10 Years of Plagues Wiping Out Wildlife on Sweden’s Western Coast

If they were a more formally religious people, the inhabitants of this scenic paradise on Sweden’s western coast might fear that their beloved blue sea was being visited by a series of biblical plagues.

It began 10 years ago, when poisonous algae nearly wiped out the commercial mussel crop, a disaster from which it has never recovered. Then an unexplained disease killed most of the edgers, a local sea bird. Two major North Sea oil spills later brought death to countless other waterfowl.

Last spring, an unexplained bloom of killer algae blanketed the surface of the sea for hundreds of miles, leaving so many dead fish on shore here and in nearby Norway and Denmark that they had to be hauled away by the truckload.

But the worst catastrophe was still to come. In recent weeks, the bloated, decomposing bodies of thousands of seals have washed onto the rocky shores of the countless small islands lining this coast. In Tanum County, just south of Stroemstad, the number of dead seals is so great that the Waterborne Fire Department spends most of each day and far into the still-light northern night circling the islands, picking up corpses reported by summer vacationers.

What is happening here is happening all the way down the Swedish west coast and around into the Baltic Sea. It has spread to seal populations throughout the Kattegat, the shallow body of water between Denmark and Sweden, and the Skagerrak, between Denmark and Norway, and along the North Sea coasts of West Germany and the Netherlands.

Four months ago, a conservatively estimated 16,000 harbor seals lived in these waters. Now only about half are believed still alive. Tero Haerkoenen, Sweden’s leading harbor seal expert, fears that before it’s all over there may be only 10% left.

So fast and so thoroughly has the destruction spread that Haerkoenen and other scientists believe that it is only a matter of time, perhaps days, before the largest congregation of European harbor seals, 25,000 off the eastern coast of Britain, are affected.

“There has been nothing like this in modern times,” Haerkoenen said. “We have no experience of a disease among marine mammals that has struck so hard.”

The seals appear to be dying of a form of viral-induced pneumonia. What is causing the epidemic is a subject of frenzied scientific investigation and political argument in each of the five countries touched by it.

For many environmentalists in northern Europe, however, the answer is simple. The North and Baltic seas are among the most polluted in the world, absorbing more than 15 billion gallons of waste every day from towns and industries around their shores. The runoff from agricultural pesticides pours additional amounts of man-made toxins into the water.

Baltic Sea levels of the poisonous industrial compound PCB are so high that an estimated 80% of female gray seals, a species centered around the Baltic but apparently unaffected by the harbor seal disease, are sterile. The total Baltic gray seal population has fallen from an estimated 100,000 at the beginning of this century to about 1,500, and a number of researchers believe the seals will be extinct by the year 2000.

In addition to shoreline contamination, all of the northern European coastal nations engaged until recently in large-scale dumping of toxic waste in the open sea, and since 1969 they also have been burning hazardous waste at sea, spewing toxic gases into the air. The environmental organization Greenpeace estimates that nearly 90,000 tons of toxic waste is incinerated in this manner each year.

Each of the coastal nations has agreed to stop open-sea dumping by the end of next year, and incinerating by 1994. Recently, after intense public pressure, West Germany’s environmental minister, Klaus Toepfer, proposed an $11-billion North Sea cleanup plan that he said would cost each four-person German household an extra $160 a year. Political opponents argued that the proposal was too little, too late and that it concentrated on new sewage treatment plants financed by individual taxpayers, while letting big industry and agriculture off the hook.

Most scientists agree that pollution is likely to be a large contributory factor to the harbor seal epidemic. Speaking before a panel of environmental experts from the governing Christian Democratic Union in Bonn, Dr. Guenther Heidemann, West Germany’s leading seal investigator, said that scientists have not yet definitively identified the cause of the deaths. But, he said, it is clear that chemicals in the water weaken the seals’ immune systems.

Even in the sea off Sweden’s Tanum County, where the water is reckoned to be the purest of any part of the Swedish coast, pollution is rampant.

“Fifty years ago, you could see straight down into the sea, 15 or 20 meters,” said Bengt Samzelius, the county environmental health officer. “Now there is a lot of vegetation, and it’s not so clear.” Microscopic forms of algae have been replaced gradually by much larger forms as they feed off the artificially increased levels of nitrogen and phosphorous spewed into the water by man.

“There have been lots of theories in the past few years” about who is principally responsible, Samzelius said. “Your scapegoat depends on who you hate the most.”

On the western Swedish coast, fingers are pointed in two directions. South of here lies the city of Goeteborg, whose sewage cleanup has been found wanting, as well as a paper pulp factory, nuclear power stations, an oil refinery and a large concentration of chemical industries. To the north is Norway, which Samzelius said is “15 to 20 years behind Sweden in industrial waste cleanup.”

Cautious About Conclusions

Although some here have blamed the deaths of the mussels, sea birds and fish on pollution, Samzelius is cautious. “In the 16th and 17th centuries,” he said, there were huge amounts of herring along the western coast, and Swedish herring oil exports went so far afield that “they burned it in the Paris street lights.”

Suddenly, however, “the herring were gone,” Samzelius said. “It was a catastrophe, but you couldn’t blame it on industrial waste. There wasn’t any then. So, you need to have a historical perspective.”

Whether pollution is responsible for the seal deaths or not, he said, the one ironic benefit to come out of the widely publicized disaster may be an increase in sorely needed resources and attention paid to the sea environment. Despite locally produced and widely distributed pamphlets telling people what is going on and offering assurances of human safety, many of the thousands of wealthy vacationers from Stockholm who maintain summer cottages here have been afraid to swim in the water or eat its fish, he said. They will take home their concern and demand that something be done.

But although pollution may have enabled the epidemic to spread more quickly among the chemically weakened seal population, few scientists believe that it is the actual cause of the disease. “The crucial thing now,” Haerkoenen said, “is to determine how it was introduced into the population. What are the trigger mechanisms behind it?”

Aborted Seals

The first dead adult seals and aborted pups were found April 12 on the Danish island of Anholt, in the Kattegat. Eventually, 95% of all pregnant females on Anholt aborted. The disease quickly spread along the Danish coast. By mid-May, dead seals were found on Sweden’s west coast, then in Norway, West Germany and the Netherlands. Most recently, dead harbor seals have been discovered at the easternmost limit of their habitat, along the lower Swedish Baltic coast.

The number of deaths has grown exponentially in all affected countries, and although some sick seals have been found alive in the water, none has been saved. Since the harbor seals tend to remain in fixed colonies in specific areas, researchers who have long studied them believe they will soon know how many, if any, are surviving. An annual air survey of Swedish seals is conducted during the late August molting season, when most seals are out of the water.

Studies of the blood and tissues of dead animals have indicated they have been infected with a virus, either of the herpes family or, more likely, of the picorna family that also causes polio in humans. Virologist Bernt Klingeborn of the Swedish biomedical center in Uppsala said he has found picorna virus in nearly all tissues. “But we have to prove the virus is causing the disease,” he said.

“The virus attacks the immune system, wiping it out,” said Haerkoenen, who is heading Sweden’s investigation of the epidemic from the Tjaernoe Marine Biology Laboratory on an island near Stroemstad. Pneumonia, the apparent direct cause of death, “sets in very rapidly,” Haerkoenen said. “What we don’t know is whether the virus itself also affects the lungs. We don’t know in what order it happens; what is cause, and what is effect.”

‘A Bit Sensational’

Haerkoenen said it is “a bit sensational” to compare the mystery seal disease with AIDS, which similarly attacks the immune system in humans, “but there are parallels.”

Unlike acquired immune deficiency syndrome, the seal disease is not transmitted sexually but in the manner of influenza and the common cold--from seals in close company breathing and sneezing on each other and spreading upper-respiratory infection. The introduction of the disease came at a particularly unfortunate time, since the harbor seals give birth in June and July, mate in late July and molt in late August--all activities that cause them to congregate in large groups on land.

“The problem is that most diseases like this strike the part of the population that is weak in one or another respect,” Haerkoenen said. “But this disease strikes the weak and the healthy in the same way. Most of the animals were in excellent condition, in their prime.”

Nearly all of the approximately 4,000 seal corpses that have been found on the Swedish coast have been taken to the Tjaernoe lab for autopsies. In addition to continuing study of the virus, an “ecological inventory” will be done on each seal, determining the level of a range of chemicals and heavy metals in each seal’s body.

British Research Asked

Haerkoenen also has asked researchers in Britain, where the only apparently healthy European seal population still remains, to capture and kill 30 animals to determine if antibodies corresponding to the killer virus are already in their blood. If they are, it will indicate whether the disease was caused by something that triggered a previously existing virus common to all European harbor seals or a new virus was introduced into those animals that were stricken.

Dutch scientists in late July announced that they had developed a vaccine for the virus and were inoculating apparently healthy seals, but results so far have been inconclusive.