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=== Article: Oligotroph ===

"Original" - Oligotrophic environments

[edit]

An ecosystem or environment is said to be oligotrophic if it offers little to sustain life. The term is commonly utilised to describe environments of water, ice, air, rock or soil with very low nutrient levels.

Oligotrophic environments are of special interest for the alternative energy sources and survival strategies upon which life could rely.[citation needed]

Antarctic

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Lake Vostok, a freshwater lake which has been isolated from the world beneath 4 km (2.5 mi) of Antarctic ice for approximately 15 million years[1] is frequently held to be a primary example of an oligotrophic environment.

"Edits" - Oligotrophic Environments

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On the contrary to copiotrophs, oligotrophs occupy environments where nutrients for survival are below the average needed for the typical organism. An ecosystem or environment is said to be oligotrophic if it offers little to sustain life. The term is commonly used to describe environments of water, ice, air, rock or soil with very low nutrient levels[2]. Nutrients lacking in these environments include nitrates, iron, phosphates, and carbon sources.[3]

Oligotrophs have acquired survival mechanisms that involve the expression of genes during periods of high and low nutrient conditions, which has allowed them to find success during long periods of nutrient scarcity. Despite the capability to live in low nutrient concentrations, oligotrophs may find difficulty surviving in nutrient-rich environments[2].

Antarctica

[edit]

Lake Vostok, a freshwater lake which has been isolated from the world beneath 4 km (2.5 mi) of Antarctic ice for approximately 15 million years[1] is frequently held to be a primary example of an oligotrophic environment. Analysis of ice samples taken from the lake depicted ecologically separated environments. Isolation of microorganisms from each environment led to the discovery of a wide range of different species present within the ice sheet.[4] While these environments displayed a diverse ecosystem, it is still considered an oligotrophic environment when compared to other microbial communities on earth.[5] Its extensive oligotrophy have led some to believe parts of lake are completely sterile.[6] While these systems are usually dominated by microbes, traces of fungi have been observed which suggests potential for complex ecosystems and unique symbiotic interactions.[4][6] This lake is a helpful tool for simulating studies regarding extraterrestrial oligotrophic life on frozen planets and other celestial bodies.[7]

Chlorophyll a analysis of plankton in Crooked Lake, an Antarctic freshwater lake, showed a thinly distributed population of heterotrophic and autotrophic microorganisms.[8] Low productivity in these environments can be attributed to low annual temperatures, which results in the lack of diversity characteristic of most lake ecosystems in Antarctica.[9] Species discovered in these environments include Ochromonas, Chlamydomonas, Scourfeldia, Cryptomonas and Akistrodesmus falcatus.[8] Despite these unfavourable conditions, a microcrustacean, Daphniopsis studeri, was found in rare occurrences. It is proposed that low competitive selection against this species has allowed the species to survive long enough to reproduce in nutrient limiting environments.[8]

--Juan Prieto (talk) 08:00, 8 October 2017 (UTC)

"Revision" - Oligotrophic Environments

[edit]

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.[10][11]

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.[10]

Antarctica

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Antarctic life offers 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 psychrophiles 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.[12] 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.[13] 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.[14] Traces of fungi have also been observed which suggests potential for unique symbiotic interactions.[15][14] The lake’s extensive oligotrophy has led some to believe parts of lake are completely sterile.[15] This lake is a helpful tool for simulating studies regarding extraterrestrial life on frozen planets and other celestial bodies.[16]

Crooked Lake is an ultra-oligotrophic glacial lake[17] with a thin distribution of heterotrophic and autotrophic microorganisms.[18] The microbial loop plays a big role in cycling nutrients and energy within this lake, despite particularly low bacterial abundance and productivity in these environments.[17] The little ecological diversity can be attributed to the lake's low annual temperatures.[19] Species discovered in this lake include Ochromonas, Chlamydomonas, Scourfeldia, Cryptomonas, 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.[18]


--Juan Prieto (talk) 09:10, 19 November 2017 (UTC)

References

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  1. ^ a b "Race against time for raiders of the lost lake". Nature. 469 (7330): 275. 2011. doi:10.1038/469275a. PMID 21248808.
  2. ^ a b Koch, A. L. "Oligotrophs Versus Copiotrophs." BioEssays : News and Reviews in Molecular, Cellular and Developmental Biology, vol. 23, no. 7, 2001, pp. 657-661.
  3. ^ Horikoshi, Koki, SpringerLink (Online service), and SpringerLINK ebooks - Earth and Environmental Science. Extremophiles Where it all Began. Springer Japan, Tokyo, 2016, doi:10.1007/978-4-431-55408-0
  4. ^ a b D'Elia, T., Veerapaneni, R., & Rogers, S. O. (2008). Isolation of microbes from lake vostok accretion ice. Applied and Environmental Microbiology, 74(15), 4962-4965. doi:10.1128/AEM.02501-07
  5. ^ Karl, D. M., Bird, D. F., Björkman, K., Houlihan, T., Shackelford, R., & Tupas, L. (1999). Microorganisms in the accreted ice of lake vostok, antarctica. Science, 286(5447), 2144-2147. doi:10.1126/science.286.5447.2144
  6. ^ a b Bulat, S. A., Alekhina, I. A., Blot, M., Petit, J., Waggenbach, D., Lipenkov, V. Y., ... & Lukin, V. V. (2002, May). Thermophiles microbe signature in Lake Vostok, Antarctica. In AGU Spring Meeting Abstracts.
  7. ^ Bulat, S. A., Alekhina, I. A., Lipenkov, V. Y., Lukin, V. V., Marie, D., & Petit, J. R. (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
  8. ^ a b c Layboum-Parry, Johanna, H. J. Marchant, and P. Brown. "The Plankton of a Large Oligotrophic Freshwater Antarctic Lake." Journal of Plankton Research, vol. 13, no. 6, 1991, pp. 1137-1149.
  9. ^ Henshaw, Tracey, and Johanna Laybourn-Parry. "The Annual Patterns of Photosynthesis in Two Large, Freshwater, Ultra-Oligotrophic Antarctic Lakes." Polar Biology, vol. 25, no. 10, 2002, pp. 744.
  10. ^ a b Koch, Arthur L. (July 2001). "Oligotrophs versus copiotrophs". BioEssays. 23 (7): 657-661. doi:10.1002/bies.1091.
  11. ^ Horikoshi, Koki (2016). Extremophiles Where it all Began. Tokyo, Japan: Springer Japan. doi:10.1007/978-4-431-55408-0. ISBN 978-4-431-55407-3.
  12. ^ Anesio, Alexandre M.; Laybourn-Parry, Johanna (April 2012). "Glaciers and ice sheets as a biome". Trends in Ecology & Evolution. 27 (4): 219–225. doi:10.1016/j.tree.2011.09.012.
  13. ^ "Race against time for raiders of the lost lake". Nature. 469 (7330): 275. 2011. doi:10.1038/469275a. PMID 21248808.
  14. ^ a b D'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. doi:10.1128/AEM.02501-07.
  15. ^ a b Bulat, 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. doi:10.1017/S1473550404001879.
  16. ^ 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.
  17. ^ a b Säwström, 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.
  18. ^ a b Layboum-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. ISSN 0142-7873.
  19. ^ 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. doi:10.1007/s00300-002-0402-y. ISSN 0722-4060.
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