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July 6, 2011

Scientists predict large Bay 'dead zone' this summer

Scientists are predicting that this summer's oxygen-starved "dead zone" in the Chesapeake Bay will be unusually bad - fueled by a wet spring that washed a heavy dose of nitrogen into the bay from the Susquehanna River and other tributaries.

Donald Scavia, a University of Michigan aquatic ecologist, who makes annual forecasts of "dead zone" sizes in the Chesapeake and Gulf of Mexico, thinks the amount of bay water with little dissolved oxygen in it will be the largest since 2003 and the sixth largest ever recorded.  See the UMich forecast here.

Nitrogen - from sewage plants, fertilizer washing off land and vehicle and power plant pollution falling out of the sky - is one of the key drivers of the bay's hypoxia, or low-oxygen condition. The amount getting into the bay has increased significantly since the 1950s, Scavia says, and this year's estimated load is the highest in more than a decade. Not surprising, since river gauges measured unusually strong spring flows down the Susquehanna - the single biggest water source for the bay.

Scavia's prediction tracks with the preliminary forecasts of bay scientists, who a few weeks ago foresaw a "moderately large" volume of water with no oxygen in it at all from spring into mid-July. If conditions don't change, they predicted this summer's dead zone could be the fourth largest in the past 26 years.

(Note that the Michigan and Maryland scientists are measuring slightly different things. Scavia tracks "hypoxic" water, which still has a little oxygen in it but not enough for fish and shellfish to do well, while the Maryland-based group has focused so far only on the truly "dead zone," anoxic water with no oxygen at all in it for crabs and other critters to breathe. Eco-Check, the Maryland-federal scientific partnership, has yet to issue its prediction for the broader hypoxic zone in the bay.)

Variations aside, the general forecast is tor a rough summer for striped bass, blue crabs and oysters, points out Beth McGee, senior scientist with the Chesapeake Bay Foundation.  When oxygen levels in the water drop, fish and shellfish become stressed.

Some might wonder why the bay's dead zone can still be so bad given the billions of dollars spent on cleanup - this past fall, for instance, Maryland farmers planted a record number of acres in "cover crops" to soak up excess nitrogen in their fields that would otherwise wash into the bay in spring.  McGee points out such efforts take years to influence water quality; much of the nitrogen from farm fields gets into the bay via ground water, she notes, and can take a decade or more to seep out into surface streams.

Posted by Tim Wheeler at 7:23 AM | | Comments (3)


You can track dissolved oxygen in the Maryland portion of the Chesapeake Bay and tributaries at the Department of Natural Resources, Eyes on the Bay website:

Tim Wheelers’ article published on 7/6/11 – “Scientists predict large Bay ‘dead zone’ this Summer” is one we should all give value to. Research from a number of reputable sources including the EPA clearly shows an ecosystem at the point of no return due to decades of bad management and degredation from nutrient overloading and widespread pollution. This leaves us with a poor shadow of the great seafood basket and recreational playground we should enjoy.

This is surely all the evidence Governor O’Malley needs to make big business such as poultry producers responsible for their waste that runs into our bay. The wealth and power wielded by this industry should make it more accountable to the people of Maryland for their actions – not the dismissive stance they currently get away with.

These are very profitable industries that need to do the right thing both ethically and philanthropically for the people who made them rich.

Why do nutrients cause low DO is not explained.

Nutrients should lead to more algae and this should lead to higher DO and not the other way around.

TW: The DO (dissolved oxygen) in the water is consumed when the algae die and decay. The process is enhanced, or aggravated, when the water doesn't mix well.

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About the bloggers
Tim WheelerTim Wheeler reports on the environment and Chesapeake Bay. A native of West Virginia, he has focused mainly on Maryland's environment since moving here in 1983. Along the way, he's crewed aboard a skipjack in the bay, canoed under city streets up the Jones Fall from the Inner Harbor, and gone deep underground in a western Maryland coal mine. He loves seafood, rambles in the country and good stories. He hopes to share some here.

Contributor Christy Zuccarini has been blogging about the local DIY craft scene for a year for She brings her pespective on all things handmade to B'More Green, where she will highlight projects you can do yourself as well as crafters who are integrating sustainable methods and materials.

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