DO - hypoxiaDissolved oxygen is critical to the survival of Chesapeake Bay's aquatic life. The amount of dissolved oxygen needed before aquatic organisms are stressed, or even die, varies from species to species.
Indicator Details
DO - hypoxia
Summer hypoxic volume below the long-term average
The average volume of hypoxic (dissolved oxygen ≤2 mg L-1), or low dissolved oxygen, water in Chesapeake Bay's mainstem during summer 2009 was 5.4 km3. This value is slightly below the long-term (1985–2006) average of 7.4 km3. Similar to the anoxic volume, the hypoxic volume recorded a drop in volume during late summer although not as severe. It then increased again, reaching a maximum in late August.
Hypoxia forecast overestimates July hypoxia volume
In spring it was forecast that the July mainstem Bay hypoxic volume would be close to average (forecast volume = 5.1 with a 67% probability of being between 2.7 and 7.4 km3). This forecast is based on a model that relates spring nutrient loads to hypoxic volume. Despite the forecast volume being different than the observed conditions, this year the forecast was the closest to the observed conditions in the three years that the July hypoxic volume has been forecasted. Additionally, these forecasting efforts improve our understanding of what conditions affect the Bay and how they change from spring to summer.
Acknowledgements:
Hypoxia forecast courtesy of Don Scavia, The University of Michigan. 2008 dissolved oxygen data provided by Jake Goodwin (CBP/CRC) and Jeni Keisman (CBP/UMCES).