Gulf Hypoxia

Gulf Hypoxia

The northern Gulf of Mexico is the second largest human-caused area of bottom-water dissolved oxygen less than 2 milligrams per liter in the world's coastal ocean. It is located primarily west of the Mississippi River, which drains 41% of the contiguous 48 United States. Besides the freshwater and sediments delivered to the northern Gulf of Mexico via the Mississippi River delta, there are also dissolved inorganic nutrients (Nitrogen and Phosphorus) and organic and inorganic suspended particles. The nutrient levels of N have risen since the mid-1950s to a level that is three times that of the last mid-century. The area of low oxygen has become larger, and the low values are more severe than they were historically. In fact, palaeoindicators dating back to the 1800s indicate that widespread low oxygen conditions did not exist historically and the low dissolved oxygen conditions worsened since the 1950s and accelerated in the 1970s coincident with the nitrogen load from the Mississippi River. Our research group has been documenting the area of low oxygen, and its areal extent since 1985. These cruises collect physical, hydrographic, sedimentological, chemical and biological data in the process of outlining the bottom area of the bottom-water low oxygen. The size of the bottom-water area of low oxygen is a benchmark for the Federal/State Mississippi River/Gulf of Mexico Hypoxia Task Force to measure progress toward an environmental goal of 2,500 kilometers square of bottom area by 2035. The reduction is size is relatled to the necessary reduction in nitrogen and phosphorus loads to the Gulf from the Mississippi River watershed. States participating in the Hypoxia Task Force have developed and attempted to reach goals for mitigation of excess nutrients, primarily from agricultural landscape, but also from cities, and atmospheric deposition.