Which group performs photosynthesis and forms the base of most marine food webs in the sunlit zone?

• A. Phytoplankton
• B. Nekton
• C. Picoplankton
• D. Plankter

Answer: (A)

In the sunlit layer of the ocean, the base of the food web is formed by phytoplankton. These microscopic organisms perform photosynthesis, turning light energy and inorganic nutrients into organic matter that becomes the food for zooplankton and other small swimmers. From there, energy flows up to larger herbivores and then to predators, linking the entire surface-dwelling ecosystem. Nekton are the swimming animals that eat other organisms; they are consumers, not producers. Picoplankton are tiny members of the phytoplankton group that also photosynthesize, but when we talk about the group that drives most marine photosynthesis and supports the bulk of the food web, the broad term phytoplankton is used. Plankter isn’t a standard group for this role.