Caspian Calamities
by John Tidwell
Apart from the caviar trade, Caspian sturgeons’ rapid decline may also be attributed to the degradation of the Caspian Sea. The largest and most voluminous inland body of water on Earth, the Caspian Sea covers about 150,000 square miles, an area nearly the size of California. Decades of waste runoff from cotton fields and factories along most of the Caspian’s 130 tributaries have flooded this sea with so many pollutants that they have begun showing up in sturgeon meat and caviar. A study last year by the Institute of Freshwater Ecology and Inland Fisheries in Berlin found that caviar from the Caspian contained levels of DDT, PCB, and cadmium possibly high enough to disrupt the sturgeons’s hormone levels during development, which could lead to infertile or mixed-gender fish. Manfred Wirth, one of the study’s authors, said it wasn’t clear what effect these pollutants might have on humans who ate the caviar from these fish.
The Caspian may also become the site of the next great oil rush, as Western oil companies vie with each other—and with the governments of Russia, Iran, Kazakhstan, Turkmenistan, and Azerbaijan—for an estimated 200 billion barrels of oil, worth roughly $4 trillion, that lies beneath the Caspian Sea. How to get it out has been more a political problem than an engineering one, with Russia worrying that its breakaway republics will steal the deal, while the U.S. keeps a nervous eye on Iran.
“It’s like the Great Game of the late 19th century,” says David Aubrey, coordinator of the Caspian Environment Project, an assessment program started by the Caspian nations and funded by organizations like the World Bank and the UN. “And it will become more like the California Gold Rush if things work out. But I think the real danger to the Caspian won’t be from oil drilling once things get going, but from a major oil spill. That could kill everything in there.”
Another threat to sturgeon is the invasion of the Caspian by a fist-sized comb jellyfish (Mnemiopsis leidyi) native to North America. Scientists suspect the alien jellyfish first arrived in the Black Sea—which is connected to the Caspian by the Don and Volga rivers—in 1982, carried in the ballast water of ships from the Chesapeake Bay. According to reports by Henri Dumont, a biologist at Ghent University in Belgium, the voracious jellyfish devoured nearly all of the Black Sea’s zooplankton, causing a massive crash of the native fish population and crippling the local fishing industry there. This comb jellyfish species, a self-fertilizing hermaphrodite, was found in the Caspian in 1999. By the summer of 2000, the entire sea was teeming with them.
“Economic losses to the fisheries may become enormous in one to two years’ time,” says Dumont. “The pelagic fisheries will collapse, and the Caspian seal [Phoca caspica] that prey on them will follow, probably becoming extinct. Kilka [Caspian sardines] may recover later, as Mnemiopsis empties the Caspian of food and then collapse themselves, as happened more or less in the Black Sea.”
Discussion among scientists and littoral state officials are underway about how to stop Mnemiopsis, including proposals to introduce its natural predators: the North American butterfish (Peprilus triacanthus) and another jellyfish, Beroe ovata.
ZooGoer 30(3) 2001. Copyright 2001 Friends of the National Zoo. All rights reserved.
