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Toxic dispersants in Gulf oil spill creating hidden marine crisis

Tom Levitt and Nicole Edmison, the ecologist
More than 200 million tons of crude oil have gushed into the Gulf of Mexico since the rupture of Deepwater Horizon. The chemicals used to clean up the spill have received less attention but could have devastating long-term effects on the marine ecosystem

Nearly two million gallons of controversial oil dispersants have been applied to the waters of the Gulf in an attempt to break up the spill – by far the largest use of such chemicals in history.

Oil dispersants are composed of two main ingredients: solvents and surfactants. With the aid of wave action, solvents work to reduce the surface tension of slicks, breaking the oil into droplets so the surfactants can penetrate the mass more deeply.

Surfactants quickly work to coat the outside of the droplets to prevent them clumping together again. Very small drops of oil are then capable of moving away from the surface of the water and dispersing throughout the water column.

However, this process of dispersing oil neither eliminates nor decreases its toxicity. In fact it creates a much more toxic cocktail of oil and chemical dispersant. Experts say this cocktail mix is now beginning a slow but sure degradation of the ecosystem from the bottom up. Despite this environmental officials in the US have allowed them to be used on an unprecedented scale

Tiny droplets of combined oil and dispersant adhere to plankton, says Dr Susan Shaw, founder and director of the Marine Environmental Research Institute (MERI). The plankton-eaters then indiscriminately gobble up the tainted particles while fish-eaters consume the poisoned plankton eaters, and so on through the marine food web…

…The Center for Biological Diversity (CBD) accuse the US government of conducting an ‘ill-conceived experiment’ and criticise US officials for allowing dispersants to be used at depths where their impacts have never been tested and could ‘cripple’ the gulf ecosystem.

‘If larval fish, for example, succumb to the toxins found in dispersed oil, what will their predators eat? What will the animals that eat those animals eat? That is a daunting question to contemplate in an ecosystem that’s considered one of the most biodiverse in the world, and which provides more than one-fifth of US seafood production,’ said CBD senior attorney Andrea Treece.

The EPA claim ‘not to have seen significant environmental impacts from the use of dispersants so far and none of the currently authorised dispersants appear to show significant endocrine-disrupting activity.’

Another watchdog, the Environmental Working Group (EWG), say the effects have not even begun to be made clear yet. ‘There remain large uncertainties about dispersant usage at the sea floor, the effects of large plums of oil and the potential of dispersed oil to effect the food web. Just because the oil is gone from the surface does not mean we are in the clear,’ said senior scientist David Andrews.

Drew Wheelan, conservation coordinator for the American Birding Association, has been reporting from the Gulf Coast since the beginning of the spill. On 4 August he came upon a massive fish die-off near Fourchon, Louisiana, that may be the tip of the dispersant iceberg.

‘One of the main problems with [dispersants] is that they use large amounts of oxygen from the system when they break down,’ he says. ‘They have sprayed much of this stuff very close to shore here.’…
(6 September 2010)

Gulf Doctors Advised to Learn to Treat Oil-Related Illnesses

Brian Merchant, treehugger
Less dramatic than the fiery explosion of the Deepwater Horizon oil rig and the multiple month-spanning underwater oil geyser that followed it are many of the BP Gulf spill’s side effects. And oil-related sicknesses are undoubtedly among the thorniest — many fishermen-turned cleanup workers have already been afflicted by close contact with oil and the chemical dispersents used to combat it. But there will probably be many more. As such, “Health Effects of the Gulf Oil Spill”, a paper recently published in the Journal of the American Medicine Association (JAMA), is advising physicians around the Gulf and beyond to learn to treat oil and dispersent-related sicknesses.

From the report:

The oil spill in the Gulf of Mexico poses direct threats to human health from inhalation or dermal contact with the oil and dispersant chemicals, and indirect threats to seafood safety and mental health. Physicians should be familiar with health effects from oil spills to appropriately advise, diagnose, and treat patients who live and work along the Gulf Coast or wherever a major oil spill occurs.
The paper is by Dr. Gina Solomon, an oil spill health expert whom I interviewed during my coverage of the Gulf spill in the beginning months of the disaster. At the time, she and the NRDC were lobbying hard to make sure that the fishermen were receiving proper protective gear (rubber boots, gloves, full-body suit, and a filtration mask should have been provided) when they were enlisted to work with the oil. At that point, they were hardly being given anything at all — and as such, many workers ended up growing ill….
(8 September 2010)
The full report is behind a paywall here.

Oxygen drops near BP spill but no “dead zone”-US

Deborah Zabarenko, Reuters
Hungry microbes feasting on spilled BP oil caused a drop in oxygen levels in the Gulf of Mexico, but did not create a marine “dead zone” near the wellhead, U.S. scientists reported on Tuesday.

The amount of oxygen decreased by 20 percent from the long-term average in areas where oil from the broken BP Macondo wellhead was detected by government and independent observers, scientists from the National Oceanic and Atmospheric Administration told reporters.

“All the scientists working in the Gulf have been carefully watching dissolved oxygen levels because excess carbon in the system might lead to a dead zone,” said NOAA’s Steve Murawski. “While we saw a decrease in oxygen, we are not seeing a continued downward trend over time.”

Summer dead zones are common in shallower areas of the Gulf of Mexico, caused by run-off from farm chemicals flowing down the Mississippi River.

Dead zones have such low oxygen levels that most marine life — including commercial important fish and shellfish — cannot survive, and scientists feared the BP spill would create such a zone in deep water around the Macondo wellhead after the April 20 blowout at the Deepwater Horizon rig.


That did not happen, Murawski said, and at this point is unlikely. He said oxygen levels had hit a “sweet spot,” with microbes consuming enough of the dispersed oil to cause what he called a sag in oxygen, but not enough to cause a low-oxygen dead zone…
(7 September 2010)