Data collected by the Maryland Department of Natural Resources and Old Dominion University show the volume of hypoxia—waters with less than 2 mg/l oxygen—was generally near or below average in the Chesapeake Bay mainstem of Maryland and Virginia in 2024.
For the year, hypoxia volumes were larger than average in May and early June, but declined to smaller than average volumes through the end of August.
In September, hypoxia was slightly above average for the period and there was no hypoxia during October sampling. Deep water hypoxia in the Bay normally dissipates after September, with no observed hypoxia in 30 out of the past 40 Octobers.
Summary results from Maryland and Virginia combined Chesapeake Bay mainstream water quality monitoring cruises are as follows:
| Cruise | 2024 Hypoxic Volume
(cubic miles) |
Historical Average Hypoxic Volume (1985-2023)
(cubic miles) |
*2024 Rank /
Number of years measured |
Graphic | ||
|---|---|---|---|---|---|---|
| May | 0.42 | 0.18 | 35th / 40 | Chart or Map | ||
| Early June | 1.03 | 0.90 | 24th / 36 | Chart or Map | ||
| Late June | 0.76 | 1.27 | 9th / 34 | Chart or Map | ||
| Early July | 1.20 | 1.59 | 11th / 39 | Chart or Map | ||
| Late July* | 0.82 | 1.62 | 5th / 39 | Chart or Map | ||
| Early August* | 0.26 | 1.31 | 1st / 37 | Chart or Map | ||
| Late August | 0.77 | 1.07 | 10th / 40 | Chart or Map | ||
| September | 0.56 | 0.41 | 26th / 40 | Chart or Map |
* The 2024 Rank column indicates this year’s result rankings, from the least hypoxic (better) to the most hypoxic volume, compared against historical results for each time period. Hypoxic volume was likely higher than reported for July 2024 because stations CB5.3, LE2.3, and CB5.2 in Maryland were not sampled due to mechanical issues with the research vessel and Virginia stations CB7.1N and CB7.3 were not sampled due to adverse weather conditions. Hypoxic volume was also likely higher than reported for early August as mechanical issues with the research vessel prevented Virginia from sampling stations CB5.4, CB5.4W, CB5.5, CB6.1, CB6.2, CB6.3, LE3.6 and LE3.7 in the upper Virginia portion of the Bay.
These monitoring results provide a comparison to the yearly seasonal forecast by the U.S. Environmental Protection Agency’s Chesapeake Bay Program, U.S. Geological Survey, University of Maryland Center for Environmental Science, and University of Michigan.
This forecast, which was released in late June, expected 2024 Chesapeake Bay mainstem hypoxic volume to be 4% higher than the 39-year average, due to increased river flows and resultant higher nitrogen loads from January through May 2024. Monitoring results indicate better dissolved oxygen conditions than the forecast predicted.
Crabs, fish, oysters, and other creatures in the Chesapeake Bay require oxygen to survive. Scientists and natural resource managers study the volume and duration of Bay hypoxia to determine possible impacts to bay life.
Ongoing efforts to reduce nitrogen and phosphorus pollution from industrial and wastewater sources, agricultural land, and cities and towns are aimed at reducing hypoxic conditions in the Bay. In the water, nitrogen and phosphorus fuel algal blooms that remove oxygen from the water when they die off and decompose.
Each year from May through October, the Department of Natural Resources computes hypoxia volumes from the water quality data collected and managed by department staff and the Virginia Department of Environmental Quality. Data collection is funded by these states and the Chesapeake Bay Program. A joint hypoxia report from Bay Program partners has been issued in tandem with this report to compare monitored versus forecasted and modeled results for 2024.
Additional Maryland water quality data and information, including the Department of Natural Resources hypoxic volume calculation methods, can be found on the Eyes on the Bay website.
