Decomposers are organisms that break down dead plant and animal matter into simpler compounds, returning nutrients to the soil and water. They include bacteria, fungi and detritivorous invertebrates that feed on leaf litter, wood and carcasses【959384396812388†L16-L61】【340181366202466†L71-L73】.
## Explanation
Decomposers are essential for nutrient cycling in ecosystems. When a plant or animal dies, its body contains complex organic molecules such as cellulose, proteins and lipids. Fungi and bacteria secrete enzymes that digest these materials externally, releasing sugars and amino acids that they absorb. Detritivores like earthworms, woodlice and millipedes physically shred organic matter, increasing its surface area for microbial action. Through these processes, decomposers convert organic material into inorganic compounds such as carbon dioxide, water, nitrate and phosphate, which can be taken up again by plants【959384396812388†L16-L61】. Without decomposers, dead matter would accumulate and essential elements would remain locked in unusable forms. Decomposition rates depend on temperature, oxygen, moisture and the chemical composition of the material. Aerobic decomposition occurs in oxygen-rich environments, producing carbon dioxide, while anaerobic decomposition occurs in waterlogged soils or sediments, generating methane and other gases. Some bacteria and fungi specialise in breaking down lignin and cellulose in wood, while others focus on animal tissues. Decomposers also help control disease by consuming dead material that could harbour pathogens.
## Roles in ecosystems
Examples of decomposers include saprophytic fungi that produce mushrooms on rotting logs, bacteria that break down fallen leaves in soil and aquatic fungi that decompose dead algae in lakes. Earthworms ingest soil and organic matter, mixing and aerating it as they digest plant residues. In tropical rainforests, termites play a major role in breaking down dead wood. Microorganisms in compost heaps decompose kitchen waste and garden clippings to form nutrient-rich humus. In the ocean, marine bacteria decompose the bodies of dead fish and plankton that sink to the sea floor. These activities release nutrients that support primary producers and maintain soil fertility.
Decomposers ensure that the building blocks of life are continuously recycled, supporting new growth and sustaining ecosystems.
**Related Terms:** Saprophyte, Detritivore, Composting, Nutrient cycling, Fungi