How is decomposers important to the health of an ecosystem?

Decomposes are essential to maintain the cycle of nutrient, mass and energy

Explanation:

Decomposers lie at the highest trophic level of an ecosystem. When an organism lying at tertiary trophic level dies, the decomposers convert the dead remains of organisms into simpler organic compounds and elements which mix into the soil.

These simpler organic compounds and elements are taken up from the soil  by the plants as nutrients essential for their growth. A well grown plants becomes capable to produce food for all other organism.

Thus, decomposes are essential to maintain the cycle of nutrient, mass and energy