Can you imagine an area of pollution in the ocean which is the size of the state of New Jersey and where no marine life can live because there is too little oxygen in the water? You would think if such a place existed then it would be featured on the nightly television news and be in the newspapers on a regular basis. After all journalists flocked to the Gulf of Mexico when the oil spill from the Deep Water Horizon occurred in 2011 and it was reported in the media on a daily basis. But indeed such a large polluted area in the ocean does exist and it is located off the coast of Louisiana in the Gulf of Mexico. Perhaps journalists ignore its’ existence because there aren’t dramatic photos to show on the television like flowing oil from a borehole on the ocean floor or multiple oiled seabirds. In fact if you sailed right through this huge polluted zone on a boat, you would not even notice it, unless of course you tried to catch a fish.

 

The lack of oxygen in this area of the Gulf of Mexico is caused by “nutrient” pollution. Essentially water flowing down the Mississippi River is full of sediment, phosphorous, and nitrogen washed off the abundant farmlands in the central part of the United States. Phosphorous and nitrogen are called nutrients because they are used by living things for growth and metabolic functions. When all those nutrients in the freshwater river flow into the salty waters of the Gulf of Mexico, two things happen. Number one, the freshwater forms a lighter layer on top of the heavier salty water in the near shore environment of the Gulf. Number two, all those nutrients in the freshwater feed the algae living at the Gulf’s surface where the sunlight is abundant. This causes the growth of massive algal blooms. When the algae eventually die, they drop to the salty bottom layer of water. The decay of the algae uses up the oxygen in the bottom salty layer of water and produces a hypoxic or dead zone. (For more information on nutrient pollution follow this link https://waterblogger.org/water-quality/nutrient-pollution/ ).

 

Scientists have been measuring the extent of the dead zone in the Gulf of Mexico for over thirty years. The size of the dead zone has gotten larger and larger and in 2017 it grew to be the largest size ever – 8776 square miles. You are probably thinking, why isn’t someone doing something about this huge dead zone in the Gulf of Mexico, like the U.S. Environmental Protection Agency (EPA), isn’t that their job? Yes it is, and the agency does have the regulatory tools under the Clean Water Act to require waters of the United States to meet Water Quality Standards. But so far, and despite recommendations to EPA in 2007 by the National Academy of Science for the agency to use their regulatory tools, the EPA instead has decided to improve water quality in the Gulf through the use of a voluntary watershed effort among the states with drainages entering the Mississippi River. A Hypoxia Task Force was established in 1997 which includes several federal agencies and the states of Iowa, Illinois, Minnesota, Wisconsin, Kentucky, Tennessee, Arkansas, Ohio, Missouri, Mississippi and Louisiana. This may seem like a lot of states, but in reality, it is not even all the states which have drainage into the Mississippi River, after all the entire Mississippi River basin covers 1,245,000 square miles – 41 percent of the lower 48 states of the United States. However, the states involved in the Task Force are the biggest contributors of nutrients to the river.

 

The Hypoxia Task Force regularly reports on progress being made to reduce nutrient pollution. The Task Force set itself a goal of reducing the hypoxic zone in the Gulf to less than 3100 square miles by the year 2035. In order to reduce the hypoxic zone to this size, the amount of nutrients entering the Gulf of Mexico must be reduced by 45 % from the average amount of nutrients measured between1980 and1996.  An interim reduction goal of 20 % has been set for the year 2025, just seven years from now. The Task Force is relying on individual state strategies to achieve these nutrient reductions. At this point all states involved with the Hypoxia Task Force have drafted or completed strategies. Each state has set very different methodologies and plans for achieving nutrient reduction goals. Other than some targeted improvements to reduce nutrients from wastewater treatment plants, most of the actions in the state strategies are voluntary.

 

The Hypoxia Task Force knows where most of the nutrient pollution is coming from, after all this problem has been studied for a long time. The U.S. Geological Survey (USGS) has been able with the help of the Natural Resource Conversation Service (NRCS) to define where the greatest amount of nutrient pollution is coming from in the Mississippi River Basin. Below is a map showing the main sources of nutrient pollution to the Gulf. The map was put together by the USGS for the EPA’s 2017 Biennial Report to Congress.

As you can see from the map, the states with the greatest nutrient contributions to the Gulf are in the northern basin of the Mississippi River. So states like Minnesota, Iowa, Illinois, Wisconsin and Indiana, which are all over a thousand miles from the Gulf of Mexico, are the biggest polluters. Most of the pollution is coming from agricultural lands. Some of the causes are over fertilization of crops, uncontrolled manure at farm animal operations, and even the growing of certain types of crops, such as soybeans, which can produce excess nitrate in the soil. According to EPA, there are numerous conservation methods identified by the Department of Agriculture which can vastly reduce these sources of pollution. Studies conducted by the NRCS on conservation practices already being implemented in the upper Mississippi River Basin show reductions of nutrients can be achieved in the order of 5 to 34 % for nitrogen and 1 – 10 % for phosphorous. The NRCS studies attribute these conservation practices within the whole Mississippi River Basin to an 18 % reduction in nitrogen and a 20 % reduction of phosphorus in the surface water entering the Gulf of Mexico.

 

With such large nutrient pollution reductions from existing conservation practices, one wonders exactly why the hypoxic zone in the Gulf is getting larger. There are a couple of reasons. Poor nutrient controls have been in place for multiple years. A lot of the old nutrients which washed off farmland years ago are now contained within the sediment of the streams and rivers forming the Mississippi River watershed. This sediment in the stream and river channels is a continuing source of nutrient pollution into the Gulf. Every time there’s a big storm or there’s lots of precipitation then sediments containing nutrients are scoured from the river and stream channels and washed further down the river toward the Gulf. Even if you were to eliminate all the nutrients in farm runoff from now into the future, there are still these legacy nutrients over which one has to worry.

 

I’m afraid we always tend to blame the farmers for all our nutrient pollution problems. Farmers are probably unfairly targeted to shoulder most of the nutrient reductions when many of the causes of the long term pollution problem in the Gulf are really a result of the over engineering and channelization of the Mississippi River to provide transportation and to reduce flooding. These activities have resulted in loss of streamside vegetation, including forests and wetlands that would have helped buffer the nutrient pollution. (Here’s a link to more reading on the problems of the Mississippi River https://waterblogger.org/water-quantity/dams-and-their-impacts-on-wetlands/  .) Scientists also blamed the increased size of the dead zone on the larger and more dispersed freshwater flow resulting from the channelization and diversion of the river into the Gulf through the lower portion of the Mississippi Delta because it has spread the nutrients and the stratification in the coastal waters over a much larger area then would have otherwise occurred.

 

So whatever pollution reduction methods are implemented by the states through their strategies, it is unlikely to produce immediate reductions in the size of the dead zone in the Gulf even by 2035. Unless of course other options like stream and river restoration activities are also incorporated into the Hypoxia Task Force’s plans.