How the Chesapeake Bay Dead Zone is looking in 2022

The “Dead Zone” of the Chesapeake Bay refers to a volume of hypoxic water that is characterized by dissolved oxygen concentrations less than 2 mg/L, which is too low for aquatic organisms such as fish and blue crabs to thrive. Within the hypoxic area life of the bay dies and a “Dead Zone” forms. The Chesapeake Bay experiences hypoxic conditions every year, with the severity varying from year to year, depending on nutrient and freshwater flows into the bay, wind, and temperature.

At the end of June, the EPA Chesapeake Bay Program, United States Geological Survey, University of Maryland Center for Environmental Science and the University of Michigan scientists released their consensus prediction for another smaller than average 2022 Dead Zone. According to the scientists, hypoxia in 2022 started relatively late in the season, similar to 2020 which had a relatively small dead zone. It was not until the beginning of June that hypoxia started to spread in the mainstem of the Bay. The volume of hypoxic water, the size of the dead zone, has stayed relatively low compared to the historical volume.

Although different types of nutrients contribute to the annual dead zone, scientist say it is the amount of nitrogen that enters the Bay during spring that is a key driver in how hypoxic conditions can vary from year-to-year. “The amount of nitrogen pollution entering the Bay during spring 2022 was 22% lower than the long-term average and included 102 million pounds of nitrogen recorded at nine river input monitoring stations and 5.7 million pounds from treated wastewater. There was 5% less water flowing into the Bay when compared to the long-term average."

Each year the Maryland Department of Natural Resources measures the actual dissolved oxygen in the Maryland portion of the Chesapeake Bay main stem and the size of the Dead Zone. While the Virginia Institute of Marine Science (VIMS), Anchor QEA and collaborators at UMCES, operate a real-time three-dimensional hypoxia forecast model using measured inputs that predicts daily dissolved oxygen concentrations throughout the Bay (www.vims.edu/hypoxia) using the National Weather Service wind monitoring data.

from VMIS

The peak of oxygen depletion occurs in July or August when water temperatures are highest and the days are longest accelerating the growth of phytoplankton that ultimately consumes all the dissolved oxygen. The dead zone is typically gone by late fall. Cooler air temperatures at that time of year chill the surface waters, while the deeper water remains warm and allows more mixing of the layers during storms. Cooler water also will hold more oxygen. The size and shape of the dead zone is variable from month to month during the summer. So far it is still looking like a promising year.

At the end of the season the Virginia Institute of Marine Science (VIMS), Anchor QEA and collaborators at UMCES compile all the collected data to report the actual results. The actual 2021 Chesapeake Bay Dead Zone report from VIMS says: “… calm winds and slightly warmer temperature in May 2021 compared to 2020 resulted in hypoxia starting earlier this year. As summer arrived, moderate winds allowed hypoxia to increase through mid-July, resulting in a maximum size of the dead zone similar to the average historical size. ... In 2021, hypoxia decreased in early August, but a period of calm winds in late August allowed the amount of hypoxia to increase again. However, hypoxia decreased abruptly at the beginning of September as the remnants of Hurricane Ida stirred Bay waters. Stronger winds prevailed following Ida, but unusually warm fall temperatures and high precipitation counteracted some of the normal autumnal reduction in hypoxia, contributing to hypoxia ending in the mainstem of the Bay considerably later than in previous years. Overall, the duration of hypoxia in summer 2021 was relatively long, but the other metrics of severity were closer to typical mid-range values.”

Read the full 2021 Report here.