Interactions between marine bacteria and dissolved-phase and beached hydrocarbons after the Exxon Valdez oil spill

Turnover times for toluene in Resurrection Bay after the Exxon Valdez grounding were determined to be decades, longer than expected considering that dissolved hydrocarbons were anticipated to drift with the current and stimulate development of additional hydrocarbon-utilizing capacity among the microflora in that downcurrent location. These turnover times were based on the recovery of 14CO2 from added [14C]toluene that was oxidized. The concentrations of toluene there, 0.1 to 0.2 microgram/liter, were similar to prespill values. Oxidation rates appeared to be enhanced upstream near islands in the wake of the wind-blown slick, and even more within the slick itself. Specific affinities of the water column bacteria for toluene were computed with the help of biomass data, as measured by high-resolution flow cytometry. They were a very low 0.3 to 3 liters/g of cells.h-1, indicating limited capacity to utilize this hydrocarbon. Since current-driven mixing rates exceeded those of oxidation, dissolved spill components such as toluene should enter the world-ocean pool of hydrocarbons rather than biooxidize in place. Some of the floating oil slick washed ashore and permeated a coarse gravel beach. A bacterial biomass of 2 to 14 mg/kg appeared in apparent response to the new carbon and energy source. This biomass was computed from that of the organisms and associated naphthalene oxidation activity washed from the gravel compared with the original suspension. These sediment organisms were very small at approximately 0.06 microns 3 in volume, low in DNA at approximately 5.5 g per cell, and unlike the aquatic bacteria obtained by enrichment culture but quite similar to the oligobacteria in the water column.(ABSTRACT TRUNCATED AT 250 WORDS)