The hazardous waste that makes more of itself
The convulsions have ebbed away but left a low-grade infection, incurable and subject to flare-up. This is the victim: the Black Sea, where Ovid passed his exile, where the Byzantine Empire rose and gave way to the Crusaders, the Golden Horde, and the Ottoman Turks. These are the waters stained by the terrible pogroms of Stalin and Hitler, caressed by generations of Russian elite on holiday.
And all that time, along the Atlantic coast of the Americas, constellations of little luminescent blobs were drifting along, here and there, out beyond the roar of the surf. This is the pathogen: the Leidy's comb jelly (Mnemiopsis leidyi), a widespread species but nothing special. Until one day in the early 1980s, when a ship enroute from - who knows? - New York, maybe, or Caracas, sailed up the Bosporus, into the Black Sea, and squirted the jelly out of its ballast water tanks.
Leidy's comb jelly eats the myriad tiny animals known collectively as zooplankton. And since nothing in the Black Sea would cat the jelly, it launched one of the most intense biological invasions ever recorded in a marine ecosystem. By late 1988, a single cubic meter of Black Sea water could contain as many as 500 jellies, most of them probably smaller than your thumb. If all of the jellies could have been hauled out of the sea that fall and weighed, the take would have come to between 900 million and 1 billion tons - at least 10 times the total world fishery catch for that year. But the anchovies and other fish that make up the sea's traditional catch had largely disappeared. The Black Sea had been poisoned by ballast water, one of the most common forms of marine pollution today - and one of the most dangerous.
Despite its apparent stability, a big ship doesn't sail simply by virtue of its design, any more than an airplane flies simply because it has wings. Keeping a ship upright takes ballast water - lots of it. Moving that water in and out of the cavernous tanks designed to hold it is as critical a part of the nautical routine as managing the rudder or the engines. Ballast water must be taken on when cargo is unloaded, or as fuel is consumed, or to provide extra stability in heavy weather, or sometimes to make the ship ride low enough to pass under a bridge. And for every reason that it's pumped aboard, there's a corresponding reason for pumping it out - taking aboard cargo, making the ship ride high enough to move into a shallow harbor, and so on. The ballast capacity of a big tanker can exceed 200,000 cubic meters - enough to fill 2,000 Olympic-sized swimming pools - and its pumps can move that water at rates as high as 20,000 cubic meters an hour. That's not gentle suction. Most ballasting is done around harbors, in shallow water, and ships sometimes scour the bottom as they're ballasting up. In the resultant turmoil, the slurry gushing into the tanks may contain hundreds of cubic meters of sediment - along with any small creatures that happen to be in the water, the mud, or on nearby harbor pilings.
The tanks of a large ship may come to support a chaotic but more-or-less permanent living community. A large ballast tank can only be emptied completely by opening it up, and that is only done during dry-dock overhaul, which on a well-maintained vessel might occur every three to five years. Routine use always leaves plenty of room for biological activity. In one recent survey of large ships reporting no ballast on board, the burden of unpumpable water and sediment in their "empty" tanks averaged 157.7 metric tons - enough to fill perhaps a dozen dump trucks.
Ballast water is a soup stocked from harbors all over the world. The holes in ballast intake grates arc usually about a centimeter wide. That's probably plenty of room for most marine organisms in larval form - most fish larvae, for instance, are small enough to pass through. Sometimes the grates fall off, allowing much larger creatures to enter. In April 1995, for example, the tanks of a ship that had come into Baltimore harbor from the eastern Mediterranean were found to contain more than 50 healthy mullet from 30 to 36 centimeters long.
But some of the most significant stowaways are microscopic: in 1991, ballast discharge from ships arriving in Peruvian ports from South Asia is thought to have unleashed the first cholera epidemic that the Western Hemisphere had seen for more than a century. The outbreak may have infected several million people and killed 10,000 of them. Ships outbound from Latin America were found to have cholera-laden ballast upon arrival in ports in Australia and the United States. In 1992, as the epidemic gained momentum in South America, more cases of imported cholera were observed in the United States than in any year since surveillance for that disease began.
There are more than 28,700 vessels in the world's major merchant fleets and they make up by far the largest part of the world's trading infrastructure. About 80 percent of the world's commodities travel by ship for at least part of the journey to their consumers, and the volume of seaborne trade is climbing steadily upward. From 1970 to 1996, the trade nearly doubled (it climbed from 10,654 billion ton-miles, the standard industry measure, to 20,545 btm). Through its ballast systems, the world merchant fleet has in effect superimposed a second set of currents on the world's oceans, and these meta-currents are far more efficient at transporting life over long distances than are the natural ones. On any day, the meta-currents are moving perhaps 3,000 different species of every conceivable ecological function: green plant, pathogen, parasite, herbivore, carnivore, scavenger. And in harbor after harbor, the same species arc appearing over and over again - the same crabs and clams, the same worms, sometimes even the same fish. The world trading system is creating an extra-geographical marine biota. (See table, page 25.)
In the Black Sea, the process was so traumatic partly because the native biota was already so sick. Over the previous several decades, the sea had grown steadily more polluted from fertilizer run-off and the raw sewage of some 170 million people. This nutrient-rich pollution was feeding clouds of algae, which were robbing the water of light and burning up oxygen as they decayed. The Black Sea is naturally anoxic (oxygen-poor) to begin with. For millennia, rafts of plant material would sweep in from the Danube and the other tributary rivers, consuming the oxygen as they rotted, and leaving only a film of aerated water riding a vast anoxic pool - the largest such pool on earth. The algae had begun to suffocate that upper layer of life. The algae were also shading out the huge shallow-water seagrass beds that had once functioned as the sea's "lungs" - and as prime habitat for fish, crustaceans, sponges, and many other creatures. But zooplankton cat algae - and zooplankton were just about all that remained of the sea's battered immune system. Then the jelly ate virtually all the zooplankton. Algae and jelly were almost the only living things in the water. At its peak, the jelly alone accounted for 95 percent of the sea's entire wet weight biomass.
By the mid-1990s, the jelly was showing signs of having exhausted its larder. Its Black Sea population has declined, but by 1992 it had invaded the Sea of Marmara, below the Bosporus, and it has turned up farther south, in the Aegean as well. Eventually, it might infest much of the Mediterranean coastline. Shipping could also take it north, up the great European rivers that run into the Black Sea, and into the Baltic. Neither the Mediterranean nor the Baltic arc in robust health and we have no way of knowing how either would cope with an M. leidyi infection. In the meantime, several jellyfish native to the Black Sea have established themselves in the Chesapeake Bay on the U.S. East Coast, and in San Francisco Bay on the West Coast.
Despite their capacity for havoc, most ballast-water invaders don't get much press. To the news media and probably to the public in general, marine pollution usually means oil spill. The 1989 Exxon Valdez spill in Alaska's Prince William Sound, for example, attracted major media coverage for months. But what about the spill that is spreading through the Sound today? In December 1997, the U.S. Fish and Wildlife Service announced that it had discovered four new species of zooplankton in the Sound, where they had been released from tanker ballast. The plankton appear to have come from East Asia via San Francisco Bay. Scientists are concerned that the invaders may develop a taste for the same foods that are needed by the Dungeness crab, an important fishery species. As more and more Alaskan oil is pumped, some scientists fear that ballast releases like these could become a general threat to the state's fisheries. The biotic spills, in other words, could become a far greater danger to Alaskan coasts than the oil spills. After all, oil spills may be a grave environmental insult, but they eventually go away. Biotic spills do not.
Biotic spills have been a major ecological side-effect of commerce for centuries, but ballast water is a fairly recent variation on the theme. Keeping a ship afloat by pumping some of the ocean into it was an innovation made possible by motorized pumps and metal hulls. By the turn of the century both of these technologies were well established and ballast tanks had become common. The first known ballast water invasion dates from the same era: a Chinese species of plankton, Biddulphia sinensis, appeared in the North Sea.
Earlier generations of sailors shoveled ballast into their ships: rocks, earth, scrap metal, any other heavy portside debris - along with the resident beetles, earthworms, sandfleas, and seeds. Ballast was supposed to be dumped and collected at specific sites around harbors. By the last century, botanists knew that these "ballast points"...