Tuesday, July 28, 2009

Gulf of Mexico and Chesapeake Bay Dead Zones 2009

Revised estimates of Gulf and Chesapeake Bay Dead Zones


Dead Zone in Gulf Is Smaller Than Forecast but More Concentrated in Parts

Published: July 27, 2009

Scientists said Monday that the region of oxygen-starved water in the northern Gulf of Mexico this summer was smaller than forecast, which means less disruption of shrimp, crabs and other marine species, and of the fisheries that depend on them.

But researchers found that although the so-called dead zone along the Texas and Louisiana coasts was smaller — about 3,000 square miles compared with a prediction of about 8,000 square miles — the actual volume of low-oxygen, or hypoxic, water may be higher, as the layer is deeper and thicker in some parts of the gulf than normal. And the five-year average size of the dead zone is still considered far too big, about three times a target of 2,000 square miles set for 2015 by an intergovernmental task force.


Bay 'dead zone' bigger than predicted
The fish-stressing "dead zone" in the Chesapeake Bay is bigger than predicted this summer, scientists say.

Just about a month ago, University of Michigan scientists had forecast that the amount of oxygen-starved water in the Chesapeake should be much lower than average for the troubled estuary. University of Maryland scientists had followed with similar predictions that the bay's ''dead zone'' -- where dissolved oxygen levels in the water are too low for fish to breathe comfortably, if at all -- was likely to be one of the smallest ever measured.

The scientists had based their predictions on below-normal flows in late spring of the Susquehanna River, which supplies half of the fresh water entering the bay. Though it rained a lot in Maryland and Virginia in May and June, it had been relatively dry in the Susquehanna's drainage basin in New York and Pennsylvania.

But based on water sampling conducted every two weeks since May, University of Maryland scientists hve found that the volume of water with little or no oxygen in it has exceeded the forecast -- increasing from below-average in late May to above normal for June and remaining about average for this month, even as rains locally subsided.

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