Decomposer

A decomposer is an organism that obtains energy by breaking down dead plants and animals, fallen leaves, wood and feces into simpler substances. Most decomposers are bacteria and fungi, along with some protozoa. Fungi are especially important in forests, where they release enzymes that digest tough plant material outside their cells and then absorb the products.

Decomposition is essential to every ecosystem because it recycles matter. As decomposers digest organic remains, they release carbon dioxide, water and simple compounds of nitrogen, phosphorus and other elements that plants and algae need to grow. Without them, nutrients would stay locked in dead bodies and soils would soon run short. Decomposers form the base of the detrital food web and drive key steps in the carbon and nitrogen cycles; in ammonification, for instance, bacteria and fungi turn the nitrogen in wastes and remains into ammonium.

Decomposers are often grouped with detritivores, larger animals such as earthworms, millipedes, termites and dung beetles that eat dead matter and break it into smaller pieces. Strictly, detritivores swallow their food while decomposers break it down chemically, but some sources use the two words loosely.