How Runoff Pollution is Suffocating Our Water Bodies
Brookline, MA
2016, Senior, Creative Writing
Today’s world community is plagued with a series of environmental disasters, ranging from global warming to the depletion of natural energy sources such as oil. While the phenomenon of climate change receives a huge amount of attention in the media as well as in the environmental community, there are many other issues that human beings must start addressing and taking action on in order to maintain the health of the planet. One of these less talked about ecological catastrophes is the destruction of the Earth’s oceans and freshwater bodies. Human activity such as agriculture and sewage treatment is polluting the world’s watersheds, as the chemicals used in these processes are being carried off land and into streams and rivers as runoff. This toxic chemical runoff is resulting in the widespread phenomenon of “dead zones” occurring in the Earth’s oceans. A dead zone is an area in which oxygen levels are so low that marine life must struggle in order to survive.
In order to understand the proliferation of dead zones, one must first understand the process of cultural eutrophication. Cultural eutrophication is defined as an increase in fertility due to anthropogenic, or unnatural, inputs of nutrients. While this process can occur naturally over extremely long periods of time during which lakes fill in with sediments that contain nutrients, human activity has greatly accelerated the rates of eutrophication in certain regions due to the release of contaminants from point and nonpoint sources. Cultural eutrophication is detrimental to the natural order of aquatic ecosystems in that it stimulates the growth of some species to the disadvantage of others (Garrison, 2014). For example, algae in water bodies in which cultural eutrophication is occurring use the excess nutrients in the ecosystem to reproduce at extremely rapid rates, a phenomenon known as algal bloom.
So, what causes cultural eutrophication? While nutrients from inorganic fertilizers are primarily responsible for this phenomenon, there are other types of runoff that can stimulate cultural eutrophication in water bodies. A few examples of these alternative pollutants are sewage, vehicular and industrial emissions, and even natural pollutants such as nutrients released from weathered sediments.
As previously discussed, cultural eutrophication oftentimes results in the phenomenon of algal bloom occurring in aquatic ecosystems. This poses a great many direct and indirect consequences to the natural order of aquatic ecosystems. For one, algal bloom results in reduced light penetration in the littoral zone of water bodies. This can lower the success of predators who rely on light to catch their prey as well as block the sun from producers in the littoral zone who rely on sunlight to conduct photosynthesis. While producers in the littoral zone are unable to conduct photosynthesis and eventually die because of this, the over productive algal cells conduct photosynthesis at extremely rapid rates. In order to conduct photosynthesis, algal cells use up free carbon atoms in the water, which raises the pH of the ecosystem to unnaturally high levels. Organisms that require a more neutral pH in order to thrive are therefore either driven out of the ecosystem, or die.
Some of the more direct consequences of algal bloom can be observed with mass die offs of the organisms living in a water body affected by cultural eutrophication. For example, excess quantities of algal cells can clog the gills of fish, causing them to suffocate and die. While most strains of algae are not poisonous, one type of algae known as cyanobacteria is deadly to organisms living in aquatic ecosystems. Algal blooms of cyanobacteria have the ability to poison and kill domestic animals, wildlife, and humans alike. These negative impacts of algal bloom result in reduced productivity and biodiversity within the ecosystem.
One of the largest problems associated with algal blooms occurring in aquatic ecosystems has to do with the availability of oxygen in the ecosystem. When large quantities of the algae die, microbes swarm to digest the dead cells, in turn using up an enormous amount of the ecosystem’s available oxygen. Thus, other organisms in the ecosystem are deprived of oxygen and eventually become stressed and die, if they are not able to migrate to a new habitat. The scientific term for an environment in which there is limited oxygen is “hypoxic,” which means low oxygen. Hypoxia is currently thought to have resulted in more mass fish die offs than any other cause, even oil spills. Thus, the impacts of dead zone have far reaching consequences both on ocean ecosystems and human economies. This detrimental process is occurring all over the world right now, resulting in the creation of dead zones in many of the Earth’s oceans and lakes.
One of the largest known dead zones is found in the Gulf of Mexico. This dead zone is estimated to be about 8,000 square miles large, an enormous stretch of ocean to be void of life. The Gulf dead zone is caused by agricultural runoff from the U.S. Midwest, particularly runoff comprised of synthetic fertilizers used on farmlands. The Mississippi River drains 41% of North American continental water into the Gulf of Mexico, and most of the states bordering the river rely heavily on industrial agriculture in order to maintain the health of their economies. Thus, the runoff produced by these states consists largely of inorganic fertilizers that contain high concentrations of synthesized nutrients such as nitrates and phosphates. The river then carries these excess nutrients into the Gulf of Mexico, resulting in a massive dead zone. The Gulf dead zone occurs seasonally; when farmers begin fertilizing their lands in preparation for crop season in the spring, the dead zone in the Gulf is at its largest. While the Gulf dead zone is one of the most commonly talked about dead zones, there are more than 400 of these zones currently occurring worldwide, an international crisis that must be addressed.
There are many economic incentives for humans to take action against the formation of dead zones. For one thing, the mass die-offs of fish and shellfish that occur with the formation of dead zones results in economic ruin for fisheries in the area. For example, the Gulf dead zone decimated the shrimp population, which resulted in a huge economic collapse in the fishing industry of that region. On top of this, the water pollution responsible for the creation of dead zones also causes the degradation of drinking water quality and increases public health risks. Normally, bacteria in rivers and streams will remove excess fertilizer from the water that allows them to convert nitrates into nitrogen gas which is then released into the atmosphere. However, scientists have discovered that rivers are unable to take up the mass amount of nitrates released into the water from anthropogenic sources. By destroying this ecosystem service, humans are forced to spend much more money on cleaning water than if the bacteria in rivers and streams were able to naturally take it up. In fact, the estimated cost of damage done by cultural eutrophication in the U.S. is approximately 2.2 billion dollars annually.
So, what can be done to mitigate the formation of dead zones and phenomenon of cultural eutrophication from occurring? Fortunately, dead zones are reversible if the sources of pollution responsible for their formation are eliminated. For example, there was a sizeable dead zone located in the Black Sea when Russia was in the process of becoming an industrialized nation. However, following the fall of the Soviets in the 1990s, the price of chemical fertilizer experienced a huge spike. Many Russians were no longer able to afford inorganic fertilizer, and thus the dead zone in the Black Sea disappeared.
Reducing the amount of inorganic fertilizers each country uses is a large scale project that would require the cooperation of the entire global community. While it would be incredible if this type of international agreement were to be reached, there are steps that individuals can take in order to reduce the amount of pollution they are putting out into the Earth’s water bodies. For example, washing one’s car on the grass rather than the pavement reduces the amount of water that will runoff into nearby rivers and streams. Using soil tests to determine how much fertilizer one’s yard needs helps to reduce excess usage of fertilizer that could potentially run off into water bodies. Citizens can encourage their local governments to create and restore wetlands that would absorb harmful water pollutants. Individuals can also take action by pressuring their lawmakers to instill more efficient flood control practices so as to prevent urban runoff. Finally, reducing one’s consumption of meat and dairy products would reduce the amount of corn needed to be grown as feed for livestock, thus lowering the amount of fertilizer used on farms.
It is crucial that the global community begin taking serious action to combat the formation of dead zones in the Earth’s oceans. The oceans regulate Earth’s climate, provide humans with major food and water supplies, and are crucial to the biodiversity of the planet. Humans cannot survive on Earth without healthy oceans, and thus must begin taking steps to reverse the damage that has already been done, before it’s too late.
Reflection
Reflection
After completing a full year of AP Environmental Science, writing this paper only reinforced the urgency with which the global community needs to begin treating the phenomenon of dead zones. It’s truly astounding to me that the U.S. in particular has done so little to combat the cultural eutrophication occurring in rivers and streams that are located nearby to regions that specialize in commercial agriculture.
Writing this paper also made me think a lot about what I can do personally to prevent harmful runoff from making it into rivers, streams, and eventually the ocean. One of the most interesting mitigating techniques I came across in my research was to eliminate meat and dairy products from my diet. Going vegan reduces the amount of animal feed needed to be grown in order to produce meat and dairy products, thus reducing the amount of fertilizer used on crop fields. If everyone in the U.S. decided to go vegan, we could probably save our oceans. While it is unrealistic to expect that an entire country could completely cut meat out of its diet, there are so many small steps people can take to reduce their impact on the Earth’s water bodies. It was so interesting to see how seemingly insignificant lifestyle changes could make such an enormous difference if enough people decided to take action. Going forward, I hope to encourage friends and family members to actively engage in combatting the destruction of our oceans by chemical runoff.