Working to Diagnose Marine Animal Die-Off
Monday, March 26, 2007
SARASOTA, Fla. -- In the summer and fall of 2005, marine animals suddenly started dying off the southwest Florida coast, with scores of bottlenose dolphins, manatees and turtles washing up on shore. In October alone, 22 dolphins became stranded and died, compared with the usual monthly average of three.
Hoping to unravel the mystery, nearly 50 researchers, part of the Working Group on Marine Mammal Unusual Mortality Events, commissioned a study of the deaths. After taking samples from 130 stranded dolphins, they concluded that red tide -- an algae bloom that creates a neurotoxin known as brevetoxin -- caused the massive die-off.
In the 16 years since it was formed under the auspices of the National Oceanographic and Atmospheric Administration, the working group has investigated scores of similar events. It is detecting a rising number of die-offs -- at the moment the panel is handling eight such cases simultaneously, an unprecedented high that reflects the environmental pressures on marine mammals and the nation's increasingly broad scientific stranding network.
Experts believe a range of factors are contributing to the algae blooms and viruses linked to the die-offs, including nutrient runoff from farming, rising ocean temperatures and discarded waste such as cat litter.
Now, the working group has 12 permanent members and enlists a shifting group of volunteer experts from the United States and overseas to help diagnose each die-off. The working group has evolved into the federal government's top detective team for these events.
Randall Wells, who heads the Sarasota Dolphin Research Program at the private Mote Marine Laboratory and helped study the 2005 red tide, said he and his colleagues are still struggling to figure out whether environmental contaminants or other factors might have weakened the mammals that fell prey to the 2005 algae bloom.
"It is so hard to do the detective work to pick all those things apart," he said.
Just last week, the rapid-response team sprang into action again after 64 dead bottlenose dolphins and numerous fish washed ashore on the Texas and Louisiana coasts within roughly three weeks.
Teri Rowles, senior scientist for NOAA's marine mammal mortality program, said the recent dolphin deaths have spurred a major response. Experts are examining the stranded dolphins' organs, taking tissue samples and extracting their lymph nodes so that NOAA scientists elsewhere can do DNA and RNA analyses, and the Coast Guard has lent air support to survey the waters for more dead animals.
"This most important thing for us, when we have an incident like this, is to see people and agencies and scientists come together to try to solve the problem," Rowles said, adding that the working group's tight budget -- it has received just $1.3 million in designated federal funding since 2001 -- hampers its ability to conduct quick analyses when an incident strikes. "It's quite frustrating to look at 60 dead animals and not have a rapid answer."
Congress chartered the working group after two large dolphin die-offs in the late 1980s off the East Coast and in the Gulf of Mexico. The group -- which enlists a variety of experts that include epidemiologists, clinical veterinarians, immunologists, and ecotoxicologists -- has studied 39 incidents so far.
Typically, marine scientists first try to determine whether a virus or an algae bloom is to blame. Rowles said she is concerned that the morbilli virus, which is similar to distemper in dogs and killed tens of thousands of European animals in 2004, may be responsible for the recent dolphin deaths in Texas and Louisiana. The virus has affected marine mammals off the Florida coast in the past, and it can spread quickly through a large population of animals.