Plankton

Plankton (singular plankter) are a diverse group of organisms that live in the hydrosphere  or atmosphere and cannot swim or fly against a current or wind. They provide a crucial source of food to many large organisms, such as fish and whales.

These organisms include drifting animals, protists, archaea, algae, or bacteria that inhabit bodies of water; that is, plankton are defined by their ecological niche rather than biological  classification.

Though many planktic (or planktonic) species are microscopic in size, plankton includes organisms covering a wide range of sizes, including large organisms such as jellyfish.

Trophic Groups
Plankton are primarily divided into broad functional (or trophic level) groups: This scheme divides the plankton community into broad producer, consumer and recycler groups. However, determining the trophic level of some plankton is not straightforward.
 * 1) Phytoplankton - live near the water surface where there is sufficient light to support photosynthesis.
 * 2) Zooplankton small protozoans or metazoans (e.g. crustaceans and other animals) that feed on other plankton and telonemia. Some of the eggs and larvae of larger animals, such as fish, crustaceans, and annelids, are included here.
 * 3) Bacterioplankton, bacteria and archaea, which play an important role in remineralising organic material down the hydrosphere (note that the prokaryotic phytoplankton are also bacterioplankton).

Size Groups
Plankton are also often described in terms of size. Usually the following divisions are used:


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Group Size range Megaplankton > 20 cm Macroplankton 2→20 cm Mesoplankton 0.2→20 mm Microplankton 20→200 µm Nanoplankton 2→20 µm Picoplankton 0.2→2 µm Femtoplankton < 0.2 µm Plankton is found on almost every non-terraformed Union planet that supports life.
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