Dead Zone, Late Season Update

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.

In June researchers from the Chesapeake Bay Program, the University of Maryland Center for Environmental Science, University of Michigan and U.S. Geological Survey announced that they were predicting the 2023 dead zone would be the smallest dead zone on record since 1985.

This week researchers at the Virginia Institute of Marine Science (VIMS) reported that hypoxia in summer 2023 began in mid-May, increased to a moderate level, and then leveled off. They believe that this leveling off resulted from a change in the average wind direction in late-May. Hypoxia has remained at low to moderate levels throughout June, July, and into August. The spring-time nutrient supply to the Bay was relatively low and June was relatively windy, both of which may have contributed to June through August having a low amount of hypoxia. 2023 is turning out to be low hypoxia year for the Bay, we’ll know sometime over the next few months if it turned out to be the lowest on record.

from VIMS

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.