Nitrogen

Abstract

Nitrogen is the most abundant gas comprising 78.084% by volume of the atmosphere. It also is an important constituent of organic matter, because protein averages about 16% nitrogen. Nitrogen is an essential nutrient for all organisms, but it only can be converted to protein by certain blue-green algae and bacteria that fix atmospheric nitrogen (N₂) or by plants that use nitrate (NC₃) or ammonium (NH₄⁺) to make protein. Proteins are composed of amino acids, and animals and bacteria must obtain certain essential amino acids from plants or dead organic matter in order to synthesize proteins for their bodies. Un-ionized ammonia (NH3) and nitrite (NO₂), can be toxic to aquatic organisms. Excessive ammonia nitrogen and nitrate in water contribute to eutrophication because they are important plant nutrients.