A Natural Phenomenon that has to be seen to be believed
Australia is blessed with natural wonders of the world that are truly remarkable and magnificent in their entirety. Have you ever wondered what it would feel like if you saw one of those wonders you never thought was possible to exist? Sparkling volcanos? Floating mountains? A colony of Unicorns? Well not unicorns, otherwise wouldn’t it be awesome if it was actually possible to see unicorns if they exist! No, its the Pink Lakes that are located across Western and South Australia.
Let the imagination flow…..
Imagine you are driving along the countryside using Google maps as your primary source of navigation, because what would we do without Google maps? We would get lost if not for our extremely helpful online friend acting as a guide to lead the way. While driving along you suddenly see a pink spot that looks like a lake? A giant spill of Strawberry juice? Melted candy floss? You look at your Navigation and just see a big blue area that signifies the presence of a lake, but guess what? You are seeing a pink lake! Australia has majestic lakes that is a popular tourist attraction namely Lake Hillier that is found on Middle Island in the Recherche Archipelago, a set of islands around 130 kilometres off the coast of Esperance in south-west WA.
By Adolf Engler, K. Prantl – Die natürlichen Pflanzenfamilien : Abt. 1a-Abt.1b. Euthallophyta, Unterabt. Schizophyta (Spaltpflanzen): Nebst ihren Gattungen und wichtigeren Arten, insbesondere den Nutzpflanzen By Adolf Engler, K Prantl Published by Engelmann, 1911, page 17., Public Domain, https://commons.wikimedia.org/w/index.php?curid=6598779
So why is the lake pink?
Before you actually leap towards swimming in the lake, it is actually concentrated with lots of salt rendering the lake salty. The distinctive pink colour of the lake is due to the presence of microorganisms such as algae and bacteria in the waters. Algae are organisms that have a pigment that helps them to perform photosynthesis, but they do not possess the anatomy of a plant such as roots, shoots, stems and leaves. Bacteria are single celled prokaryotic organisms that exists in a variety of shapes.
Now let’s delve into the science details of these microorganisms that are responsible for the pink coloured appearance of the lake. The algae that is responsible for the bright pink appearance is Dunaliella salina. D.salina is well adapted to the salty environment where other algae cannot. The optimal growth of D.salina is at the concentration of 1.5-3.0 M of Sodium chloride(NaCl) which is essentially a chemical name for salt. This is 3-6 times more concentrated than the average salt concentration of seawater amongst the beach shores!.
The reason why the algae thrives in salty environments is due to the absence of a definite cell wall, allowing it to expand and contract to maintain a liveable internal salt concentration. A sudden increase in salinity in the waters enables the initial growth of the algae at the start. The final growth of the algae is dependant upon the final magnitude of the salinity in the lakewaters. Salinity in simple terms refers to the salt concentration in the waters. Furthermore, D.salina is pink because it has very high levels of a carotenoid pigment called Beta carotene. It might be interesting to know that Beta carotene is a pigment responsible for the orange colour of carrot juice and other distinctive colours of fruits and vegetables.
Genetic analysis of the lakewater also revealed the presence of a bacteria called Salinibacter ruber, a salt loving microorganism that produces a red pigment. Salinibacter ruber thrives in salt concentrations ranging between 20-30%. The bacteria produces a pigment, called bacterioruberin, which helps the organism harvest light for energy. Bacteriorubin is spread across the entire bacterial cell that also contributes to the pink colour of the lake.
The lake is not always pink
The bright colours of these lakes are influenced by external factors such as climate and weather. The pink colour is most visible on warmer months and after rainfall. Rainwater enables nutrients and minerals to wash onto the lakes that are beneficial for the microorganisms like algae and bacteria to thrive. As a result of these factors, the colour of the lake varies from bright pink to lilac purple.
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