Dolphin Deaths in Gulf Coast Prompt Scientific Probe
The largest cluster of dolphin deaths since the widely reported dolphin “die-off” along the East Coast in 1987 has sparked an investigation by federal scientists and environmentalists.
Since January more than 300 dead or dying bottlenose dolphins have washed ashore in Texas, Alabama and other Gulf states, more than twice the number that would normally be expected to turn up on Gulf beaches over the same period, according to the National Marine Fisheries Service.
Scientists have yet to identify the cause of the dolphin deaths--most have been too badly decomposed to yield useful tissue samples--and the numbers are still far below the several thousand that are estimated to have died in the Atlantic coast episode.
Moreover, researchers caution that fluctuations in population are not in themselves cause for alarm and that the excess deaths might not even have been noticed if the earlier episode had not sparked public concern.
Still, the unusual number of deaths has prompted inquiries into a range of possible causes, from an outbreak of the poisonous “red tide” algae implicated in the 1987 case to unusually cold weather to possible immune system damage from toxic waste or other environmental pollution.
“Certainly there is cause for concern, but it is nowhere near on the order of magnitude as the Atlantic die-off,” said Dean Wilkinson, marine resource management specialist for the NMFS. “Probably we had heightened sensitivities as a result of the events on the Atlantic side.”
In that case, hundreds of dead and dying dolphins, many of them with lesions and showing signs of emaciation, washed ashore from New Jersey to Florida, raising alarms that some man-made hazard was at work. A government research team subsequently blamed the deaths on natural toxins present in the red tide, although their findings are still the subject of some controversy.
Scientists have estimated that 3,000 bottlenose dolphins, half of those normally present along the East Coast, were wiped out by the red tide.
As in that case, the Gulf Coast deaths have puzzled some scientists for reasons that go beyond sheer numbers. While most dolphin “strandings” typically occur during the first quarter of the year, they usually involve newborns or mothers weakened by calving. But these deaths have involved dolphins of all sexes and ages, according to the NMFS.
“There is pretty much of a balance between males and females,” said Wilkinson. “This doesn’t quite match the composition of stranding peaks.”
The NMFS, working with scientists from Texas A&M; University and the Armed Forces Institute of Pathology, among other places, hopes to complete its analyses of tissue samples within a few weeks, although their work has been hampered by the lack of fresh carcasses. In addition, government aircraft have conducted flights over the Gulf to look for algae blooms, and water samples have been collected, although so far the results have been inconclusive.
Much of the sample collection thus far has depended on a network of volunteers as well as the environmental group Greenpeace, which has criticized the government for moving too slowly in its investigation. “This is the second such event in three years, and I think it’s very important that we find out what’s going on,” said Bruce McKay, an ocean ecologist for Greenpeace.
But Daniel Odell, scientific coordinator of the southeastern U.S. marine mammal stranding network, suggested that the federal response thus far has been appropriate. “At this point, there’s nothing to indicate what has happened here,” he said. “The important thing is that everybody is aware of what’s going on.”