Chemical Changes and the Environment in the Gulf of Mexico

The Destruction of the Gulf / Photo by kris krüg (kk+)

In yesterday's post, I referenced some of the health and environmental concerns surrounding the heavy use of dispersants to break up the oil slick as oil pours from the broken riser. Today the EPA finally issued its own judgment about the safety of the chemicals that BP is using, and it appears that their research is incomplete.

The first round of government tests of the chemical dispersants that are being used to break up the massive oil spill in the Gulf of Mexico found that they aren't overly damaging to shrimp and small fish, but more tests are needed to determine what happens when they're mixed with oil.

The Environmental Protection Agency also said Wednesday that tests on eight chemical dispersants found that they don't damage the body's glands and hormones in ways that can harm development or reproductive, immune and neurological systems.

The EPA also said that BP had reduced the amount of chemical dispersants it was using by almost as much as the government ordered it to do in May. The EPA and the Coast Guard on May 26 told BP to reduce dispersant use by 75 percent from peak use. BP reduced it by 68 percent over the next month.

Further:

The EPA said that Corexit 9500 and another dispersant, JD-2000, were generally less toxic to small fish, and JD-2000 and SAF-RON GOLD were least toxic to mysid shrimp, small crustaceans found in the northern Gulf of Mexico.

The next round of tests will examine the toxicity of the oil spewing from BP's broken well and a combination of the oil and each of the eight dispersants.

The data from the first round of tests, Anastas said, show the dispersants degrade in "weeks to months," while oil can remain for years....

Much remains unknown about the effects of the chemicals on living things, including people who work with them, and on the environment.

Still, Anastas said, "the data is telling us that these are not posing the same types of hazard as the terrible hazards we're seeing in the oil."

So BP will continue using heavy amounts of Corexit and other dispersants, but in a volume somewhat reduced from their peak dispersant use in May. The EPA's report, while somewhat reassuring, leaves a lot of questions unanswered. I expect that we will be learning more about how beneficial or harmful these dispersants are as the environmental disaster progresses. To that extent the gulf is in the midst of a frightening science experiment that no one really wanted to perform.

One harmful chemical change that we know is happening is caused not by dispersants but by methane, which is mixed with the oil gushing from the well.

Scientists are confronting growing evidence that BP's ruptured well in the Gulf of Mexico is creating oxygen-depleted "dead zones" where fish and other marine life cannot survive.

In two separate research voyages, independent scientists have detected what were described as "astonishingly high" levels of methane, or natural gas, bubbling from the well site, setting off a chain of reactions that suck the oxygen out of the water. In some cases, methane concentrations are 100,000 times normal levels.

Other scientists as well as sport fishermen are reporting unusual movements of fish, shrimp, crab and other marine life, including increased shark sightings closer to the Alabama coast.

Larry Crowder, a marine biologist at Duke University, said there were already signs that fish were being driven from their habitat.

The trouble with methane is what it triggers:

Joye said her preliminary findings suggested the high volume of methane coming out of the well could upset the ocean food chain. Such high concentrations, it is feared, would trigger the growth of microbes, which break up the methane, but also gobble up oxygen needed by marine life to survive, driving out other living things.

Joye said the methane was settling in a 200-metre layer of the water column, between depths of 1,000 to 1,300 metres in concentrations that were already threatening oxygen levels.

"That water can go completely anoxic [extremely low oxygen] and that is a pretty serious situation for any oxygen-requiring organism. We haven't seen zero-oxygen water but there is certainly enough gas in the water to draw oxygen down to zero," she said.

This is pretty disturbing, as many larger organisms depend on dissolved oxygen in the water to survive. The hypoxia may account for some of the kills of marine organisms (especially fish) that have not been connected directly to petroleum poisoning. Either way, it is disturbing and promises to amplify the usual seasonal dead zones at the mouth of the Mississippi River.