"Detritus represents an enormous supply of energy for marine systems. The major sources of detritus are decaying plant and algal matter (that is not consumed by grazing herbivores), animal wastes, and bits and pieces of animal tissue. All of this material contains energy trapped in the organic compounds that compose them. As the detritus rains down through the water column, it serves as an important food source for pelagic bacteria and some zooplankton. When detritus settles to the bottom, it is consumed by animals, such a worms or clams, that in turn can channel the energy to larger animals when they are consumed. Although the formation of detritus represents an initial loss of energy to the organisms in the water column, the detritivores feeding on the detritus return the energy to food chains."
-- Introduction To Marine Biology, by Karleskint, Turner and Small, 3rd edition, page 34.