Surge of dolphin deaths alarm, puzzle scientists

MIAMI – Like a macabre marine mystery, the carcasses first turned up along the coast of New Jersey in June. Soon, droves of them washed up in Virginia, the Carolinas, Georgia and most recently Florida, their winter home.

Nearly 1,000 bottlenose dolphins – eight times the historical average – have washed up dead this year along the Eastern Seaboard, a vast majority of them victims of morbillivirus. Many more are expected to die from the disease in the coming months.

The high death toll from the resurgence of the virus, which killed 700 dolphins in an outbreak 25 years ago, has alarmed marine scientists, who say it remains unclear why the dolphins have succumbed to the disease. The deaths, along with a spate of other unrelated dolphin die-offs along Florida’s east and west coasts, raise new questions about the health of the ocean in this part of the country and what role environmental factors may be playing, scientists said.

The deaths have puzzled scientists. They show no discernible demographic pattern, affecting dolphins that are young and old, male and female. One possible explanation is that some of those that have died this year were not alive during the first outbreak and may not be immune to the virus.

The causes of death appear to be unrelated; each group of dolphins faces separate challenges that in some cases remain scientifically murky – disease, a polluted environment, infection and possible residue from the BP Deepwater Horizon oil spill in 2010.

“It is alarming when you see so many different die-offs of marine mammals going on at once,” said Erin Fougeres, a marine mammal biologist with the National Oceanic and Atmospheric Administration’s fisheries service, which is tracking and investigating the deaths. “We can’t say they are linked. But it says there are a lot of challenges that marine mammals are facing.”

There is little scientists can do to stop the airborne virus, which cannot be spread to humans. During the last outbreak, the virus killed off dolphins for 10 months, which means this time, dolphins may continue to die through May.

Other threats remain, chief among them the possibility that the virus could spread to Gulf Coast dolphins and the vulnerable population in the Indian River Lagoon.

“The results could be catastrophic,” said Stephen D. McCulloch, program manager for marine mammal research at Florida Atlantic University’s Harbor Branch, adding, “There is some degree of coastal interaction between dolphins in the inlets.”