This photo was taken by Uwe Kils. It shows an amphipod, a type of plankton. The photo was taken using magnification so users can see the amphipod in detail. In reality, most amphipods are only 1 mm to 140 mm in length. Click on image for full size (179 Kb) Courtesy of Wikipedia Commons

Phytoplankton—these are photosynthetic autotrophs (i.e., they can feed themselves using light from the Sun). They are typically single-celled organisms and can be either eukaryotic or prokaryotic (with or without a nucleus). They live in water that is shallow enough for sunlight to shine through. Phytoplankton are responsible for producing a large fraction of the world’s oxygen, and they serve as food for a wide variety of other organisms. Phytoplankton are generally considered the foundation of most of the world’s marine food chains.

Zooplankton—this is a broad group of heterotrophic organisms (i.e., they depend on other organisms for food) that live throughout the water. The zooplankton range in size from single-celled creatures to larger animals like jellyfish, mollusks, and crustaceans, and they feed on other forms of plankton as well as on organic wastes in the water.

Bacterioplankton—this group is composed of the bacteria that drift throughout open water. They can be autotrophic or heterotrophic. They play a large role in a number of critical geochemical cycles, where elements like nitrogen, carbon, and a variety of minerals are processed by the bacteria to keep organic and inorganic (or biologically accessible and biologically inaccessible) forms of each in the proper balance in the ocean. In this way, bacterioplankton are often thought to serve as the ocean’s recyclers.

This photo was taken by Uwe Kils. It shows an amphipod, a type of plankton. The photo was taken using magnification so users can see the amphipod in detail. In reality, most amphipods are only 1 mm to 140 mm in length. Click on image for full size (179 Kb) Courtesy of Wikipedia Commons

Phytoplankton—these are photosynthetic autotrophs (that is they can feed themselves using light from the Sun). They are typically single-celled organisms and can have a nucleus or not. They live in water that is shallow enough for sunlight to shine through. Phytoplankton are responsible for producing a lot of the world’s oxygen, and they serve as food for many other organisms. Phytoplankton are considered the foundation of most of the world’s marine food chains.

Zooplankton—this is a broad group of heterotrophic organisms (that is they depend on other organisms for food). The zooplankton range in size from single-celled creatures to larger animals like jellyfish, mollusks, and crustaceans. They feed on other forms of plankton and on organic wastes in the water.

Bacterioplankton—this group is composed of the bacteria that drift in open water. They can be autotrophic or heterotrophic. They play a large role in important geochemical cycles, like the nitrogen and carbon cycles. In this way, bacterioplankton are often thought to serve as the ocean’s recyclers.

This photo was taken by Uwe Kils. It shows an amphipod, a type of plankton. The photo was taken using magnification so users can see the amphipod in detail. In reality, most amphipods are only 1 mm to 140 mm in length. Click on image for full size (179 Kb) Courtesy of Wikipedia Commons

All plankton are drifters. Some can move up and down, but all drift with the water current in the body of water where they live.

Plankton can live in salt water like the ocean and in fresh water.

They can be so tiny that you can't see them with your eye. You'd need a microscope! They can also be bigger like jellyfish, mollusks, and crustaceans. Remember, if it depends on water moving to move side to side, it's plankton!

Plankton are usually divided into three groups - phytoplankton which use photosynthesis to make food, zooplankton which depend on other organisms for food, and bacterioplankton which are the bacteria that drift in open water.