The carcasses of dozens of the marine mammals, seven times more than normal, have been washing up on beaches this summer, and scientists are struggling for answers to the die-off.
In Virginia alone, at least 164 dead dolphins have been found this year, said Joan M. Barns, public relations manager for the Virginia Aquarium in Virginia Beach. Almost half of those, 78, have washed ashore in August, she said.
As of Tuesday, federal authorities say, they have recorded 228 dolphin deaths this year from New York to Virginia. In all of 2012, 111 deaths were recorded.
The National Oceanic and Atmospheric Administration has issued an Unusual Mortality Event in response to the deaths. The declaration brings special federal attention to deaths as something that serves as an indicator of ocean health and may give “insight into larger environmental issues which may also have implications for human health and welfare,” according to NOAA’s website.
The current declaration for the mid-Atlantic bottlenose dolphins is one of 60 Unusual Mortality Events the agency has issued since they were established under the Marine Mammal Protection Act in 1991. Causes, including infections, biotoxins, human intervention and malnutrition, have been determined for the 29 of those cases.
Early speculation into the latest deaths, which have spiked this month, is focused on an infection.
“Based on the rapid increase in strandings over the last two weeks and the geographic extent of these mortalities, an infectious pathogen is at the top of the list of potential causes for this UME, but all potential causes of these mortalities will be evaluated,” NOAA said in announcing the mortality event. “Work is underway to determine whether an infectious agent affecting these dolphins is present in collected tissue samples.”
Susan Barco, research coordinator for the Virginia Aquarium and Marine Science Center, said necropsies are providing clues.
“We’re starting now to see lesions in their lungs that are consistent with some sort of a respiratory infection,” she said. “We’re seeing very active lymph nodes, which means they’re actively fighting an infection.”