Question

What is the detritus food chain made up of? How do they meet their energy and nutritional requirements?

Answer 1

Hint: Detritus means waste or debris. This is the food chain that starts from detritus.
The organisms that feed on dead organic matters or detritus, are known as detritivores or decomposers. Later on these detritivores are eaten by their predators.

Complete Answer:
- Detritus food chain starts from the dead and decaying organic matter. These dead organic materials are decomposed by microorganisms.

- Heald (1969) and W.E. Odum (1970) described a detritus food chain based on the mangrove leaves. In Southern Florida, the leaves of Rhizophora mangle (the red mangrove) fall into the shallow, warm water. These fallen leaves are then acted on by some saprotrophs such as fungi, bacteria, protozoa etc and colonized by phytoplankton and benthic algae.

- Now these partially decomposed leaf fragments are eaten and re-eaten by a group of small animals which include crabs, insect larvae, nematodes, copepods, bivalve molluscs etc. All these animals are detritus consumers, i.e., detritivores.
- They are very large in number and they ingest large amounts of plant detritus. The detritivores are in turn eaten by small game fish, minnows etc. that are the primary carnivores.
- These small carnivores serve as the major food for larger game fishes and fish eating birds which are the top carnivores. In terms of trophic levels, the detritus consumers consist of a mixed group. They include herbivores, omnivores and primary carnivores.
- Detritus food chains are less dependent on direct solar energy. They depend chiefly on dead organic matter or detritus for their energy requirement. As a group, some of the detritus feeders obtain energy directly from the plant material; most of them obtain energy secondarily by consuming microorganisms, and some tertiarily by eating carnivores that have fed on micro or macro-organisms that have digested plant material.

Note: As the detritus food chain begins with and obtains energy from detritus, it ensures maximum utilization of organic matter and minimum wastage. It also helps in the fixation of inorganic nutrients.