Hypoxic Waters
THE Fight FOR OXygen
According to the Mississippi River Basin Watershed Nutrient Task Force of 2010 hypoxia can be characterized as waters that contain dissolved oxygen concentrations of less than 2-3 ppm. The low oxygen levels are caused by the combination of excess nutrients and the subsequent algae blooms that deplete the oxygen. The depletion of dissolved oxygen can become so severe that the water becomes anoxic,meaning there is little or no oxygen.6 When an aquatic area becomes anoxic anaerobic bacteria can flourish and create bad smelling compounds such as hydrogen sulphide,thioalcohols, and ammonia. Most life cannot be sustained in an area that has hypoxic waters, this decreases the biodiversity of certain areas. The loss of oxygen causes some organisms to leave their habitat. This can severely decrease the populations of organisms with specialized niches, endemic species, and foundational species. 10
The loss of dissolved oxygen in marine water affects the biomes because there is not enough oxygen to sustain the organism that live there. Some fish require a lot of oxygen, and therefore the amount of fish that live there has to decease. Bigger fish typically require more oxygen than smaller fish. When there is a smaller quantity of larger fish, or tertiary species, they can't control the population of smaller fish and organisms. This then throws off the balance of the ecosystem.4 The decrease in fish population affects local fisheries located near dead zones as well as the primary productivity of the biome itself. The loss of fish can affect the economy of the coastal towns located near the dead zones. When waters become hypoxic large quantities of fish die and the region can become unstable due to the loss of adult fish; and smaller quantities of young organisms who are less likely to reach adulthood. The loss of dissolved oxygen can make an entire region unstable due to the impacts it has on the biome. 10