That goes for natural habitats too. With less rain falling in the middle of the country during the current drought, there’s less polluted runoff to the Mississippi. That means that the river’s discharge to the Gulf of Mexico is a lot cleaner than usual.
An analysis of the Gulf from Aug. 15-21 covered more than 1,200 miles of cruise track, from Texas to Louisiana. The team found no hypoxia off the Texas coast while only finding hypoxia near the Mississippi River delta on the Louisiana coast.
Hypoxia is a condition in which the ocean waters have very low levels of dissolved oxygen present, which means that living things can’t survive there. Fish do breathe, but through their gills.
“We had to really hunt to find any hypoxia at all and Texas had none,” says Steve DiMarco, associate professor of oceanography at Texas A&M University. “The most severe hypoxia levels were found near Terrabonne Bay and Barataria Bay off the coast of southeast Louisiana.
Basically, the dissolved fertilizer from agriculture stimulates high levels of algae growth in the waters. When they die, they sink and decay, which uses up the oxygen in the water. Then everything dies. As long as the amount of chemical nutrients coming into the system is in balance with the dynamics of the waterbody, the oxygen level fluctuates within bounds that local life can tolerate. Pollution by industry, agriculture, or local sewer systems can upset that balance.