Hurricane Barry could affect the environment of the Gulf coast and Lower Mississippi Valley in numerous ways, from accelerating runoff of farmland nutrients to toppling trees and damaging wildlife habitat and fisheries, scientists say. But the extent of the damage—and whether it will be at least partially offset by benefits such as disruption of the notorious Gulf of Mexico "dead zone"—is hard to predict, they say. That's because the region faces a rare 1-2-3 punch: the storm's anticipated tidal surge and torrential downpour, combined with record-high water levels in the Mississippi River, the AP reports. "We don't know how the system is going to respond to all this because it's so unusual," said Melissa Baustian, a coastal ecologist with the Water Institute of the Gulf in Baton Rouge, Louisiana.
Rainfall washes manure and chemical fertilizers from Midwestern corn and soybean fields into streams, smaller rivers and eventually the Mississippi. The nutrients—especially nitrogen—overfeed aquatic plants that eventually die and decompose, leaving a large section of the Gulf with little or no oxygen each summer. The National Oceanic and Atmospheric Administration predicted that this year's dead zone will be roughly the size of Massachusetts. In addition, Barry's could topple lots of trees, their roots weakened by the saturated ground. Also vulnerable are Louisiana's famed coastal marshes, already hammered by development and flood control measures that prevent natural coastal shoreline replenishment. Scientists also will keep watch for stranded dolphins. About 290 have been found along the Gulf coast since Feb. 1—triple the usual number—and nearly all have died. (Barry misses New Orleans.)