There have been conflicting reports coming from coastal Lousiana since October 22, suggesting that large areas of East and West Bays near Southwest Pass are covered with long streamers of what appears to be weathered oil, possibly originating from the BP / Deepwater Horizon spill. Some of the local fishermen insist it’s oil; the Coast Guard thinks it’s an algal bloom. Samples taken by the Coast Guard are awating analysis. [UPDATE 10/28/10 10:00 am ET – LSU scientists confirm the substance is mostly algae with only trace amounts of oil]

At SkyTruth we’re concerned that fishing activity could potentially stir up any oil that’s sitting on the seafloor, resuspending it in the water column. We don’t know if that’s what has happened near Southwest Pass. But we do know that bottom-trawling for shrimp in the Gulf routinely churns up the muddy seafloor, creating long sediment-laden plumes that trail for miles behind the trawlers and can be seen on satellite images. Check out our gallery of trawling images, and read more about it on this blog.

NOAA reports they haven’t yet found any signs of oil sitting on the Gulf seafloor. Other scientists claim they found inches-thick layers of oil on the seafloor on research cruises in September and “vast amounts” of oil on the seafloor in October. It seems reasonable to assume that if those scientists are correct, and if bottom-trawling for shrimp is occurring now in places where layers of oil are sitting on the seafloor, that oil will be disturbed by trawling.

We don’t know what the effects of that could be. It might help the oil biodegrade more quickly. But it will also repeatedly expose marine life, including commercially important species, to oil that would otherwise remain on the ocean floor.

This suggests to us that it’s very important to quickly, accurately and thoroughly survey the Gulf seafloor for residual oil, so we can let shrimpers know what areas to avoid for now.