The first link in a food chain is always a green plant. Only organisms with Chlorophyll, such as green plants, can make food. For example, the first link in aquatic food chains is algae. Most algae are microscopic green plants that produce food by photosynthesis. In photosynthesis, energy from sunlight converts carbon dioxide and water to sugar. Tiny fish in lakes, streams, and oceans eat algae. In turn, these tiny fish are eaten by larger fish.The largerfish areeaten by still larger fish. The food supply for fish is made by algae. The food is then passed through the food chains as one animal eats another.