An aerial view shows hoverboats on the ice of lake Baikal near the village of Bolshoye Goloustnoye in Irkutsk region, Russia, March 8, 2021. Lake Baikal remains one of the world's cleanest fresh water reservoirs. But pollution and the growth of weeds are harming microorganisms, sponges and some molluscs that filter its waters. The Baikal pulp and paper mill and its sewage treatment facilities were closed seven years ago, but pollution has spread significantly since then, according to local media. That, some experts say, is because pollution left behind at the industrial site is draining into the lake. Picture taken with a drone. REUTERS/Maxim Shemetov SEARCH "GLOBAL WATER" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES TPX IMAGES OF THE DAY