Shrimpy invaders.A new type of shrimplike crustacean crustacean (krŭstā`shən), primarily aquatic arthropod of the subphylum Crustacea. Most of the 44,000 crustacean species are marine, but there are many freshwater forms. has appeared in the Great Lakes Great Lakes, group of five freshwater lakes, central North America, creating a natural border between the United States and Canada and forming the largest body of freshwater in the world, with a combined surface area of c.95,000 sq mi (246,050 sq km). , and that's not necessarily a good thing. [ILLUSTRATION OMITTED] These crustaceans, called mysid shrimp mysid shrimp: see shrimp. , normally live in rivers near the western coast of the Caspian Sea Caspian Sea (kăs`pēən), Lat. Mare Caspium or Mare Hyrcanium, salt lake, c.144,000 sq mi (373,000 sq km), between Europe and Asia; the largest lake in the world. in eastern Europe. In November, researchers from the National Oceanic and Atmospheric Administration Noun 1. National Oceanic and Atmospheric Administration - an agency in the Department of Commerce that maps the oceans and conserves their living resources; predicts changes to the earth's environment; provides weather reports and forecasts floods and hurricanes and (NOAA NOAA abbr. National Oceanic and Atmospheric Administration Noun 1. NOAA - an agency in the Department of Commerce that maps the oceans and conserves their living resources; predicts changes to the earth's environment; ) found invading mysid shrimp in a channel in Lake Michigan. Now, NOAA reports that large numbers of the animal, called Hemimysis anomala, are living in southeastern Lake Ontario. "I predict it will be a highly disruptive species," says Anthony Ricciardi of McGill University in Montreal. Mysid shrimp devour microscopic animals, which many young fish in the Great Lakes also eat. A heavy dose of new competition for food may harm fish populations. The invasion is not a total surprise. From the 1970s through the 1990s, many creatures from the same area of eastern Europe entered the Great Lakes in ships that carry seawater seawater Water that makes up the oceans and seas. Seawater is a complex mixture of 96.5% water, 2.5% salts, and small amounts of other substances. Much of the world's magnesium is recovered from seawater, as are large quantities of bromine. to help keep them stable. This water is called ballast water. It's often dumped as ships load and unload cargo wherever they happen to be. In 1998, Ricciardi and a colleague came up with a list of 17 more European species that would probably arrive next. Hemimysis was on this list. Although most European ships entering the Great Lakes now dump nearly all the water (and the critters living in it) from their ballast tanks before leaving Europe, a small amount still remains on board. That's still enough water to harbor species such as Hemimysis anomala. This water can end up in the Great Lakes while ships unload and take on cargo. New guidelines recommend that ships flush their tanks with saltwater before entering the Great Lakes. This "swish and spit" technique should be enough to kill any freshwater species that have come along for the ride. It's not yet clear how Hemimysis will affect Great Lakes ecosystems. Larger fish might find the shrimp appetizing, but these fish could then become more toxic to people. Mysid shrimp are fatty, so they can collect high doses of pollutants in their bodies. These pollutants then work their way up the food chain. H. anomala look small and innocent, but don't underestimate their ability to shake things up. "This is not," Ricciardi says, "a species to ignore."--E. Sohn |
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