“One of the tragedies of Baikal is that top-level, senior scientists who are themselves never on a field expedition mistakenly believe that the lake can never be eutrophied because it is too huge, too pure and full of too much water,” Dr. Timoshkin said. “It’s an easy idea to have, but it’s wrong.”

Even as federal aid stalls, some people are attempting to address the problems where they live, organizing beach cleanups and trying to find ways to put the thousands of pounds of washed-up Spirogyra to use as fertilizer or material for making traditional Siberian paper.

Marina Rikhvanova, an award-winning environmental activist in Irkutsk who helped raise initial awareness about the Spirogyra outbreaks, persuaded a local investor to fund a plan for a prototype sewage treatment plant. “More and more people with various specialties and interests are working together for the lake,” she said. “This, at least, is a source of optimism.”

Eutrophication, however, is not the only threat to Lake Baikal.

Mongolia is planning to build up to eight hydroelectric dams on the Selenga River and its tributaries, the source of 50 percent of Lake Baikal’s surface water. Despite hearings and protests in Russia and Mongolia, the Mongolian government — which imports around 8 percent of its energy from Russia and 12 percent from China — argues that the dams will help achieve energy independence and cut back on coal use.

Some experts think there must be a better way. Mongolia can technically produce around 100 gigawatts of power from wind and solar in their part of the Gobi Desert alone — about 90 times the country’s current capacity, said Eugene Simonov, an international coordinator with the nonprofit Rivers Without Boundaries Coalition.

“Instead, the plan is to first build dams, then to develop a huge capacity to produce thermal energy from coal, then to build the next generation of big dams to offset the negative effects of coal on the climate and then, finally, to use some of the proceeds to build true renewables.”