When the amount of oxygen in water drops, fish and other aquatic animals cannot survive. Areas with low or no oxygen are called “hypoxic zones”, and are found in nutrient-rich waters where microscopic phytoplankton multiply boundlessly and then in turn die and decay. The decay ‘uses up’ the oxygen in the water, making it impossible for other aquatic creatures to survive there. This is why hypoxic zones are called “dead zones”.
In the Mississippi River System, the dead zone forms at the mouth of the river and extends for miles out into the Gulf of Mexico. This is depicted clearly in this video from the National Oceanic and Atmospheric Administration. The Gulf dead zone peaks in the spring of the year and extends from New Orleans westward to the Louisiana-Texas border. The world’s largest hypoxic zone is in the Baltic Sea, where overfishing has exacerbated the problem by reducing the number of fish available to feed on the phytoplankton. Read about that here. Other dead zones occur in Chesapeake Bay, Green Bay, and Lake Erie. Circle of Blue’s Codi Kozachek writes about dead zones around the world, and their impact on human health and the economy in this article.
In Lake Michigan, the dead zone forms in Green Bay where the Fox River carries nutrient pollution into the Bay and overwhelms the ability of this ecosystem to manage the influx. Here, scientists estimate that a 50% reduction in the amount of nutrients coming into the Bay may be enough to take care of the problems. Like in the Mississippi River watershed, the amount of pollutants in the Fox River from point sources has been steadily declining, but the nonpoint contribution (primarily from agriculture) remains high. This topic was discussed at the LWV Wisconsin’s Annual Convention in 2016 in a discusion of "the Economic Case for Water Quality" – see the video here.
The title of this blog post, “Dead Zone season is coming again to a major water body affected by you“, refers to the fact that if you are reading this, chances are that the water you flush probably goes to the Mississippi River eventually, meaning that we are all part of the problem here. We need to know that this problem is not a hoax, is not going away and still must be solved. We know that changing agricultural practices so that the earth is covered most of the time will help, and that effective fertilizer and manure management is needed to prevent loss of valuable crop nutrients to waterways.
LWV UMRR’s Annual Meeting on May 6 will focus on ways to move ahead in advocacy on this critical topic. Join us in La Crosse and become part of the solution. Sign up here today!