Few Clues on Dolphin Deaths in Florida Keys

SUMMERLAND KEY, Fla. — Biologists are investigating whether sonar used in U.S. Navy submarine exercises or red tide bacteria contributed to the deaths of more than 30 rough-toothed dolphins in a mass stranding in the Florida Keys last week.

Scientists began testing Monday for bacterial, viral and tissue infections during necropsies on nine of the dead dolphins, including a stillborn calf.

An estimated 70 to 110 rough-toothed dolphins, which normally swim in deeper continental shelf waters, turned up in shallow waters on sand flats near Marathon, south of Miami, Wednesday.

Some scientists speculate that the stranding could be related to sonar that may have disoriented the marine mammals, causing them to surface too quickly and suffer decompression sickness.

The submarine USS Philadelphia, based at Groton, Conn., conducted training exercises with Navy Seals in the Florida Keys a day before the stranding.

Navy officials are "working this issue," said Lt. Cdr. Jensin Sommer of Norfolk, Va.-based Naval Submarine Forces Monday.

Biologists also tested for toxicology related to red tide, an algae bloom that reproduces at an explosive rate and is harmful to marine mammals such as manatees. An unseasonable red tide formed off southwest Florida in early January.

"There's no smoking gun," said Alex Costidis, a Florida Fish & Wildlife Research Institute biologist in St. Petersburg, Florida. "They all had empty stomachs, which is pretty typical of a stranding, indicating they had not eaten in the last two or three days."

The dolphins were mostly adult females and young. Of the total stranded, 10 to 15 were able to swim away.

"We still don't know how many were stranded. We definitely had a maternal pod. It was mostly moms and babies," said Celeste Weimer, stranding coordinator for the Florida Keys Mammal Rescue Team.

Several of the females in the group had stillbirths.

At the Mote Marine Laboratory on Summerland Key, about 25 miles east of Key West, an adult female dolphin -- nurtured by another dolphin behaving as a labor coach and wetsuit-clad volunteers who hydrated the creatures -- struggled more than 12 hours Monday to deliver a stillborn calf.

Two other dolphins delivered stillborn babies in Key Largo, Fla., and another aborted a near-term fetus at a facility on Key Biscayne, near Miami, Weimer told Reuters.

The Marine Mammal Conservancy is rehabilitating nearly two dozen dolphins at a protected lagoon in Key Largo.