ShareAtmosphere - The Nitrogen Cycle
Nitrogen is very important to organisms. Nitrogen is required to make amino acids, which are the building blocks of proteins. The air that we breathe is 78% nitrogen. Most organisms, including humans, can't use the free gaseous form of nitrogen found in the air. We need other organisms and natural processes to "fix" nitrogen into a solid form that plants and animals can use.
Most of the nitrogen that plants and animals use is made by bacteria. Bacteria in the soil can change nitrogen in the atmosphere (N2) into ammonia (NH3), a form that plants can use. Other types of bacteria, that form large lumps or nodules around the roots of peas, beans, and clover take in nitrogen from the atmosphere (N2) and change it into nitrites and nitrates. These compounds contain nitrogen and oxygen, and are commonly used in fertilizers.
Animals
receive the nitrogen that they need from the consumption of plants. When
plants, animals, and other organisms die, decomposers return nitrogen
to the soil.
What effect do humans have on the nitrogen cycle? As mentioned above, humans use fertilizers on plants to get them to grow better; and nitrogen is a major component of most fertilizers. Is this a concern? It can be.
Nitrogen additions, in excessive amounts, pollute our ecosystems. This can change the functioning of the ecosystem, and the communities that are supported by it.
Human activity has also increased the global concentrations of nitrous oxide (N2O). This gas is a strong greenhouse gas. (It is also used to make trips to your local dentist less stressful.) The amount of nitrogen that is transported in rivers and groundwaterhas increased. This can accumulate in the final destination and can lead to eutrophication of lakes, which basically kills most of the wildlife living there.
Other changes we have made in the natural nitrogen cycle might include an increased loss of biodiversity, especially with plants that have adapted to the low levels of nitrogen in the soil. This also affects the animals and microbes that depend on this vegetation.
