What are Decomposers?
Decomposers are organisms that feed on dead organic matters (for example, scavengers like vultures and crows), and further breaking down the dead matter by other decomposing agents like bacteria and various microorganisms.
Decomposers are saprophytes; they feed on dead and decaying organisms and their excreta (waste such as urine and faeces) and bring about their decay or decomposition. Saprophytes include all fungi and certain bacteria, especially those that live in soil. Some saprophytes like mushrooms, toadstools and mould can be easily seen. Most, however, are microscopic, they cant be seen with the naked eye for example, they are known as micro decomposers
The decomposers feed on the dead organisms at each and every level. They change them into various substances such as nutrients, organic and inorganic salts essential for soil fertility. Organisms of an ecosystem are linked together through a food chain
In the absence of decomposers, no ecosystem could function for long; dead organisms would pile up without rotting just the same way as would waste products, It would not be long before and an essential element, phosphorus, for example, would be first in short supply and then gone completely, the reason is the dead corpses littering the landscape would be hoarding the entire supply. The decomposers tear apart organisms and in their metabolic processes release to the environment atoms and molecules that can be reused again by autotrophic point of view. Instead they are important from the material (nutrient) point of view. Energy cannot be recycled, but matter can be. Hence it is necessary to release energy into ecosystem to keep up with the dissipation of heat or the increase in entropy. Matter must be recycled again and again by an ecological process called biogeochemical cycle.
What do Decomposers do?
Decomposers play an important role in the cycling of nutrients in ecosystems. Although they are not shown in some food chains, they form the link between the producers, consumers and the abiotic environment in all food chains. Decomposers may be fitted into food chain.
Decomposer secrete enzymes onto their food source such as a decaying leaf. These enzymes break down complex organic compounds (food) like carbohydrates and proteins into simple soluble inorganic compounds. A lot of the chemical energy in the inorganic compounds is lost as unusable heat energy. The decomposers only absorb a small amount of nutrients and energy for their use however, the rest is released into the soil, water and air. When decomposers die other decomposers feed on them. The inorganic compounds released during decay include gases like carbon dioxide, ammonia, hydrogen sulphide, water vapour and salt like nitrates sulphates, phosphates and potassium ions.
By enabling the recycling of nutrients , decomposers allow ecosystems to function accordingly, hence decomposers also prevents and unsightly accumulation of the remains and wastes of living organisms on earths surface.
Why are Decomposers Important?
The activity of decomposers releases the nutrient in simple forms. Green plant can absorb such nutrients through their roots and leaves and use them to manufacture energy-rich food. This food can support several populations of consumers before its energy is dissipated. The nutrients are again returned to the abiotic environment by decomposers to be used by green plants. This use and reuse of nutrients is called recycling. This is also common with elements like nitrogen, carbon and oxygen , they are being recycled in nature.
Generally, all living organisms require a constant supply of nutrients for growth. The death and decomposition of plants and animals, with release of nutrients constitutes an essential link in the maintenance of nutrient cycles. When an organism dies, an initial period of rapid leaching takes place and populations of macromolecules. The dead organism is disintegrated beyond recognition. Enzyme action breaks down the disintegrating parts of the litter. Animals invade and either eat the rapidly recolonized by micro- organisms, and the litter biomass decreases. It becomes simpler in structure and chemical composition.
Process of Decomposition
The process of decomposition involves three interrelated components such as:
Leaching– leaching is a physical phenomenon operating soon-after litter fall. Soluble matter is removed from detritus by the action of water. Sometime over 20% of the total nitrogen content of litter maybe leached off.
Catabolism– the process in a plant or animal by which living tissue is changed into waste products.
Comminution– Comminution means the reduction in particle size of detritus. During the course of feeding, the decomposer animals community detritus physically. And utilize the energy and nutrients for their own growth (secondary production). In due course, the decomposers themselves die and contribute to the detritus.
Examples of Decomposers
The examples of decomposer organisms includes several bacteria, fungi, protests and invertebrates. The different species in such a community function in an integrated manner. For example, a fungus decomposes plant litter and is eaten by an animal. Upon death, bacteria decompose the animal, and protozoa may eat the bacteria. Fungi and bacteria are the principal organisms that break down organic matter. Certain protozoa, nematodes, annelids and arthropods strongly influence their functioning (i.e. of fungi and bacteria) due to their feeling activities. Micro-arthropod fauna, comprising mainly of orbited mites besides other mites and collembolans, are abundant in most forest, grassland and desert ecosystem.
However, some decomposer organisms cannot be given a fixed position in the food Web; their trophic relations may vary from time to time. They include:
- Nectroph- some decomposers are nectrophs; they cause rapid death of the foodsource because they have a short-term exploitation of living organism. Examples of nectrophs include plant parasitic microbes as well as some herbivores, predators, and microtrophs (organisms which feed on living bacteria and fungi.)
- Biotrophs: biotopes are known for long-term exploitation of their living food resource. For example, root-feeding nematodes and aphids, obligate plant parasites- for example and mycorhizae and root nodules.
- Saprotophs- this group of decomposers utilize food already dead, and majority of the decomposers are categorized into this group.
Functions of Decomposition
- The mineralization of essential elements,
- The formation of soil organic matter to inorganic form.
The formation of soil organic matter in nature is a slow process. The decomposition of any piece of plant detritus may take hundreds of years to complete. However, some residues of decomposition within this period do contribute to the formation of soil organic matter
Increased mineralization of nitrogen, phosphorus and potassium has been reported to be mediated by micro arthropods in several studies. In the same way, the interactions of micro-arthropods with soil fungi are also quite important in nutrient cycling. Studies of this aspect are made in mycorrhizal fungi and the micro-arthropods which feed upon these fungi: It is found that Mycorrhizal pump massive amounts of nutrients form detritus and represent a sizable nutrient reservoir themselves. The orbited mites and other micro-arthropods feed on myocardial fungi they act like herbivorous pests, and can alter nutrient relations/cycling in terrestrial ecosystems.