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.

Nitrogen and phosphorous from agricultural runoff are the primary culprits, but sewage, vehicular and industrial emissions and even natural factors also play a role in the development of dead zones.

Human activities can increase the flow of nutrients such as nitrogen into a water body. Excess nutrients are one type of factor that can lead to dead zone formation. When dead zones occur, human resources use can be negatively impacted. For example, fish may be scarce and fisheries could lose money.

Elevated nutrient levels and algal blooms can also cause problems in drinking water in communities nearby and upstream from dead zones. Harmful algal blooms release toxins that contaminate drinking water, causing illnesses for animals and humans.

Conservation tillage: Reducing how often fields are tilled reduces erosion and soil compaction, builds soil organic matter, and reduces runoff. Managing livestock waste: Keeping animals and their waste out of streams, rivers, and lakes keep nitrogen and phosphorus out of the water and restores stream banks.

Dead zones are not irreversible. From 1985-2000, the North Sea dead zone had nitrogen reduced by 37% when policy efforts by countries on the Rhine River reduced sewage and industrial emissions of nitrogen into the water. Solutions. Voluntarily stop fertilizer and waste runoff into lakes, rivers, and streams.

What Can Be Done? Dead zones are reversible if their causes are reduced or eliminated. For example, a dead zone in the Black Sea largely disappeared in the 1990s, following the fall of the Soviet Union, when the cost of chemical fertilisers skyrocketed.

Dead zones occur in coastal areas around the nation and in the Great Lakes — no part of the country or the world is immune. The second largest dead zone in the world is located in the U.S., in the northern Gulf of Mexico.

Some occur seasonally. Some are permanent. Dead zones are areas within water bodies, usually in deep water near sediments, where there is insufficient oxygen to support life. …

about 3000 meters

Use of chemical fertilizers is considered the major human-related cause of dead zones around the world. However, runoff from sewage, urban land use, and fertilizers can also contribute to eutrophication.

Humans are overloading ecosystems with nitrogen through the burning of fossil fuels and an increase in nitrogen-producing industrial and agricultural activities, according to a new study. While nitrogen is an element that is essential to life, it is an environmental scourge at high levels.

Scientists have determined that humans are disrupting the nitrogen cycle by altering the amount of nitrogen that is stored in the biosphere. The chief culprit is fossil fuel combustion, which releases nitric oxides into the air that combine with other elements to form smog and acid rain.

As dead plants and animals decompose, nitrogen is converted into inorganic forms such as ammonium salts (NH4+ ) by a process called mineralization. The ammonium salts are absorbed onto clay in the soil and then chemically altered by bacteria into nitrite (NO2- ) and then nitrate (NO3- ).

Plant and animal wastes decompose, adding nitrogen to the soil. Bacteria in the soil convert those forms of nitrogen into forms plants can use. Plants use the nitrogen in the soil to grow. People and animals eat the plants; then animal and plant residues return nitrogen to the soil again, completing the cycle.

Nitrogen is not stable as a part of a crystal lattice, so it is not incorporated into the solid Earth. This is one reason why nitrogen is so enriched in the atmosphere relative to oxygen. Thus, over geological time, it has built up in the atmosphere to a much greater extent than oxygen.

78 percent

A small amount of nitrogen is fixed by lightning, but most of the nitrogen harvested from the atmosphere is removed by nitrogen-fixing bacteria and cyanobacteria (formerly called blue-green algae). The nitrogen cycle transforms diatomic nitrogen gas into ammonium, nitrate, and nitrite compounds.

Nitrogen is the most abundant gas in the atmosphere. Air is composed of 78 percent nitrogen. Oxygen accounts for 21 percent, and the inert noble gas argon makes up 0.9 percent of the air. The remaining 0.1 percent consists of several trace gases.