Dead Zones Are a Clear Threat To Earth’s Ecosystems
by James Mrohs


Zak Koretz | The Bottom Line


With spring break coming up, it’s not too difficult to imagine yourself lying on the beach, lightly dipping your toes into the crystal clear ocean water as the waves invite you to dive into the nearly translucent ocean. Little do you realize that within that transparent water, you are the only living organism present. You have stumbled upon what is known aptly as a dead zone, an area unable to support any life. This is an issue which most people are sadly unfamiliar with, despite the possible impacts it may have on them, even on vacation.

Dead zones are areas where the water is hypoxic. This means the levels of dissolved oxygen in the water have reached levels too low to support the majority of marine life. The waters are clear because they are devoid of even the most basic life forms, phytoplanktons and algaes, which normally taint the translucence of the water. Without these basic biological building blocks, no large fish or sea creature can survive in these areas. It would be akin to a human walking into a room without any air. While large air breathing mammals could transverse these waters, they have no reason or incentive to, as no food or prey lies within these waters now. What formally may have been prime habitat for many types of fish, crustaceans, and sea flora is now an empty area, incredibly attractive by human standards, but worthless ecologically.

While hypoxia can occur naturally in certain marine ecosystems, these cases are rare and generally not the cause of any dead zones you may find. Instead, most are caused by a process known as eutrophication, the ultimate result of modern farming techniques. If there are no protections against excess watering or rain and the soil with nutrients is not fixed when farms are laid out, fertiliser runoff from the fields can occur, wherein the overly-nutrient rich soil will flow into local water supplies. When these nutrients flood a river, they cause the ecosystem there to turn completely on its head. Phytoplankton will go on an effective feeding frenzy due to the excess of nutrients in the area, causing the population to rise incredibly fast, too fast for the other animals to respond. What then occurs is called an algal bloom, where the surface of the water is filled to the brim with these algae, turning the surface a variety of bright red or green colors. This blocks out the sunlight and uses up massive amounts of oxygen. This stage lasts a while and causes most of the life in the water to die out quickly. Eventually the algae dies off due to overshooting the sustainable population of the area, filling the water with detritus. Bacteria, generally the last living organisms in the area, feed off the detritus, further reducing the level of oxygen in the water to fully hypoxic levels. At this point, the water is effectively a dead zone.

While these zones can and do occur in lakes, they are especially damaging in rivers, as they disturb the entire ecosystem for any animals that transverse it regularly. Additionally, in high current rivers the dead zone flows into the ocean, bringing the now salinized dead spot into ocean areas. The other way dead zones occur in marine systems is from having the nutrients simply run off straight into the ocean, where the eutrophication process then occurs. This is especially common for the most well known and significant dead zone in the Gulf of Mexico, where runoff from the Mississippi River brings nutrients to the ocean abundantly and rapidly.

While tourists appreciate being able to see straight to the bottom of the ocean, and not having to fear any creatures disturbing them, these dead zones have a tremendous impact on the environment and local businesses. In the Gulf of Mexico the dead zone is roughly the size of New Jersey which significantly impacts the local fishing, especially shrimp fishing, businesses. As the dead zone grows in size more fish are forced into surrounding waters which cannot support the expanding new life populace. Over time animals die off, reducing the amount of fish available for any harvest. Perhaps more significant to tourism is the fact that the rising number of shark attack incidents along the Gulf of Mexico are related to these dead zones. Scientist believe that due to these dead zones decreasing both the quantity of fish and the location of fish in relation to where the sharks generally hunt they are forced towards shores while they are hungry. While shark attacks are still very rare incidents and should not be seen as a grave threat, it nonetheless is the most dramatic evidence of the harmful effects these dead zones can have on local ecosystems and the environment, human and wild.

Dead zones do dissipate naturally over time, assuming no new nutrient overflow fills the area, but this process can take decades. Preventing nutrient overflow and runoff doesn’t mean that artificial or excessive fertilizers can’t be used, but instead should simply be used wisely, safely, and with regard for local water supplies. This issue impacts many more people than those who realize it, and is simply a matter of being aware. So keep this in mind during spring break if you see any especially clear beaches, while they may fulfill an ideal tropical fantasy, they are actually a man-made ecological disaster, and not one of nature’s wonders.