What types of organisms typically make the bass middle and top of the food chain

In the food chain, producer makes the base, primary and secondary consumers are present in the middle and tertiary consumers is present on the top.

Explanation:

Producers are the organisms which makes their own food such as plants. They are placed at the base due to high population. Primary and secondary consumers are placed in the middle due to less population than producer and tertiary consumers are placed on the top due to very low population.

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