Lake Retba has lost its vibrant pink hue this rainy season. As can be seen from the “before and after” with the satellite imagery of NASA’s Earth Observatoryit is shown how the waters of the rosy lake have turned a more typical blue-green following a downpour of torrential rain.
Lake Retba is located in Senegal, West Africa and it owes its coloring to unicellular algae called Dunaliella salinaan alga that is typically green, but produces protective red-orange beta-carotene pigments under difficult conditions, and we see an example of this phenomenon in this lake.
Because the lake can be flooded by the waters of the Atlantic Ocean, it turns out to be super salty, and in fact, the water is so rich in salinity that people can easily float in it just like in the Dead Sea.
While this is good for salt miners, the high-salinity water stresses D. salina and forces them to pump out protective pigments, resulting in the usually eye-catching color of the lake.
Other special features on the Retba lake
The lake is typically more pink during the dry season between November and Junebut the color fades during the region’s rainy season, July to October, when the salty waters are diluted by rainwater.
This rainy season proved to be exceptionally rainy, with heavy rains in early August and early September causing deadly flooding in the capital Dakar and surrounding areas.
Another consequence of this was the flood that reached Lake Retba and inundated it with fresh water, and as a result, the resident algae stopped producing its protective pigments and the lake returned to a greenish color.
All of this was captured by Landsat satellites that rotated the globe in low earth orbit, with the images being released recently showing Lake Retba on May 19 looking beautiful and rosy, while another image, taken on September 16, then shows the lake appearing roughly the same color as the nearby Atlantic Ocean.
Lake Retba isn’t the only body of water with this distinctive pink color. The Lonar lake is located in a meteorite impact crater in India, about 500 kilometers (311 miles) east of Mumbaiand also in this case, just like the pink lake of Senegal, this water often takes on a vivid shade of pinkish red due to the salinity and the presence of the same algae.
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