Which aquatic microorganisms eat phytoplankton and then become food for fish, crustaceans and other large species?

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SSC CPO 2022 Tier-I Official Paper (Held On 11 Nov 2022 Shift 3) [Answer Key]

Answer 1

The correct answer is Zooplankton.

Key PointsZooplankton

It is a tiny aquatic microorganism found in the water column and includes crustaceans, rotifers, open-water insect larvae, and aquatic mites.
The zooplankton population is made up of primary consumers, which consume free-floating algae, and secondary consumers, which eat other zooplankton. Examples – are copepods, amphipods, krills, Jellyfish, Segmented worms, Conger Eel, etc.
In the food chain, these creatures act as intermediate species by moving energy from planktonic algae, which are the primary producers, to the bigger invertebrate predators and fish, who in turn eat them.
Changes in aquatic habitats have a significant impact on zooplankton.
Changes in species composition, abundance, and the distribution of body sizes can be used as good indicators of change in nutrient pollution over time.

Additional Information

Planktons

The base of both the freshwater and marine food pyramids is composed of microscopic organisms known as plankton.
Saltwater and freshwater both contain plankton.
An indicator of a significant plankton population in a body of water is its clarity.
In comparison to more green or brown water, very clear water often contains less plankton.

There are two main types of plankton

Phytoplankton

Through the process of photosynthesis, phytoplankton converts carbon dioxide into oxygen and use it as fuel.
One of the most important oxygen producers on the planet and is responsible for almost half of all photosynthesis.
To survive, phytoplankton is dependent on environmental nutrients including calcium, phosphate, and nitrate.

Virioplankton	Viruses in aquatic ecosystems. Examples- Tupanvirus, etc. In tropical coastal lagoons, salinity regulates Virioplankton abundance but not production.
Bacterioplankton	The bacterial component of plankton is called bacterioplankton. They are prokaryotic organisms. Some of them function in aquatic ecosystems as primary consumers and producers, such as blue-green algae (Cyanophyta), which can perform photosynthesis (e.g. marine and freshwater ecosystems). Cyanophyta is the only prokaryotic algal group and therefore also considered bacteria. Since they are engaged in the processes of organic material's remineralization, bacterioplankton is crucial to the health of the environment. They propel the elements' worldwide biogeochemical cycles (e.g. carbon fixation, nitrogen fixation, denitrification, nitrification, etc.
Zooxanthellae	Zooxanthellae are microalgae from the Phylum Dinoflagellata that are autotrophic (make their own food). Single-cell algae, ZOOXANTHELLAE makes symbiotic relations with corals.