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Oligotroph

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Anoligotrophis anorganismthat can live in an environment that offers very low levels ofnutrients.They may be contrasted withcopiotrophs,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-dwellingolm;the bacterium "CandidatusPelagibacter communis",which is the most abundant organism in the ocean (with an estimated 2 × 1028individuals in total); andlichens,with their extremely lowmetabolic rate.

Etymology[edit]

Etymologically,the word "oligotroph" is a combination of theGreekadjectiveoligos(ὀλίγος)[1]meaning "few" and the adjectivetrophikos(τροφικός)[2]meaning "feeding".

Plant adaptations[edit]

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 asnitrogen-fi xingroot nodules,mycorrhizaeandcluster roots.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 maintainturgor pressure,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[edit]

Oligotrophsoccupy 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.[3][4]

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.[3]

Antarctica[edit]

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 ofpsychrophilesthat are well adapted to living in an Antarctic biome. Most oligotrophs live in lakes where water helps support biochemical processes for growth and survival.[5]Below are some documented examples of oligotrophic environments in Antarctica:

Lake Vostok,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.[6]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.[7]Traces of fungi have also been observed which suggests potential for unique symbiotic interactions.[8][7]The lake’s extensive oligotrophy has led some to believe parts of the lake are completely sterile.[8]This lake is a helpful tool for simulating studies regarding extraterrestrial life on frozen planets and other celestial bodies.[9]

Crooked Lakeis an ultra-oligotrophic glacial lake[10]with a thin distribution ofheterotrophicandautotrophicmicroorganisms.[11]Themicrobial loopplays a big role in cycling nutrients and energy within this lake, despite particularly low bacterial abundance and productivity in these environments.[10]The little ecological diversity can be attributed to the lake's low annual temperatures.[12]Species discovered in this lake includeOchromonas,Chlamydomonas,Scourfeldia,Cryptomonas,Akistrodesmus falcatus,andDaphniopsis studeri(a microcrustacean). It is proposed that low competitive selection againstDaphniopsis studerihas allowed the species to survive long enough to reproduce in nutrient limiting environments.[11]

Australia[edit]

The sandplains andlateritic soilsof southernWestern Australia,where an extremely thickcratonhas precluded any geological activity since theCambrianand there has been noglaciationto renew soils since theCarboniferous.Thus, soils are extremely nutrient-poor and most vegetation must use strategies such ascluster rootsto gain even the smallest quantities of such nutrients asphosphorusandsulfur.

The vegetation in these regions, however, is remarkable for itsbiodiversity,which in places is as great as that of atropical rainforestand produces some of the most spectacular wildflowers in the world. It is however, severely threatened byclimate changewhich has moved the winter rain belt south, and also by clearing foragricultureand through use offertilizers,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[edit]

An example of oligotrophic soils are those on white-sands, withsoil pHlower than 5.0, on theRio Negrobasin on northernAmazoniathat house very low-diversity, extremely fragile forests and savannahs drained byblackwater rivers;dark water colour due to high concentration oftannins,humic acidsand other organic compounds derived from the very slow decomposition of plant matter.[13][14][15]Similar forests are found in the oligotrophic waters of thePatía Riverdelta on the Pacific side of the Andes.[16]

Ocean[edit]

In theocean,thesubtropical gyresnorth and south of theequatorare regions in which thenutrientsrequired forphytoplanktongrowth (for instance,nitrate,phosphateandsilicic acid) are strongly depleted all year round. These areas are described as oligotrophic and exhibit low surfacechlorophyll.They are occasionally described as "ocean deserts".[17]

Oligotrophic soil environments[edit]

The oligotrophic soil environments include agricultural soil, frozen soil,et cetera.[18][19]Various factors, such asdecomposition,soil structure,fertilizationandtemperature,can affect the nutrient-availability in the soil environments.[18][19]

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 animaldebrisare consumed quickly by other microbes, resulting in the lack of nutrient in the deeper level of soil.[18]In addition, the metabolic waste produced by the microorganisms on the surface also causes the accumulation of toxic chemicals in the deeper area.[18]Furthermore, oxygen and water are important for some metabolic pathways, but it is difficult for water and oxygen to diffuse as the depth increases.[18]Some factors, such as soil aggregates, pores and extracellular enzymes, may help water, oxygen and other nutrients diffuse into the soil.[20]Moreover, the presence of mineral under the soil provides the alternative sources for the species living in the oligotrophic soil.[20]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.[20]

Collimonasis one of the species that are capable of living in the oligotrophic soil.[21]One common feature of the environments whereCollimonaslives is the presence of fungi, becauseCollimonashave the ability of not only hydrolyzing thechitinproduced by fungi for nutrients, but also producing materials (e.g.,P. fluorescens2-79) to protect themselves from fungal infection.[21]The mutual relationship is common in the oligotrophic environments. Additionally,Collimonascan also obtain electron sources from rocks and minerals byweathering.[21]

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.[19]The most abundant species in the frozen soil areActinomycetota,Pseudomonadota,AcidobacteriotaandCyanobacteria,together with a small amount of archaea and fungi.[19]Actinomycetotacan maintain the activity of their metabolic enzymes and continue their biochemical reactions under a wide range of low temperature.[19]In addition, the DNA repairing machinery inActinomycetotaprotects them from lethal DNA mutation at low temperature.[19]

See also[edit]

References[edit]

  1. ^ὀλίγος.Liddell, Henry George;Scott, Robert;A Greek–English Lexiconat thePerseus Project
  2. ^τροφικός.Liddell, Henry George;Scott, Robert;A Greek–English Lexiconat thePerseus Project
  3. ^abKoch, Arthur L. (July 2001). "Oligotrophs versus copiotrophs".BioEssays.23(7): 657–61.doi:10.1002/bies.1091.PMID11462219.S2CID39126203.
  4. ^Horikoshi, Koki (2016).Extremophiles Where it all Began.Tokyo, Japan: Springer Japan.doi:10.1007/978-4-431-55408-0.ISBN978-4-431-55407-3.S2CID199493176.
  5. ^Anesio, Alexandre M.; Laybourn-Parry, Johanna (April 2012). "Glaciers and ice sheets as a biome".Trends in Ecology & Evolution.27(4): 219–225.Bibcode:2012TEcoE..27..219A.doi:10.1016/j.tree.2011.09.012.PMID22000675.
  6. ^Schiermeier, Q. (2011)."Race against time for raiders of the lost lake".Nature.469(7330): 275.Bibcode:2011Natur.469..275S.doi:10.1038/469275a.PMID21248808.
  7. ^abD'Elia, T.; Veerapaneni, R.; Rogers, S. O. (13 June 2008)."Isolation of Microbes from Lake Vostok Accretion Ice".Applied and Environmental Microbiology.74(15): 4962–4965.Bibcode:2008ApEnM..74.4962D.doi:10.1128/AEM.02501-07.PMC2519340.PMID18552196.
  8. ^abBulat, Sergey A.; Alekhina, Irina A.; Blot, Michel; Petit, Jean-Robert; de Angelis, Martine; Wagenbach, Dietmar; Lipenkov, Vladimir Ya.; Vasilyeva, Lada P.; Wloch, Dominika M.; Raynaud, Dominique; Lukin, Valery V. (January 2004)."DNA signature of thermophilic bacteria from the aged accretion ice of Lake Vostok, Antarctica: implications for searching for life in extreme icy environments".International Journal of Astrobiology.3(1): 1–12.Bibcode:2004IJAsB...3....1B.doi:10.1017/S1473550404001879.
  9. ^Bulat, S. A.; Alekhina, I. A.; Lipenkov, V. Ya.; Lukin, V. V.; Marie, D.; Petit, J. R. (6 December 2009). "Cell concentrations of microorganisms in glacial and lake ice of the Vostok ice core, East Antarctica".Microbiology.78(6): 808–810.doi:10.1134/S0026261709060216.S2CID8906848.
  10. ^abSäwström, Christin; Anesio, M. Alexandre; Granéli, Wilhelm; Laybourn-Parry, Johanna (31 October 2006). "Seasonal Viral Loop Dynamics in Two Large Ultraoligotrophic Antarctic Freshwater Lakes".Microbial Ecology.53(1): 1–11.doi:10.1007/s00248-006-9146-5.PMID17075732.S2CID1833362.
  11. ^abLayboum-Parry, Johanna; Marchant, H.J.; Brown, P. (1991). "The plankton of a large oligotrophic freshwater Antarctic lake".Journal of Plankton Research.13(6): 1137–1149.doi:10.1093/plankt/13.6.1137.ISSN0142-7873.
  12. ^Henshaw, Tracey; Laybourn-Parry, J. (October 2002). "The annual patterns of photosynthesis in two large, freshwater, ultra-oligotrophic Antarctic lakes".Polar Biology.25(10): 744.Bibcode:2002PoBio..25..744H.doi:10.1007/s00300-002-0402-y.ISSN0722-4060.S2CID42895583.
  13. ^Janzen, D. H. (1974). "Tropical Blackwater Rivers, Animals, and Mast Fruiting by the Dipterocarpaceae".Biotropica.6(2): 69–103.Bibcode:1974Biotr...6...69J.doi:10.2307/2989823.JSTOR2989823.
  14. ^Sioli, Harald (1975)."Tropical rivers as expressions of their terrestrial environments".In Golley, F. B.; Medina, E. (eds.).Tropical Ecological Systems/Trends in Terrestrial and Aquatic Research.New York: Springer. pp.275–288.ISBN978-0-387-06706-3.
  15. ^German, Laura A. (2004). "Ecological praxis and blackwater ecosystems: a case study from the Brazilian Amazon".Human Ecology.32(6): 653–683.doi:10.1007/s10745-004-6831-1.S2CID153566259.
  16. ^Del Valle-Arango, Jorge Ignacio (2003). "Cantidad, calidad y nutrientes reciclados por la hojarasca fina en bosques pantanosos del Pacífico sur colombiano".Interciencia.28(8): 443–452.(in Spanish)
  17. ^"Study Shows Ocean" Deserts "are Expanding".NOAA.2008-03-05.Retrieved2009-07-17.
  18. ^abcdeMorita, Richard Yukio (1997).Bacteria in oligotrophic environments: Starvation-survival life style.New York: Chapman & Hall. pp. 50–89.ISBN9780412106613.
  19. ^abcdefMakhalanyane, Thulani Peter; Goethem, Marc Warwick Van; Cowan, Don Arthur (2016)."Microbial diversity and functional capacity in polar soils".Current Opinion in Biotechnology.38:159–166.doi:10.1016/j.copbio.2016.01.011.hdl:2263/52220.PMID26921734.S2CID241167.
  20. ^abcFinn, Damien; Kopittke, Peter M.; Dennis, Paul G.; Dalal, Ram C. (2017)."Microbial energy and matter transformation in agricultural soils"(PDF).Soil Biology and Biochemistry.111:176–192.Bibcode:2017SBiBi.111..176F.doi:10.1016/j.soilbio.2017.04.010.
  21. ^abcLeveau, Johan H. J.; Uroz, Stéphane; De Boer, Wietse (2010-02-01). "The bacterial genus Collimonas: mycophagy, weathering and other adaptive solutions to life in oligotrophic soil environments".Environmental Microbiology.12(2): 281–292.Bibcode:2010EnvMi..12..281L.doi:10.1111/j.1462-2920.2009.02010.x.ISSN1462-2920.PMID19638176.

External links[edit]

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