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Going Green: Deepwater mysteries

Two years after the BP oil spill, worries loom in the Gulf of Mexico

By Lisa Duchene
July 05, 2012

In early 2011, about nine months after BP’s Deepwater Horizon disaster, Gulf of Mexico fishermen reported strange lesions on snapper and other Gulf finfish. Steve Murawski, the former National Oceanic and Atmospheric Administration chief fishery scientist, had just assumed his new post as research professor at the University of Southern Florida in Tampa.

Murawski had seen pictures of fish with sores and wondered what was going on. So last July and August, his research team chartered three longline vessels to investigate. 

The surveys covered the distribution of red snapper, collecting 4,000 samples of 90 different species from the Dry Tortugas to Louisiana at depths of 60 to 600 feet.

They found 10 percent of tilefish and southern hake samples from the oil-affected area had skin lesions, compared to none of those species gathered off Florida’s western coast in an area relatively untainted by oil and used as a control area. The snapper had a slightly elevated rate of lesions, but not in any significant numbers.

Murawski’s team tested the fish for polycyclic aromatic hydrocarbons (PAHs), a toxic component of crude oil. The data are still coming in, but early observations include high levels of PAHs in the fish’s bile, and low levels in the tissue, says Murawski. 

The fish, stresses Murawski, are perfectly safe to eat. The U.S. government has taken 8,000 samples of fish in that area and PAH amounts have all been well below action levels. Murawski’s work is related to fish health, he emphasizes; his research is looking at whether the fish have impaired reproductive potential or changed growth rates.

Another huge question is whether any health effects are due to the Deepwater Horizon blowout or are a result of something else, perhaps chronic exposure to hydrocarbons — about 1,000 natural seeps leak 400,000 barrels of oil into the Gulf annually. It’s a difficult question to answer, notes Murawski, because there are no similar, baseline sampling surveys that pre-date the well blowout for comparison.

There have been no mass die-offs of fish or shellfish and no fish populations have crashed. Oysters are struggling after an influx of freshwater that was part of the spill response. 

A SeaFood Business analysis of Louisiana’s 2011 seafood landings compared to an average year during the 10-year period (2000-2009) before the spill, according to NMFS data for Louisiana, found brown shrimp landings down 20 percent, white shrimp down down 22 percent, blue crab up 6.4 percent, crawfish down 13.5 percent and red snapper down 41 percent.

So far, post-spill shrimp harvest numbers seem to be within the normal variation for shrimp, says Larry Mc-Kinney, executive director of the Harte Research Institute for Gulf of Mexico Studies.

While economically devastating for Gulf fishermen, scientists say the emergency fishing closures to prevent tainted seafood from reaching the market held a “conservation benefit” by removing the stress of fishing. The closed area peaked at 88,522 square miles, or 37 percent of Gulf waters on June 2, 2010.

“There was kind of a system reboot because of the reduced fishing pressure,” says McKinney.

There is concern about what fractions of generations of fish may be missing after larvae were exposed to toxins, says Murawski. Hopefully some answers will come from $500 million in research funded by BP, and also from the Natural Resource Damage Assessment and Restoration Program that will determine BP’s liability. Results of NRDA research are not yet public. 

Contributing Editor Lisa Duchene lives in Bellefonte, Pa. 

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