TRACES OF HIGH SEISMIC ACTIVITY IN THE UPPERMOST SEDIMENTS OF LAKE BAIKAL, SIBERIA

Sedimentation in Lake Baikal is significantly affected by continuous seismic activity in the Baikal Rift Zone. Our study shows that historical earthquakes, as well as recent seismic events, considerably influenced sedimentation in this deep tectonic basin. Here we present some of the results of extensive international research activities during the period of 1996–2019. To identify traces of seismic events in the uppermost sediments (<1.5 m), short cores were recovered from many coring stations throughout the entire lake. Based on lithological descriptions, measurements of magnetic susceptibility, and concentration of inorganic and organic components, we identified earthquake indicators in the sediment cores. Impacts of historical earthquakes were traced within South Baikal (near the Sharyzhalgai Station and the Station 106-km of the Circum-Baikal railway, hereafter CBR) and Proval Bay (near the Selenga River delta)

СЛЕДЫ ВЫСОКОЙ СЕЙСМИЧЕСКОЙ АКТИВНОСТИ В ПОВЕРХНОСТНЫХ ОТЛОЖЕНИЯХ ОЗЕРА БАЙКАЛ, СИБИРЬ

Sedimentation in Lake Baikal is significantly affected by continuous seismic activity in the Baikal Rift Zone. Our study shows that historical earthquakes, as well as recent seismic events, considerably influenced sedimentation in this deep tectonic basin. Here we present some of the results of extensive international research activities during the period of 1996–2019. To identify traces of seismic events in the uppermost sediments (<1.5 m), short cores were recovered from many coring stations throughout the entire lake. Based on lithological descriptions, measurements of magnetic susceptibility, and concentration of inorganic and organic components, we identified earthquake indicators in the sediment cores. Impacts of historical earthquakes were traced within South Baikal (near the Sharyzhalgai Station and the Station 106-km of the Circum-Baikal railway, hereafter CBR) and Proval Bay (near the Selenga River delta).Осадконакопление в озере Байкал происходит на фоне постоянной сейсмической активности Байкальской рифтовой зоны. Современные и исторические землетрясения оказывают значительное влияние на формирование донных отложений в этом глубоком тектоническом бассейне. В статье представлены результаты международных исследований за период 1996–2019 гг. Для обнаружения следов сейсмических событий в самых верхних слоях отложений (<1.5 м) были отобраны короткие керны по всему озеру. Приведены карты с точками отбора кернов и сейсмичностью озера. Литологический состав, данные измерения магнитной восприимчивости, оценка органических и неорганических компонентов осадков позволяют определить индикаторы землетрясений в донных отложениях озера. Следы исторических землетрясений были обнаружены в пределах Южной котловины Байкала (районы станций Шарыжалгай и 106-й км Кругобайкальской железной дороги) и в заливе Провал рядом с дельтой р. Селенги

Changing nutrient cycling in Lake Baikal, the world's oldest lake

Lake Baikal, lying in a rift zone in southeastern Siberia, is the world's oldest, deepest, and most voluminous lake that began to form over 30 million years ago. Cited as the "most outstanding example of a freshwater ecosystem" and designated a World Heritage Site in 1996 due to its high level of endemicity, the lake and its ecosystem have become increasingly threatened by both climate change and anthropogenic disturbance. Here, we present a record of nutrient cycling in the lake, derived from the silicon isotope composition of diatoms, which dominate aquatic primary productivity. Using historical records from the region, we assess the extent to which natural and anthropogenic factors have altered biogeochemical cycling in the lake over the last 2,000 y. We show that rates of nutrient supply from deep waters to the photic zone have dramatically increased since the mid-19th century in response to changing wind dynamics, reduced ice cover, and their associated impact on limnological processes in the lake. With stressors linked to untreated sewage and catchment development also now impacting the near-shore region of Lake Baikal, the resilience of the lake's highly endemic ecosystem to ongoing and future disturbance is increasingly uncertain

Mercury loading within the Selenga River basin and Lake Baikal, Siberia

Mercury (Hg) loading in Lake Baikal, a UNESCO world heritage site, is growing and poses a serious health concern to the lake’s ecosystem due to the ability of Hg to transform into a toxic form, known as methylmercury (MeHg). Monitoring of Hg into Lake Baikal is spatially and temporally sparse, highlighting the need for insights into historic Hg loading. This study reports measurements of Hg concentrations from water collected in August 2013 and 2014 from across Lake Baikal and its main inflow, the Selenga River basin (Russia, Mongolia). We also report historic Hg contamination using sediment cores taken from the south and north basins of Lake Baikal, and a shallow lake in the Selenga Delta. Field measurements from August 2013 and 2014 show high Hg concentrations in the Selenga Delta and river waters, in comparison to pelagic lake waters. Sediment cores from Lake Baikal show that Hg enrichment commenced first in the south basin in the late-19th century, and then in the north basin in the mid-20th century. Hg flux was also 20-fold greater in the south basin compared to the north basin sediments. Hg enrichment was greatest in the Selenga Delta shallow lake (Enrichment Ratio (ER) = 2.3 in 1994 CE), with enrichment occurring in the mid- to late-20th century. Local sources of Hg are predominantly from gold mining along the Selenga River, which have been expanding over the last few decades. More recently, another source is atmospheric deposition from industrial activity in Asia, due to rapid economic growth across the region since the 1980s. As Hg can bioaccumulate and biomagnify through trophic levels to Baikal’s top consumer, the world’s only truly freshwater seal (Pusa sibirica), it is vital that Hg input at Lake Baikal and within its catchment is monitored and controlled

Constraining modern day silicon cycling in Lake Baikal

Constraining the continental silicon cycle is a key requirement in attempts to understand both nutrient fluxes to the ocean and linkages between silicon and carbon cycling over different timescales. Silicon isotope data of dissolved silica (δ30SiDSi) are presented here from Lake Baikal and its catchment in central Siberia. As well as being the world's oldest and voluminous lake, Lake Baikal lies within the seventh largest drainage basin in the world and exports significant amounts of freshwater into the Arctic Ocean. Data from river waters accounting for c. 92% of annual river inflow to the lake suggest no seasonal alteration or anthropogenic impact on river δ30SiDSi composition. The absence of a change in δ30SiDSi within the Selenga Delta, through which 62% of riverine flow passes, suggest a net balance between biogenic uptake and dissolution in this system. A key feature of this study is the use of δ30SiDSi to examine seasonal and spatial variations in DSi utilisation and export across the lake. Using an open system model against deep water δ30SiDSi values from the lake, we estimate that 20-24% of DSi entering Lake Baikal is exported into the sediment record. Whilst highlighting the impact that lakes may have upon the sequestration of continental DSi, mixed layer δ30SiDSi values from 2003 and 2013 show significant spatial variability in the magnitude of spring bloom nutrient utilisation with lower rates in the north relative to south basin

ПОЗДНЕГОЛОЦЕНОВОЕ ОСАДКОНАКОПЛЕНИЕ В АКТИВНЫХ ГЕОЛОГИЧЕСКИХ СТРУКТУРАХ ЧУКОТСКОГО МОРЯ

The article presents the detailed analysis results considering bottom sediments from the Chukchi Sea. Two core samples, b16 and НС–8 were taken from the northern Herald Canyon 150 km northeast from NE Wrangel Island. Core b16 has been studied in more detail. According to the 210Pb measurements, the recent sedimentation rate amounts to 0.9 mm/y–1 at the sampling point. In the bottom layer of the core sample, the minimum concentrations of biogenic components (SiO2bio, Corg, Ntot, and Br) and the increased concentrations of cold-water diatom species Thalassiosira antarctica may result from low biological productivity during the Maunder Minimum. A correlation with recent global warming (11–22 years) is shown by the increased concentrations of SiO2bio, Corg, Ntot, and Br and the decreased values of magnetic susceptibility and X-ray density in the top layer (1–2 cm) of the same core sample. The results of our geochemical and diatom analysis support the available literature data and confirm that the Late Holocene sedimentation in the Chukchi Sea takes place in the zone wherein the water transits from the Pacific to the Arctic Ocean.Представлены результаты комплексного исследования вещественного состава донных осадков, вскрытых двумя кернами в северной части каньона Геральд Чукотского моря. Одна из полученных колонок была выбрана для более детального исследования. Скорость современного осадконакопления в точке отбора этого керна, измеренная по 210Pb, составляет 0.9 мм/год. Минимальные концентрации биогенных компонентов (SiO2биог., Сорг., Nобщ., Br) и увеличение содержаний холодноводного вида диатомей Thalassiosira antarctica в нижнем слое колонки, вероятно, объясняются низкой биологической продуктивностью во время минимума Маундера. Повышенные концентрации SiO2биог, Сорг, Nобщ, Br, пониженные значения магнитной восприимчивости и рентгеновской плотности в самом верхнем интервале разреза (до 1–2 см) соответствуют последним 11–22 годам глобального потепления климата. Результаты геохимического и диатомового анализов подтверждают имеющиеся в литературе данные о том, что позднеголоценовая седиментация в Чукотском море происходит в зоне транзита тихоокеанских вод в Северный Ледовитый океан

Types of Holocene deposits and regional pattern of sedimentation in Lake Baikal

Abstract Results of research into recent sediments and their distribution in Lake Baikal are presented. Five areas with different mechanisms of sedimentation have been recognized: (1) deep-water plains with pelagic mud and turbidites; (2) littoral zones without turbidites; (3) underwater ridges (rises) with hemipelagic mud accumulated under calm sedimentation conditions; (4) delta (fan) areas near the mouths of large rivers, where sediments consist mainly of terrigenous material; and (5) shallow-water Maloe More with poorly sorted terrigenous material and abundant sand. The rate of sedimentation differs considerably in various Baikal areas. The highest rates appear near the mouths of large rivers, lower ones occur in the deep lake basins, and the minimum rates are developed on underwater ridges. A map of the distribution of Holocene sediments in Lake Baikal has been compiled for the first time. The obtained results show that the lake bottom morphology significantly determines the type of sediments in the lake

Correction: Diatom evidence of 20th century ecosystem change in Lake Baikal, Siberia.

[This corrects the article DOI: 10.1371/journal.pone.0208765.]