Recent rain, heat causes oxygen levels to drop in the Chesapeake Bay

The Chesapeake Bay saw oxygen levels hit record lows this summer.

That’s according to the hypoxia measurement, which is performed twice a month. Hypoxia happens when water has less than 2 mg/l of oxygen.

“We look at this because it’s an important habitat measure, because the aquatic organisms need oxygen, just like we need oxygen here on land,” said Mark Trice, program manager for water quality informatics with the Maryland Department of Natural Resources.

He said hypoxia levels in the Chesapeake Bay were triple the normal level in their late June report. That was the largest volume of hypoxia measured in Maryland since the program started monitoring it.

“Flow and heat and no major wind to mix the water columns, such as a tropical storm or something like that, sets up these perfect conditions for larger than average hypoxia zones,” Trice said.

He said in early July, crabbers saw some dead crabs in their pots.

“We believe that was due to hypoxia, that it was aided by these wind conditions that basically pushed up this bottom dissolved oxygen of water that was bad in the bay up toward the Western Shore that sort of contributed to that,” he said.

There was not any hypoxia measured in May. Trice also said it can impact the amount of wildlife and what type can survive.

“It can cause stress to the organisms. It can reduce the size of the habitat. It can increase predation when you have smaller areas that everything has to be confined within, the mobile creatures can obviously find other places to go most often, but some of the bottom-dwelling creatures, like oysters and clams and worms, are not able to get away,” he said.

He recommended a bolstering of wastewater treatment plants to attempt to bring those levels of hypoxia down.

“Preventing the stormwater runoff and agricultural runoff, and managing fertilizers from lawns, as well as even atmospheric deposition of nitrogen, reducing that can all play a great role in reducing these zones of hypoxia,” he said.

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