Code Pink: Why do lakes change colour?
In July, the Lonar Lake in Maharashtra turned bright pink. Some gawked at the marvellous overnight makeover, others were concerned that it might have been caused by a dangerous pollutant.
For locals however, life at the edge of an oval-shaped lake that formed after a meteorite hit the earth some 50,000 years ago suddenly got a lot more interesting. Many fielded endless calls and texts from friends and acquaintances about the strange development. “For months, people who wanted to visit kept asking ‘Is this true?’ ‘Did someone colour the water?’ ‘Is the colour still the same?’,” says Sailesh Sadar, a local tourist guide. For Zahir Sheikh, who works on short contract projects for the forest department, the rise in tourist interest during the pandemic was also a concern.
But Lonar Lake’s water turned back to its green colour in around two weeks. And it turns out, there is not much to worry about. Water bodies tend to change colour when an already saline lake sees an increase in salinity even when nothing but some algae and bacteria grows, says Prashant Dhakephalkar, microbiologist and director of the Pune-based Agharkar Research Institute.
Dhakephalkar was part of the team that submitted a report to the government about this phenomenon at Lonar. He says the pink was caused by a combination of factors, and precipitated by the lockdown. The lake’s rocks are basaltic, which makes the water highly saline. This salinity gets diluted with the rains. But with high temperatures and fewer visitors in 2020, there was greater evaporation, increasing the salinity of the water by around 6%. “It caused a growth of halophilic microorganisms or salt-loving bacteria which outgrew other organisms. Some of these bacteria produce a pink pigment which gave the pink colour to the lake,” he says. The colour is restored when the salinity goes down again.
Social media reports show that it happens everywhere. In the UAE’s Ras Al Khaimah emirate, a pink lake was discovered just last month, with high salinity the cause once again. Experts there say that excess salt turns some lakes pink every year in that area. The ones that have stayed pink for a long time, such as Lake Hillier in West Australia and the Great Salt Lake in Utah, have become popular tourist destinations. When the lake at Hutt Lagoon in Australia turned pink in 2014, it even became a sort of status symbol. Wealthy Chinese tourists flocked to the region, to show off that they had travelled somewhere unique.
But tourists might not always get the shade of pink they seek, or saw in touched-up social-media posts. In Lonar, the hue faded in around two weeks, and even at their most intense, pink lakes are rarely as opaque as the pictures make them seem. Pink Lake in Esperance, Australia, lost its pink hue around 2007 because of changes in natural water flow, reduced evaporation, and salt harvesting. Now, scientists are working out a way to give it back its colour.
Faiyaz Khudsar, wildlife biologist and scientist-in-charge at the Yamuna Biodiversity Park, has been working on ecological diversity and its restoration around water bodies. He says there might be an economic upside to this phenomenon. “The colour comes from the carotenoids present in the algae and bacteria which are the only life in this water,” he says. “These carotenoids can be used to make anti-oxidants for dietary supplements and even cosmetics.”
For the moment, we can neither predict a colour change not hold on to the hue. And in a time when we’ve struggled stay in control of the world around, the mystery posed by a colour changing lake is perhaps the best way to celebrate serendipity.