From the Latin detritus "worn out.

Detritus is the remains of decomposed animals and plants suspended in the water column or deposited on the bottom of the reservoir with bacteria developing on them. Detritus serves as food for many aquatic animals, mainly benthic hydrobionts - filter feeders and detritophages.

Clastic material consisting of fragments of shells, skeletal parts of animals or scraps of plants, cemented or uncemented.

A distinction is made between fine-detrital and coarse-detrital detritus.

Dead material and excrement in aquatic ecosystems are usually transported by the water flow; smaller particles tend to be transported farther or remain in suspension longer. In freshwater bodies of water, organic material from plants can form silt, known as mulma or humus, on the bottom. This material, which some call undissolved organic carbon, breaks down into dissolved organic carbon and can bind to heavy metal ions through chelation. It can also break down into colored dissolved organic substances such as tannin, a specific form of tannic acid. In saline waters, organic material breaks down to form sea snow. This example of detritus usually consists of organic material such as dead phytoplankton and zooplankton, the outer walls of diatom algae and coccolithophores, dead fish skin and scales, and fecal pellets. This material will slowly sink to the seafloor, where in some areas it makes up most of the sediment. Once settled, the material will not only contribute to the sediment, but also help feed various species of detritivores, organisms that feed on the detritus, such as ringworms and sea cucumbers, to name a few. The exact composition of this detritus varies by location and time of year, as it is very closely related to primary production.