Experts from the Maryland Department of Natural Resources are reporting that the 2020 dead zone is the second smallest observed in Maryland's Chesapeake Bay since monitoring began in 1985.
In their 2020 Chesapeake Bay Dead Zone Report Card, researchers from the Virginia Institute of Marine Science also reported that throughout the entire Bay this year’s dead zone was smaller than most recorded in the past 35 years (80%).
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In June 2020, researchers from the Chesapeake Bay Program, the University of Maryland Center for Environmental Science, University of Michigan and U.S. Geological Survey forecasted that the Bay would see a slightly smaller than average dead zone this year, due to reduced spring rainfall and less nutrient-rich runoff flowing into the Bay from the watershed.
In the short-term, experts believe that several factors, including more average river flows and unseasonably cool temperatures in May and September contributed to the smaller dead zone.
Over the long-term, the continued implementation of nutrient and sediment reduction strategies put in place by the six states in the Chesapeake Bay watershed (Delaware, Maryland, New York, Pennsylvania, Virginia and West Virginia) and the District of Columbia are continuing to help decrease pollution in the Bay and reduce the size of the dead zone.
Strong winds from Hurricane Isaias in August helped to mix the waters of the Bay, reducing the dead zone; hypoxia returned in September but quickly dissipated due to cooler temperatures and windy conditions.
This year’s dead zone started later and ended earlier than it has in the past several years.
Additionally, no anoxic areas were noted in the mainstem of the Bay this year.
It's been true at least since I arrived in the Chesapeake Bay region (1985) that the interannual variation in the hypoxia problem in Chesapeake Bay can be accounted for by weather events, and thus, ascribing any improvement due to the Chesapeake Bay Diet, and other clean up efforts is tenuous at best.