Figure below shows a marine food chain. Phytoplankton form the base of the food chain. phytoplankton in the oceanic food chain Bing Images Phytoplankton form the basis of life in the ocean. Phytoplankton food chain in the ocean . They are consumed by zooplankton and other fish as well. The food chain is organized into trophic levels, and the base trophic level, or bottom rung of this system, contains organisms that make their own food. Hurricanes churn the ocean, bringing up nutrients like nitrogen, phosphate, and iron from the depths of the ocean and introducing them to the surface levels where plankton live. Phytoplankton is the base of several aquatic food webs. Then zooplanktons are fed by fish larva and some small fishes. Besides that, zooplankton are other small animals and invertebrates are the primary consumers of phytoplankton. Like land plants, they take up carbon dioxide, make carbohydrates using light energy, and release oxygen. They form the basis of ...