Why are decomposers and detritivores essential parts of all food webs?

Detritivores improve the nutritional value and the texture of the soil: This makes the soil productive to plant life which translates to availability of food for the herbivores and carnivores like human beings. They however do not complete the energy cycle as their wastes are energy products that need to be decayed.

Decomposers help in converting the leftovers of animals and plants to useful substances for other living organisms. They are mainly bacteria and fungi. Have you ever wondered what would happen if the decomposers and consumers were not in the ecosystem?

Detritivores play a very important in the cycle as they are the consumers of dead leaves, old skin, carcasses and manure. They include millipedes, earthworms and slugs that feed on dead plants and animals but leave some parts and their feces that are converted to energy by the decomposers. Players in the energy cycle function hand in hand, a decomposer is found at the lowest part of the cycle as it deals with the remains. They complete the energy cycle. The roles of the decomposers and detritivores almost coincide.

Hope this helps ;)

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."