Smaller-than-normal dead zone predicted for the Chesapeake in 2020
Below-average spring rainfall brings less nitrogen pollution into the Bay
After three years of predicting above-average dead zones for the Chesapeake Bay, experts from the Chesapeake Bay Program, University of Maryland Center for Environmental Science, University of Michigan and U.S. Geological Survey estimate that in 2020, dead zone size will be nine percent lower than average when compared to the past 34 years.
The dead zone, or hypoxic region, is an area of little to no oxygen that forms when excess nutrients, including both nitrogen and phosphorus, enter the water through polluted runoff and feed naturally occurring algae. This drives the growth of algae blooms, which eventually die and decompose, removing oxygen from the surrounding waters faster than it can be replenished. When this happens, underwater life can be suffocated and available habitat for plant and animal species reduced.
A key driver in predicting the size and duration of the annual dead zone is the amount of nitrogen that enters the Bay from January-May each year. This period in 2020 saw a reduced amount of rainfall, leading to more typical river flows into the Bay, and less nitrogen pollution, especially when compared to 2019.
“The river flows and nutrient loads were closer to average conditions in spring 2020”, said Scott Phillips, co-chair of the Chesapeake Bay Program’s Scientific Technical Assessment and Reporting Workgroup. “The more normal spring flows, along with the nutrient reduction efforts of the Chesapeake Bay Program, should result in smaller amounts of hypoxia this summer compared to 2018 and 2019, when near-record levels of spring rains washed more nutrients into the Bay.”
Since 2007, a model developed by the University of Michigan has been used to forecast the volume of summer hypoxia for the Chesapeake Bay. However, this year, experts worked to update, refine and transfer this model to the Chesapeake Bay Program. This enhanced model now features hypoxia projections for an average July, average summer and annually. The model is fed by data from the U.S. Geological Survey, who records freshwater flow and nitrogen pollution at nine river input monitoring stations (RIM) throughout the watershed.
“We are excited to see our research forecast model transferred into operations at the Chesapeake Bay Program, ensuring its continuity, updates and refinements,” said Don Scavia, professor emeritus at the School for Environment and Sustainability at the University of Michigan.
In spring 2020, the Bay received 17% nitrogen pollution from its rivers and streams, slightly below average when compared to the long-term average. Overall nitrogen loads entering the Bay included 111 million pounds recorded at the nine RIM stations and 7.3 million pounds from treated wastewater.
There are several ways you can track the size and duration of the Bay’s dead zone from home this summer. The Eyes on the Bay website shares the most recent information from the Maryland-portion of the Bay, recorded from monitoring cruises conducted by the Maryland Department of Natural Resources. Updates for the Virginia portion of the Bay can be found on the Virginia Estuarine and Coastal Observing System, or VECOS, website. Additionally, the most current river flow and pollutant load data are provided by the U.S. Geological Survey.
A Bay-wide assessment of the 2020 dead zone will be available this fall.
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