If you could "get inside the head" of a person experiencing auditory hallucinations, you would most likely find that:

The person actually produces nerve signals of sound in his brain

they each offer a fresh glut of resources to the organisms that can arrive and exploit them. as individuals and new species continue to appear, they actively and passively alter the environment. competition for shared resources increases, local abiotic and biotic conditions shift, and the relative abundances of species change accordingly. the process is called ecological succession, and it is one of the earliest and most well-known concepts in ecology.

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