Dead Zones

What are dead zones in the ocean? Dead zones are also more commonly known as hypoxia, these are regions where the oxygen concentrations are low in the water. Dead zones are areas in the ocean of such low oxygen concentration that animal life suffocates and ends up either eventually dying or the habitat living in that area leave. The low oxygen is caused by an interaction between biological, chemical and physical factors. According to a study conducted by the Smithsonian climate change is likely to make existing dead zones worse, “Warmer water holds less oxygen, and the researchers found that 94 percent of the world’s dead zones are in areas expected to see a temperature rise of 2 degrees Celsius or more by the end of the century.”  There are many causes that can lead to dead zones in large bodies of water. One major cause is an increase in chemical nutrients in the water that lead to excessive blooms of algae that deplete underwater oxygen levels. The primary chemicals that are responsible are nitrogen and phosphorus from agricultural runoff. Also, sewage, vehicular and industrial emissions are factors that can play a role in the overall development of dead zones.  Sewage causes many dead zones within Africa and South America. Engineers have been working on sewage facilities for years and are finding ways to alleviate the sewage going into the dead zones. Airborne nitrogen contributes to these areas because when vehicles and power plants burn fossil fuels, they emit large amounts of nitrogen into the air. The particles set into the waterways and eventually make it to the oceans.

Dead zones occur all over the world in both fresh water and saltwater systems, but, are primarily seen around areas with heavy agricultural and industrial activity that end up spilling nutrients into the water and compromise its quality. However, some dead zones can also occur naturally. The most commonly known marine dead zones are found in the Gulf of Mexico, the Baltic Sea, the Black Sea, off the coast of Oregon, and in the Chesapeake Bay.   The largest dead zones within the United States are in the Gulf of Mexico and off the coast of Oregon. There are two major reasons for the density of the dead zones along the Atlantic and Gulf coasts. The first reason is that there is a large amount of people within the area, as well as many animals and farms to feed them. The second reason is that there are not many rivers draining into the Pacific Ocean. This means that with fewer rivers carrying the runoff, fewer dead zones form.

According to the National Oceanic and Atmospheric Administration also referred to as NOAA it is said that “dead zones are a major water quality issue with an estimated total of more than 550 occurring annually worldwide.”  The impacts of dead zones have a pretty negative effect on our ecosystems. The one major impact is the mortality of marine organisms including fish and their food base, there are high losses of the bottom of the ocean dwelling plants and animals. With this information it can be said that there is than a reduction in the number of species that these habitats were once able to care for. Another impact is that dead zones cause a disruption of fish spawning and migration. According to Sea Web “impacts have accrued from fisheries especially the extreme levels of bycatch and the damage to seabed habitats.”

http://www.onearth.org/earthwire/devil-deep-blue-sea

http://www.teachoceanscience.net/teaching_resources/education_modules/dead_zones/learn_about/

http://www.scientificamerican.com/article/ocean-dead-zones/

http://www.noaanews.noaa.gov/stories2015/080415-gulf-of-mexico-dead-zone-above-average.html