The coastline of North Carolina is littered with barrier islands, protecting a lagoon from the stormy seas of the Antlantic. This has made it historically a biodiversity hotspot, however, today dead zones proliferate across the Pamlico Sound, suffocating marine life that stumbles upon them. However, this was not the case half a century ago. Thanks to poor environmental management and a booming agriculture sector, the region is no longer a haven for marine life. Massive amounts of nutrient rich water enter the Pamlico Sound and create dead zones which severely damage the health of ecosystems surrounding the lagoon. The Pamlico Sound is a great example of the detrimental impacts humans have made on the local environment and how we can reduce them.
Dead zones form as a result of high levels of nutrient rich waste in a body of water (lake, ocean, etc), notably high levels of nitrogen. When excess nutrients enter the ocean or lagoon, algae populations explode. The main nutrients that cause the blooms is nitrogen. Usually nitrogen levels are not abundant in the Pamlico, however due to factors that will be discussed later in the article, they are currently above average. These increased levels cause algae populations to explode as they consume all available nitrogen, and this change is clearly visible as the water becomes a light shade of green. However, the algae do not pose a major threat to marine life- another group of organisms take up the job: Bacteria. As the algae eventually die off, bacteria decompose the algae and consume a lot of oxygen in the process. When the algae is consumed by the bacteria, oxygen levels are decreased to less than 3 mg/L, suffocating all fish and crustaceans in the affected area. When the oxygen level in an area cannot support marine life any longer, it is officially classified as a dead zone. Virtually, all algae blooms become dead zones within a week.
Agriculture, especially CAFOs (concentrated animal feeding operations) are Pamlico Sound’s main source of high nutrient waste run-off. The Tar-Pamlico river basin (which feeds into the Pamlico Sound) has a large portion of land dedicated to cropland and other agricultural operations. More importantly, there are massive CAFOs especially for poultry and swine; about 7 million chickens reside in one of the many CAFOs that litter the region. Due to CAFOs harboring a high concentration of animals (hence the name) in one area, lots of manure is produced. The disposal of this waste is extremely unregulated, especially for the growing poultry industry in the Tar Pamlico basin. As a result, around 40% of all nitrogen which ends up in the Tar and Pamlico rivers is from CAFOs. This is due to the creation of ammonia from the poorly disposed manure; the ammonia enters the air and due to prevailing wind directions, ends up in the Sound or in one of its tributaries. Another large source of nitrogen is fertilizers. Most of the feed given to these animals is produced in the basin, the majority of crops used being soy and corn. These crops rely heavily on fertilizers, which are in essence nitrogen and other molecules that help it bind to plants more easily. Most of these fertilizers get into the waterways which lead to the Pamlico Sound.
Pamlico Sound is a textbook example of agriculture’s direct impact on marine ecosystems. There are many other examples of dead zones created by agricultural run-off. For example, the oceans surrounding the mouth of the Mississippi have had some of the largest dead zones ever created, alongside the Pearl River in southern China which occasionally has large dead zones, detrimental to the fisheries which help feed the region's 80 millions inhabitants. These dead zones damage the environment, causing harm to local communities around the world.
Nevertheless, there is an upside. Due to changing practices and more knowledge on dead zones, some are beginning to shrink and hopefully one day might disappear. New legislation which regulates the disposal of manure is being put into place, and farmers are beginning to use less fertilizer or use it in ways that lead to less run-off. Overall, this issue is beginning to be tackled, as we hope that the day in which these ecosystems return to their pristine conditions will dawn soon.
Comments