The oxygen-starved 'dead zone' in the Chesapeake Bay, which covered a record third of Maryland's portion of the estuary in June, has grown still more, according to state scientists.

Samples taken by the state Department of Natural Resources in early June found that 33 percent of Maryland's bay waters had little or no dissolved oxygen, which crabs, fish and oysters need to breathe. That's the most recorded for that time in the summer since regular measurements began in 1985, DNR says.

The dead zone shrank slightly over the next several weeks, but samples taken in late July found poor oxygen levels in 39 percent of the state's bay waters - another record, according to DNR.

Scientists had predicted worse-than-average oxygen levels in bay waters this summer, based on high spring flows of fresh water into the bay. The US Geological Survey reported that fresh-water flows from the Susquehanna River by late spring had already matched what pours from the bay's largest tributary in an average year.

The extra-heavy flow flushed more nutrients into the bay from farms, sewage plants and urban and suburban land, fueling massive algae "blooms" that suck the oxygen out of the water when they die and decay. Low oxygen levels stress and can even suffocate fish and shellfish.

For more on the dead zone and other bay conditions, check DNR's Eyes on the Bay.  And listen here to a report on the dead zone by WYPR's Joel McCord.

(Algae bloom on Middle River near Essex. 2008 Baltimore Sun photo by Glenn Fawcett)