30 Sep 2022
 | 30 Sep 2022

Diatom responses and geochemical feedbacks to environmental changes at Lake Rauchuagytgyn (Far East Russian Arctic)

Boris K. Biskaborn, Amy Forster, Gregor Pfalz, Lyudmila A. Pestryakova, Kathleen Stoof-Leichsenring, Jens Strauss, Tim Kröger, and Ulrike Herzschuh

Abstract. This study is based on multiproxy data gained from a 14C-dated 6.5 m long sediment core and a 210Pb-dated 23 cm short core retrieved from Lake Rauchuagytgyn in Chukotka, Arctic Russia. The main objectives are to reconstruct the environmental history and ecological development of the lake during the last 29k years and to investigate the main drivers behind bioproduction shifts. The methods comprise age-modeling and accumulation rate estimation, light-microscope diatom species analysis (74 samples), organic carbon, nitrogen, and mercury analysis. Diatoms have appeared in the lake since 21.8 cal ka BP and are dominated by planktonic Lindavia ocellata and L. cyclopuncta. Around the Pleistocene-Holocene boundary, other taxa including planktonic Aulacoseira and benthic fragilarioid (Staurosira) and achnanthoid species increase in their abundance. There is strong correlation between variations of diatom valve accumulation rates (DAR, mean 176.1 109 valves m2 a1), organic carbon accumulation rates (OCAR, mean 4.6 g m-2 a-1), and mercury accumulation rates (HgAR, mean 63.4 µg m-2 a-1). We discuss the environmental forcings behind shifts in diatom species and found responses of key-taxa to the cold glacial period, postglacial warming, Younger Dryas, and the Holocene Thermal Maximum. The short core data likely suggest recent change of the diatom community at 1907 CE related to human-induced environmental change. Significant correlation between DAR and OCAR in the Holocene interglacial indicates within-lake bioproduction as the main source of carbon deposited in the lake sediment. During both glacial and interglacial episodes HgAR is mainly bound to organic matter in the lake associated to biochemical substrate conditions. There were only ambiguous signs of increased HgAR during the industrialization period. We conclude that pristine Arctic lake systems can serve as CO2 and Hg sinks during warming climate driven by insolation-enhanced within-lake primary productivity. Maintaining intact natural lake ecosystems should therefore be of interest to future environmental policy.

Boris K. Biskaborn et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-985', Anonymous Referee #1, 10 Nov 2022
    • AC1: 'Author reply on RC1', Boris K. Biskaborn, 06 Mar 2023
  • RC2: 'Comment on egusphere-2022-985', Anonymous Referee #2, 14 Feb 2023
    • AC2: 'Reply on RC2', Boris K. Biskaborn, 06 Mar 2023

Boris K. Biskaborn et al.

Data sets

Sedimentological and biogeochemical dataset for Arctic glacial lake Rauchuagytgyn, Chukotka, Russia Vyse, Stuart Andrew; Herzschuh, Ulrike; Pfalz, Gregor; Diekmann, Bernhard; Nowaczyk, Norbert R; Pestryakova, Luidmila A; Biskaborn, Boris K

Boris K. Biskaborn et al.


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Short summary
Sediment cores from a mountain lake in the Russian Arctic were investigated for micro algae, organic matter and mercury, dated back to the last glacial. The species assemblages responded strongly to environmental changes such as Younger Dryas cold event and the Holocene Thermal Maximum. Organic carbon correlated with rates of micro algae deposition only during warm episodes, but not during the cold glacial. This highlights the importance of pristine lakes as carbon sinks during climate warming.