Pollution caused by human activities has created large areas in the bay where fish, crabs, oysters and other aquatic animals can no longer survive. Plant and animal life often cannot survive in hypoxic environments, which is why the area is known as a dead zone. Marine species, such as fish and crabs, have to move away from these areas or swim above or below them in the water column. Incidents known as “fish deaths”, when dead fish reach shore, are often caused by dead areas in the water.
Other species, such as oysters, which establish their habitat in a specific place that cannot be moved, are particularly vulnerable to dead zones, since they cannot move. The dead zone appears every year in parts of the bay and its tidal rivers during the warmer months, creating areas where oxygen levels are so low that water cannot support fish, blue crabs, oysters and other types of aquatic life. The dead zone is due to algae blooms fueled by nitrogen and phosphorus pollution. These cloud the water and cause damage, mainly during the warmer months.
Dead zones are characterized by a volume of deep water with oxygen concentrations of less than two milligrams per liter. With these levels of dissolved oxygen, marine animals such as fish and blue crabs don't thrive and may even die from lack of oxygen.
Chesapeake Bay
experiences hypoxic conditions every year, and the main drivers are nutrient inputs, wind and temperature. The size and extent of hypoxia in the estuary are recorded as a key indicator of the health of the bay.Dead zones are areas with low oxygen content (less than 2 milligrams per liter of oxygen) that form in the deep waters of the Bay when nutrients enter the water through contaminated runoff and feed natural algae. The United States Geological Survey (USGS) provides data on stream flow levels and of nitrogen and phosphorus entering Chesapeake Bay. According to a preliminary USGS assessment, nitrogen pollution entering the bay from around the watershed was close to the historical average from January to May, which probably contributed to the fact that the dead zone was also close to the average this summer. High levels of nitrogen and phosphorus, nutrients such as nitrogen and phosphorus, are the main cause of poor water quality in the Chesapeake Bay.
Climate change has caused the Chesapeake Bay region to experience more severe storms and warmer average temperatures. The dead zone in Chesapeake Bay this year is the smallest since monitoring began in 1985, according to data released today by the Maryland Department of Natural Resources, Old Dominion University and the Virginia Institute of Marine Science. A dead zone is an area of Chesapeake Bay that doesn't have enough dissolved oxygen to support aquatic life. The annual report on dead zones is prepared using a computer model based on the Chesapeake Bay Environmental Forecast System (CHEFS).
The results of the monitoring cruises are posted on the Eyes on the Bay website for the Maryland part of the bay and on the VECOS website for the Virginia part. Pollution reduction practices implemented by Delaware, Maryland, New York, Pennsylvania, Virginia, West Virginia, and the District of Columbia help reduce the amount of nutrients entering local waterways and Chesapeake Bay from sources such as wastewater, agriculture, and stormwater runoff. William & Mary's Batten School & VIMS and Anchor QEA have released their 2024 dead zone report book detailing the volume and duration of hypoxia or lack of oxygen conditions in Chesapeake Bay. Throughout the year, researchers measure oxygen and nutrient levels as part of the Chesapeake Bay Monitoring Program, a bay-wide cooperative effort involving watershed jurisdictions, several federal agencies, 10 academic institutions and more than 30 scientists.
The size of the Chesapeake Bay dead zone changes every season, depending on the amount of rain, temperature and wind, and the prevalence of nutrient runoff. The Chesapeake Bay Foundation is a non-profit, tax-exempt charitable organization under Section 501 (c) () of the Internal Revenue Code. This shows that nutrient reduction is having a positive impact on the health of the bay and its habitat. In addition to weather conditions, the size and duration of the bay's dead zone are affected by the amount of nutrients that enter Chesapeake from the surrounding watershed.
Since 1985, there have been approximately 17 cruises each year, and more cruises take place in the warmer summer months, when hypoxia becomes the biggest problem for the Chesapeake Bay ecosystem.