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Chemicals used on Gulf spill carry unknown risks, scientists say

The timing could not be worse for the bluefin tuna. The majestic, deepwater giant — threatened by overfishing — had just lost a bid for protection as an endangered species when oil started gushing into its spawning grounds in the Gulf of Mexico.

Now, a part of the emergency response to the oil — the large-scale use of dispersants — could further imperil the species by sinking the oil beneath the Gulf’s surface and into the zone where its eggs and larvae are floating, marine biologists say.

The chemical dispersants — a standard tool in the oil cleanup business — are being used by the Deepwater Horizon response team to break up the oil offshore in hopes of preventing thick crude from wrecking delicate marshlands, mangroves and pristine beaches.

The federal government — the National Oceanic and Atmospheric Administration, the Environmental Protection Agency, the U.S. Coast Guard and other agencies — has signed off on BP’s use dispersants as a necessary part of the company’s damage-control strategy in the wake of the April 20 accident aboard the Deepwater Horizon drilling rig.

But the chemicals, which are being used in unprecedented volumes and in previously untested ways, may come with a big tradeoff, scientists say. That’s because no one can accurately predict how large the impact will be on the mammals, fish and turtles that inhabit the open ocean.

“It’s a whole new ball game,” said Ted Van Vleet, a professor of chemical oceanography in the college of Marine Science at the University of South Florida. “People are totally unsure as to how it is going to affect the ecosystems."

Dispersants themselves are toxic. But a bigger concern in the scientific community is what happens in dispersing the oil, which is far more hazardous to living creatures.

Typically, dispersant is sprayed on the surface of the water, where the oil naturally comes to rest, and works a bit like a dishwashing detergent on grease. It breaks down the slick into millions of tiny oil droplets that then become suspended below the surface, normally in the top 30 to 50 feet of the ocean. There, over the course of weeks and months, oil-eating bacteria, sunlight and wave action help break the oil down into its chemical components, which are then diluted throughout the water.

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But in the interim, the oil droplets drift in the upper layer of water, where many sea creatures live and reproduce.

“The fact that (dispersants) remove oil from the surface doesn’t mean it’s not toxic,” said Van Vleet. “It moves oil down into the water column, where other marine animals are exposed to it. ... It trades one ecosystem for another.”

Unprecedented, untestedIn the Deepwater Horizon accident, the response team has used more than 670,000 gallons of chemical dispersants as of Friday — far surpassing any previous use in the United States. Most of it has been sprayed from airplanes, but the Deepwater Horizon response team also has applied at least 55,000 gallons in a completely untested way — injecting it at the well’s leaking riser, some 5,000 feet below the surface.

Tag-a-Giant Foundation Dr. Steve Wilson of Stanford University tags a 700-pound bluefin tuna off Canada with a satellite monitoring tag. The fish was tracked in 2009 as it travelled to the Gulf of Mexico, where the fish spawn, now the site of the Deepwater Horizon oil spill.

While the dispersant may result in fewer oily egrets in the marsh, the bluefin is one of the creatures that may suffer greatly instead. The oil spill area overlaps with only known spawning area for one of two remaining bluefin populations. This bluefin population spends about 10 months of the year in the cold waters of the north Atlantic and then swims thousands of miles to reach an area near the Deepwater Horizon well to disseminate sperm and eggs in the warm Gulf waters between April and June. The larvae float about 10 to 15 feet below the surface in early stages of growth. No one is certain whether the oil will destroy the eggs or kill the larvae, but scientists fear that could happen.

“It is a critical habitat … and this is the most delicate life stage,” said Barbara Block, a professor at Stanford University studies bluefin tagged with sophisticated tracking devices. “The biodiversity of bluefin is at stake right now. … If we lose the year (of new bluefin) it will have a very large impact on a population of bluefin that is on the edge of extinction.”

This is the spawning ground for many other species, including marlin, swordfish and yellowfin tuna, which arrive in the summer.

Some of the chemical components distributed throughout the water will remain toxic for decades, and it's not clear what the impact could be on future generations of bluefin or other creatures — sperm whales, Bryde’s whales, offshore dolphin populations and seabirds — that fish far from shore.

 

www.msnbc.msn.com/id/37282611/ns/gulf_oil_spill/