Solution:Concept- The aquatic ecosystem is defined as the food chain that coexists there. Similar to other trophic levels, in this one, the producer is at the bottom, followed by herbivorous and eventually flesh-eating creatures, such as phytoplankton, zooplanktons, tiny fish, and fish.
Here, phytoplankton may produce their food since they are autotrophs. Zooplankton is dependent on herbivorous phytoplankton. Big fish eventually consume the zooplankton that small fish consume. The Phytoplankton are microscopic marine algae. In a balanced ecosystem, they give food to a wide range of sea creatures. The Phytoplankton are also known as microalgae. They are similar to terrestrial plants because they have chlorophyll and need sunlight to survive.
Hence, the correct answer is option 3.