Advertisement

Bay “Dead Zone” Back Down from Historic Levels

The Bay’s oxygen-poor “dead zone” was back down to average size in late August– after reaching near-record size earlier in the summer.

The Maryland Department of Natural Resources (DNR) says the hypoxic water volume in the Maryland portion of the Bay was down to 1.06 cubic miles in late August, compared to 1.77 cubic miles in early August. In late July, the hypoxic water volume was up at 2.01 cubic miles– the second-largest it’s been in 34 years.

Advertisement

The late August hypoxia conditions were near average, DNR says, a big improvement from earlier in the summer.

Graphic: Maryland DNR

Hypoxic water volume refers to waters with less than 2 mg/l of dissolved oxygen. With very little oxygen in the water, “fish, crabs, oysters, and other aquatic animals literally suffocate,”according to the Chesapeake Bay Foundation, hence the common name “dead zone.” Dead zones are caused by excessive nitrogen and phosphorus pollution flowing into waterways.

So what caused the dead zone to shrink in late August? Water temperatures lowered, and cooler waters are able to hold more oxygen. “Salinities, which were low due to record freshwater flows in late 2018 and early 2019,” DNR explains,are rising toward average conditions.

In the beginning of June, scientists predicted a large hypoxic volume for the bay in 2019 due to higher flows last fall and this spring, and higher nitrogen loading from the Susquehanna and Potomac Rivers. July and early August proved those predictions right.

Bay hypoxia monitoring and reports will continue until the end of summer, based on data collected by Maryland and Virginia monitoring teams. Scientists and natural resource managers study the volume and duration of dead zones to determine possible impacts to bay life.

-Meg Walburn Viviano

Advertisement
Share

Recent Stories

Md. Striped Bass Spawning 70% Below Average, Va. Numbers Stable

Maryland and Virginia have both released results of their annual "young of year" striped bass surveys, which measure rockfish reproduction…

October 17, 2019

VIDEO: Annapolis Flooding Impacts U.S. Sailboat Show

The coastal flooding that seeped into several bayfront communities this past weekend posed a special challenge in flood-prone downtown Annapolis,…

October 15, 2019

SLIDESHOW: Coastal Flooding Felt All Over Bay Region

High water levels on the Chesapeake Bay waterfront are not an unusual sight, but this weekend's extra-high "sunny day" coastal…

October 15, 2019

Va. Shore’s Barrier Islands Center Celebrates Anniversary

On the lower Eastern Shore, the Barrier Islands Center isn't just a museum to memorialize past island life, it's a…

October 15, 2019

Port of Va. Set for 55-Foot Channel Dredging

The Port of Virginia is set to become the deepest port on the East Coast within the next five years,…

October 15, 2019

Md. Names 1st “Master Angler Award” Winner

Maryland's new fishing award program gets its very first winner. The Department of Natural Resources (DNR) FishMaryland Master Angler Award…

October 15, 2019