Low oxygen levels caused by intense algae blooms, sediment runoff, the availability of substrate to rebuild oyster reefs, and poaching in closed bars affect oyster populations. The sediments coat the substrate of the reefs and prevents oyster larvae from attaching to them. Low dissolved oxygen levels reduce oysters' resistance to disease. The biggest challenge is the lack of habitat for reefs.
Oyster shells, the preferred natural substrate, have limited quantities, so scientists are testing alternative materials. Learn more about the challenges faced by Chesapeake oysters. The lack of dissolved oxygen is often the result of eutrophication. This occurs when there are too many nutrients in the water that cause proliferation.
from algae. When algae die and decay, the decay process consumes the oxygen dissolved in the water. The amount of oxygen dissolved in water is critical to the survival of aquatic life in Chesapeake Bay. A lack of dissolved oxygen is often the result of eutrophication, which occurs when there are too many nutrients (such as nitrogen and phosphorus) in the water, causing the growth of dense algal blooms.
When algae die and decay, the decay process consumes oxygen dissolved in the water, reducing the oxygen available to fish, blue crabs and other organisms, which can become stressed or even die. When there are excessive amounts of nitrogen and phosphorus in the water, algae can flourish to harmful levels. Dead zones form when algae die, sink to the bottom and are broken down by bacteria, a process that removes dissolved oxygen from the surrounding water. Dense algal blooms also block sunlight, preventing the growth of underwater grasses.
In turn, the animals that rely on these pastures for food and shelter also suffer. A new report on oxygen levels in Chesapeake Bay showed that the bay was a healthier place this summer for fish, crabs and oysters. To view dissolved oxygen levels throughout Chesapeake Bay, visit Eyes on the Bay (for Maryland waters) or the Virginia Estuary and Coastal Observation System (for Virginia waters). Chesapeake Bay Story is a partnership between the University of Maryland Environmental Science Center and the state of Maryland.
Like humans, all the living things in Chesapeake Bay, from the fish and crabs that swim through its waters to the worms that burrow into its muddy bottom, they need oxygen to survive. The Chesapeake Bay Foundation is a non-profit, tax-exempt charitable organization under Section 501 (c) (of the Internal Revenue Code). All living things in Chesapeake Bay, from the fish and crabs that swim through its waters to the worms that burrow into its muddy bottom, need oxygen to survive. However, some parts of Chesapeake Bay often suffer from hypoxia, a situation in which oxygen levels in the water drop dangerously.
Excess nitrogen and phosphorus are the two main pollutants in the bay, which fuel the proliferation of algae that cloud the water and consume the oxygen necessary for life when they die and decay., causing the dead zone in the bay. Resources such as the Chesapeake Bay hypoxia forecast from the Virginia Institute of Marine Science (VIMS) and monthly hypoxia reports, such as those from the Maryland Department of Natural Resources (DNR), provide data for these simulations, but acquiring that data is an ongoing challenge. With funding provided by the Environmental Protection Agency, the Chesapeake Bay Trust awarded a contract to Caribbean Wind to develop a small buoy with sensors that measure dissolved oxygen, temperature and salinity at multiple depths. Areas of the bay that have low levels of dissolved oxygen are the result of a complex interaction of several natural and man-made factors, such as temperature, nutrient pollution, water flows, and the shape of the bay floor.
On average, the Chesapeake Bay dead zone covers 1.2 cubic miles during the summer months, when water is warmer and oxygen levels are historically higher bass. Salt concentration, or salinity, is a function of the mixing of fresh water from Chesapeake Bay tributaries with ocean waters, which contain approximately 32 ppts (parts per thousand) of salinity.