Answer:
Bacteria are vital in keeping nitrogen cycling through the ecosystem, and nitrogen is vital to plant growth. Without bacteria around to break down biological waste, it would build up. And dead organisms wouldn't return their nutrients back to the system
Explanation:
I believe that's is answer C because your ask about and increasment on the velocity in this observation
Benthos are "organisms inhabiting the seafloor" according to one source, so I would say the answer is C.