The Upshot

Scientists think BP oil is already having toxic effects on Gulf food chain

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Back when federal officials were keen to claim that all the oil spilled over the months-long BP disaster had simply gone away, skeptics — including some on the government payroll — insisted that the toxic substance was still very much around. It was just that BP's aggressive use of oil dispersants had driven much of the oil out of sight — breaking it up into molecular units, driven far beneath the Gulf's surface.

Now it seems that more evidence is bolstering the case that the spilled oil is very much a threat in the Gulf. In a report for the Sarasota Herald-Tribune, Kate Spinner writes that significant amounts of oil are harming what's known as beneficial algae — a critical component in the plankton anchoring the oceanic food chain. Spinner's report comes shortly after a report in the New Orleans Times-Picayune indicating that oil lurking in the Gulf may be killing off coral beds, another major element in the sea-life ecosystem.

David Hollander, a chemical oceanographer at the University of South Florida, contends that even plumes containing extremely low levels of oil are harming the algae. The plankton that thrive off the algae feed a fish called menhaden, which is used widely for fishmeal — the main ingredient in feed for many farm animals, including pigs and chicken.

Spinner spells out what a major Gulf die-off of beneficial algae could mean for the U.S. food economy — and indeed, throughout the world:

It starts with plankton, a diverse community of tiny, sometimes microscopic, plants and animals. Plankton includes algae, fully grown microscopic animals, and the larvae of crabs, oysters, fish and other sea creatures. Some fish only eat plankton, including one that ranks as one of the most commercially important fish in the nation. Gulf menhaden, or pogey as the locals call it, represents the second-largest commercial fishery in the nation by weight, with landings of nearly 470,000 tons annually. More than 90 percent of that catch comes from Louisiana. Nobody eats menhaden. Instead the small fish are ground into fishmeal, an important protein source for animal feed.

"That's what they feed the chicken that allows us to have such a big chicken crop in our country," (Loyola University professor Bob) Thomas said. "It ties together a lot of things you don't necessarily connect."

Fish oil from menhaden also goes into supplements, trendy health foods and cosmetics.

So plankton feeds menhanden, menhaden feeds chicken, chicken feeds people. In the Gulf of Mexico, the chain becomes more complex. The plankton feed thousands of different animals that go on to feed hundreds more in a complex dynamic called the food web. When one element disappears, connections get mixed up.

Spinner goes on to suggest that the sea-life fallout in the Gulf may be very close to what happened with herring in Alaska following the Exxon Valdez spill. Immediately after that disaster, she says, "the fish came back in force, bringing a sense of relief." Four years later, however, the herring crop collapsed entirely — and two decades after the accident, it has yet to come back.

"When you are perturbing the food web from its foundation, the ultimate ecological response could be catastrophic," Hollander told the Herald-Tribune.

(Photo of microscopic plankton: AP)

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