We collected water samples from the river surface in the center of the Olenekskaya Channel near Samoylov Island using a pre-rinsed HDPE 1 L bottle. During the open water period (June to October), water was sampled from a small boat, and during ice-covered period (November to May), through a hole drilled through the river ice. Some samples during the river ice break-up (between May and June) as well as some samples during the ice freeze-up in October were taken from the shore due to the inaccessibility of a more centered location on the river channel. Water samples were filtered through a 0.45 μm cellulose acetate filter (which had been rinsed with 20 ml sample water) for Ge concentration and Si isotope composition measurements. The Ge concentration was determined by ICP-mass spectrometry (ICP-MS, ICAPQ Thermo Fisher Scientific, Earth & Life Institute, UCLouvain, Belgium). The detection limit for Ge is 0.04 nM and the analytical precision of the measurement is ± 8% for Ge concentrations 0.013 nM. The germanium to silicon ratio was calculated using the silicon concentration available form Juhls et al 2020 (https://doi.org/10.1594/PANGAEA.913197). The standard deviation (SD) on Ge/Si ratio determination is 10%. The silicon isotope composition (δ30Si) was analyzed by MC-ICP-MS (Neptune Plus™ High Resolution Multicollector ICP-MS, Thermo Fisher Scientific, Earth & Life Institute, UCLouvain, Belgium) in wet plasma mode after Si separation using a two-stages column chemistry procedure using an anion exchange resin (Biorad AG MP-1) followed by a cation exchange resin (Biorad AG50W-X12). The instrumental mass bias was corrected using the standard-sample bracketing technique and an external Mg doping. The δ30Si compositions are expressed in relative deviations of 30Si/28Si ratio from the NBS-28 reference standard using the δ-notation (‰) as follows: δ30Si = [(30Si/28Si)sample/(30Si/28Si)NBS-28 -1] × 1000. Each single δ-value represents one sample run and two bracketing standards. The δ30Si values are reported as the mean of isotopic analyses from multiple analytical sessions at least in duplicate (± SD).