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Dead zones are hypoxic (low-oxygen) areas in the world's oceans and large lakes. Hypoxia occurs when dissolved oxygen (DO) concentration falls to or below 2 ml of O 2 /liter. [ 2 ] When a body of water experiences hypoxic conditions, aquatic flora and fauna begin to change behavior in order to reach sections of water with higher oxygen levels.
The exaerobic zone is found at the boundary of anoxic and hypoxic zones. Hypoxia can occur throughout the water column and also at high altitudes as well as near sediments on the bottom. It usually extends throughout 20–50% of the water column, but depends on the water depth and location of pycnoclines (rapid changes in water density with depth).
Histotoxic hypoxia, the inability of cells to take up or use oxygen from the bloodstream; Anemic hypoxia, Blood is not able to take sufficient amount of oxygen due to Anemia; Hypoxemic hypoxia or hypoxemia, a deficiency of oxygen in arterial blood; Hypoxic hypoxia, a result of insufficient oxygen available to the lungs
Scientists prepare to collect near-bottom water aboard the R/V Pelican to verify oxygen measurements used to determine the size of the Gulf of Mexico hypoxic zone. (NOAA/LUMCON/LSU) A "dead zone ...
A fish's hypoxia tolerance can be represented in different ways. A commonly used representation is the critical O 2 tension (P crit), which is the lowest water O 2 tension (P O 2) at which a fish can maintain a stable O 2 consumption rate (M O 2). [2]
Hypoxic environments are often found in tumors where the cells are dividing faster that angiogenesis can occur. It is important to study hypoxia as an aspect of cancer because hypoxic environments have been shown to be resistant to radiation therapy. [68] Radiation has been shown to increase the amounts of HIF-1. [69]
Tissue hypoxia refers to low levels of oxygen in the tissues of the body and the term hypoxia is a general term for low levels of oxygen. [2] Hypoxemia is usually caused by pulmonary disease whereas tissue oxygenation requires additionally adequate circulation of blood and perfusion of tissue to meet metabolic demands. [4]
This kills off marine life or forces it to leave the area, removing life from the area and giving it the name dead zone. Hypoxic zones or dead zones can occur naturally, but nutrient pollution from human activity has turned this natural process into an environmental problem. [29] There are five main sources of nutrient pollution.