Dr. Giblin of Woods Hole spent the summer at the field station here, midway between the Arctic Circle and the Arctic Ocean, researching the nitrogen content of lakebed sediment  not the inert nitrogen that makes up 80 percent of air, the reactive nitrogen that Dr. Galloway referred to. In forms like nitric acid, nitrous oxide, ammonia and nitrate it plays a variety of roles.

Nitrogen is part of all living matter. When plants and animals die, their nitrogen is passed into soil and the nitrogen in the soil, in turn, nourishes plants on land and seeps into bodies of water. Dr. Giblin is pursuing her research because as the Arctic warms, the tundra’s permafrost will thaw, and the soil will release carbon and nitrogen into the atmosphere.

When an ecosystem has too much nitrogen, the first response is that life blossoms. More fish, more plants, more everything. But this quickly becomes a kind of nitrogen cancer. Waters cloud and are overrun with foul-smelling algae blooms that can cause toxic “dead zones.” Scientists call this process eutrophication, but the laymen’s translation is that the water gets mucked up beyond all recognition. A recent such plague bedeviled China when its Yellow Sea was smothered in algae at Qingdao, the planned site of Olympic sailing events this summer. More than mere inconvenience, such problems routinely threaten many coastal areas and riverside communities.

Nancy Rabalais, executive director of the Louisiana Universities Marine Consortium, is known as Queen of the Dead Zone. She cruises around the Gulf of Mexico every summer in the research vessel Pelican to look for damage from nitrogen-rich river flows into the gulf. This year, she expects a dead zone that will beat the Massachusetts-size 8,500-square-mile bloom of 2002.

One of the problems, Dr. Rabalais said, is that the Mississippi River involves so many communities that it requires stronger federal guidance, which she said was not a part of the Bush administration’s policies. She is part of a national research committee financed by the Environmental Protection Agency and run by the National Academies of Science, but, she said, “it’s so much talk and not enough action.”

She continued: “Because you’re not just going up against the agribusiness lobby, but also the livelihood of farmers. It’s not exactly popular in the Midwest.”

Fertilizer use is largely inefficient. With beef, only about 6 percent of nitrogen used in raising cows ends up in their meat; the rest leeches out into air or water supplies. With pork, it is 12 percent; chicken, 25 percent. Milk, eggs and grain have the highest efficiency, about 35 percent, or half of what, in the metric of report cards, is a C-minus.