Manatees, already endangered, had a bad year. Some 400 of the big aquatic mammals died in 1996, the largest death toll in 22 years and nearly double the previous record. Although they are routinely run over by powerboats, last spring they fought a subtler enemy: a red tide--an explosive bloom of toxic algae--killed at least 158 of them. The problem began with an unusually cold Florida winter. About 800 manatees swam up the Caloosahatchee River in west central Florida to hang out in the warm water around a power plant. In the early spring, as the weather warmed, the manatees began to swim downriver, heading for their usual coastal haunts. That’s when they ran into trouble. As they were coming out, the red tide was coming in. It was a matter of bad timing, says Scott Wright, a marine mammalogist at the Florida Department of Environmental Protection. Autopsies found algal toxins in the manatees’ stomachs, lungs, kidneys, and livers. The Florida dep is considering steps to protect them from future red tides. The algae don’t survive well in low-salinity water, says Wright, One thing to do is to make the water less salty. You can do that by pushing freshwater into an area with a lot of red tide. The total manatee population now stands at around 2,200.