A preliminary study of Pangong lake’s bacterial community structure along the contested India-China Line of Actual Control in Ladakh has shed light on the influence of increased human actions on the Indian side of the high-altitude saltwater body.

Researchers at National Center for Microbial Resource-National Center for Cell Science, Pune unpacked details of sticky microbial assemblages, called biofilm, near the Pangong Tso shore adjoining Maan village in Ladakh, India.

A biofilm is a sticky, viscous, slimy, structured assemblage of single or multiple microbial species (mixed species) that can grow on many different surfaces. In a biofilm, bacteria are held within a non-crystalline extracellular matrix of proteins, polysaccharides, and small molecules. Dental plaque, for example, is a biofilm.

“Microbial films are formed in response to increasing nutrient inputs; Pangong Tso is a landlocked lake, and we do not expect the inflow of nutrients to this lake from other sources, so anthropogenic sources are the most probable cause,” said environmental microbiologist Praveen Rahi of National Centre for Cell Science, Pune.

Researchers used massive/massively parallel sequencing technique that involves sequencing of large numbers of DNA templates simultaneously, to decipher the composition of bacterial communities in water, sediments with microbial biofilms, and sediments without biofilms from the Pangong Tso’s nearshore zone near Maan village.

Bacteria play an important role in biogeochemical cycles in different ecosystems, including lakes, and are sensitive to fluctuations in the external environment. In the recent past, many lakes worldwide have been affected by eutrophication, mostly due to an increase in external nutrient inflow to these lakes.

“Our research indicates the impact of increased human activity, especially from tourists staying in the villages near Pangong Tso that may trigger a change in the lake ecosystem,” said Rahi. “More detailed studies are required to confirm the triggering factor for biofilm formation. Much stronger policies are required to protect this pristine lake ecosystem, and appropriate actions are required to dispose of human waste.”

Hugged by the arid Himalayan mountains at 4,266-metres above sea level, the long and narrow Pangong Tso (Tso means lake regionally) is bisected by the India-China LAC with part of the lake controlled by India. It is a saline and alkaline lake, which remains frozen for about three months during winters and holds low biodiversity of fishes, phytoplankton, etc, due to such harsh environmental conditions. The lake receives glacier meltwater in summers, while water loss occurs only through evaporation as it is a landlocked lake.

Scientists underscore the importance of a deeper understanding of high-altitude lakes as lake ecosystem changes can point to climate change-associated aberrations early on. They are impacted by regional and global factors such as global warming-driven glacier melt that may send surging levels of meltwater into high altitude lakes, upsetting the water’s alkaline and acidic balance and influencing bacterial communities. According to the Intergovernmental Panel on Climate Change, species composition and abundance have markedly changed in high mountain ecosystems in recent decades, partly due to changes in the cryosphere.

Biofim (an assemblage of microbes in response to nutrients) on Pangong Tso sediment (a pebble). Photo credit: Praveen Rahi

Anand Jain of the National Center for Polar and Ocean Research, who was not involved in the study, said Pangong Tso is an ideal site for monitoring the impact of climate change and human activities on the lake system. “Pangong Tso is a glacial lake that receives meltwater of the glaciers in summers,” Jain said. “Due to its geographical location in-between the Indo-China LAC, it has been facing a lot of human activities due to militarisation as well as tourism.”

Jain said the National Centre for Cell Science-Pune study offers a starting point for a more detailed and comprehensive evaluation of high altitude lakes’ ecosystem health using microbial biofilms as indicators. “More detailed and long-term monitoring studies are required to evaluate the impact of climate change and human activities on the lake ecosystem,” Jain told Mongabay-India.

An influx of nutrients for bacteria

The proliferation of specific phyla, like Verrucomicrobia, Deinococcus-Thermus and Cyanobacteria favoured in the microbial biofilm samples near Maan, points to an increase in nutrients like nitrogen and phosphorus and suggests carbon fixation and cycling in this lake.

“The inflow of nutrients like nitrogen and phosphorus may lead to cyanobacterial growth, which is a carbon-fixer and promotes the growth of specific bacteria,” reiterated Rahi. “We noticed such microbial biofilm formation near the village Maan, which has many tent house accommodation near the lake’s banks. Therefore, we hypothesis that human activities might lead to an increase in the inflow of such nutrients into the lake.”

While the researchers did not find anything unexpected, they unravelled exciting observations, which need further validation: the higher abundance of Deinococcus-Thermus in the biofilm samples. “These organisms (extremophiles) can withstand ultraviolet radiations and extremes of temperatures, and in Lake Gudzhirganskoe (Russia), their higher abundance was linked to the indirect evidence of groundwater inflow from a thermal spring. Till now, we did not find any information on the inflow of thermal spring at Pangong Tso,” said Rahi.

The relative abundance of Enterobacter was higher in sediment samples, which was not unusual as the sampling site was close to the village, and human activity is expected. Enterobacter are natural residents of the human intestinal tract, soil, water, animals, plants and are common in foods. They are the cause of various hospital-acquired infections in immunocompromised patients. A similar pattern on the increased abundance of Enterobacter was linked with the increased anthropogenic activities in Russia’s Khakassia saline lakes.

“The bacterial communities of Pangong Tso are similar to other high-altitude saltwater lakes (Qinghai Lake, Erhai Lake, Gahai Lake, and Chaka Lake) and pro-glacial channels and the associated downstream fjord ecosystem of a valley glacier in Svalbard, as all these ecosystems receive sediments and nutrients from glacial meltwater,” said Rahi.

Pangong Tso sediments without biofilm formation. Photo credit: Praveen Rahi

Lake sensitive to climate change

The study builds upon research such as a 2011 paper on Pangong lake’s ecology and biodiversity and its inlet stream in Ladakh by Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir. Anand Jain adds that high altitude lakes are sensitive indicators of climate change, as they are less influenced by anthropogenic activities than the other habitats.

“However, medium and long-range transport of atmospheric pollutants, alien species introduction, tourism, mountain farming, and climate change are posing serious threats to these pristine ecosystems,” said Jain. “Therefore, it is important to study the impact of these processes on the high altitude lakes’ biodiversity and microbial ecology.”

It was tough to look for information on the Pangong lake, divulged Rahi, but “old books” came to his rescue.

“There were very few studies on bacterial communities of the Pangong Tso, but there is enough information available on high-altitude lakes across the globe,” he elaborated. “It was really difficult to find information about the Pangong Tso in general. I read a very old book like The Jummoo and Kashmir territories: a geographical account (Frederick Drew, 1875) and found an old article Pangong: A Glacial Lake in the Tibetan Plateau (Ellsworth Huntington, 1906), but I enjoyed reading these old descriptions of Pangong Tso.”

The lake’s physical-chemical properties on the Chinese side are different from the Indian side because Rahi explained, the “Chinese side receives most fresh meltwater. The water on this side of the lake is drinkable. On the Indian side, the water is alkaline and has high salt concentrations. A recent study on Pangong Tso published in Current Science highlighted the shift in the level of this lake.”

Apart from building on the ecological data on Pangong Tso, data from such studies aid conservation education which is essential in the light of the shifting baseline syndrome. Due to short life-spans and faulty memories, humans have a poor conception of how much of the natural world has been degraded by our actions because our “baseline” shifts with every generation, and sometimes even in an individual. In essence, what we see as pristine nature would be seen by our ancestors as hopelessly degraded, and what we see as degraded our children will view as “natural”.

“We are inherently influenced by our sense of what is ‘normal’ and what are acceptable changes from that starting point,” added Rahi. “In Pangong Tso, its water is crystal clear with no visible turbidity. Even the sediments, including the pebbles and small rocks, are devoid of any visible biofilm or microbial mats and have been considered a pristine lake. What we now think degraded or the initiation of degradation might appear to be pristine for future generations. Shifting Baseline Syndrome can lead to underestimation of ongoing ecological decline.”

Biofilm formation on sediments near Maan village along Pangong Tso. Photo credit: Praveen Rahi

This article first appeared on Mongabay.