hen I tell Monty Graham about my own experiences swimming off Long Island over the years -- watching the jellyfish bloom even as medical waste, sewage, and garbage-barged debris washed ashore more and more frequently -- he says that he can't tell me whether the pollution and the jellies are related. All he can say is that it's a good possibility.
Then Graham describes an episode that I will come to think of as Apocalypse By Jellyfish. In 1982, comb jellyfish were inadvertently dumped into the Black Sea -- Europe's most contaminated sea -- when a U.S. ship emptied its ballast water. The Black Sea had never seen a comb jelly before, and it contains no native fish or jellyfish populations that prey on combs. Moreover, overfishing had slashed the fish populations that would have otherwise competed with the comb jellies for food.
The Black Sea is semi-closed, so, initially, no new predators could get in to check the comb jellies once they started to multiply. And multiply they did. Reproducing fast and furiously in this enormous new habitat, comb jellies soon crowded out almost all other fish. By 2000, incredibly, the total weight of the Black Sea's comb jellies was more than ten times the weight of all fish caught throughout the world in a year.
Since 1997, another jellyfish species introduced with ballast water has been eating comb jellies in the Black Sea, thereby reducing their numbers. But the comb population explosion has cost the Black Sea fishing industry more than $350 million and ravaged tourism in the area. The sea's vulnerability to comb jellies was neatly defined by Colin Woodard in his recent book about ocean pollution, Ocean's End: "As a weakened man easily succumbs to disease, so damaged ecosystems readily fall victim to attacking forces."
The collapse of the Black Sea fishery, says Graham, has inspired more government and public concern about the jellies of the Gulf of Mexico, Narragansett Bay, and the Bering Sea. He emphasizes that he doesn't expect a worldwide jelly Armageddon. After all, some degraded water bodies remain free of jellyfish blooms. And some jellyfish blooms may reflect long-term population fluctuations that are not yet understood.
Nevertheless, scientists cannot dismiss the possibility that jellyfish could one day push other troubled waters into ecological freefall. Adds Claudia Mills, "Yes, the ocean is vast, and over the past 4 billion years it has been quite able to take care of itself. But it is now demonstrating at nearly every turn that humans are overtaxing its resources."
This summer, things could get worse before they get better. Graham points out that droughts over much of the United States this year mean that less freshwater is flowing to the sea, which in turn means that coastal waters will be saltier. And jellyfish like salty water -- raising the possibility of bumper crops. So if, while swimming in the ocean this summer, you have a jellyfish encounter that makes your skin crawl, remember: What you may be feeling are the long tentacles of environmental change.