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Lobsters Die Warm Water*
November 9, 2002
Warming Waters and Dying Lobsters
By KIRK JOHNSON
TONY BROOK, N.Y. The first clue that something had once again gone seriously wrong in Long Island Sound was the color of the blood being spilled. Lobsters are not supposed to bleed orange.
But it was the timing that really piqued Alistair D. M. Dove's interest. Orange-blooded lobsters began showing up in his pathology lab here at the State University of New York in mid-August, the very week researchers reported a sudden increase in the Sound's water temperature after a year of record-breaking warm weather.
Through 20 subsequent autopsies, a pattern emerged. The animals had been killed by a buildup of calcium, the rough equivalent of kidney stones in humans, and all the evidence pointed to one cause: water so warm that it was impairing their ability to process minerals. The lobsters were dying from the stress of an environment that had become hostile to their ancient internal thermostats, Dr. Dove concluded.
"The correlation is very strong," he said. "Not proven, but strong. Climate is the killer here."
Dr. Dove's words are cautious. There is, as he points out, no airtight proof that warmer water is at the root of the precipitous decline in Long Island Sound lobsters over the last three years. Some researchers, along with many people in the lobster fishing industry, still say that the main culprits are pesticides, which were sprayed in the Sound's watershed areas to combat mosquitoes bearing the West Nile virus.
But many scientists say Dr. Dove's work adds significant weight to the argument that warmer waters caused by climate change are the cause. If he is right, the implications are ominous for the Sound's lobsters and lobster fishermen: unlike pollution or pesticides, temperature is a problem without an easy cure, or a villain to hold accountable.
"If Long Island Sound is becoming inhospitable for lobsters or other animals because water temperature is too high, that means they're not going to stay there and there's nothing anybody is going to do about it," said Gordon Colvin, the director of marine resources for the New York State Department of Environmental Conservation.
Science has learned a lot about lobsters since a severe die-off battered the Sound's lobster population in 1999.
Altogether, 17 research projects are under way, including the marine animal disease lab at Stony Brook that Dr. Dove, a pathologist and senior research associate on assignment from Cornell University, was hired this year to help create.
This invasion of lobster science is allowing researchers to find calcium stones the size of sand grains (which, by the way, do not pose any known threat to people who eat lobsters), and it also enables them to see the broader pattern. In 1999 and again this year, water temperatures at the bottom of the Sound where lobsters live reached their highest sustained levels of the last 10 years, researchers said, surpassing the lobsters' so-called thermal limit of about 69 degrees Fahrenheit.
And in both years, rather the way fever signals the flu, overly warm water was clearly associated with the onset of disease. The immediate cause of death in 1999 is still being investigated, but is believed to be a parasite called paramoeba; this year it is a calcium buildup, called calcinosis. Through whatever combination of problems, the Sound's lobster harvest is off by 10 percent or more in many fishing areas compared with last year. Dr. Dove and other researchers have prepared a paper on this year's problems for Diseases of Aquatic Organisms, a journal, and are also working on a paper on the larger climate connections.
Other people say the warm-water explanation has been bolstered by default because scientists looking into the leading alternative theory for the 1999 disaster, pesticide poisoning from the mosquito-spraying program, have so far come up short in their search for proof.
"There are researchers who are sure it was pesticide and the lobster fishermen are sure but personally I now think there's very little chance," said Jack Mattice, the director of the New York Sea Grant Institute, which is helping oversee the lobster research. "I believe that it was primarily temperature, and I think most people would probably say that temperature was a direct or indirect cause."
Other scientists insist that the 1999 mystery remains unsolved. Long Island Sound, they say, has always been at the temperature frontier for the American lobster, which generally prefers the colder waters off New England. The Sound's lobster population had also exploded to record highs in the late 1990's, perhaps precipitating a natural crash from heightened competition for food. An oxygen deficiency in the water, called hypoxia, was severe that year.
As in some tangled mystery story, there is no shortage of suspects. In the central and eastern sections of the Sound, the lobster catch is still down as much as 60 percent, compared with 1998. In the western end, where the devastation was greatest, the lobster harvest is about one-tenth what it was.
Few scientists say that warmer water alone accounts for the lobsters' decline, and some, including Dr. Dove, say that a pesticide explanation for the 1999 die-off may still be compatible with the warm water hypothesis. Stress from high temperatures, they say, may suppress lobster immunity systems, making them more susceptible to poisons or diseases they could otherwise fight off.
In an environmental impact study of West Nile spraying programs, New York City's health department said last year that pesticides applied just before a major storm could produce crustacean deaths in the bays where rainwaters drain. The 1999 lobster deaths occurred right after Hurricane Floyd hit the region, and some scientists, along with the lawyers representing a group of lobster fishermen who are suing four pesticide companies, say that the timing is too close to be coincidental.
"They were able to withstand pollution in the past, and this time they didn't," said Lance Stewart, an associate extension professor at the University of Connecticut who has studied the Sound's lobsters for more than 25 years and who believes that pesticides played a role.
Other people, including at least one of Dr. Stewart's colleagues at the University of Connecticut, are looking at the same set of facts and reaching a different conclusion altogether. Richard French, an associate professor of veterinary pathology, and one of the leading researchers into the 1999 die-off, said he thought that pesticide poisoning did not fit the geographic or timing pattern of the lobster deaths in 1999. High water temperatures, he said, do fit the facts.
"When temperatures are elevated a lot of other things change; there's also growth in algae, and that depletes oxygen on the ocean floor, and that brings in hydrogen sulfides and other ions into the water, and changes the whole chemistry," he said. "When everything is lined up, disease breaks."
Lobster fishermen say the main characteristic of the 1999 die-off was its suddenness. This year, despite a supposedly similar pattern, they say, the problem has been incremental and chronic.
"We just want our fishery back, but it doesn't appear we're going to get it back," said Nick Crismale, the president of the Connecticut Commercial Lobstermen's Association. Mr. Crismale is also a plaintiff in the pesticide industry lawsuit. "Seems to me the only people making out on this are the researchers," he added. "The researchers get the grants, and the lobstermen get nothing."
Back in the lab, Dr. Dove said he had still not been able to figure out the exact connection between the calcium stones and the altered color of the lobsters' blood. Pale pink, clear or even green can be normal for lobsters depending on the time of year and the sex of the animal. Orange remains a mystery.
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