Copepods (coop-podz) are a group of small crustoceans found in the sea and nearly every freshwater habitat.  Many species are planktonic (drifting in sea waters), but more are benthic (living on the ocean floor), and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests, bogs, springs, ephemeral ponds and puddles, damp moss, or water-filled recesses (phytotelmata) of plants such as bromeliads and pitcher plants.  Many live underground in marine and freshwater caves, sinkholes, or stream beds.  Copepods are sometimes used as bioindicators.  Planktonic copepods are important to global ecology and the carbon cycle.  They are usually the dominant members of the zooplankton, and are major food organisms for small fish, whales, seabirds and other crustaceans such as krill in the ocean and in fresh water.  Some scientists say they form the largest animal biomass on Earth.  They complete for this title with Antarctic krill (Euphausia superba).