Bay's 'dead zone' returns

After an early-summer respite, the Chesapeake Bay's "dead zone" of oxygen-starved water has rebounded to above-average size. (Kim Hairston, 2012 / August 25, 2014)

After shrinking for a while to its smallest size in 30 years, the Chesapeake Bay's "dead zone" has made a late-summer comeback, and that's not good for crabs, fish and oysters.

The Maryland Department of Natural Resources reports that the volume of bay water with too little oxygen in it for fish to breathe -- also known as the "dead zone" -- rebounded in early August to its 8th largest size. 

In early July, the zone had dipped to a record-low volume in early July, a shift scientists attributed to Hurricane Arthur stirring the bay's waters as the storm passed by Maryland on its way up the Atlantic coast. 

With the dead zone back to above-average, the volume of low-oxygen water in the main bay was estimated last week to be 1.32 cubic miles.  That's about what government and University of Maryland scientists had predicted early in the summer, based on high river flows resulting from a wetter spring this year than in 2013. 

Heavy rains and snow melt tend to wash more nitrogen and phosphorus off the land into the water, where the plant nutrients stimulate algae blooms, followed by a dip in oxygen levels in the bay's depths.