. Each treatment supplied an eq uivalent amount of nitrogen and phosphorus. Concentrations of residual hydr ocarbons normalised to the biomarker 17 alpha(H),21 beta(H)-hopane showed t hat after two months the oil was significantly (p<0.001) more biodegraded i n the treated plots than in the controls. On average, the oil in the nutrie nt amended plots was 37% more: degraded than that found in the controls. Th ere was no evidence that the bioremediation treatments increased the toxici ty of the oiled sediment. The results confirm that bioremediation can be us ed to treat a mixture of crude and heavy fuel oil on a pebble beach. In par ticular, the data suggest that the application of a slow-release fertilizer alone may he a cost-effective method of treating low-energy, contaminated shorelines after a spill incident.