Explanation:

- Virioplankton: These are viruses found in aquatic environments. They infect bacteria and other microorganisms but do not eat phytoplankton.

- Zooplankton: These are small animals and protozoans that feed on phytoplankton. Zooplankton serve as a crucial food source for fish, crustaceans, and other larger marine species.

- Bacterioplankton: These bacteria decompose organic materials in the water. They play a role in nutrient cycling but do not typically consume phytoplankton.

- Zooxanthellae: These are symbiotic dinoflagellates that live within the tissues of certain marine animals like corals. They perform photosynthesis and don't consume phytoplankton.

Correct Answer: Zooplankton