{{Short description|Pink lake phenomenon and examples}} {{other uses}} [[File:Lake Hillier 2 Middle Island Recherche Archipelago NR IV-2011.JPG|thumb|Lake Hillier, Western Australia]][[File:Picture of Pink Lake.jpg|thumb|upright|Pink Lake, Victoria, Australia]] [[File:Pink lake.jpg|alt=#Wiki Loves Africa in Namibia 2023#|thumb|upright|Pink lake in Namibia]] A '''pink lake''' is a lake that has a red or pink colour. This is often caused by the presence of salt-tolerant algae that produces carotenoids, such as ''Dunaliella salina'', usually in conjunction with specific bacteria and archaea, which may vary from lake to lake. The most common archaeon is ''Halobacterium salinarum''.
==Causes== Pink lakes arise from a combination of factors, which include climate and hydrology of the continent beneath them, in particular the level of salinity. The orange/pink colour of salt lakes across the world has often been attributed to the green alga ''Dunaliella salina'', but other work has shown that bacteria or archaea are also involved.<ref name="Salleh 2022">{{cite web | last=Salleh | first=Anna | title=Why Australia has so many pink lakes and why some of them are losing their colour| website= ABC News |series= ABC Science| publisher= Australian Broadcasting Corporation| date=4 January 2022 | url=https://www.abc.net.au/news/science/2022-01-05/pink-lakes-why-does-australia-have-so-many/100664354 | access-date=21 January 2022}}</ref>
===Alga=== ''Dunaliella salina'' is the most halophilic (salt-tolerant) alga known and can grow in salinity as high as 35% NaCl<ref name=ie2018>{{cite web | last=McFadden | first=Christopher | title=Lake Hillier: Australia's Pink Lake and the Story Behind It | website=Interesting Engineering | date=24 July 2018 | url=https://interestingengineering.com/lake-hillier-australias-pink-lake-and-the-story-behind-it | access-date=22 January 2022}}</ref><ref name=oren2021>{{cite journal | last=Oren | first=Aharon | title=A hundred years of Dunaliella research: 1905–2005 | journal=Saline Systems | volume=1 | date=2 June 2021 | pmid=16176593 | doi=10.1186/1746-1448-1-2 | page=2| pmc=1224875 | doi-access=free }}</ref> (in comparison to seawater, which contains approximately 3% NaCl).<ref>{{cite web | title=U.S. Geological Survey | website=Why is the ocean salty? | date=26 September 2013 | url=https://www.usgs.gov/faqs/why-ocean-salty | access-date=23 January 2022}}</ref> The single-celled green alga plays a key role in primary production in hypersaline environments around the world. At high salinity, temperature, and light, this alga accumulates the red carotenoid pigment, beta-carotene. This is the same pigment that gives carrots, which contain 0.3% of beta-carotene, their colour.<ref name=ie2018/> ''D. salina'' can adapt to a very wide range of concentrations of salt. The beta-carotene protects the alga against damage from high light, coating the green chlorophyll and giving the alga an orange/red colour. The alga, which was found not to contain a high intracellular concentration, was named after Michel Félix Dunal who first recognised the red colour of certain salt lakes in France was due to an organism.<ref name=oren2021/>
It was thought for a long time that the colour of pink lakes was the result of this alga, as it has been found in many pink lakes.<ref name=cassella/>
===Bacteria/archaea=== Some bacteria and archaea also produce a carotenoid pigment within their cell membranes, which may either contribute to or be the only cause of the pink colouration.<ref name=ie2018/>
In some of the hundreds of Australian pink lakes, a red bacterium, ''Salinibacter ruber'', may be involved in producing their colour. Work done by molecular biologist Ken McGrath at on Lake Hillier, on Middle Island in Western Australia led by molecular biologist Ken McGrath in 2015 showed that, while ''D. salina'' was present in only tiny quantities (0.1% of DNA sampled), while ''S. ruber'' formed 20<ref name="Salleh 2022"/> to 33%<ref name=discovery>{{cite web | title=Here's the Real Reason Why Australia Has Bubblegum Pink Lakes | website=Discovery | date=24 December 2019 | url=https://www.discovery.com/science/Australia-Bubblegum-Pink-Lakes | access-date=22 January 2022}}</ref><ref name=outback>{{cite web | title=Why is Pink Lake on Middle Island, off the coast of Esperance, pink? | website=Australia's Golden Outback | date=18 January 2021 | url=https://www.australiasgoldenoutback.com/whyispinklakehillierpink | access-date=22 January 2022 | others=Includes extract from ''Australian Geographic'' article. | archive-date=12 February 2022 | archive-url=https://web.archive.org/web/20220212134549/https://www.australiasgoldenoutback.com/whyispinklakehillierpink | url-status=dead }}</ref><ref name=cassella>{{cite web | last=Cassella | first=Carly | title=How an Australian lake turned bubble-gum pink | website=Australian Geographic | date=13 December 2016 | url=https://www.australiangeographic.com.au/topics/science-environment/2016/12/australias-pink-lakes/ | access-date=22 January 2022}}</ref>{{efn|Conflicting reports of percentage.}} of the DNA recovered from the lake.<ref name="Salleh 2022"/> They found 10 species of halophilic bacteria and archaea as well as several species of ''Dunaliella'' algae, nearly all of which contain some pink, red or salmon-coloured pigment.<ref name=outback/>
Molecular biologist Ken McGrath, while researching the loss of colour of the lake since the 1990s (attributed to excessive salt harvesting from it), has a hunch{{fact|date=September 2024}} that all pink lakes are caused by ''S. ruber'', rather than ''D. salina'', but proving this is challenging, because bacteria are so much smaller and more difficult to find than algae. A project is being planned to pump more salt into the lake from local agricultural land, where high salinity is a problem.<ref name="Salleh 2022"/> Lake Retba in Senegal, in West Africa, contains the same bacterium.<ref name=ie2018/>
''S. ruber'' produces a pigment called bacterioruberin, which helps it to trap and use light for energy in the photosynthesis process. While the pigments in algae are contained within the chloroplasts, bacterioruberin is spread across the whole cell of the bacterium. This makes it more likely that the colour of the lake is that of ''S. ruber''.<ref name=cassella/>
The archaea ''Halobacterium salinarum'' (formerly ''Halobacterium cutirubrum''), which is pink in colour and generally grows within the salt crust on the bottom of the lake, has been found to be involved in the colour of some pink lakes, such as the lake in Melbourne's Westgate Park. The exact colour of the lake depends on the balance between ''D. salina'' and ''H. salinarium'', with salt concentration having a direct impact.<ref>{{cite web | title=Westgate Park's Pink Lake | website=ToMelbourne.com | date=8 July 2018 | url=https://tomelbourne.com/westgate-parks-pink-lake/ | access-date=23 January 2022}}</ref><ref>{{cite web | title=Pink Lake In The Fringe of CBD | website=Pink Lake In The Fringe of CBD | url=https://www.weekendnotes.com/pink-lake-westgate-park/ | language=af | access-date=23 January 2022}}</ref>
==Characteristics== The majority of pink salt lakes change their colour which is often linked to rainfall. A lake in Westgate Park, Melbourne, Australia, was coloured pink in March 2017<ref name=nyt2017>{{cite web | title=A Lake Turned Pink in Australia. It's Not the Only One. | website=The New York Times | date=10 March 2017 |first=Joanna|last= Klein| url=https://www.nytimes.com/2017/03/10/science/pink-lake-westgate-melbourne-australia.html | access-date=22 January 2022}}</ref> and then again in September 2019, but since then and {{as of|January 2022|lc=yes}} had taken on a dark green hue. Warmer weather and lower rainfall appears to make it turn pink.<ref name="Salleh 2022"/> As water evaporates, the salinity increases, but salinity is not the only factor at work. Sediment and the organisms living in the lake affect its colour, and the shade of pink that it takes on.<ref name=nyt2017/>
Pink lakes such as Lake Hillier can be up to ten times saltier than seawater (the Dead Sea in Israel is around nine times so).<ref name=nyt2017/> It is safe to swim in Lake Hillier, but it is not advisable to drink it owing to the effect of its hypersalinity on the human body, and the possibility of micro-organisms which may be harmful to human health.<ref name=ie2018/> In 2022 extreme rainfall events linked to climate change temporarily diluted Lake Hillier's hypersalinity, disturbing the pigment-producing microbial community and causing the lake to turn blue-gray; scientists expect the pink colour to return within the next decade as evaporation restores salinity levels<ref>{{Cite web |title=Розовое озеро Ретба: природный феномен Сенегала |url=https://retba.ru/ |access-date=2026-05-28 |website=retba.ru}}</ref>.
==Examples== ===Africa=== * Kleinzee Yacht Club in Kleinzee, Northern Cape, South Africa * Lake Natron near Mount Kilimanjaro, Tanzania * Lake Magadi in the Kenyan Rift Valley, Kenya * Lake Retba or Lac Rose, in Senegal<ref name=ie2018/><ref name=best2019/>
===Americas=== * Dusty Rose Lake in British Columbia, Canada<ref name=cassella/><ref name=best2019/> * Laguna Colorada, Bolivia<ref name=nyt2017/><ref name=best2019/> * On the Yucatán Peninsula, Mexico<ref name=nyt2017/>
===Asia=== thumb|Lipar Pink Wetland, Chabahar, Iran * Aralsor, Kazakhstan * Burlinskoye, Altai Krai, Siberia, Russia<ref>{{cite web | title=Why a Train Runs Directly Through This Pink Lake in Siberia | website=The Drive | url=https://www.thedrive.com/news/39789/why-a-train-runs-directly-through-this-pink-lake-in-siberia | access-date=26 May 2023| date=March 2021}}</ref><ref>{{cite web | title=Crimson treasure of Siberia, the salt lake that turns pink on sunny days | website=The Siberian Times | url=https://siberiantimes.com/other/others/features/crimson-treasure-of-siberia-the-salt-lake-that-turns-pink-on-sunny-days/ | access-date=26 May 2023| date=July 2019}}</ref> * Koryakovka (lake), Kazakhstan * Krasnovishnevoye, Novosibirsk Oblast, Russia * Lipar Pink Wetland in the Chabahar, Sistan, Iran * Lonar Lake in Maharashtra, India * Malinovoye, Altai Krai, Siberia, Russia * Masazirgol (Masazir Lake), near Baku, Azerbaijan<ref name=best2019/> * Maharloo Lake near Shiraz, Iran
===Australasia=== * Champagne Pool, Waiotapu thermal region, New Zealand<ref name=best2019/> * Hutt Lagoon in midwest Western Australia, covering {{cvt|70|km2}}<ref>{{cite web | title=Feature by Simon Webster The amazing pink lakes of Western Australia | website=Western Australia | url=https://www.westernaustralia.com/en/plan_your_trip/travelstories/pages/the_amazing_pink_lakes_of_western_australia.aspx | access-date=22 January 2022| date=October 2018}}</ref><ref name=best2019/> * Lake Bumbunga near Lochiel, South Australia * Lake Grassmere, near Marlborough, New Zealand<ref>{{cite web | title=World Famous in New Zealand: Marlborough's startling alien-like salt lake | website=Stuff | date=12 December 2021| first=Pamela| last=Wade | url=https://www.stuff.co.nz/travel/destinations/nz/marlborough/300469527/world-famous-in-new-zealand-marlboroughs-startling-alienlike-salt-lake | access-date=22 January 2022}}</ref><ref>{{cite web | title=Lake Grassmere Saltworks | website=Marlborough, New Zealand | date=21 January 2021 | url=https://www.newzealand.com/au/feature/lake-grassmere-saltworks/ | access-date=22 January 2022}}</ref> * Lake Hillier in the Recherche Archipelago, Western Australia<ref name=best2019/> * Pink Lake (Western Australia) near Esperance *Pink Lake (Quairading), at Badjaling, near Quairading, WA<ref name=best2019/> * Pink Lake (Victoria) in the Murray-Sunset National Park, in the state of Victoria, Australia<ref name=best2019>{{cite web | title=Top 10 Best Pink Lakes In the World | website=Traveleering | date=19 August 2021 | url=https://traveleering.com/10-best-pink-lakes-world/ | access-date=22 January 2022 | archive-date=22 January 2022 | archive-url=https://web.archive.org/web/20220122103727/https://traveleering.com/10-best-pink-lakes-world/ | url-status=dead }}</ref>
===Europe=== * Koyashskoye Salt Lake, on the southern coast of Kerch Peninsula, Crimea, Ukraine * Las Salinas de Torrevieja, near Torrevieja in Alicante province, Spain<ref name="nyt2017" /><ref name="best2019" /> * Lake Lemuria, in the Kherson region of Ukraine<ref>"[https://oktv.ua/turizm/mertvoe-rozovoe-ozero-hersonshchini--put-k-istseleniyu Мертвое Розовое озеро Херсонщины – путь к исцелению , Портал oktv.ua]". oktv.ua. Retrieved 2021-01-19.</ref> * Les Salins d'Aigues-Mortes, in the Camargue in France * Pačir lake, Bačka Topola, Serbia
== See also == * Watermelon snow
==Footnotes== {{notelist}}
==References== {{reflist}}
==External links== *{{cite web | website=Atlas Obscura | url=https://www.atlasobscura.com/videos/why-is-lake-hillier-in-australia-bright-pink| format= Video| title=Why Is This Lake in Australia Bright Pink?}} Video of Lake Hllier. {{portalbar|Lakes}}
Category:Lakes by type