Dolphin Deaths Laid to Common Ocean Bacterium

WASHINGTON —  Scientists investigating the mysterious deaths of more than 200 dolphins along the Atlantic Coast said Wednesday that the mammals were infected by a common ocean bacterium, but they still do not know why the organism has killed so many of them.

Dr. Joseph R. Geraci, head of a federal scientific team investigating the phenomenon, said laboratory tests show that vibrio, a bacterium found in both clean and insanitary ocean waters, is responsible for bottle-nosed dolphins dying in record numbers from New Jersey to Virginia.

Although the organism is common, the phenomenon puzzled scientists because the bacterium is not known to cause widespread deaths among dolphins. Scientists said they will continue to perform autopsies on the mammals and conduct further tests at their headquarters in Virginia Beach, Va.

Geraci, a marine pathologist and wildlife disease expert at the University of Guelph in Ontario, said it is also unclear whether rising levels of ocean pollution--especially off the New Jersey shore--have contributed to the dolphin deaths.

The bacteria that scientists have isolated “are normally present in the marine environment and in the terrestrial environment,” he said. “But what we are really dealing with is a condition in which it seems these animals are pre-sensitized to invasion by bacteria that otherwise are rather innocuous.”

One explanation may be that Atlantic waters are warmer than usual this summer, a condition in which the bacteria can flourish, Geraci said. Also, there may be an excess of nutrients in the ocean waters, which is considered unhealthy for marine mammals, he said.

Lab Tests

Geraci and other scientists based their conclusions on lab tests of dolphin tissue and blood samples conducted by the National Veterinary Services Laboratory in Ames, Iowa. Their work has been funded by the National Oceanic and Atmospheric Administration and other federal maritime agencies.

Marine biologists believe that the sudden wave of deaths, which began last month, is threatening the survival of about 1,500 dolphins roaming near the Eastern Seaboard. A larger school of more than 14,000 dolphins farther off shore has not been affected.

Most of the dolphins that washed ashore in Virginia, Maryland and Delaware have been covered with ulcerous lesions, and many had excess amounts of fluid and parasites in their lungs, scientists have reported. Autopsies determined that many of them died from brain hemorrhages and bronchial pneumonia.

Mass of Garbage

Along the New Jersey coast, a large number of dolphins have also displayed rotting mouths and tongues. A mass of garbage, timber fragments and hospital waste offshore there this weekend caused officials to close 30 miles of beaches.

Robert Schoelkopf, who directs the state’s Marine Mammal Stranding Center, said such pollution may be “a clear factor” in the dolphin deaths and noted that vibrio infections are often spread to marine mammals in insanitary waters by punctures or wounds.

State officials discovered a multitude of syringes in the hospital wastes last weekend, he said, and it “is hard to overlook” the relationship between such debris and deaths among the dolphins, which have been swimming in the same waters.