Oil or algae? Photo of West Bay, Louisiana taken October 22. Source: Matthew Hinton via the Times-Picayune. Photo gallery here.
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.
Google Earth image showing muddy plume of sediment raised by a shrimp trawler at work along the Louisiana coast. Image taken before the BP spill.
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.
Shrimp trawler working in mysterious substance floating in West Bay, Louisiana on October 23. Note plume behind the trawler. Source: Erika Blumenfeld via Trouthout.