Which is a longitudinal wave that requires a medium to move

Longitudinal wave are those in which the motion of the particles is along the direction of the medium. It always requires the medium to travel.We can say that a wave that oscillates back and forth that means moving  in same interval.

And sound is the longitudinal wave that requires a medium to move.

Explanation: Oxygen plays a very vital role in the life of aquatic animals. The dissolved oxygen in the water helps them to breathe under water.

Optimum level of oxygen for deep living animals like oysters, bottom feeders, crabs is around (1-6 mg/L), while the animals living on the upper side like fishes require a higher amount of around (4-6 mg/L).

If the oxygen concentration in the pond is not optimum, there will no aquatic life and hence, the ecosystem will be affected.

Hence, oxygen concentration affects the fishes that live in the pond to a higher extent.