In the short-term, experts believe that several factors, including calm winds, increased precipitation and warm temperatures throughout the late summer of 2021 contributed to the larger dead zone. Overall, the 2021 dead zone lasted for 141 days-46 days longer than 2020. In the annual Dead Zone Report Card, the Virginia Institute of Marine Science (VIMS) announced that the 2021 Chesapeake Bay dead zone covered an average of 1.5 cubic miles during the summer, slightly larger than most recorded in the past 36 years (67%). What is the size of the most recent dead zone?ĭata from Virginia Institute of Marine Science. This is due to the amount of rainfall that occurs during the spring, which washes excess nutrients off the land and into the water, as well as hot temperatures and weak winds in the summer which cause the dead zone to grow larger and last longer. Dead zones most often occur during the warm summer months. Also, when algae die, they fall to the bottom of the water and remove oxygen. The dead zone is most pronounced in the deep waters of the Bay's mainstem because there is generally less oxygen toward the bottom of a body of water. Other species like oysters, which set up habitat in a specific location that cannot be moved, are particularly vulnerable to dead zones since they cannot relocate. Incidents known as “fish kills,” when dead fish wash up on shore, are often caused by dead zones in the water. Marine species like fish and crabs have to move away from these areas or swim above or below them in the water column. Plant and animal life are often unable to survive in hypoxic environments, which is why the area is referred to as a dead zone. This creates hypoxic-or low oxygen-conditions that can suffocate marine life and shrink the habitat available to fish, crabs and other critters. This drives the growth of algae blooms, which eventually die and decompose, removing oxygen from the surrounding waters faster than it can be replenished in the process. The "dead zone" is an area of little to no oxygen that forms when excess nutrients enter the water through polluted runoff and feed naturally occurring algae. Image by Will Parson/Chesapeake Bay Program
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