A lake that has been referred to as a strawberry milkshake or a bubblegum lake, but does anyone truly know why its so incredibly pink?

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Lake Hillier, Australia – Source Extreme Microbiome

Lake Hillier is a lake located on the middle Island that make up Recherche Archipelago, Western Australia. The lake is 600 metres in length so it is not the size that you will find spectacular but the unusual pink coloured water body. It is a highly saline lake ten times saltier than the ocean to be precise, and sits at the edge of the island where it is separated from the Southern Ocean by a strip of vegetation and surrounded by a mixture of both sand and vegetation.

A lake with history

The unusual pink lake was first discovered in 1802 by and English navigator and cartographer: Matthew Flinders. It was a year later in 1803 that he named the lake, he named it after a crew member that died that year from dysentery; an infection of the intestines.

A few years later in 1889 a European had the idea to extract the salt and utilise it, this then proceeded and the lake was used for salt mining. However, the salt from the lake had toxic properties and mining stopped. The salt mine at Lake Hillier was closed six years after opening and many years later it became part of the Recherche Archipelago Nature Reserve, thus giving it a protective status where it is only available to scientists working, and the public section is highly restricted.

So why is it pink?

The lakes peculiar colour has baffled scientist creating an abundance of research into the reasons as to why the water is this pink colour. This is unusual as even when the water is removed from the water mass it is able to retain its pink hue, meaning that it is something within the water itself causing it to be coloured, as if the water has been dyed.

There has been much speculation about what causes the water to be pink, the reasoning behind the water colour has not been definitely identified yet but some scientists believe that it a caused by a microalgae.

So, what causes this pink colour you ask? It has been researched and explored to find out that there the potential cause is that the lake has a salt – loving microalgae living within it called Dunaliella salina, often found in salt based water such as; ponds and lakes. This is because D.salina is responsible for the primary production in hyper-saline environments (environments where the water salinity is greater than that of seawater). It has been observed that this microalgae can produce a pigment called carotenoid, which is a compound that absorbs light similar to the pigment beta carotene which is found in carrots and red cabbage. Duneliella salina has the ability to produce carotenoid in large amounts and this pigment which is found in the microalgae is soluble (dissolves in water) and is also used in cosmetics and dietary supplements. This gives reasoning as to why the water when removed from the lake is still pink, because initially the water has been dyed by the pigment produced by D. Salina. It has also been found that there are pink halophytic bacteria that live within the salt crusts around the edge of the lake and this can also be a contributing factor to the pink water colour.

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Dunaliella salina a microalgae found in Lake Hillier – taken from google images

There have also been many other speculations made as to why the lake is pink, such as that it is in fact no D.salina that causes the colouration but a combination of nutrients found in the water adding to the natural activity of bacteria and other algae found within Lake Hillier.

The importance in Science

Lake Hillier receives a large amount of attention from scientists and the public due to its obvious bright pink colour. Its pink water colour seems to mesmerise scientists and research into the saline lake show that the surrounding habitat serves as a base to a substantial amount of research. The lake and its habitat have been studied by two foundations: Association of Biomolecular Resource Facilities and The Extreme Microbiome Project) that concentrate on microbes which is why Lake Hillier is such a fascinating habitat to them. The research carried out makes the effort to find out the mysteries of the microorganisms and the adaptation that they have in order to live in such a high salt concentrated place.

Lake Hillier and its surrounding habitat has a high bird biodiversity and is under no threat due the it being heavily protected. The nature reserve has a limited tourist visitation policy and only licensed operators are permitted to operate there. Making the lake and its habitat free from anthropogenic threats (environmental pollution caused by humans) and any human intervention, unless by scientific research.

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Salt crusts and vegetation of Lake Hillier – Source Extreme Microbiome

Other pink lakes of the world

There are many other pink lakes that have been discovered around the world, places such as Spain, Canada, Senegal. These other pink coloured lakes have been found to have similar properties as Lake Hillier, in the way that they are high in salt content and algae to create the pink coloured water however they are dependent on the quantity of sunlight that interacts with the algae. The lake that does not have any similar properties is a lake in Canada. The Dusty rose lake in Canada is an exception as it is not highly saline but in fact formed by glacial melt and its pink colour is due to minerals, which actually have a pale purple hue.

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