Detritus Food Chains
Detritus food chains begin with dead organic matter which is an important source of energy. A large amount of organic matter is contributed by the death of plants, plant parts, animals and their excretion products. These types of food chains are present in all ecosystems but they are over dominating in forest ecosystems and shallow water communities. Various species of microscopic fungi, bacteria and other saprophytes play a prominent role in decomposing organic matter to obtain energy needed for their survival and growth. In this process they release various nutrients, locked in dead organic matter, which are used readily by the green plants. Detritus food chains are interconnected with grazing food chains and other auxiliary food chains through certain specific common organisms to permit crossing over of energy and material flow from one circuit to another.
For example, cattle do not assimilate all of the energy stored in plants, undigested residues in faeces become available for the decomposers and the detritivores. Detritus food chains are located mainly in the soil or in the segments of aquatic ecosystems. They form an essential component of natural ecosystems and are necessary for self-sustenance and for maintaining ecological balance. Detritus food chains can be of great practical value for modern man for sewage treatment and control of water pollution. Most of the natural ecosystems possess both grazing and detritus types of food chains. Their relative importance however, varies from one ecosystem to another. In terrestrial and shallow water ecosystems, detritus food chains dominate because a major proportion of the annual energy flow passes through this circuit. In case of tidal marshes, almost 90 per cent of the primary production is routed through the detritus food chains. In deep water aquatic systems rapid turnover of organisms and high rate of harvest are responsible for the dominance of grazing food chains.