BROOKLIN, Maine — A marine toxicologist from Maine who traveled to New Orleans earlier this month to get a firsthand look at the oil spill in the Gulf of Mexico and the effects of the chemicals used to fight it said she was horrified by what she saw.

Dr. Susan Shaw of Brooklin, who accompanied a London Times crew to the gulf May 20-22, said the damage done by the Deepwater Horizon oil spill is rivaled by the harm done by the dispersants British Petroleum is using to break up the viscous fluid.

“We’re actually doing a pretty good job of poisoning the sea, and we’re calling it a chemical remedy,” Shaw said.

Bathed in Vaseline, Shaw snorkeled several miles off the coast for about eight hours, she said. She described the oil spill as an “amazing, horrible batch of brown pudding.”

Shaw is the founder and director of the Blue Hill-based Marine Environmental Research Institute, an organization dedicated to “scientific research and education on the impacts of pollution on marine life and human health, and to protecting the health and biodiversity of the marine environment for future generations,” according to MERI’s website.

Shaw, who is one of the few experts who has swum in the spill to gauge its impact, said she saw an oil and dispersant mixture on May 21 and that the dispersants work. But they work too well, she said. Instead of the oil collecting on beaches and harming marine animals, it is being broken down into smaller globs that affect animals further down the food chain, such as phytoplankton, Shaw said.

“It’s a double-edged sword,” she said. “They’re definitely breaking up the oil and globs,” but smaller fish such as herring or anchovy eat the poisoned phytoplankton, and they become poisoned for larger animals who eat them.

“My view from being down there is that we should not be using these dispersants in such unprecedented volumes,” she said.

Reduced populations of forage fish like herring and poisoned food supplies will contribute to a decline in larger animals, Shaw said. She added that “exposure for fish is very high right now.”

Last week the U.S. Environmental Protection Agency ordered BP to immediately select a less toxic dispersant. The company has used more than 800,000 gallons of Corexit, a chemical manufactured by Nalco Co. — to which BP has close ties — to treat the spill. Corexit 9527, which BP has sprayed in the gulf, contains 2-butoxyethanol, a chemical that ruptures red blood cells and causes bleeding when ingested, according to Shaw. Its replacement, Corexit 9500, contains surfactants and petroleum solvents that are caustic, accumulate in animals and can cause chemical pneumonia if breathed into the lungs, she said. Corexit is more toxic and less effective than dispersants made by Nalco’s competitors, according to EPA data.

In a statement released May 24, the EPA reported, “We are still deeply concerned about the things we don’t know. The long-term effects on aquatic life are still unknown, and we must make sure that the dispersants that are used are as nontoxic as possible. Those unknowns — and the lengthening period of this crisis — are why we last week directed BP to look for a more effective, less toxic alternative to their current dispersant.”

The president of BP, in a May 20 letter to the EPA and the Coast Guard, said he believes Corexit is still the best dispersant for the gulf oil spill because the five other possible chemicals degrade to nonylphenol, a potential endocrine disrupter, which remains in the environment for years. He went on to ask the EPA and Coast Guard for a meeting to discuss the alternatives.

The EPA wrote back to say, “The EPA and the Coast Guard believe your response to the directive was insufficient. We believed the response lacked sufficient analysis and focused more on defending your initial decisions than analyzing possible better options.” The letter went on to reiterate the EPA’s demand that BP reduce its dispersant use.

“What I see unfolding is that we’re going to lose these stitches in the food web … and that will devastate all the higher organisms,” Shaw said.

She plans to participate in a live interview on CNN International on Monday about her experiences in the gulf.