How does the behavior of deep water species affect the balance of life higher up?

Deep sea has species such as archaea that thrive in hydrothermal vents and turn inorganic molecules into organic molecule through chemosynthesis. This provides the start of the food chain that ends up higher up the waters. Also in the deep oceans are scavengers that feed off dead fish that sink to the bottom of the ocean. They help recycle these nutrients by consuming the carcasses.

the sphincter muscles at the end of the digestive tract is the anus.

i think that d. wind is the answer.   i missed the question when i answered a. currents.