So far this year, nearly 1,000 bottlenose dolphins — eight times the historical average — have washed up dead along the Eastern Seaboard from New York to Florida, 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 Indian River Lagoon, a diverse estuary, has been tainted by huge algae blooms caused in part by too much nitrogen. Research on some of the dead dolphins in the estuary — 76 died this year, the third series of deaths since 2001 — has showed that some had high levels of mercury, fungal diseases, antibiotic-resistant bacteria and oral-genital tumors. The dolphins found were emaciated.
“You have to think, ‘Where does antibiotic-resistant bacteria come from in dolphins?’ ” said Dr. Bossart, who is involved in a long-term study of the Indian River Lagoon dolphins. “One thought is that it comes from environmental pollution.”