Post-glacial diatom and geochemical records of ecological status and water level changes of Lake Vorota, Western Beringia

In this study, radiocarbon-dated geochemical and diatom records from Lake Vorota located within the informal meteorological ‘pole of cold’ of the northern hemisphere (Yakutia, Russia) were used to asses responses of the lake’s ecosystem to climate dynamics at the Late Pleistocene–Holocene boundary and over the Holocene. Geophysical research revealed relatively great depths (40–65 m) and a 4-m undisturbed thin-layered sedimentary structure in the central part of the lake where the short sediment core (V3-2014, 85 cm, spanning the last 13.2 kyr) was taken. One-hundred diatom species and intraspecific taxa were identified in the core. The most abundant were planktonic diatom species with predominance of centric Lindavia minuta and Aulacoseira subarctica. The most diverse were benthic diatoms—widespread, indifferent toward salinity, preferring mildly alkaline conditions—xeno-oligosaprobic and oligosaprobic species. We identified four diatom zones indicating the main periods in lake level change (in cal. kyr BP): ~ 13.2–9.0 (relatively deep lake), ~ 9.0–8.3 (decrease of lake level with minimum depths at ~ 8.7–8.6 cal. kyr BP), ~ 8.3–5.5 (maximum level of the lake) and ~ 5.3–0.4 (moderate decrease of lake level). The highest abundance of A. subarctica and the planktonic to benthic biotope diatom taxa ratio (P/B) mark the maximum depth of the lake at ~ 8.3–5.5 cal. kyr BP. Geochemical components are grouped into three types of proxies: terrigenous, biogenic and rather diagenetic, which have essentially different distributions along the core depth. The first ones probably indicate the changes during permafrost thawing and varying inputs from several sources of terrigenous matter. It was found that the lake had a high productivity during the Younger Dryas and the 8.2 cal. kyr BP cooling. The duration of maximal biogenic silica productivity was 11.0–10.1 and 9.7–9.0 cal. kyr BP. Our data suggest that the onset of the Holocene thermal maximum at the study site could have taken place 1.3 kyr earlier than at the same latitudes (~ 62°N) of the Central Yakutia and may correspond to the maximal lake level (~ 8.3–5.5 cal. kyr BP).