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A Very Large 'Dead Zone'

A Very Large 'Dead Zone'

Author: Hugh Bollinger/Monday, June 10, 2019/Categories: natural history, wildlife conservation, marine life, sustainability, environment

                                           Mississippi River Watershed Map, 6-10-2019 (credit: NOAA)gulg

The National Oceanic and Atmospheric Administration (NOAA) predicts a very large 'dead zone' in the Gulf of Mexico this year. The reason for this dire forecast is the volume of water flowing from mid-western agrocultural states down the Mississippi River into the Gulf. Agrochemicals running off industrial farms, containing nitrogen and phosphorus fertilizers in the region, enter the Gulf providing the food source for algae. Resulting Algal blooms pull oxygen out of the water creating a 'dead zone' or hypoxia. According to NOAA's 2019 prediction of an area:

"of low to no oxygen, that can kill fish and marine life of ~7,829 square miles, could reach size of Massachusetts"

NOAA used US Geological Survey (USGS) water-monitoring data in their predictive models which showed that in May 2019 , the Mississippi and Atchafalaya rivers were flowing ~67% above average when compared to the past 38 years. This larger than average volume carried ~160,000 metric tons of nitrates and ~25,000 metric tons of phosphorus fertilizers into the Gulf that month alone. These nitrogen levels were ~18% above the long-term average and ~50% of phosphorus loads. Their new forecast is:

"near the record of ~8,800 sq.mi. set in 2017 and larger than the 5-year average of ~5,800 sq.mi. The excess nutrient pollution has resulted from urban and agricultural runoff, throughout the Mississippi River watershed. The agrochemicals simulate algal growth, which eventually die and sink to the ocean floor to decompose. The resulting low oxygen levels inhibits the growth and survival of most marine life."

A marine scientist gave a conference presentation in New Orleans outlining the causes of 'dead zones' and their consequences:

The irony of this water pollution is most of the nutrients spread on corn, soybeans, and canola oil seed fields isn't efficiently utilized by these crops. It enters the rivers, flows to the Gulf of Mexico, and fertilizes algae instead. 

WHB

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