SAN ANTONIO -- Environmentalists say fertilizer use in the Mississippi River basin must be cut by 25 percent to stop an expanding "dead zone'' in the Gulf of Mexico.

Environmental experts addressed environmental attorneys at a two-day conference that opened yesterday at San Antonio's Hyatt Hill Country Resort.

One was researcher Andrew Solow of the Woods Hole Oceanographic Institution in Massachusetts. He says studies specify the reduction in fertilizer use and wetland restoration as keys to containing the five-thousand-square-mile "dead zone.''

The area of oxygen-depleted water is located in the Gulf near the mouth of the Mississippi River. Solow says it stretched toward the Texas coast for the first time this summer.

He says shrimp and fish can escape the zone. But he says crabs and other slow-moving species can die where trillions of tiny sea plants called phytoplankton sink, die and decay.

Meanwhile, he says marshes and wetlands that catch sediment and nutrients, reducing nutrient-laden runoff, continue to shrink.