Phytoplankton are very important to marine organisms, because as primary producers in the oceans, phytoplankton are crucial to the development and survival of most, if not all marine animals at some level. Phytoplankton are tiny floating organisms (such as unicellular algae, diatoms and dinoflagellates) in the kingdom Protista (protozoa and algae) which serve the same role in the food chains of the oceans as vegetation serves on land; namely small things eat them, which are in turn eaten by bigger things, and so on as the food chain progresses. Many coral reef animals such as clams and other bi-valves, soft corals, sponges and feather duster worms feed directly on phytoplankton, and even those that do not, such a most stony corals, rely ultimately on the nutrition gained from phytoplankton and other marine algae eaten by the zooplankton they feed on. Some essential nutrients gained from marine algae, phytoplankton in particular, cannot be synthesized by animals, and are therefore extremely important components of a healthy diet.
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