Pink lake

Key takeaways

Pink lake belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Pink lake to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Pink lake from memory before moving on to harder problems.

Reference excerpt

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.

Alga Dunaliella salina is the most halophilic (salt-tolerant) alga known and can grow in salinity as high as 35% NaCl (in comparison to seawater, which contains approximately 3% NaCl). 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. 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. 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.

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. 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 to 33% of the DNA recovered from the lake. 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. 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 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. Lake Retba in Senegal, in West Africa, contains the same bacterium. 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. 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.

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 and then again in September 2019, but since then and as of January 2022 had taken on a dark green hue. Warmer weather and lower rainfall appears to make it turn pink. 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. 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). 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. 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.

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

Americas Dusty Rose Lake in British Columbia, Canada Laguna Colorada, Bolivia On the Yucatán Peninsula, Mexico

Asia

Aralsor, Kazakhstan Burlinskoye, Altai Krai, Siberia, Russia 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 Maharloo Lake near Shiraz, Iran

Australasia Champagne Pool, Waiotapu thermal region, New Zealand Hutt Lagoon in midwest Western Australia, covering 70 km2 (27 sq mi) Lake Bumbunga near Lochiel, South Australia Lake Grassmere, near Marlborough, New Zealand Lake Hillier in the Recherche Archipelago, Western Australia Pink Lake (Western Australia) near Esperance Pink Lake (Quairading), at Badjaling, near Quairading, WA Pink Lake (Victoria) in the Murray-Sunset National Park, in the state of Victoria, Australia

Europe Koyashskoye Salt Lake, on the southern coast of Kerch Peninsula, Crimea, Ukraine Las Salinas de Torrevieja, near Torrevieja in Alicante province, Spain Lake Lemuria, in the Kherson region of Ukraine Les Salins d'Aigues-Mortes, in the Camargue in France Pačir lake, Bačka Topola, Serbia

Illustrations

Worked examples

Example 1 — a first encounter with Pink lake

Start with the simplest possible case. Write down what Pink lake claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Pink lake before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Pink lake ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Pink lake

In research: Pink lake appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Pink lake in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Pink lake is common in secondary-school and first-year university syllabi. It links to neighbouring topics Lakes by type, so understanding it makes those chapters shorter.
In everyday life: Look for Pink lake outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Pink lake in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Pink lake means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Pink lake out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Pink lake in simple terms?

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.

Why does Pink lake matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Pink lake?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Pink lake.