Pink hue in Lonar Lake due to salt-loving bacteria, says report
Scientists have identified salt-loving bacteria as the reason for change in water colour at Lonar Crater Lake in Buldhana in June, which could also hold true for the pink hue spotted at Talawe wetlands in Navi Mumbai in May.
A report by Agharkar Research Institute (ARI) in Pune, an autonomous body under the Department of Science and Technology, said the change in water colour from green to pink was due to the dominance of a pink pigment producing halophilic microbes that grow in an extremely high-saline environment giving a bright pink or reddish appearance.
The report, released on Thursday and received by the state forest department on Friday, will be submitted before the Nagpur bench of Bombay high court (HC) on July 22.
“Change in colour was due to a salt-loving bacteria (red-coloured archaeal strains classified as halophilic archaea or haloarchaea). It is associated with high salinity and alkalinity (pH),” said Prashant K Dhakephalkar, director of ARI, who carried out the study with Monali Rahalkar, Sumit Dagar, and Karthik Balasubramaniam.
A section of the flamingo feeding ground at Talawe wetlands near NRI Complex in Navi Mumbai also witnessed a similar change in water colour in May. “While we did not collect samples from Navi Mumbai area, a similar phenomenon could hold true as characteristic changes in surface water were similar. However, more research is needed,” said Dhakephalkar.
Meanwhile, flamingo presence was reported at Lonar Lake in December 2019 and February 2020. ARI’s study identified this as an incidental observation and a unique aspect that might be related to the change in colour. “Flamingos have characteristic pink plumage caused from carotenoids ingested from carotenoid-abundant food sources. Whenever these birds consume food having high halobacterium growth (rich in carotenoid), it helps them gain this pink plumage,” said Dhakephalkar.
Manoj Khairnar, deputy conservator of forest, Akola, confirmed flamingo numbers were much higher at Lonar lake this year. The Bombay Natural History Society (BNHS) had said 25% more flamingos had visited Mumbai wetlands this migratory season, surpassing 1.5 lakh in April alone.
The presence of deep pink colour was noticed towards a section, enclosed from three sides, towards the southeastern end of Talawe from May 13-19. “The enclosed section from three sides allowed stagnation of water where salt concentration increased, allowing rapid bacteria growth,” Dhakephalkar said.
The surface water at the 113-hectare Lonar Lake turned reddish-pink during first week of June. Worried about increasing water pollution, the Maharashtra forest department requested ARI Pune and the National Environmental Engineering Research Institute (NEERI), Nagpur to assess the cause of discolouration. “NEERI will be submitting its report directly to the HC next week. Open defecation and sewage discharge was a cause of concern but ARI’s report denies any increase in water pollution,” said Khairnar.
At Lonar Lake, alkaline (pH) levels were 9.8 as opposed to 7 which is neutral. Salinity was over 6%, whereas over 3% is considered a high-saline environment, said Dhakephalkar adding, “Due to the lockdown there was no dilution in water. High-salinity and pH allowed rapid conducive growth of halobacteria. When the rains set in both parameters dropped, and green algae growth allowed normal water colour to return.”
The study also reported presence of an algal species (Dunaliella algae) in Lonar Lake, previously reported from Mumbai saltpans and Rajasthan’s Sambhar Lake. “We initially thought the pink hue was an algal bloom, but on studying water samples we realised that halobacteria population was much higher than algae.”