By Janet Raloff
Second of two parts. Part I: “Dead Waters“
Every second, the mighty Mississippi gushes another 4.5 million gallons of water into the Gulf of Mexico. Along with the water come nitrate and other pollutants. In the Gulf and other large bodies around the globe, plant nutrients—especially nitrate—have created coastal dead zones. The nutrients fertilize the growth of algae, which soon die, settle to the seafloor, and decay. Bacteria feeding on the algal corpses consume so much oxygen that the water becomes unsuitable for most forms of life.
In the face of an increasing number and persistence of dead zones worldwide (SN: 6/5/04, p. 360: Dead Waters), some researchers are trying to stem the flood of plant nutrients into rivers and eventually seas. The U.S. government limits major releases of nitrate into the environment because high concentrations of the nutrient can be toxic to wildlife and even people.