Dead zones, explained
Jan 21, · That is why these areas are called dead zones. Dead zones occur because of a process called eutrophication, which happens when a body of water gets too many nutrients, such as phosphorus and nitrogen. At normal levels, these nutrients feed the growth of an organism called cyanobacteria, or blue-green algae. With too many nutrients, however, cyanobacteria grows out of . What is a dead zone? "Dead zone" is a more common term for hypoxia, which refers to a reduced level of oxygen in the water. At 2, square miles, the hypoxic zone in the Gulf of Mexico is the 3rd smallest ever measured in the year record, measured from July 25 to August 1.
When nitrogen and phosphorus how to manage extreme anxiety off into our water systems, algae bloom growth increases, robbing the water of oxygen.
A big source of nitrogen and phosphorus run off is the use of fertilizers, whose main components are nitrogen and phosphorus. Nitrogen and phosphorus are washed into our streams, lakes, bays and oceans, promoting the growth of phytoplankton blooms, and in turn zooplankton which feed off of phytoplankton.
When phytoplankton and zooplankton waste decomposes, oxygen is used faster than can be replaced, leading to the formation of dead zones. Dead zones can form naturally, but human activity can play a role, contributing to the growth and severity hos dead zones. The Virginia Institute of Marine Scientists estimate that over dead zones exist worldwide. The second largest dead zone is located zonfs the Gulf of Mexico covering 7, — 8, square miles. Other U. Marine organisms occupying areas where dead zones occur are at risk, affecting their physiological stress, growth, reproduction and survival.
For those marine organisms that cannot escape, dead zones are deadly. Dead zones can have xo drastic effect on commercial and recreational fisheries. If you're a homeowner, you can be part of the dead zone solution by being careful which products you or your lawn care service utilize to maintain the health of your lawn. By choosing to incorporate organic practices into your lawn care maintenance ritual or by purchasing lawn care services from companies using organic products, you can help limit the amount of nitrogen and phosphorus that run into our local waterways.
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The Gulf dead zone threatens seafood production, recreation and marine life.
Jul 31, · Published July 31, • 8 min read. Share. Tweet. Email. “Dead zones” are deadly: Few or no organisms can survive in their oxygen-depleted, or hypoxic, waters. . Dead zones begin to form when excess nutrients, primarily nitrogen and phosphorus, enter coastal waters and help fertilize blooms of algae. Major nutrient sources include fertilizers, wastewater, and the burning of fossil fuels. Dec 27, · A quick look at a map of dead zones will reveal that they tend to form along heavily populated coastlines – again pointing to the impact of human-contributed nutrients to the ocean as the most common source of dead zones. Share this Image On Your Site.
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Because most organisms need oxygen to live, few organisms can survive in hypoxic conditions. That is why these areas are called dead zones. Dead zones occur because of a process called eutrophication , which happens when a body of water gets too many nutrient s, such as phosphorus and nitrogen.
At normal levels, these nutrients feed the growth of an organism called cyanobacteria , or blue-green algae. With too many nutrients, however, cyanobacteria grows out of control, which can be harmful.
Human activities are the main cause of these excess nutrients being washed into the ocean. For this reason, dead zones are often located near inhabit ed coastline s.
Understanding the eutrophication process provides the clearest picture of how and why dead zones develop. Causes of Eutrophication Eutrophic events have increased because of the rapid rise in intensive agricultural practices, industrial activities, and population growth. These three processes emit large amounts of nitrogen and phosphorous. These nutrients enter our air, soil, and water.
Human activities have emitted nearly twice as much nitrogen and three times as much phosphorus as natural emissions. Different regions of the world emit different levels of these nutrients.
In developed countries, such as the United States and nations in the European Union, heavy use of animal manure and commercial fertilizer s in agriculture are the main contributors to eutrophication. Runoff from large agricultural fields enters creek s and bays because of rain or irrigation practices. In developing countries of Latin America, Asia, and Africa, untreated wastewater from sewage and industry mainly contribute to eutrophication.
Factories and sewage facilities are less regulated than they are in developed countries, and sometimes wastewater is simply dumped into creeks, rivers, lakes, or the ocean.
Atmospheric sources of nitrogen also contribute to eutrophication in some areas of the world. Fossil fuel s and fertilizers release nitrogen into the atmosphere. This atmospheric nitrogen is then redeposited on land and water through the water cycle —rain and snow. The Chesapeake Bay, on the East Coast of the United States, has one of the first dead zones ever identified, in the s.
The western part of the bay is full of factories and urban centers that emit nitrogen into the air. Atmospheric nitrogen accounts for about a third of the nitrogen that enters the bay. The eastern part of the bay is a center of poultry farming, which produces large amounts of manure. The Chesapeake still has a dead zone, whose size varies with the season and weather.
Eutrophication and the Environment The eutrophication process has severe environmental impacts. Dead zones result from these impacts, which include algal bloom s and hypoxia. Algal Blooms Phosphorous, nitrogen, and other nutrients increase the productivity or fertility of marine ecosystem s.
This rapid development of algae and phytoplankton is called an algal bloom. Algal blooms can create dead zones beneath them. They also prevent oxygen from being absorbed by organisms beneath them. Sunlight is necessary for plants and organisms like phytoplankton and algae, which manufacture their own nutrients from sunlight, water, and carbon dioxide. Oxygen is necessary for almost all aquatic life, from sea grass es to fish.
The number and diversity of benthic , or bottom-dwelling, species are especially reduced. Red tides actually have nothing to do with tide s. They also have nothing to do with algae. The organism that causes red tides is a bacteria , called cyanobacteria.
Algal blooms also cause larger-scale problems, such as human illness. Shellfish , such as oysters, are filter feeder s.
As they filter water, they absorb microbe s associated with algal blooms. Many of these microbes are toxic to people. People may become sick or even die from shellfish poisoning. Algal blooms can also lead to the death of marine mammal s and shore birds that rely on the marine ecosystem for food. Wading bird s, such as herons, and mammals, such as sea lions, depend on fish for survival.
With fewer fish beneath algal blooms, these animals lose an important food source. Algal blooms can also impact aquaculture , or the farming of marine life. Algal blooms usually die soon after they appear. The ecosystem simply cannot support the huge number of cyanobacteria.
The organisms compete with one another for the remaining oxygen and nutrients. Hypoxia Hypoxia occurs when algae and other organisms die from lack of oxygen and available nutrients. Hypoxia events often follow algal blooms. The cyanobacteria, algae, and phytoplankton sink to the seafloor, and are decompose d by bacteria. Even though oxygen can now flow freely through the aquatic ecosystem, the decomposition process uses up almost all of it. This lack of oxygen creates dead zones in which most aquatic species cannot survive.
The Gulf of Mexico has a seasonal hypoxic zone that forms every year in late summer. Its size varies from fewer than 5, square kilometers 1, square miles to approximately 22, square kilometers 8, square miles, or the size of Massachusetts. Its mission is to reduce the five-year running average of the Gulf of Mexico dead zone to less than 5, square kilometers.
Increased runoff from agricultural fertilizers and sewage has sped up the eutrophication process. Overfish ing of Baltic cod has intensified the problem. Cod eat sprat s, a small, herring-like species that eat microscopic zooplankton , which in turn eat algae. Fewer cod and more sprats mean more algae and less oxygen. Categorizing Eutrophic Systems Scientists have identified dead zones worldwide.
Hypoxic areas have increased dramatically during the past 50 years, from about 10 documented cases in to at least in As a result of the dramatic increase in dead zones, scientists have categorized coastal systems experiencing any symptoms of eutrophication. An area of concern is a coastal system that exhibits effects of eutrophication, such as elevated nutrient levels, harmful algal blooms, and negative changes in the benthic community.
Areas of concern are at the most risk of developing hypoxia. Major concentrations of areas of concern are located along the western coast of Central and South America, and the coastlines of Great Britain and Australia. There are areas of concern around the world. A system in recovery is one that once exhibited low oxygen levels and hypoxia, but is now improving.
For example, the Black Sea once experienced annual hypoxic events, but is now in a state of recovery. These are the results of better industrial and wastewater controls. There are only 13 coastal systems in recovery around the world. Natural Dead Zones Not all dead zones are caused by pollution. The largest dead zone in the world, the lower portion of the Black Sea, occurs naturally. Oxygenated water is only found in the upper portion of the sea, where the Black Sea's waters mix with the Mediterranean Sea that flows through the shallow Bosporus strait.
Also called cyanobacteria and in freshwater habitats pond scum. Carbon dioxide is also the byproduct of burning fossil fuels. Also called blue-green algae even though it is not algae and in freshwater habitats pond scum. Seaweed can be composed of brown, green, or red algae, as well as "blue-green algae," which is actually bacteria.
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