An oligotroph is an organism that can live in an environment that offers very low levels of nutrients. They may be contrasted with copiotrophs, which prefer nutritionally rich environments. Oligotrophs are characterized by slow growth, low rates of metabolism, and generally low population density.The adjective oligotrophic may be used to refer to environments that offer little to sustain life, organisms that survive in such environments, or the adaptations that support survival. Etymologically, the word "oligotroph" is a combination of the Greek adjective oligos (ὀλίγος) meaning "few" and the adjective trophikos (τροφικός)) meaning "feeding".Oligotrophic environments include deep oceanic sediments, caves, glacial and polar ice, deep subsurface soil, aquifers, ocean waters, and leached soils.Examples of oligotrophic organisms are the cave-dwelling olm, the bacterium, Pelagibacter ubique, which is the most abundant organism in the oceans with an estimated 2 × 1028 individuals in total, and the lichens with their extremely low metabolic rate.