Did you know that there is currently an area the size of New Jersey in the Gulf of Mexico that can be deadly to fish and other marine animals? What’s worse is that this area, known as a dead zone, shows up every summer and this year it is bigger than it has ever been.
The dead zone is actually a hypoxic area, or an area with low oxygen content. Hypoxic waters typically have dissolved oxygen concentrations of less than 2-3 ppm. The cause of these hypoxic areas is typically an excess of nutrients, namely nitrogen and phosphorus. These excess nutrients in water can promote the growth of harmful algal blooms. An overgrowth of algae in the water can lead to a variety of problems. One problem is that some types of algal blooms can produce dangerous toxins that are capable of causing sickness and, in severe cases, death to humans and animals. Another problem comes when these algal blooms begin to die off. As algae dies and decomposes it absorbs oxygen from the surrounding water and leads to areas of low oxygen. The lack of oxygen forces fish out of the hypoxic areas, but the less mobile species, such as young fish and shellfish, are often times killed during the process. This inability to support life is the reason these areas are known as dead zones.
The largest dead zone in the U.S. and one of the largest in the world, is the one located in the Gulf of Mexico. Scientist first began mapping the zone in 1985. Over the last 5 years, the average size of the dead zone was approximately 5,806 square miles. However, in 2017, the zone was measured to be an alarming 8,776 square miles, the largest recording ever. The primary cause for this specific dead zone is runoff from the Mississippi River. The watershed of the Mississippi River is the fourth largest watershed in the world, covering about 40% of the lower 48 states. With this huge watershed, comes a huge amount of pollution in the form of nutrient runoff. A large portion of this nutrient runoff comes from the use of fertilizers for agriculture in the upper midwest. All of these excess nutrients then work their way down the Mississippi and are then dumped into the Gulf of Mexico. The reason for the spike in size of the Gulf dead zone is directly tied to an increase in rainfall in the midwest this year.
Map showing the size and location of the 2017 dead zone in the Gulf of Mexico.
Knowing that we, as humans, are contributing to the size of the dead zone, the question becomes what can we do to reduce our impact. In 1997, the EPA created the Hypoxia Task Force (HTF) to address the problem that is the Gulf of Mexico dead zone. The primary goal of this task force is to reduce the size of the gulf hypoxic zone to 1,950 square miles by 2035. In order to meet this goal, the HTF agreed on an interim target to obtain a 20% reduction in the nutrient load being discharged into the Gulf of Mexico by the year 2025. In addition to the actions being made at the federal and state levels, individuals can also find ways to reduce their impact. Firstly, we can cut down on the use of fertilizers on farms, lawns and gardens. If fertilizers are necessary, it is important to use them at the appropriate times to limit the amount that can enter our waterways. Other ways to reduce the impact is to use phosphate free cleaning products, have septic tanks inspected on a regular basis, and clean up pet waste. Overall one of the biggest keys to achieving the goal of a smaller dead zone is to raise awareness of it. The majority of people are not even aware of the issue, but just because we can’t see the dead zone, doesn’t mean that we will not feel the harsh impact that it has on our environment.