The Perfect Warm – The Long Island Sound Die-Off
by Mike Crowe

In September 1999 the lobster fishery in western Long Island Sound sustained a sudden 98 percent die-off .

The disaster put many lobster fishermen in the Sound out of business. The states of New York and Connecticut began investigations into the dramatic event. The immediate focus was on a parasite, a paramoeba, found in the flesh of some lobsters. Another early suspect were the pesticides used in the West Nile virus scare that same fall.

This spring at the Fishermen’s Forum, March ’05, in Rockland, Me., scientists who have studied the problem in the years since, presented their findings in an all-day seminar. Scientists from Maine, Connecticut, New York, Georgia and Canada reported on various aspects of the problem; a few had the some of the same conclusions to offer.

Some fishermen were convinced that the die-off was the result of chemicals sprayed along the coast. The chemicals were sprayed to kill mosquitoes believed responsible for the West Nile virus. Others blamed the paramoeba. None of the scientists identified a very specific cause, but many at the Forum agreed that lobster are very temperature-sensitive. This, many agreed, could be critical to understanding whatever it was that killed the lobster in such great numbers.

Dr. Carmella Cuomo presented information gathered as a research scientist at Yale University in New Haven, Conn. Cuomo coordinates the marine biology program at the University of New Haven. Having done research on low oxygen marine systems, she was one of the scientists asked to study the lobster die-off. Cuomo’s presentation brought together lobster stress factors that had been known to exist in the Sound. These factors and others were brought together, she believes, by a weather event that led to a weakening of lobsters to a point where practically anything would have killed them. Other scientists at the forum had studied the effects of various substances in the environment on the health of lobster. Cuomo studied the condition of the lobster habitat at the time of the die off.

As background to the event, Western Long Island Sound was described as “heavily industrialized, and all of the Sound, basically a large estuary, has seen a growing increase in organic matter emptied into it since Europeans arrived”, Cuomo said. Organic matter comes from agricultural fertilizers, the 140 sewage treatment plants on Long Island Sound, runoff and the many rivers that bring more of the same.

Cuomo noted that when bacteria break down this organic matter, they use up oxygen and creates ammonia. There are other bacteria that use hydrogen sulfate, which naturally occurs in sea water, instead of oxygen, to break down organic matter. These bacteria generate sulfide. Sediments where this occurs therefore, have fewer oxygen producing animals in them. One of the results of this is oxygen depleted sediments and water high in ammonia and sulfide. The Western Sound is muddy compared the eastern, ocean end of the Sound is sandy and cooled by ocean currents.

Water low in oxygen is hypoxic. Cold water holds more oxygen, but as water temperatures rise there is less dissolved oxygen. Long Island Sound had been invisibly growing low in oxygen and high in ammonia and sulfide. Oxygen levels have been a concern for decades. In 1952 low oxygen levels were seen in the Western Sound. In 1971 hypoxia led to fish and lobster kills in the sound. By 1980 the Connecticut department of Environmental Protection reported a consistent trend of dips in oxygen levels in the months of July and August in Long Island Sound.

Central Park air temperature records kept since 1880 show a trend of rising temperatures on the earth’s surface. That rise increases considerably around 1980. In 1990 there were areas of the sound nearly depleted of oxygen. In addition, there has been a trend toward heavier rainfall which has affected salinity levels.

These factors, said Dr. Cuomo, along with a weather event, triggered the 1999 die off. In the summer the water in the Sound is stratified, there is warmer water layered over colder water denser water on the bottom. But in September of 1999, a storm with high winds de-stratified the water, mixing the warm and cold. The result was a two degree increase in water temperature in six hours.

Then, hurricane Floyd roared in dumping heavy rains and re-stratifying the water, but trapping warm water on the bottom. These temperature changes were recorded by Coast Guard and NOAA buoys in the sound. It was what scientists were calling the perfect warm. At 18 degrees centigrade to 20.8 degrees centigrade life gets difficult for lobster. The 20.8 mark is considered a “health-line”. In 1999 temperatures were 22 degrees centigrade at the west end of the Sound. Lobsters- temperature sensitive, surviving on low oxygen, moving around in ammonia and sulfide, immune systems stressed and living at the southern edge of their range- were overwhelmed.

In 2003 scientists at the National Marine Fisheries Service reproduced what they thought were the environmental conditions in the sound during the die off. The lobsters in the experiment died.

Dr. Cuomo, said the paramoeba would have found less resistance in these weakened lobsters. The pesticides, thought to have been used at levels too low to be the sole cause, may have had a greater impact on lobsters at the edge of collapse.

Robin Miller, a representative from HydroQual, Inc., sited the results of the company’s hydrodynamic model of Long Island sound. The model was developed over thirty years for the EPA. It enables researchers to view currents, fresh water inflows, temperatures, nutrients, et cetera. Other variables can be added, such as pesticides, to observe their effects on the data. Actual water samples are not taken, but the computer model generates outcomes. Higher levels of pesticide applications introduced to the model did not produce the toxicity believed necessary to kill lobster. Miller said this supported the conclusion that malathion was not the cause.

Michael Horst, from the medical school at Mercer University in Macon, Ga., who has studied the effects of pesticides on the American lobster, discussed the many pesticides that get into the water and their effects on lobster. His conclusion was that it is just unknown how the many things introduced into the lobster’s environment are affecting them. His recommendation was that it is necessary to be careful with the environment we are using.

Dr. Bob Bayer, from the Lobster Institute, addressed the effect of pesticides on lobsters under stress. The effect, he said, of a combination of pesticides in the environment, he said, is that there are more variables and therefore greater difficulty in assessing the result.

While many scientists have been organized to help answer the questions raised by the die off, Dr. Kathy Castro, who has worked for years on shell disease in Rhode Island, thinks more communication among the people and organizations in the fishery is needed. Citing input from fishermen regarding changes in shell growth rates and molts, she said, “We need to be aware we are doing this all together.” Maine waters are generally colder than Long Island Sound. However, warming trends could effect bays and estuaries in similar ways if they are stressed further with the by products of human activity. These by products include, run off, fertilizers, lawns chemicals, industrial and domestic and sewage.

Michael Horst ended his comments with, “Let’s be careful out there.”