Marine Biology: Plankton

Plankton are a very important part of our environment. Many of them are so small it is easy for people to go through life without knowing they even exist! The kind of plankton you find depends on where and how you take your sample. Phytoplankton and zooplankton are just like any other kind of plant or animal; each type of plankton needs to live in a certain kind of environment to survive. Plant plankton needs sunlight so that they can make food for themselves through photosynthesis. Many types of zooplankton eat phytoplankton; but they need to be in very cold water to survive. Most types of plankton are microscopic, but some can be very, very big! Jellyfish are examples of big plankton.

Even though many people are not aware that plankton exists, we depend on it every day because plant plankton provides our atmosphere with oxygen just like trees in the rainforest.


Approximately 50% of the oxygen in our atmosphere comes from phytoplankton and 50% comes from plants on land.

Surface tow on a sunny day with no wind = more phytoplankton, surface tow on a windy or turbulent day = more zooplankton

Zooplankton are animals that like cold water at the bottom of the ocean. Since they eat other organisms, they don’t need sunlight.

Jellies are considered plankton because they are not strong enough to swim against wind and currents in the ocean.

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