Hypoxia; sometimes referenced to as a “dead zone”is a lack of oxygen in the water.
Aquatic organisms require adequate dissolved oxygen to survive. The occurrence of Hypoxia, or low dissolved oxygen has increased substantially. In “1960 there was 12 documented cases of U.S. Coastal areas experiencing Hypoxia, now there is over 300 hundred.”(Diaz & Rosenberg.2008.SAH.p11.)
The inability of immobile species, such as mussels and oysters, to escape these low oxygen areas, makes them vulnerable to Hypoxia. These organisms can become stressed and may die due to Hypoxia, resulting in significant impacts on marine food webs and the coastal economy.(SAH. p.12) Crabs and fish, although they are mobile are still affected by the Hypoxia.
New research is clarifying when Hypoxia will cause fish to die as opposed to triggering an avoidance behavior by the fish. The avoidance behavior of the fish has an impact on our economy and habitat loss, such as reduced growth in commercially harvested species and loss of biodiversity, habitat, and biomass.( SAH.p.13)
The surge in the number of U.S. Waters developing Hypoxia is linked to eutrophication due to nutrient ( nitrogen and phosphorus) and organic matter enrichment resulting from human activities. ( Diaz & Rosenberg. 2008. SAH.p.11) Although, coastal Hypoxia can be caused by natural processes, such as the change in our weather, such as El-Nino.
Oregon has one of the largest Hypoxia zones in the U.S.; the Oregon Continental Shelf. It is harder to implement strategies that have helped other areas, because Oregon's Hypoxia is driven primarily by natural processes linked to variations in climate. Scientists are studying how up-welling, a normal event can turn deadly for the Oregon coast, as Hypoxia is linked to the up-dwelling and down-dwelling systems. Researchers from the Pisco program, along with fish and
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