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An oligotroph is an
organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
that can live in an environment that offers very low levels of
nutrients A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...
. They may be contrasted with
copiotrophs A copiotroph is an organism found in environments rich in nutrients, particularly carbon. They are the opposite to oligotrophs, which survive in much lower carbon concentrations. Copiotrophic organisms tend to grow in high organic matter, organic s ...
, which prefer nutritionally rich environments. Oligotrophs are characterized by slow growth, low rates of metabolism, and generally low population density. Oligotrophic environments are those that offer little to sustain life. These 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 olm or proteus (''Proteus anguinus'') is an aquatic salamander in the family Proteidae, the only exclusively cave-dwelling chordate species found in Europe. In contrast to most amphibians, it is entirely aquatic, eating, sleeping, and br ...
; the bacterium " ''Candidatus'' Pelagibacter communis", which is the most abundant organism in the oceans with an estimated 2 × 1028 individuals in total; and the
lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.metabolic rate Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
.
Etymologically Etymology ()The New Oxford Dictionary of English (1998) – p. 633 "Etymology /ˌɛtɪˈmɒlədʒi/ the study of the class in words and the way their meanings have changed throughout time". is the study of the history of the form of words an ...
, the word "oligotroph" is a combination of the
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
adjective ''oligos'' (ὀλίγος) meaning "few" and the adjective ''trophikos'' (τροφικός)) meaning "feeding".


Plant adaptations

Plant adaptations to oligotrophic soils provide for greater and more efficient nutrient uptake, reduced nutrient consumption, and efficient nutrient storage. Improvements in nutrient uptake are facilitated by root adaptations such as
nitrogen-fixing Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmos ...
root nodule Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria. Under nitrogen-limiting conditions, capable plants form a symbiotic relationship with a host-specific strain of bacteria known a ...
s,
mycorrhiza   A mycorrhiza (from Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plant ...
e and
cluster roots Cluster roots, also known as proteoid roots, are plant roots that form clusters of closely spaced short lateral rootlets. They may form a two- to five-centimetre-thick mat just beneath the leaf litter. They enhance nutrient uptake, possibly by chem ...
. Consumption is reduced by very slow growth rates, and by efficient use of low-availability nutrients; for example, the use of highly available ions to maintain
turgor pressure Turgor pressure is the force within the cell that pushes the plasma membrane against the cell wall. It is also called ''hydrostatic pressure'', and is defined as the pressure in a fluid measured at a certain point within itself when at equilibri ...
, with low-availability nutrients reserved for the building of tissues. Despite these adaptations, nutrient requirement typically exceed uptake during the growing season, so many oligotrophic plants have the ability to store nutrients, for example, in trunk tissues, when demand is low, and remobilise them when demand increases.


Oligotrophic environments

Oligotrophs occupy environments where the available nutrients offer little to sustain life. The term “oligotrophic” is commonly used to describe terrestrial and aquatic environments with very low concentrations of nitrates, iron, phosphates, and carbon sources. Oligotrophs have acquired survival mechanisms that involve the expression of genes during periods of low nutrient conditions, which has allowed them to find success in various environments. Despite the capability to live in low nutrient concentrations, oligotrophs may find difficulty surviving in nutrient-rich environments.


Antarctica

Antarctic environments offer very little to sustain life as most organisms are not well adapted to live under nutrient-limiting conditions and cold temperatures (lower than 5 °C). As such, these environments display a large abundance of
psychrophile Psychrophiles or cryophiles (adj. ''psychrophilic'' or ''cryophilic'') are extremophilic organisms that are capable of growth and reproduction in low temperatures, ranging from to . They have an optimal growth temperature at . They are found in ...
s that are well adapted to living in an Antarctic biome. Most oligotrophs live in lakes where water helps support biochemical processes for growth and survival. Below are some documented examples of oligotrophic environments in Antarctica:
Lake Vostok Lake Vostok (russian: озеро Восток, ''ozero Vostok'') is the largest of Antarctica's almost 400 known subglacial lakes. Lake Vostok is located at the southern Pole of Cold, beneath Russia's Vostok Station under the surface of the cent ...
, a freshwater lake which has been isolated from the world beneath 4 km (2.5 mi) of Antarctic ice is frequently held to be a primary example of an oligotrophic environment. Analysis of ice samples showed ecologically separated microenvironments. Isolation of microorganisms from each microenvironment led to the discovery of a wide range of different microorganisms present within the ice sheet. Traces of fungi have also been observed which suggests potential for unique symbiotic interactions. The lake’s extensive oligotrophy has led some to believe parts of lake are completely sterile. This lake is a helpful tool for simulating studies regarding extraterrestrial life on frozen planets and other celestial bodies. Crooked Lake is an ultra-oligotrophic glacial lake with a thin distribution of
heterotroph A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...
ic and
autotrophic An autotroph or primary producer is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) using carbon from simple substances such as carbon dioxide,Morris, J. et al. (2019). "Biology: How Life Works", ...
microorganisms. The
microbial loop The microbial loop describes a trophic pathway where, in aquatic systems, dissolved organic carbon (DOC) is returned to higher trophic levels via its incorporation into bacterial biomass, and then coupled with the classic food chain formed by phy ...
plays a big role in cycling nutrients and energy within this lake, despite particularly low bacterial abundance and productivity in these environments. The little ecological diversity can be attributed to the lake's low annual temperatures. Species discovered in this lake include ''
Ochromonas ''Ochromonas'' is a genus of algae belonging to the family Chromulinaceae. The genus has cosmopolitan distribution. Chlorosulfolipids, a class of biologically active compounds, was first discovered in some ''Ochromonas'' species. Species Acc ...
,
Chlamydomonas ''Chlamydomonas'' is a genus of green algae consisting of about 150 speciesSmith, G.M. 1955 ''Cryptogamic Botany Volume 1. Algae and Fungi'' McGraw-Hill Book Company Inc of unicellular flagellates, found in stagnant water and on damp soil, ...
, Scourfeldia,
Cryptomonas ''Cryptomonas'' is the name-giving genus of the Cryptomonads established by German biologist Christian Gottfried Ehrenberg in 1831. The algae are common in freshwater habitats and brackish water worldwide and often form blooms in greater depths ...
, Akistrodesmus falcatus,'' and '' Daphniopsis studeri'' (a microcrustacean). It is proposed that low competitive selection against ''Daphniopsis studeri'' has allowed the species to survive long enough to reproduce in nutrient limiting environments.


Australia

The sandplains and lateritic soils of southern
Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...
, where an extremely thick
craton A craton (, , or ; from grc-gre, κράτος "strength") is an old and stable part of the continental lithosphere, which consists of Earth's two topmost layers, the crust and the uppermost mantle. Having often survived cycles of merging and ...
has precluded any geological activity since the
Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...
and there has been no
glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betw ...
to renew soils since the
Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...
. Thus, soils are extremely nutrient-poor and most vegetation must use strategies such as
cluster root Cluster roots, also known as proteoid roots, are plant roots that form clusters of closely spaced short lateral rootlets. They may form a two- to five-centimetre-thick mat just beneath the leaf litter. They enhance nutrient uptake, possibly by chem ...
s to gain even the smallest quantities of such nutrients as
phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...
and
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
. The vegetation in these regions, however, is remarkable for its
biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
, which in places is as great as that of a
tropical rainforest Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as ''lowland equatori ...
and produces some of the most spectacular wildflowers in the world. It is however, severely threatened by
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
which has moved the winter rain belt south, and also by clearing for
agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to ...
and through use of
fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
s, which is primarily driven by low land costs which make farming economic even with yields a fraction of those in Europe or North America.


South America

An example of oligotrophic soils are those on white-sands, with
soil pH Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the neg ...
lower than 5.0, on the Rio Negro basin on northern
Amazonia The Amazon rainforest, Amazon jungle or ; es, Selva amazónica, , or usually ; french: Forêt amazonienne; nl, Amazoneregenwoud. In English, the names are sometimes capitalized further, as Amazon Rainforest, Amazon Forest, or Amazon Jungle. ...
that house very low-diversity, extremely fragile forests and savannahs drained by
blackwater river A blackwater river is a type of river with a slow-moving channel flowing through forested swamps or wetlands. As vegetation decays, tannins leach into the water, making a transparent, acidic water that is darkly stained, resembling black te ...
s; dark water colour due to high concentration of
tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' (from Anglo-Norman ''tanner'', ...
s,
humic acid Humic substances (HS) are organic compounds that are important components of humus, the major organic fraction of soil, peat, and coal (and also a constituent of many upland streams, dystrophic lakes, and ocean water). For a long era in the 19th ...
s and other organic compounds derived from the very slow decomposition of plant matter. Similar forests are found in the oligotrophic waters of the
Patía River The Patía River () is a river in southwestern Colombia. It flows over to drain into the Pacific Ocean north of Tumaco. The Patía River is the longest river on the Colombian Pacific Coast. The last is navigable by boat. Geography The Patía ...
delta on the Pacific side of the Andes.


Ocean

In the
ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...
, the subtropical gyres north and south of the
equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can als ...
are regions in which the
nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...
s required for
phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'. Ph ...
growth (for instance,
nitrate Nitrate is a polyatomic ion A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...
,
phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phospho ...
and
silicic acid Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...
) are strongly depleted all year round. These areas are described as oligotrophic and exhibit low surface
chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...
. They are occasionally described as "ocean deserts".


Oligotrophic soil environments

The oligotrophic soil environments include agricultural soil, frozen soil, ''et cetera''. Various factors, such as
decomposition Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...
, soil structure,
fertilization Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Proce ...
and
temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...
, can affect the nutrient-availability in the soil environments. Generally, the nutrient becomes less available along the depth of the soil environment, because on the surface, the organic compounds decomposed from the plant and animal
debris Debris (, ) is rubble, wreckage, ruins, litter and discarded garbage/refuse/trash, scattered remains of something destroyed, or, as in geology, large rock fragments left by a melting glacier, etc. Depending on context, ''debris'' can refer to ...
are consumed quickly by other microbes, resulting in the lack of nutrient in the deeper level of soil. In addition, the metabolic waste produced by the microorganisms on the surface also causes the accumulation of toxic chemicals in the deeper area. Furthermore, oxygen and water are important for some metabolic pathways, but it is difficult for water and oxygen to diffuse as the depth increases. Some factors, such as soil aggregates, pores and extracellular enzymes, may help water, oxygen and other nutrients diffuse into the soil. Moreover, the presence of mineral under the soil provides the alternative sources for the species living in the oligotrophic soil. In terms of the agricultural lands, the application of fertilizer has a complicated impact on the source of carbon, either increasing or decreasing the organic carbon in the soil. ''
Collimonas ''Collimonas'' is a genus of bacteria in the family Oxalobacteraceae. Culturable representatives of this genus have the ability to lyse chitin, to use fungal hyphae as a source of food, to produce antifungal molecules and to be effective at weath ...
'' is one of the species that are capable of living in the oligotrophic soil. One common feature of the environments where ''
Collimonas ''Collimonas'' is a genus of bacteria in the family Oxalobacteraceae. Culturable representatives of this genus have the ability to lyse chitin, to use fungal hyphae as a source of food, to produce antifungal molecules and to be effective at weath ...
'' lives is the presence of fungi, because ''
Collimonas ''Collimonas'' is a genus of bacteria in the family Oxalobacteraceae. Culturable representatives of this genus have the ability to lyse chitin, to use fungal hyphae as a source of food, to produce antifungal molecules and to be effective at weath ...
'' have the ability of not only hydrolyzing the
chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...
produced by fungi for nutrients, but also producing materials (e.g., ''P. fluorescens'' 2-79) to protect themselves from fungal infection. The mutual relationship is common in the oligotrophic environments. Additionally, ''
Collimonas ''Collimonas'' is a genus of bacteria in the family Oxalobacteraceae. Culturable representatives of this genus have the ability to lyse chitin, to use fungal hyphae as a source of food, to produce antifungal molecules and to be effective at weath ...
'' can also obtain electron sources from rocks and minerals by
weathering Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...
. In terms of polar areas, such as Antarctic and Arctic region, the soil environment is considered as oligotrophic because the soil is frozen with low biological activities. The most abundant species in the frozen soil are
Actinomycetota The ''Actinomycetota'' (or ''Actinobacteria'') are a phylum of all gram-positive bacteria. They can be terrestrial or aquatic. They are of great economic importance to humans because agriculture and forests depend on their contributions to soi ...
,
Pseudomonadota Pseudomonadota (synonym Proteobacteria) is a major phylum of Gram-negative bacteria. The renaming of phyla in 2021 remains controversial among microbiologists, many of whom continue to use the earlier names of long standing in the literature. The ...
,
Acidobacteriota Acidobacteriota is a phylum of Gram-negative bacteria. Its members are physiologically diverse and ubiquitous, especially in soils, but are under-represented in culture. Description Members of this phylum are physiologically diverse, and can be ...
and
Cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...
, together with a small amount of archaea and fungi.
Actinomycetota The ''Actinomycetota'' (or ''Actinobacteria'') are a phylum of all gram-positive bacteria. They can be terrestrial or aquatic. They are of great economic importance to humans because agriculture and forests depend on their contributions to soi ...
can maintain the activity of their metabolic enzymes and continue their biochemical reactions under a wide range of low temperature. In addition, the DNA repairing machinery in
Actinomycetota The ''Actinomycetota'' (or ''Actinobacteria'') are a phylum of all gram-positive bacteria. They can be terrestrial or aquatic. They are of great economic importance to humans because agriculture and forests depend on their contributions to soi ...
protects them from lethal DNA mutation at low temperature.


See also

*
Oligotrophic lake The Trophic State Index (TSI) is a classification system designed to rate water bodies based on the amount of biological productivity they sustain. Although the term "trophic index" is commonly applied to lakes, any surface water body may be inde ...
*
Eutrophic lake The Trophic State Index (TSI) is a classification system designed to rate water bodies based on the amount of biological productivity they sustain. Although the term "trophic index" is commonly applied to lakes, any surface water body may be ind ...
* ''
Pelagibacter ubique "''Candidatus'' Pelagibacter", with the single species "''Ca.'' P. communis", was isolated in 2002 and given a specific name, although it has not yet been described as required by the bacteriological code. It is an abundant member of the SAR11 c ...
'', most abundant species on Earth and a streamlined oligotroph


References


External links

* Special issue abou
Lake oligotrophication
published in ''Freshwater Biology'' {{modelling ecosystems Edaphology Aquatic ecology Limnology