Disappearance and biological effects of crude oils after sedimentation on subtidal soft-bottom seabed sediments : experiments in a laboratory seabed mesocosm

The environmental impacts of oil spills stranded on beaches were discussed in comparison to oil spills on subtidal sediments. The impacts differ significantly with respect to seawater action, sediment settling/resuspensions, oil characteristics, weathering conditions, oil disappearance, effects on organisms, and the cleanup strategies. In this study, subtidal soft-bottom seabed sediments were spiked with fresh crude oils in two sediment concentrations to study their impact on the seafloor. This study is part of a 3-year program to develop operational tools for oil spill contingency planning. Seabed sediments were transferred from a non-polluted site to a laboratory mesocosm where oils were introduced to the top of the seabed sediments. Samples were observed and measured for a 4 month period at 9 to 11 degrees C with constant seawater flow through. Gas chromatography-flame ionization detector (GC/FID) and gas chromatography-mass spectrometry (GC/MS) chemical analysis were conducted to determine oil compound disappearance from the sediments. Sediment oxygen consumption (SOC) measurements indicated the ultimate biodegradation. The data will be implemented as part of the OSCAR 2000 model established in the Advanced management of Oil Spills (AMOS) program. 23 refs., 6 tabs., 5 figs