Concept:Producers synthesise their own food through photosynthesis and form the first trophic level in an ecosystem.
Explanation:In an aquatic environment, phytoplankton are microscopic, free-floating organisms that contain chlorophyll.
They capture sunlight and convert it into food, so they function as the primary producers.
Thus, phytoplankton form the base of the aquatic food chain, supporting all other organisms.
Birds, zooplankton, and fishes are consumers because they depend on other organisms for nutrition.
Zooplankton feed on phytoplankton, fishes feed on zooplankton or smaller fish, and birds feed on fish.
Therefore, among the given options, only phytoplankton are aquatic producers.
Answer:B. phytoplankton