Question

Animals or organisms floating on the surface of the water are known as
A. Plankton
B. Pelagic
C. Benthon
D. Neritic

Answer 1

Hint:Aquatic organisms are of wide variety living near the sea bed or even near the water surface. Organisms living on the surface of the water are usually microorganisms that perform photosynthesis.

Complete answer:An aquatic ecosystem consists of a variety of plants, animals, and other organisms that are somehow responsible for the nature of our planet. Mostly, microorganisms in oceans produce oxygen that is taken up by other aquatic organisms, they also help in nitrogen fixation.
Organisms floating on the surface of the water are known as planktons. Planktons are microorganisms that are of two types; Phytoplankton, are tiny plants that are autotrophic i.e. they produce their own food by photosynthesis. Hence, they require sunlight which is possible only if they are near the surface of the water and not deep inside the ocean. Ex. Gonyaulax.
The second type of planktons is zooplankton, these are marine organisms that are heterotrophs and mostly they feed on phytoplankton. Zooplanktons drift with the water current and can be divided into two types, permanent planktons also known as holoplankton that live their whole life as planktons Ex. Protozoa. Temporary planktons are also known as meroplankton live and feed like planktons until they become an adult. Ex. Starfish, worms.

Hence, the correct option will be option A-Plankton.

Note: Aquatic mammals like whales have to periodically come near the surface of ocean water to breathe. Hence, if organisms floating on the water surface are asked you should consider aquatic mammals also. Phytoplanktons help in the reduction of carbon dioxide levels, as they use carbon dioxide for performing photosynthesis.