Food chain refers to the sequence of events in an ecosystem, where one organism eats another and then is eaten by another organism. It starts with the primary source like the sun or hydrothermal vents where producers make food, continues with consumers or animals who eat the food, and ends with the top predator.
Here are examples of food chains in aquatic environments:
All plants and animals are part of a food chain. These examples of food chains are only a small part of the food chains; but, they are included to show the variety of plants and animals involved in any particular food chain.