Lobster Graveyard.

When lobstermen hauled in traps on Long Island Sound last September, their catch was more than disappointing--it was dead. Ninety-five percent of last season's lobster population died in the 145 kilometer (90-mile)-long stretch of Atlantic Ocean between Connecticut and Long Island.

The culprit? Lobstermen blame mosquito pesticides, pest-killing chemicals sprayed over Northeastern U.S. states last summer to halt the mosquito-borne West Nile virus, a disease-causing micro-organism that has so far killed eight people in New York and New Jersey. But it turns out the chemicals aren't only toxic to the mosquito--they also poison its close arthropod cousin, the lobster.

Arthropods are invertebrate (spineless) animals covered by a hard, segmented, or jointed, shell. "A lobster is nothing more than an insect with gills," says lobster expert Bill Smith of the conservation group Fish Unlimited in Shelter Island Heights, N.Y. "So it's likely that mosquito chemicals windblown into the Atlantic are responsible for the mass lobster die-off."

But scientists at the University of Connecticut have made an additional link. They found a Paramoeba parasite (a single-celled, microscopic organism that lives off other creatures) swimming in hundreds of samples taken from dead lobsters. The parasite destroys the lobster's nervous system, a network of cells that control body movement. "A healthy lobster can fight off this parasite," counters Smith. "But the pesticides make lobsters susceptible to infection."

Parasite, pesticide, or both? The Environmental Protection Agency (EPA) has launched a $3.5 million investigation to settle the debate.