What the researchers found was alarming: diatoms have been declining rapidly as the lake gets warmer. This is bad as these algae provide essential nutrients to other creatures in the water, such as plankton, fish and the world’s only freshwater seal, the Nerpa, found only in Lake Baikal. Currently, the Nerpa are safe, but “the potential risk is that as diatoms change, this could, in time, lead to impacts further up the food chain that ultimately impact the Nerpa and their food,” Swann said.

The scientists found that other diatoms have been replacing the native diatom species. The invading diatoms, found more commonly in other parts of the world, are lighter and have grow faster. This change is having a ripple effect on the lake, causing a shift in feeding patterns, and possibly the lake’s natural cycle of energy and nutrients.

Lake Baikal is located in mountainous Siberia, in southern Russia. Source: Google Maps

“We already see changes in population numbers of different types of zooplankton which eat the algae,” Swann said. “We can also speculate that a warmer lake may become more vulnerable to invasive species, several of which, including some aquatic plants, have already gained a foothold in the bays and coastal reaches.” The scientists learned about changes in the ecosystem by examining sediment drawn from the lake.

“After death, diatoms sink through the water column with their fossilized remains accumulating alongside other mud at the bottom of the lake,” Swann said. “We collected mud that contains these fossils from across the lake, and used a microscope to examine what species were present. By then dating this mud, we can see how the diatom species have changed across Lake Baikal over the last 100 years.”

While the entire lake is warming, the decline of native diatoms currently is confined to only one part of the lake, its south basin. Also, while the shoreline of Lake Baikal is suffering from pollution — there already are algae blooms along long stretches of the shoreline — there is no evidence yet that it is hurting diatoms in the deeper open waters.