Decomposers are
organisms that break down dead or decaying organisms; they carry out
decomposition, a process possible by only certain kingdoms, such as
fungi.[1] Like
herbivores and
predators, decomposers are
heterotrophic, meaning that they use
organic substrates to get their
energy,
carbon and
nutrients for growth and development. While the terms decomposer and
detritivore are often interchangeably used, detritivores ingest and digest dead matter internally, while decomposers directly absorb nutrients through external chemical and biological processes.[2] Thus,
invertebrates such as
earthworms,
woodlice, and
sea cucumbers are technically detritivores, not decomposers, since they are unable to absorb nutrients without ingesting them.[3]
Fungi
The primary decomposer of litter in many
ecosystems is
fungi.[4][5] Unlike
bacteria, which are unicellular organisms and are decomposers as well, most
saprotrophic fungi grow as a branching network of
hyphae. While bacteria are restricted to growing and feeding on the exposed surfaces of organic matter, fungi can use their hyphae to penetrate larger pieces of organic matter, below the surface. Additionally, only
wood-decay fungi have evolved the
enzymes necessary to decompose
lignin, a chemically complex substance found in wood.[6] These two factors make fungi the primary decomposers in
forests, where litter has high concentrations of lignin and often occurs in
large pieces. Fungi decompose organic matter by releasing enzymes to break down the decaying material, after which they absorb the nutrients in the decaying material.[7] Hyphae are used to break down matter and absorb nutrients and are also used in reproduction. When two compatible fungi hyphae grow close to each other, they will then fuse together for reproduction, and form another fungus.[7]
Bear, MH; Hendrix, PF; Cheng, W (1992). "Microbial and faunal interactions and effects on litter nitrogen and decomposition in agroecosystems". Ecological Monographs. 62 (4): 569–591.
doi:
10.2307/2937317.
JSTOR2937317.
S2CID86031411.
Hunt HW, Coleman DC, Ingham ER, Ingham RE, Elliot ET, Moore JC, Rose SL, Reid CPP, Morley CR (1987) "The detrital food web in a shortgrass prairie". Biology and Fertility of Soils 3: 57-68
Smith TM, Smith RL (2006) Elements of Ecology. Sixth edition. Benjamin Cummings, San Francisco, CA.