Non-essential for an ecosystem:

Consumers

Explanation:

An ecosystem is a community of living and non-living things interacting with each other. It includes producers, consumers, and decomposers. Producers are the organisms that make their own food using sunlight, water, and nutrients. Consumers are the organisms that eat other organisms for their energy needs. Decomposers are the organisms that break down dead organic matter into simpler substances and release nutrients back into the soil.

Minerals are essential for the growth and development of living organisms. They are required in small amounts but are important for maintaining the balance of the ecosystem.

Producers are the primary source of food for other organisms in the ecosystem. They are responsible for converting sunlight into usable energy for other organisms.

Consumers, on the other hand, are not essential for the ecosystem. They depend on other organisms for their survival and can be replaced by other species. In fact, some ecosystems can function without consumers, such as in the case of deep sea hydrothermal vents, which rely solely on chemosynthetic bacteria for their energy needs.

Therefore, the correct answer is option D, consumers, as they are not essential for the functioning of the ecosystem.