Gulf Ecosystem Still Feeling Effects of Deepwater Horizon Spill

Four years after the Deepwater Horizon oil spill, marine researchers are finding that the waters and shores of the Gulf of Mexico have not recovered as well as many may have thought. Oil in the form of "sand patties" continues to wash up along the coast, and an abundant breed of one fish exposed to the oil is showing signs of swimming impairment.

In one study, published in the journal Environmental Science & Technology, marine scientists found sand patties in onshore salt marshes neighboring the Gulf.

The researchers say they know the oil in the patties is from the Macondo Well, which was tapped by the Deepwater rig, because of tests perfected by the Bigelow Laboratory for Ocean Sciences and the Woods Hole Oceanographic Institution that identify the source of a given oil. A joint team from Bigelow and Woods Hole conducted the research.

Another study shows as much as a 37 percent decrease in overall swimming performance of mahi-mahi exposed to the Deepwater spill. That report, issued by the University of Miami Rosenstiel School of Marine and Atmospheric Science, also was published in Environmental Science & Technology.

"If you harm a fish's ability to swim, you also harm its ability to perform actions that are critical for survival, such as catching prey and evading predation," said Miami's Edward Mager, lead author of the study.

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In a lab experiment, researchers exposed larvae and young mahi-mahi to Deepwater Horizon crude oil harvested from the Gulf's surface three months after the spill. They found that larval mahi-mahi exposed for 48 hours, then transferred to clean water suffered a 37 percent loss in swimming velocity when they grew to juvenile mahi-mahi. The juvenile mahi-mahi exposed to the oil for 24 hours had a 22 percent decline in swimming velocity.

The Deepwater Horizon, an offshore oil well in the Gulf of Mexico near New Orleans, was owned by BP and Anadarko Petroleum Corp. It exploded in April 2010, killing 11 rig workers and spewing crude oil into the Gulf for nearly three months.

By Andy Tully of Oilprice.com