Oban-based scientists assist crisis response
CONFIRMATION that diesel has begun leaking from the stranded Transocean Winner platform, which ran aground on the Isle of Lewis last Monday, has sparked concern over the likely destination and environmental impact of the oil spill, writes Dr Keri Wallace, of the Scottish Association for Marine Science (SAMS).
Scientists from SAMS are providing ongoing expert input into the response process for the crisis.
At the time of writing, the exact quantity of diesel oil leaked off Lewis was still unknown but the make-up of the substance being released, already tells us quite a lot.
Marine diesel is usually broken up into tiny droplets by wind and wave action, and moved away from the spill-site by ocean currents within a day or less. For this reason there is seldom any oil to physically recover from the water’s surface. The tiny oil droplets dispersed throughout the body of water don’t just disappear. They tend to stick to small particles floating in the seawater, before eventually sinking and settling- out on the seabed.
Images of thick black oil slicks are not usually associated with spills of marine diesel such as this. Instead diesel oil is not sticky or viscous, and at the coast is washed off the shore- line quickly by waves and tidal currents. Where the fuel does penetrate into coastal soils or sands it is naturally degraded by microbes in one to two months.
Diesel is commonly regarded as one of the most toxic types of fuel oil, capable of killing most marine life that comes into direct contact with it. In open water however, diesel spills are usually dispersed so quickly that few fish and birds are affected. This is particularly the case in exposed coastal locations such as those found around the Western Isles.
It is the location and unique circumstances of each diesel leak that determine which specific environmental impacts are most likely. For example, consequences can be serious where diesel is trapped and concentrated in coastal areas or where prevailing conditions transport the fuel into nesting bird colonies, fish farms or areas of conservation importance. For this reason it is important for emergency oil spill responders to understand exactly how dispersed diesel spills will be moved by currents and tidal flows around the site.
Oceanographers at SAMS have expertise in oil spill trajectory modelling and are currently providing ocean forecasts to Marine Scotland Science, the central co- ordinators of the crisis response.