Low water level in the Selenga River and reduction of silica input to Lake Baikal

摘要

The main producer of organic matter in Lake Baikal is diatoms, whose development largely depends on silica concentrations in the lake water. Silica is introduced to the lake from inflowing surface waters. The Selenga River, the main tributary of the lake, delivers ～50% of the total surface water inflow and more than half of the chemical inputs to Lake Baikal. The average annual input of silica to the lake is ～114 000 t during years when water level in the river approximates the long term average. The period under study (2001–2017), however, was characterized by exceptionally low water levels in the Selenga River and an annual average reduction of silica input to Lake Baikal up to 56 000 t. Since the beginning of the 21st century, the total deficit of silica input to the lake from the Selenga River is ～650 000 t. Currently, the silica concentrations in the Selenga River Shoal have declined to values that limit the development of dominant diatom species in Lake Baikal.