Where does the energy for most ecosystems originate? How is this converted into the energy in food?

Explanation:

"Energy is transferred between organisms in food webs from producers to consumers. The energy is used by organisms to carry out complex tasks. The vast majority of energy that exists in food webs originates from the sun and is converted (transformed) into chemical energy by the process of photosynthesis in plants."

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