It's a known fact that human activity is continuously destroying natural ecosystems, one of which includes creating areas in bodies of water where life stops being able to be sustained. Continue reading to find out more about what causes these dead zones and how they are ultimately harmful to the environment and to survival of aquatic species.
What are Dead Zones?
Dead zones refer to the areas in bodies of water, such as oceans and lakes, that have little oxygen, and therefore aren't ideal conditions for organisms to be able to live and thrive in. Many marine animals, despite living underwater, need oxygen in order to survive, which is why it's important for marine plants to be able to perform photosynthesis in order to produce that oxygen. However, external factors, such as the harmful human activity of dumping huge amounts of nutrients in the ocean, cause these declines in the health of natural ecosystems.
Dead zones appear as a result of a process, eutrophication, which means that when an overwhelming amount of excess nutrients, including nitrogen and phosphorus, gets added to the aquatic environment, it facilitates the growth of cyanobacteria, also known as algae. The bacteria grows out of control as it feeds off the nutrients, resulting in algal blooms, which prevent light from being able to reach past the ocean's surface and reach marine plants in the water. This can lead to hypoxia (extremely low oxygen concentration) or even anoxia (no oxygen in the area of water). Sunlight is essential for plants to perform photosynthesis in order to survive, and cutting off this essential resource creates an unlivable environment for them. The plants end up dying and being unable to maintain the level of oxygen in that area of the water, causing other species to be unable to live there as well.
What Are The Impacts of Human Activity?
Although there are natural nitrogen and phosphorus cycles, due to human activity, the amounts of these nutrients in bodies of water are often 2-3 times as much as there would be naturally. Agriculture, industrial, and population growth cause large quantities of nitrogen and phosphorus to be produced. The runoff of the different substances, as well as waste getting dumped into oceans and other bodies of water, lead to unnatural increases in bacterial growth, which is a big reason why many dead zones can be found close to densely populated coastlines, especially those with farms or factories.
Other human activities, including burning fossil fuels and using fertilizers, cause the release of nitrogen into the air. This atmospheric nitrogen is also part of the nitrogen cycle that gets redistributed into the land and water.
What Do Dead Zones Look Like?
These areas of unsustained life can be identified as a layer of algae or bacteria on the ocean surface and lack of sunlight below that. The area beneath dead zones is dark, and no sunlight is able to reach below the surface. Green algae is a big identifier, but large masses of pollution also create dead zones.
How Are Dead Zones Harmful?
Besides from endangering many aquatic species and destroying ecosystems, dead zones also have harmful impacts on the human population. Algal blooms can cause illnesses in humans, which can occur due to shellfish absorbing the microbes in algal blooms as they filter the water, and the microbes poisonous to humans can lead to sickness or even death from shellfish poisoning.
In addition, because of the lack of sea animals, birds, and mammals such as sea lions and seagulls will no longer have an abundant food source, causing those populations to decline as the food web isn't supported with adequate prey. Furthermore, humans will have a decrease in seafood due to species of fish becoming endangered by these dead zones as well as overfishing and overhunting.
There are currently a total of 415 major dead zones around the world, the majority of which are along the coasts of the United States, Baltic States, Japan, and the Korean Peninsula. The number has significantly increased and will continue to if climate change continues due to our pattern of living.
Please remember to reduce the amount of pollution in oceans by throwing away trash or even picking up litter! A small action of help can lead to great effects and help save our planet.
Written by: Janice Le
References:
“Hypoxia and Anoxia- Rhode Island.” Department of Environmental Management, www.dem.ri.gov/programs/emergencyresponse/bart/hypoxia.php.
National Geographic Society. “Dead Zone.” National Geographic Society, 9 Oct. 2012, www.nationalgeographic.org/encyclopedia/dead-zone.
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