Yury Azhichakov set out early by bike for Senogda Bay, his favorite beach, on the northwestern shore of Lake Baikal in Siberia. The world’s oldest, deepest and most voluminous lake, Baikal holds 20 percent of the planet’s unfrozen freshwater. It is often described as the world’s cleanest lake.
    As Mr. Azhichakov discovered, that is no longer the case. Senogda’s once pristine sands were buried under thick mats of reeking greenish-black goo.
    “This stuff stretched far into the distance, for several kilometers,” said Mr. Azhichakov, 61, a retired ecological engineer. “The beach was in terrible condition.”
    The muck, scientists have discovered, follows mass algal blooms at dozens of sites around Lake Baikal’s 1,240-mile perimeter. Confined to shallow water and shores near towns and villages, the problem seems to stem from an influx of untreated sewage – the result of inadequate wastewater treatment.
    Algal blooms threaten iconic freshwater bodies around the world, including the Great Lakes, Lake Geneva, and Lake Biwa in Japan. But Lake Baikal is especially precious: a World Heritage site home to more than 3,700 species, more than half found nowhere else.
    “People are dumping sewage, waste and rubbish around the lake, creating pretty appalling conditions in some places,” said Anson MacKay, an environmental scientist at University College London.

Disponível em: www.nytimes.com. Acesso em: 15 nov. 2018 (adaptado).

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