Editing Stromatolite (section)

==Modern occurrence==
[[File:Lake Thetis-Stromatolites-LaRuth.jpg|thumb|Stromatolites at [[Lake Thetis]], [[Western Australia]]]]
[[File:20130118-HighbormeCay-Stromatolite-03.JPG|thumb|Stromatolites at Highborne Cay, in the [[Exumas]], [[The Bahamas]]]]

===Formation===
Time lapse photography of modern microbial mat formation in a laboratory setting gives some revealing clues to the behavior of cyanobacteria in stromatolites. Biddanda ''et al.'' (2015) found that cyanobacteria exposed to localized beams of light moved towards the light, or expressed [[phototaxis]], and increased their [[Photosynthesis|photosynthetic]] yield, which is necessary for survival.<ref name="Biddanda-2015">{{Cite journal|last1=Biddanda|first1=Bopaiah A.|last2=McMillan|first2=Adam C.|last3=Long|first3=Stephen A.|last4=Snider|first4=Michael J.|last5=Weinke|first5=Anthony D.|date=2015-01-01|title=Seeking sunlight: rapid phototactic motility of filamentous mat-forming cyanobacteria optimize photosynthesis and enhance carbon burial in Lake Huron's submerged sinkholes|journal= Frontiers in Microbiology|pages=930|doi=10.3389/fmicb.2015.00930|pmc=4561352|pmid=26441867|volume=6|doi-access=free}}</ref> In a novel experiment, the scientists projected a school logo onto a petri dish containing the organisms, which accreted beneath the lighted region, forming the logo in bacteria.<ref name="Biddanda-2015" /> The authors speculate that such motility allows the cyanobacteria to seek light sources to support the colony.<ref name="Biddanda-2015" /> 

In both light and dark conditions, the cyanobacteria form clumps that then expand outwards, with individual members remaining connected to the colony via long tendrils. In harsh environments where mechanical forces may tear apart the microbial mats, these substructures may provide evolutionary benefit to the colony, affording it at least some measure of shelter and protection. 

[[Lichen stromatolite]]s are a proposed mechanism of formation of some kinds of layered rock structure that are formed above water, where rock meets air, by repeated colonization of the rock by [[endolithic lichen]]s.<ref name="CKLS">Lichen Stromatolites: Criterion for Subaerial Exposure and a Mechanism for the Formation of Laminar Calcretes (Caliche), Colin F. Klappa, [[Journal of Sedimentary Petrology]], Vol. 49 (1979) No. 2. (June), Pages 387–400, [http://archives.datapages.com/data/sepm/journals/v47-50/data/049/049002/0387.htm?doi=10.1306%2F212F7752-2B24-11D7-8648000102C1865D] {{Webarchive|url=https://web.archive.org/web/20141028133556/http://archives.datapages.com/data/sepm/journals/v47-50/data/049/049002/0387.htm?doi=10.1306%2F212F7752-2B24-11D7-8648000102C1865D|date=28 October 2014}}</ref><ref name="TTKP">Paleobotany: The Biology and Evolution of Fossil Plants, Edith L. Taylor, Thomas N. Taylor, Michael Krings, page [http://archives.datapages.com/data/sepm/journals/v47-50/data/049/049002/0387.htm?doi=10.1306%2F212F7752-2B24-11D7-8648000102C1865D] {{Webarchive|url=https://web.archive.org/web/20141028133556/http://archives.datapages.com/data/sepm/journals/v47-50/data/049/049002/0387.htm?doi=10.1306%2F212F7752-2B24-11D7-8648000102C1865D|date=28 October 2014}}</ref>

=== Saline locations ===

Modern stromatolites are mostly found in [[hypersaline lake]]s and marine lagoons where high saline levels prevent animal grazing.<ref>{{Cite web |url=https://www.britannica.com/science/stromatolite |title=Stromatolite &#124; geology}}</ref><ref>{{Cite news |url=https://economictimes.indiatimes.com/news/science/oldest-evidence-of-life-on-earth-found-in-australia/articleshow/61658155.cms?from=mdr |title=Oldest evidence of life on Earth found in Australia |newspaper=The Economic Times}}</ref> One such location where excellent modern specimens can be observed is [[Hamelin Pool Marine Nature Reserve]], [[Shark Bay]] in [[Western Australia]]. In 2010, a fifth type of [[chlorophyll]], namely [[chlorophyll f]], was discovered by [[Min Chen (biologist) |Min Chen]] from stromatolites in Shark Bay.<ref name="chen2010">{{Cite journal | year=2010 | journal=Science | title=A Red-Shifted Chlorophyll | first6=H. . | volume=329 | issue=5997 | doi=10.1126/science.1191127 | pages=1318–1319 | pmid=20724585 | last6=Scheer | first5=B. A. | first2=M. . | last2=Schliep | first1=M. . | last3=Willows | first3=R. D. | last5=Neilan | first4=Z. -L. | last4=Cai | last1=Chen |bibcode=2010Sci...329.1318C | s2cid=206527174 }}</ref> ''[[Halococcus hamelinensis]]'', a [[halophile |halophilic]] [[archaea |archaeon]], occurs in living stromatolites in [[Shark Bay]] where it is exposed to extreme conditions of [[ultraviolet |UV]] radiation, [[salinity]] and [[desiccation]].<ref name="Leuko2011">Leuko S, Neilan BA, Burns BP, Walter MR, Rothschild LJ. Molecular assessment of UVC radiation-induced DNA damage repair in the stromatolitic halophilic archaeon, Halococcus hamelinensis. J Photochem Photobiol B. 2011 Feb 7;102(2):140-5. doi: 10.1016/j.jphotobiol.2010.10.002. Epub 2010 Oct 23. PMID: 21074452</ref> ''H. hamelinesis'' possesses genes that encode enzymes employed in the repair of UV induced damages in [[DNA]] by the processes of [[nucleotide excision repair]] and [[photolyase |photoreactivation]].<ref name="Leuko2011" />

Other locations include [[Pampa del Tamarugal National Reserve]] in Chile; [[Lagoa Salgada]], [[Rio Grande do Norte]], Brazil, where modern stromatolites can be observed as both bioherms (domal type) and beds; in the [[Puna de Atacama]] of the Andes; and near Sheybarah Island in [[Saudi Arabia]].<ref name="CU-20231206">{{cite news |last=Strain |first=Daniel |date=6 December 2023 |title=Deep within an inhospitable desert, a window to first life on Earth |url=https://www.colorado.edu/today/2023/12/06/deep-within-inhospitable-desert-window-first-life-earth |url-status=live |archiveurl=https://archive.today/20231230225404/https://www.colorado.edu/today/2023/12/06/deep-within-inhospitable-desert-window-first-life-earth |archivedate=30 December 2023 |accessdate=30 December 2023 |work=[[University of Colorado]]}}</ref><ref>{{Cite web |last=Banias |first=M. J. |date=2024-06-03 |title=New Study Says Life on Earth May Have Originated in Saudi Arabia 3.48 Billion Years Ago |url=https://thedebrief.org/new-study-says-life-on-earth-may-have-originated-in-saudi-arabia-3-48-billion-years-ago/ |access-date=2025-02-04 |website=The Debrief |language=en-US}}</ref>

Inland stromatolites can be found in saline waters in [[Cuatro Ciénegas Basin]], a unique ecosystem in the Mexican desert. [[Oriental_Basin#Lake_Alchichica|Alchichica Lake]] in [[Puebla]], Mexico has two distinct morphologic generations of stromatolites: columnar-dome like structures, rich in [[aragonite]], forming near the shore line, dated back to 1,100 [[years before present]] (ybp) and spongy-cauliflower like thrombolytic structures that dominate the lake from top to the bottom, mainly composed of [[hydromagnesite]], [[huntite]], [[calcite]] and dated back to 2,800 ybp.<ref>{{cite journal |author1=Kaźmierczak, J. |author2=Kempe, S. |author3=Kremer, B. |author4=López-Garcia, P. |author5=Moreira, D. |author6=Tavera, R. |name-list-style=amp |date=2011 |title=Hydrochemistry and microbialites of the alkaline caldera Lake Alchichica, Mexico |journal=Facies |volume=57 |page=543–570 |doi=10.1007/s10347-010-0255-8 |doi-access=free}}</ref> The only open marine environment where modern stromatolites are known to prosper is the [[Exuma]] Cays in the Bahamas.<ref>{{cite web |url=http://sepmstrata.org/Bahamas/pages/217-Stromatolites-Lee-Stocking-Exumas-Bahamas.html |title=217-Stromatolites-Lee-Stocking-Exumas-Bahamas Bahamas |access-date=2011-12-08 |archive-url=https://web.archive.org/web/20100326211512/http://sepmstrata.org/Bahamas/pages/217-Stromatolites-Lee-Stocking-Exumas-Bahamas.html |archive-date=26 March 2010 |url-status=dead}}</ref><ref>{{cite journal |vauthors=Feldmann M, McKenzie JA |doi=10.2307/3515490 |title=Stromatolite-thrombolite associations in a modern environment, Lee Stocking Island, Bahamas |journal=PALAIOS |date=April 1998 |volume=13 |pages=201–212 |issue=2 |bibcode=1998Palai..13..201F |jstor=3515490}}</ref>

===Freshwater locations===
[[File:Pavilion Lake microbialite towers.jpg|thumb|upright|[[Microbialite]] towers in [[Pavilion Lake]], [[British Columbia]]]]
[[Lake Bacalar|Laguna de Bacalar]] in Mexico's southern [[Yucatán Peninsula]] has an extensive formation of living giant [[microbialite]]s (that is, stromatolites or thrombolites). The microbialite bed is over {{convert|10|km|mi|abbr=on}} long with a vertical rise of several meters in some areas. These may be the largest sized living freshwater microbialites, or any organism, on Earth.<ref name=Gischler2008>{{cite journal|author=Gischler, E.|author2=Gibson, M.|author3=Oschmann, W.|name-list-style=amp|title=Giant Holocene Freshwater Microbialites, Laguna Bacalar, Quintana Roo, Mexico|journal=Sedimentology|volume=55|pages=1293–1309|year=2008|doi=10.1111/j.1365-3091.2007.00946.x|issue=5|bibcode = 2008Sedim..55.1293G |s2cid=129828647 }}</ref>

A 1.5&nbsp;km stretch of reef-forming stromatolites (primarily of the genus ''[[Scytonema]]'') occurs in [[Chetumal Bay]] in [[Belize]], just south of the mouth of the [[Rio Hondo (Belize)|Rio Hondo]] and the Mexican border.<ref>{{cite journal|author=Rasmussen, K.A.|author2=Macintyre, I.G.|author3=Prufert, L|name-list-style=amp|title=Modern stromatolite reefs fringing a brackish coastline, Chetumal Bay, Belize|journal=Geology|volume=21|issue=3|pages=199–202|date=March 1993|doi=10.1130/0091-7613(1993)021<0199:MSRFAB>2.3.CO;2|bibcode = 1993Geo....21..199R |url=http://doc.rero.ch/record/14025/files/PAL_E1070.pdf }}</ref> Large microbialite towers up to 40 m high were discovered in the largest [[soda lake]] on Earth, [[Lake Van]] in eastern Turkey. They are composed of [[aragonite]] and grow by precipitation of [[calcite]] from sub-lacustrine karst-water.<ref>{{cite journal|author1=Kempe, S. |author2=Kaźmierczak, J.|author3=Landmann, G.|author4=Konuk, T.|author5=Reimer, A.|author6=Lipp, A.|name-list-style=amp |title=Largest known microbialites discovered in Lake Van, Turkey|journal=Nature|volume=349|date= 1991|issue=6310|page=605–608|doi=10.1038/349605a0|bibcode=1991Natur.349..605K|s2cid=4240438}}</ref> Freshwater stromatolites are found in [[Lake Salda]] in southern Turkey. The waters are rich in [[magnesium]] and the stromatolite structures are made of [[hydromagnesite]].<ref>{{cite journal|author1=Braithwaite, C. |author2=Zedef V |name-list-style=amp |title=Living hydromagnesite stromatolites from Turkey|journal=Sedimentary Geology|volume=106|date=November 1996|page=309|doi=10.1016/S0037-0738(96)00073-5|issue=3–4|bibcode=1996SedG..106..309B}}</ref>

Two instances of freshwater stromatolites are found in Canada, at [[Pavilion Lake]] and [[Kelly Lake, British Columbia|Kelly Lake]] in [[British Columbia]]. Pavilion Lake has the largest known freshwater stromatolites, and [[NASA]] has conducted [[xenobiology]] research there,<ref>{{cite journal|title=Modern Freshwater Microbialites from Kelly Lake, British Columbia, Canada|vauthors=Ferris FG, Thompson JB, Beveridge TJ |journal=PALAIOS|volume=12|date=June 1997|jstor=3515423|issue=3|pages=213–219|doi=10.2307/3515423|bibcode=1997Palai..12..213F }}</ref> called the "[[Pavilion Lake Research Project]]." The goal of the project is to better understand what conditions would likely harbor life on other planets.<ref>{{cite journal|doi=10.1016/j.chemgeo.2010.03.016|author=Brady, A.|title=Photosynthetic isotope biosignatures in laminated micro-stromatolitic and non-laminated nodules associated with modern, freshwater microbialites in Pavilion Lake, B.C|journal=Chemical Geology|author2=Slater, G.F.|author3=Omelon, C.R.|author4=Southam, G.|author5=Druschel, G.|author6=Andersen, A.|author7=Hawes, I.|author8=Laval, B.|author9=Lim, D.S.S.|year=2010|volume=274|issue=1–2|pages=56–67|bibcode=2010ChGeo.274...56B}}</ref><ref>
{{cite web
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|title = NASA Help NASA Find Life on Mars With MAPPER
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Microbialites have been discovered in an open pit pond at an abandoned asbestos mine near [[Clinton Creek]], [[Yukon]],
Canada.<ref>Power, I.M., Wilson, S.A., Dipple, G.M., and Southam, G. (2011) ''Modern carbonate microbialites from an asbestos open pit pond, Yukon, Canada'', http://onlinelibrary.wiley.com/doi/10.1111/gbi.2011.9.issue-2/issuetoc {{Webarchive|url=https://web.archive.org/web/20120211140309/http://onlinelibrary.wiley.com/doi/10.1111/gbi.2011.9.issue-2/issuetoc |date=11 February 2012 }} Geobiology. 9: 180–195.</ref> These microbialites are extremely young and presumably began forming soon after the mine closed in 1978. The combination of a low sedimentation rate, high calcification rate, and low microbial growth rate appears to result in the formation of these microbialites. Microbialites at an historic mine site demonstrates that an anthropogenically constructed environment can foster microbial carbonate formation. This has implications for creating artificial environments for building modern microbialites including stromatolites.

[[File:'Crayback' stromatolite - Nettle Cave, Jenolan Caves, NSW, Australia.jpg|thumb |alt='Crayback' stromatolite – Nettle Cave, Jenolan Caves, NSW, Australia |'Crayback' stromatolite – Nettle Cave, [[Jenolan Caves]], [[NSW]], [[Australia]]]]
A very rare type of non-lake dwelling stromatolite lives in the Nettle Cave at [[Jenolan Caves]], [[New South Wales|NSW]], Australia.<ref>{{cite web |url=http://www.jenolancaves.org.au/compulsive_self-guided_cave_tour.php |title=Nettle Cave Self-guided tour |author=Jenolan Caves Reserve Trust |access-date=22 May 2011 |archive-url=https://web.archive.org/web/20110910062514/http://www.jenolancaves.org.au/compulsive_self-guided_cave_tour.php |archive-date=10 September 2011 |url-status=dead}}</ref> The cyanobacteria live on the surface of the limestone and are sustained by the calcium-rich dripping water, which allows them to grow toward the two open ends of the cave which provide light.<ref>{{cite journal|journal=Geomicrobiology Journal|volume =7|issue=4|year=1989|title=Cyanobacterially deposited speleothems: Subaerial stromatolites|doi=10.1080/01490458909377870|vauthors=Cox G, James JM, ((Leggett KEA)), ((Osborne RAL)) |pages=245–252}}</ref> 

Stromatolites composed of calcite have been found in both the [[Blue Lake (South Australia)|Blue Lake]] in the dormant volcano, [[Mount Gambier (volcano)|Mount Gambier]] and at least eight [[cenote]] lakes including the [[Little Blue Lake]] in the [[Limestone Coast|Lower South-East of South Australia]].<ref>{{cite journal|last=Thurgate|first=Mia E.|title=The Stromatolites of the Cenote Lakes of the Lower South East of South Australia|journal=[[Helictite (journal)|Helictite, Journal of Australasian Cave Research]]|year=1996|volume=34|issue=1|page=17|url=http://helictite.caves.org.au/pdf4/34.01.Issue.Print.pdf|issn=0017-9973|access-date=14 March 2014|archive-url=https://web.archive.org/web/20140205061253/http://helictite.caves.org.au/pdf4/34.01.Issue.Print.pdf|archive-date=5 February 2014|url-status=live}}</ref>