Environmental News: OnEarth Magazine
The Blobs Of Summer
continent away from the gulf lies another jellyfish-cursed body of water. This is the Bering Sea, the frigid but highly productive waters that separate Alaska and Siberia. So fish-full is the Bering Sea that it accounts for more than half of the U.S. catch of fish and shellfish. But today, commercial fish species are increasingly competing for food with growing numbers of native jellyfish, particularly the pizza-sized Chrysaora melanaster, whose frilly mouth parts and tentacles extend for yards.
Since the early 1990s, the jellyfish population of the Bering Sea has increased more than tenfold, according to Claudia Mills of the University of Washington's Friday Harbor Marine Laboratory. Mills helped analyze data on Bering Sea marine life that has been collected regularly since 1979 by the Alaska Fisheries Service Center. One area off the Alaskan Peninsula, she says, is now so thick with jellyfish that its nickname is the Slime Bank. (Mills has the typically wacky jellyologist's sense of humor. She tells me that the menu at the jellyfish blooms conference included -- but of course -- jellyfish, which are considered a delicacy in Asia. "The appeal is in the crunch," Mills jests. "It's a textural thing.")
The $10,000-per-day cost of running a research vessel in the remote Bering Sea complicates the study of its jellyfish. Theories abound about their population explosion, however. Most of them center on the uncanny synchrony between its timing and an abrupt climatic shift in the Bering -- one of those weather phenomena that can't be proven a result of climate change, but bear its hallmarks.
The climatic shift has favored greater ice cover in winter and delayed the annual spring melt. The timing of the ice melt affects jellyfish because it usually triggers a pivotal pulse of plankton growth. According to a theory advanced by Richard Brodeur of the National Oceanic and Atmospheric Administration, the later in the spring this pulse occurs, the more it is amplified by the increased sunlight. By forcing this ice melt further toward the summer, the climatic shift could be increasing plankton food for jellyfish. Hence, the Slime Bank (and other jelly-swamped areas in the Bering Sea). "The ocean," Mills says, "has gone from a wild, unknowable place to something defiled at all levels and locations by human activities."
Climate change may also be affecting another much studied jelly haven: Rhode Island's Narragansett Bay. Dominating the jellyfish population of the bay is the fist-sized, non-stinging comb jellyfish (Mnemiopsis leidyl). (The comb jellyfish does not belong to the same phylum as other jellyfish, despite its name, but it is biologically similar to them.)
So numerous are Narragansett's comb jellies, which glow naturally in the dark, that diver/biologist Wes Pratt rhapsodically compares night-diving in the bay to "exploring a galaxy of little green lanterns." (Pratt willingly confesses to a high "yuck tolerance.") One less sanguine observer is John Torgan, baykeeper with Save the Bay, who recently pulled his research nets from the bay and was dismayed to find them laden exclusively with comb jellies.
If the past is any indication, the nets will only get heavier. Since 1971, Narragansett's comb jelly population has at least doubled, says the University of Rhode Island's Barbara Sullivan -- affectionately known locally as Queen of the Comb Jellies. "I'm certain that these jellies are playing an increasingly important role in the bay ecosystem," affirms Sullivan. At their annual peak, the comb jellies are dense enough to consume half the fish eggs in the upper reaches of the bay.
Sullivan has correlated Narragansett's comb jelly explosion to an increase of almost 2 degrees centigrade in average winter water temperatures. Comb jellies prefer warmer water. The temperature rise could be the reason some clusters are now surviving the winter -- an entirely new development.
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Photo: Dan Martin
OnEarth. Summer 2002
Copyright 2002 by the Natural Resources Defense Council
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