Working to Diagnose Marine Animal Die-Off

Many dolphins are already decomposed when they wash ashore, Rowles added, making it even more difficult for scientists to make a diagnosis. "The poor body condition really hurts a lot of what we can do," said Rowles, who is also NOAA's top veterinarian.

The challenges associated with examining dead marine mammals have prompted some scientists to suggest that monitoring healthy dolphins could aid investigations during a crisis. In a paper that Wells and Rowles co-authored in 2004, the researchers wrote that regularly examining unharmed dolphin populations would allow scientists "to not only monitor the risks to the populations themselves, but to be able to use them as sentinels of the health of marine ecosystems."

Frances Gulland, who has collaborated with the working group on several cases and directs veterinary science at the Marine Mammal Center in Sausalito, Calif., said a major increase in gray whale strandings in Alaska less than a decade ago illustrates how global warming is affecting the region.

"There are some big changes in the Bering Sea ecosystem, likely due to climate change," Gulland said. "Something has changed in the Arctic, and we need to start being concerned."

Gulland has also studied why dozens of California sea lions started having seizures in 1998. She and other scientists ultimately determined that domoic acid, a biotoxin that can cause disease and death in humans, caused the sea lions' illnesses and deaths. The toxin stemmed from an algae bloom off the California coast.

"It's not just cute dolphins," Gulland said, adding that marine mammals dying in waves can serve as indicators for human health. "They can be early messengers, really, for broader changes" such as rising pollution levels and global warming.

Even after scientists determine what set off a wave of marine mammal deaths, they often keep digging to see how the mortalities may have transformed a region.

While a group of Sarasota Bay bottlenose dolphins that Wells has studied for 37 years emerged unscathed from the 2005 red tide, a year later several got caught in local fishing gear. Wells now suspects that happened because many of the fish that the dolphins depend on for sustenance, including pinfish and mullet, died off during the earlier algae bloom.

"It's not a smoking gun, but we suspect they were going after the bait because their prey had declined," he said.

These revelations, Rowles said, are helping researchers decipher how marine ecosystems function.

"The program is still very much in its infancy, though I think we're beyond the neo-natal stage," she said. "It's not just looking at sick animals."