A suborder of CRUSTACEA, order Diplostraca, comprising the water fleas. They are benthic filter feeders that consume PHYTOPLANKTON. The body is laterally compressed and enclosed in a bivalved carapace, from which the head extends.

A diverse genus of minute freshwater CRUSTACEA, of the suborder CLADOCERA. They are a major food source for both young and adult freshwater fish.

Minute free-floating animal organisms which live in practically all natural waters.

A class of minute animals of the phylum Aschelminthes.

A huge subclass of mostly marine CRUSTACEA, containing over 14,000 species. The 10 orders comprise both planktonic and benthic organisms, and include both free-living and parasitic forms. Planktonic copepods form the principle link between PHYTOPLANKTON and the higher trophic levels of the marine food chains.

Water containing no significant amounts of salts, such as water from RIVERS and LAKES.

Number of individuals in a population relative to space.

The pattern of any process, or the interrelationship of phenomena, which affects growth or change within a population.