From ancient times, humans have been drawn to the Black Sea, a kidney-shaped basin the size of California nestled between Eastern Europe and Asia Minor. Its anchovy and sturgeon stocks sustained Ancient Greece, medieval Byzantium, the Ottoman Empire and Imperial Russia.
In the 20th century, millions of tourists flocked each summer to its beaches in Turkey and on the “Communist Riviera,” which stretched from Bulgaria and Romania to Soviet Russia. They swam, feasted on fish and basked in the sunshine, recuperating from winter months in the factories of Budapest and Birmingham.
Then, with astonishing suddenness, the ecosystem collapsed in the early 1990s due to a combination of fertilizer and sewage pollution runoff, destruction of wetlands and the introduction of an aggressive, non-native, jellyfish-like species. Given the plethora of critical ocean ecosystems now in jeopardy, the Black Sea collapse provides a cautionary tale about the fragility of marine ecosystems, say marine scientists.
“The Black Sea is a microcosm of the environmental problems of the planet,” warns Janet Lubchenco, a professor of marine biology at Oregon State University. “Solutions to the Black Sea crisis may enlighten, inform and inspire our global challenges.”
Few saw it coming. The Black Sea had been subject to pollution for decades: Industrial wastes, oil spills and radiation from the 1986 Chernobyl nuclear accident had been carried to the sea by its tributaries — apparently without dramatic effect. But it was the buildup of raw sewage and fertilizer runoff — coupled with the accidental introduction of an alien, plankton-devouring species, the comb jelly — that triggered the near-death of the sea.
The sea's largest tributary, the Danube River, drains half the European continent during its 2,000-mile journey from the Black Forest of Switzerland to Romania's Black Sea delta. The last half of that journey winds through Eastern Europe, where for decades every village, town and city flushed its untreated sewage into the river. Starting in the late 1960s, state-owned farms used huge quantities of subsidized chemical fertilizers on their fields, and much of it ran off into the streams feeding the Danube. Hydroelectric projects and navigational canals also damaged or bypassed wetlands that once acted as the river's natural filtering system. And Romania's dictator, Nicolae Ceausescu, waged all-out war on the Danube delta — Europe's greatest wetland — in an ill-conceived attempt to convert it to rice production.
As a result, concentrations of nitrogen and phosphorous nutrients in the Black Sea's ecologically critical northwestern shelf dramatically increased between 1960 and 1980. The nutrients fueled enormous algae blooms in the late 1980s, smothering bottom life by using up the oxygen it needed. As the microscopic plants decomposed, they consumed still more oxygen in vast stretches of the sea, suffocating most other creatures.
Then in 1982, Mnemiopsis leidyi, an inch-long comb jelly native to North America, was introduced to the sea in the ballast water of a passing ship. The creature established itself amid the gathering chaos and proceeded to graze the waters clean of survivors. With no natural predators, it ultimately achieved a biomass of 1 billion tons — 10 times the weight of all the fish caught by all the world's fishermen in a year.
“The biomass of other zooplankton dropped sharply, and the catches of commercial fish sharply decreased,” noted Yuvenaly P. Zaitsev chief scientist at the Odessa office of the Ukrainian National Academy of Science. “Mnemiopsis . . . is usually held responsible for much of what happened.”
By the early 1990s, total fish landings had fallen to one-seventh of their previous level, and the signature anchovy catch fell by 95 percent. Slicks of ugly, stinking slime drove tourists from the beaches and prompted long closures at the height of summer. Hundreds of bathers became ill and several died from cholera and other infectious diseases that thrived in the algae-choked environment. In 1999 the World Bank estimated the economic damage to the fisheries sector at $300 million a year and $400 million to tourism.
The past five years have seen considerable progress, however, as the European Union — with its strict environmental regulations — expanded to include 10 former communist countries, including Slovakia, Hungary, Romania, Bulgaria and other nations in the Danube's middle and lower basin.
“When these countries joined the EU, they had to adopt new environmental policies and regulations, which has had the benefit of improving the overall water quality situation in the Danube basin,” notes Ivan Zavadsky, program director of the Danube/Black Sea Regional Program in Vienna, a joint project of the United Nations and World Bank, which has pumped $70 million into cleanup projects in the region.
New sewage treatment plants have been built in recent years, and many of the most polluting factories and agricultural enterprises collapsed in the early 1990s. As a result, Zavadsky notes, concentrations of phosphorus and nitrogen — the nutrients that ravaged the Black Sea — have dropped 50 percent and 20 percent, respectively, since 1989. Meanwhile, the Mnemiopsis' population dropped precipitously after the arrival of the Beroe, another invading comb jelly that feeds exclusively on Mnemiopsis. Once the Beroe had eaten all the Mnemiopsis, its food source was depleted, so Black Sea populations of both species have now been decimated.
“We're witnessing the first signs of a recovery of the Black Sea ecosystem,” says Zavadsky, citing reduced algae blooms and an increase in some bottom plants and animals. “But the situation remains on a knife's edge.”
But Janos Zlinszky, the government and public affairs manager of the Regional Environmental Center for Central and Eastern Europe in Szentendre, Hungary, is concerned that many of the gains could be lost if the region's economic recovery outpaces its environmental investments. “Romania and Bulgaria have just joined the EU,” he says. “If they decide to focus on intensive agriculture rather than the organic market, we could see great increases in fertilizer and pesticide use.”
“There's an extraordinary window of opportunity to take action,” says Laurence Mee, director of the Marine Institute at the School of Earth, Ocean and Environmental Sciences at the University of Plymouth, in England. “But it can easily be lost.”