William & Mary’s Batten School & VIMS and Anchor QEA have released their 2024 Dead Zone Report Card detailing the volume and duration of hypoxic, or low-oxygen, conditions in the Chesapeake Bay. The annual report suggests this year’s dead zone was somewhat larger than the long-term average from 1985-2023 but had a slightly shorter duration.
Dead zones are characterized by a volume of deep water with oxygen concentrations less than two milligrams per liter. At these dissolved oxygen levels, marine animals such as fish and blue crabs fail to thrive and can even die from lack of oxygen. The Chesapeake Bay experiences hypoxic conditions every year, with primary drivers being nutrient inputs, wind and temperature. The size and extent of hypoxia within the estuary is tracked as a key indicator of Bay health.
“This year’s dead zone began in early May and reached its highest levels in June — this is early compared to historical peaks, which usually occur in July or early August. Initially, we saw above average hypoxia, but it dropped dramatically following the passage of the remnants of Hurricane Debby in early August and a low volume of hypoxic waters persisted until early October,” said Marjy Friedrichs, a professor at the Batten School of Coastal & Marine Sciences & VIMS and co-author of the report card.
In summer 2024, hypoxia increased throughout May and was higher than the long-term average in the first half of June, following a period of relatively calm winds. Elevated winds in the second half of June likely resulted in a decrease in hypoxia from the early-June peak. Hypoxia decreased substantially after Hurricane Debby, until cooling temperatures helped end it for the year in early October. Overall, even though the duration of hypoxia was less than the long-term average, the total annual amount of hypoxia was somewhat higher than the long-term average.
The annual Dead Zone Report Card is created using a computer model based on the Chesapeake Bay Environmental Forecast System (CBEFS). The computer modeling complements the Maryland Department of Natural Resources’ (DNR) 2024 Final Hypoxia Report, which is based on semi-monthly monitoring cruises measuring dissolved oxygen. Both reports are used by the Chesapeake Bay Program to monitor the health of the Bay in relation to established nutrient management and water quality goals. Today, CBP issued a press release summarizing the Batten School & VIMS and the Maryland DNR assessments.
“This year’s results are in line with spring forecasts from the Chesapeake Bay Program’s statistical model, which uses springtime streamflow and nutrient loading data,” said Aaron Bever of Anchor QEA and co-author of the report. Friedrichs added: “The past few years of near-or below-average, Bay-wide hypoxia levels are a positive sign that Chesapeake Bay nutrient management actions are working, but such reductions must be continued if we are to outpace water quality degradation due to climate change.”
The Dead Zone Report Card is available on the Batten School & VIMS website along with real-time CBEFS estimates of Bay-wide salinity, temperature, oxygen, and other water quality variables.