Environmental News Scientists elucidate role elements play in eutrophication New findings that silicon and iron play an important role in coastal eutrophication were announced at a September conference of the Estuarine Research Federation, an international educational organization. Water managers for too long have focused only on nitrogen and phosphorus as a cause of excess algal production, overlooking the significant role played by other nutrients scientists said. A drop in the ratio of silicon to nitrogen in the Mississippi River has altered the composition of the food chain in the vicinity of the Gulf of Mexico's oxygen-poor dead zone, said Gene Turner, an ecologist at Louisiana State University in Baton Rouge. Thanks to human activities such as farming and dam building, nitrogen levels have tripled, while silicon levels have lowered to half of their historic values in the Mississippi River he said. Scientists hypothesize that when algae containing silicon die and drop to the river bottom dams hold back sediment and prevent the silicon from reentering the system Farm fertilizers have elevated historic levels of nitrogen Turner's research shows that when the silicon-to-nitrogen ratio falls below 1 to 1, diatoms—algae with silicon coatings—cannot grow. Diatoms are the favorite food of zooplankton, whose numbers decline along with falling diatom levels. This reduction in turn depresses the populations of small larval fish that feed on the zooplankton. The problem with nutrient loading in die Mississippi River is not just excess algal production but a change in nutrient ratios mat has altered the aquatic community favoring less edible species of algae and perhaps PVPT1
harmful Turner said The conventional wisdom that nitrogen availability limits algal growth in most estuaries has been challenged by new results from Alan Lewitus, physiological ecologist at the University of South Carolina's Baruch Institute. Lewitus has shown that forests
Experts expect that eutrophication conditions will worsen in more than half of the nation's estuaries, and along all of the coasts, by 2020.
provide the organically bound iron needed by algae. Clear-cutting coastal forests reduces the amount of biologically available forms of iron, which limits the growth of algae. Lewitus suspects that iron limitation leads to the loss of diatoms, a favorite food species, and excess production of less desirable blue-green algae. These results are "extremely significant" in light of die just released National Estuarine Eutroph-
ication Assessment, said Suzanne Bricker, physical scientist witii die National Oceanic and Atmospheric Administration (NOAA). NOAA's assessment found tiiat 84 of 139 estuarine systems have moderate to high levels of eutrophication. Many of tiiese estuaries have not been well studied, and the new research highlights die need for a comprehensive approach to monitoring and studying tiiese systems, she said. JANET PELLEY
Legislators, environmentalists, and states up in arms over anti-environmental rider Because a rider signed into law this fall as part of the fiscal year 2000 defense appropriations bill could shield the Pentagon from penalties for violating environmental standards, some influential groups are agitating for its repeal. Proponents of a bill introduced in the House of Representatives this November to repeal the rider have vowed to renew their efforts to defeat the law when Congress reconvenes this month. Despite calls for a veto over the rider by Congress and environmentalists, President Bill Clinton signed the $268 billion Defense Appropriations Act in late October. Days
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later, fears that the rider could affect ongoing work at dozens of Pentagon facilities across the country, including the Massachusetts Military Reservation and South Weymouth Naval Air Station in his home state, spurred Rep. Bill Delahunt (D-Mass.) to introduce a bill repealing it. By mid-November, Delahunt had rallied 62 cosponsors from both parties and had launched a Web site to inform citizens about his bill (www.house. gov/delahunt) The National Association of Attorneys General, the Environmental Council of the States, and a number of environmental orga-
