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Lake Baikal’s most important tributary is the Selenga River, which contributes about 50 to 60% of its surface water influx (Chalov et al. 2015; Opp 1994; Törnqvist et al. 2015). Moreover, the Selenga’s 447.060-km watershed covers 82% of the Lake Baikal Basin (Nadmitov et al. 2014) (Fig. 1), which means that any environmental changes along the Selenga and its tributaries may ultimately impact Lake Baikal. However, north of the Buryatian capital Ulan Ude, the Selenga River branches into the largest freshwater inland delta in the world (Logachev 2003). The associated wetland constitutes a unique ecosystem (Гармаев and Христофоров 2010) and acts as the final geobiochemical barrier before the Selenga discharges into Lake Baikal (Chalov et al. 2016). Therefore, it has a great impact on pollution delivery to Lake Baikal, storing up to 60–70% of the sediment load of the Selenga River (Chalov et al. 2017). The protection of Lake Baikal and the planning of water management measures in the Selenga river basin require a good understanding of current trends regarding hydrology, water quality, aquatic and riparian zone ecology of the Selenga and its key tributaries (Karthe et al. 2016), and geoand biochemical processes governing the ecological functioning of the Selenga delta (Khazheeva et al. 2004). The following anthropogenic impacts constitute threats to the ecology of the Selenga from its tributaries down to its delta: Various mining activities are found in the Selenga river basin, including the exploitation of coal, gold, copper, molybdenum and wolfram (Sandmann 2012; Timofeev et al. 2015). As a consequence, elevated levels of heavy metals and other mining-related pollutants (cyanides, phosphorus) have been detected in the water and sediments of the Selenga and its tributaries, as well as floodplain soils and groundwater (Battogtokh et al. 2014; Brumbaugh et al. 2013; Chalov et al. 2015; Inam et al. 2011; McIntyre et al. 2016; Nadmitov et al. 2014; Pavlov et al. 2008; Pfeiffer et al. 2015; Stubblefield et al. 2005; Thorslund et al. 2012). Even though contaminant transport towards the Selenga delta does take place (Chalov et al. 2015; Khazheeva et al. 2004; Karthe et al. 2014), it should be noted that contaminations currently have the largest effects in local hot spots (Hofmann et al. 2010; Inam et al. 2011; Pfeiffer et al. 2015). Currently, there are different views regarding their impact on Lake Baikal itself (Chebykin et al. 2010; Pavlov et al. 2008). However, bioaccumulation and toxicological effects observed in aquatic biota ranging from insects to fish provide indication that water quality deterioration in the Selenga river system does have an ecological impact (Avlyush 2011; Kaus et al. 2016; Komov et al. 2014). * Sergey Chalov [email protected]