oligotroph

An oligotroph is an organism adapted to grow in environments that offer extremely low concentrations of nutrients. The term comes from Greek oligos "few" and trophé "nourishment." Oligotrophic environments, such as many open-ocean waters and some nutrient-poor lakes, are characterized by low primary production, low algal biomass, and often high water clarity.

In microorganisms, oligotrophs tend to have high-affinity uptake systems, low maximum growth rates, and streamlined metabolisms. They efficiently scavenge scarce nutrients and often rely on energy-efficient pathways. Because resources are limited, they may invest in maintenance and survival rather than rapid replication. Genomes can be reduced in size relative to copiotrophs.

Examples include Prochlorococcus, a photosynthetic cyanobacterium abundant in oligotrophic oceans, and the SAR11 clade (Pelagibacterales), among the most abundant marine bacteria; both display traits associated with oligotrophy. In soils, certain bacteria and fungi persist in nutrient-poor horizons as oligotrophs.

Ecological significance: oligotrophs underpin nutrient cycling in low-nutrient systems; they support long-term stability but may be outcompeted in nutrient-rich conditions. Eutrophication can shift communities toward copiotrophs, increasing productivity but reducing water clarity and, at depth, depleting dissolved oxygen. The term oligotroph can describe both organisms adapted to low-nutrient environments and, more broadly, the environments themselves, which are characterized by limited nutrient availability.