Federal regulators today reopened commercial and recreational fishing in all federal waters of the Gulf of Mexico that were closed to fishing due to the BP Deepwater Horizon oil spill.

Most Gulf waters were already open. This red snapper was pulled from waters offshore of Louisiana March 3, 2011. [Environment News Service]

The three-month-long spill was triggered by the April 20, 2010 blowout of BP's Macondo exploratory well 40 miles off the Louisiana coast. The explosion killed 11 workers and resulted in the largest offshore oil spill in U.S. history - some 4.9 million barrels of crude oil.

At its peak, the closed area was 88,522 square miles, or 37 percent of federal waters in the Gulf of Mexico.

The National Oceanic and Atmospheric Administration, NOAA, today reopened the 1,041 square miles of gulf waters immediately surrounding the Deepwater Horizon wellhead. After several failed attempts to stop the undersea gusher, the wellhead was capped in July.

No oil or sheen has been documented in the area since August 4, 2010.

"I am pleased to announce that all federal waters affected by the spill are now open to all fishing," said NOAA Administrator Jane Lubchenco.

"I thank fishermen and the public for their patience and FDA for its support and cooperation throughout this process while we worked diligently to ensure the integrity of gulf seafood," she said.

This reopening was announced after consultation with the U.S. Food and Drug Administration and under a reopening protocol agreed to by NOAA, the FDA, and the Gulf states.

NOAA sampled this area between November 11 and November 14, 2010, March 12 and March 16, 2011, and March 28 and April 1, 2011, for potentially affected finfish, including tuna, swordfish, and escolar.

Sensory analyses of 86 finfish samples and chemical analyses of 112 finfish samples found no detectable oil or dispersant odors or flavors, and NOAA says the results of chemical analysis for oil-related compounds and dispersants are "well below the levels of concern."

An aircraft releases dispersant over an oil discharge from the Deepwater Horizon off the shore of Louisiana, May 5, 2010. [U.S. Coast Guard]

Dispersants are chemicals used to break oil spills into tiny droplets, enabling microorganisms to eat the oil and also diluting more quickly than if it were left untreated.

As announced on October 29, 2010, NOAA and FDA developed and implemented a chemical test to detect the presence of dispersants in fish, oysters, crabs and shrimp.

The level of concern for dispersants is 100 parts per million for finfish and 500 parts per million for shrimp. The test can reliably detect dioctyl sodium sulfosuccinate at levels of 2,000 times below the lowest level of concern.

The results of chemical testing showed that 99 percent of samples contained no detectable dispersant residues, and the few samples that did contain dispersant residues showed levels more than 1,000 times lower than FDA levels of concern.

"Throughout this process, public health and safety has been our primary goal," said FDA Commissioner Margaret Hamburg, MD. "This has been an extraordinary team effort and the reopening of these federal waters serves as a dramatic example of what cooperation between federal agencies can accomplish."

NOAA continues to work closely with the FDA and the Gulf states to ensure seafood safety. Thousands of test results, all publicly available, prove Gulf seafood is safe from oil and dispersant contamination.

However, the Center for Biological Diversity is concerned that dispersants may harm endangered species or their habitats.

An aircraft releases dispersant over an oil discharge from the Deepwater Horizon off the shore of Louisiana, May 5, 2010. (Photo courtesy U.S. Coast Guard) The Center today filed an official notice of its intent to sue the U.S. Environmental Protection Agency for authorizing the use of dispersants without ensuring that these chemicals would not cause harm to endangered species or the habitats they need to survive.

"The Gulf of Mexico disaster was a wake-up call about the inadequacy of current oil-spill response technology," said Deirdre McDonnell, an attorney with the Center for Biological Diversity. "Before the next spill happens, the government needs to ensure that these dispersants don't do more harm than good to threatened and endangered species."

The EPA must pre-approve the use of chemical dispersants in the event of an oil spill, but has not taken steps to ensure that the use of these chemicals will not jeopardize endangered wildlife.

The Center's notice requests that the agency immediately study the effects of dispersants on endangered and threatened species such as sea turtles, endangered whales, piping plovers and corals.

McDonnell points to studies showing that oil treated by the dispersant Corexit 9527 damages the insulating properties of seabird feathers more than untreated oil, making the birds more susceptible to hypothermia and death.

Other studies have found that dispersed oil is toxic to fish eggs, larvae and adults, as well as to corals, and can harm sea turtles' ability to breathe and digest food, McDonnell says.

Formulations of the dispersants being used by BP, Corexit 9500 and 9527, have been banned in the United Kingdom due to concerns over their impacts on the marine environment.