Hurricane Irene Purges Bay’s Dead Zones… And Churns Up Sediment

Hurricane Irene’s high winds breathed a little life into the polluted Chesapeake Bay, bringing some short-term relief to wildlife by temporarily eliminating the estuary’s vast dead zone, according to the Maryland Department of Natural Resources. The bay’s dead zone, a stretch of deep water running from Baltimore to Virginia with dissolved oxygen levels too low to support most aquatic life, emerges every summer and naturally fades with the fall. This year’s dead zone diminished earlier than usual after Irene whipped the area, mixing layers of water containing varying levels of oxygen.

The revived waters could provide habitat for marine life in places that were previously not livable, said Jenn Aiosa, Maryland senior scientist for the Chesapeake Bay Foundation. The massive dead zone in the bay is largely responsible for choking out fish and oyster and blue crab populations over the past several decades. Ultimately, similar conditions will return next spring and the hurricane will have likely made little impact on the bay’s long-term status, scientists said. This year’s dead zone would have dissipated by mid-September regardless of the hurricane, DNR Resource Assessment Director Bruce Michael said, but an early flush will not hurt.

On the other hand, satellite imagery shows large plumes of sediment slowly flowing downstream through local rivers as well as the Chesapeake Bay. The plumes are so thick they have turned waters that normally show up as blue on satellites into a brownish color. The Department of Natural Resources says it is no surprise when you consider how much debris, including trees, uprooted plants and other things are floating downstream right now. The sediment plume, a result of all the rain, could linger for weeks and push more debris onto local shorelines.