Over a year ago in June 2020, the Lonar Lake in Maharashtra’s Buldhana district underwent an unusual change. The water in this 52,000-year-old lake suddenly turned pink, leaving many confused and worried. Since this incident happened in a lake that had its own touristic importance, the matter was highlighted in the national and international media. The government also came into action and ordered tests to find the reason behind the water turning pink. While some speculated that it was the effect of global warming, many superstitious theories also popped up.
However, this was not the first time that something like this had happened. In fact, there are several lakes across the globe that have a natural pink colour.
So, what causes this change of colour? Well, the one thing common in all the instances of pink lakes is that they all have salty water. The salinity of water produces different types of microbes that cause pigmentation water resulting in colour change.
In the case of Lonar Lake, studies revealed that the change in colour was caused by Haloarchaea or halophilic archaea bacteria which is found in water saturated with salt. The absence of rain, high temperature and less human interference during the COVID-19 lockdowns, had resulted in the evaporation of water which increased the salt and pH Value of the water.
The increased salinity gave a suitable environment for the growth of halophilic microbes which eventually led to the water turning pink. As the biomass of these bacteria grew, the water turned pink and returned to its original colour with the fall in the biomass.
The Lonar lake also turned to its natural colour with fresh rainwaters allowing the dilution of water and bringing the pH level down. Further, it was found that Haloarchaea microbes were ingested by Flamingos. These microbes acted as pigment-rich food for the birds. Flamingos get their red pink colour from special colouring chemicals called pigments found in the algae and invertebrates they eat.
While the water of these lakes may not be suitable for drinking, it can be used for other purposes. Even swimming in it has no harm.
But unlike the Lonar lake, many permanent pink lakes like Australia’s Hutt Lagoon or Lake Hillier do not change their colour because the water salinity and pH remain constant. Incidents of lakes turning pink were also reported in Argentina earlier this year, however, in their case, the change in the colour was caused by the infusion of preservative sodium sulfite.
The antibacterial preservative was used by fish factories for preparing shrimp and prawns for exporting and left behind a foul smell. The move to use harmful preservatives was slammed by environmentalists and common citizens who said that it was harming the ecological balance.
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