How Agriculture is Contributing to The Gulf of Mexico’s Hypoxic Zone

There’s a dead zone growing in the Gulf of MexicoLocated off the Louisiana-Texas coastline, this murky blight is causing marine life to either flee or die in massLeft unchecked, it could cause irreversible harm to local economies that depend on fishing and water-based activities 

What’s to blame for the creation of this hypoxic zone? The simple answer is the Mississippi River. The Mississippi discharges more water than any river in the US, and its outflow leads directly into the gulf’s hypoxic zone.  

The river’s fresh water is filled with nitrates and sulfates, floating above the gulf’s salty ocean water. These nutrients cause a boom in algae and plankton growth. When the algae and plankton die, they sink down, consuming the waters oxygen along the way. 

The end result is hypoxia, creating a dead zone where marine life cannot survive. 

But why is the Mississippi so filled with nitrates and sulfates in the first place? There are a few theories, but the main culprit is believed to be agriculture.  

Modern Farming and the Pollution of the Mississippi River 

Water run-off and soil erosion are serious issues for farmers everywhere. Today’s farming practices such as tillage and repeat crop planting cause serious damage to soil. Tillage breaks up soil structure, increasing erosion. Meanwhile, continuously planting the same crops drains the soil of nutrients, making it less effective at nurturing plants and absorbing water. 

To compensate for the damaged soil, farmers increasingly use manure and synthetic fertilizers. While this can temporarily help with crop growth, it does nothing for soil health. In fact, it may be damaging the soil even further by destroying carbon. 

So, the runoff continues, and potentially increases, carrying extra nitrates and phosphorus left behind by the manure and fertilizers. These nutrients ultimately end up in local rivers and water supplies. Since the Mississippi runs through some of the US’s leading farm territories, it falls victim to a lot of runoff. 

A recent increase in Midwest rainfall has only served to intensify this process.  

Despite being one of the smaller states touching the Mississippi, Iowa is believed to be one of its biggest contributors of nitrates. To combat this, the state started The Iowa Nutrient Reduction Strategy, a program designed to assess and reduce the introduction of contaminants to Iowa’s water supplies and the Gulf of Mexico. One hope for reduction is through Iowa’s own Conservation Reserve Program 

Next week, we’ll discuss why CRP might be the best defense against local water contamination and the leading cure for the Gulf of Mexico’s hypoxic zone.