The microphytes growing on the bottom sediments, stones, submerged macrophytes, and other objects in the water column are called _____.

Correct option is A

Correct Answer: (a) Periphyton
Explanation:
→ Periphyton are assemblages of algae, bacteria and micro-organisms attached to submerged surfaces (stones, sediments, macrophytes).
→ They form biofilms and are important primary producers and food for grazers.
Information Booster:
→ Epiphytes specifically live on plants; neuston occupy the surface film; nekton are free-swimming organisms.
Additional Information (Other Options):
(b) Epiphytes: attached to plants (a subset concept).
(c) Neuston: air–water interface dwellers.
(d) Nekton: swimmers like fish.