Gulf Hypoxia & Iowa

THE TERM “GULF HYPOXIA” references

Hypoxia, or low oxygen, is an environmental phenomenon where the concentration of dissolved oxygen in the water column decreases to a level that can no longer support living aquatic organisms. Hypoxic areas, or "Dead Zones," have increased in duration and frequency across our planet's oceans since first being noted in the 1970s.

The largest hypoxic zone currently affecting the United States, and the second largest hypoxic zone worldwide, is the northern Gulf of Mexico adjacent to the Mississippi River.

Hypoxia in the northern Gulf of Mexico is defined as a concentration of dissolved oxygen less than 2 mg/L (2 ppm). This figure is based on observational data that fish and shrimp species normally present on the sea floor are not captured in bottom-dragging trawls at oxygen levels < 2mg/L. In other oceans of the world, the upper limit for hypoxia may be as high as 3-5 mg/L.

The average size of the hypoxic zone in the northern Gulf of Mexico over the past 30 years (1985-2014) is about 13,650 square kilometers (or 5,300 square miles.

gulfhypoxia.net, Louisiana Universities Marine Consortium

IOWA

In Iowa, nitrates in water has increased through the years with, for example, measures of nitrates annual median milligrams per liter across time being: 1905: 1-2; 1940: 4; today: 9   Corn and soybeans involves perhaps 23 million acres in Iowa and, of course, across these years, the addition of artificial fertilizers to cropland was initiated and has increased.

The Iowa Environmental Council suggests that “Concentrations of nitrate in Iowa’s streams and groundwater have been found to rank among the highest in the U.S., even higher than elsewhere in the Corn Belt and Northern Great Plains.” [from Donnelle Eller, “Concerns voiced about nitrate levels,” Des Moines Register, 9/30/16, (bold, Kinseth)]

While the drainage basin of the Mississippi River includes a vast landmass, the concentration or “density” of intensive agricultural production that requires chemical applications to produce the volume of grain that is taken annually in Iowa makes Iowa agriculture a big polluter.

30% of U.S seafood comes from the Gulf.

While hypoxia occurs on the seafloor.  It is the consequence of nutrients in the upper water strata, so that water is highly modified vs. natural.  In addition, there are myriad chemicals that are toxic and flowing into the Gulf Of Mexico.

BEYOND THE GULF 

Coastal hypoxia zones are not limited to the Gulf.

The occurrence of hypoxia in shallow coastal and estuarine areas is human-caused vs. hypoxia in deep oceans, and it appears to be increasing.