Explanation

Primary producers are autotrophic organisms that synthesize organic matter from inorganic substrates through photosynthesis or chemosynthesis, forming the energetic foundation of marine trophic levels.

– 2. Cyanobacteria (Correct): Often referred to as blue-green algae, these aquatic photosynthetic bacteria utilize chlorophyll pigments and sunlight to fix carbon dioxide and release oxygen, generating significant marine primary biomass.
– 3. Diatoms (Correct): Single-celled microalgae characterized by siliceous cell walls (frustules). They represent one of the most abundant classes of phytoplankton, contributing up to 40% of all oceanic primary production.
– 1. Copepods (Incorrect): Tiny aquatic crustaceans classified as zooplankton. They are primary consumers (herbivores) that filter-feed on microscopic phytoplankton like diatoms.
– 4. Foraminifera (Incorrect): Single-celled heterotrophic protists featuring porous shells (tests). They feed actively on bacteria, diatoms, and organic detritus.

Therefore, only 2 and 3 are primary producers — Option B.