That means that over 100×10^6 US gal (380 Ml) (2.4 million barrels) remained in the Gulf.[59] As of January 2011[update], tar balls, oil sheen trails, fouled wetlands marsh grass and coastal sands were still evident. Subsurface oil remained offshore and in fine silts.[66] In April 2012, oil was still found along as much as 200 mi (320 km) of Louisiana coastline and tar balls continued to wash up on the barrier islands.[67] In 2013, some scientists at the Gulf of Mexico Oil Spill and Ecosystem Science Conference said that as much as one-third of the oil may have mixed with deep ocean sediments, where it risks damage to ecosystems and commercial fisheries.[68]