Lena Delta hydrology and geochemistry: long-term hydrological data and recent field observations

The Lena River forms one of the largest deltas in the Arctic. We compare two sets of data to reveal new insights into the hydrological, hydrochemical, and geochemical processes within the delta: (i) long-term hydrometric observations at the Khabarova station at the head of the delta from 1951 to 2005; (ii) field hydrological and geochemical observations carried out within the delta since 2002. Periods with differing relative discharge and intensity of fluvial processes were identified from the long-term record of water and sediment discharge. Ice events during spring melt (high water) reconfigured branch channels and probably influenced sediment transport within the delta. Based on summer field measurements during 2005–2012 of discharge and sediment fluxes along main delta channels, both are increased between the apex and the front of the delta. This increase is to a great extent connected with an additional influx of water from tributaries, as well as an increase of suspended and dissolved material released from the ice complex. Summer concentrations of major ion and biogenic substances along the delta branches are partly explained by water sources within the delta, such as thawing ice complex waters, small Lena River branches and estuarine areas

Химические характеристики снежного покрова в высокоширотной Арктике (мыс Баранова, остров Большевик, архипелаг Северная Земля)

For the first time, features of the chemical composition of the snow cover during its accumulation on the Bolshevik Island (the area of the research station «Cape Baranov» Ice base») were studied. In winter 2018/19, the following elements density, conductivity, total acidity, pH, NH4+, NO2-, NO3-, PO43-, and Si and, additionally, Na+, К+, Ca2+, Mg2+, Cl-, and SO42-, were measured in new and old snow. Regularities of changes in the parameters of these two types of snow with time have been found. New snow is characterized by negative time trends in density, pH, conductivity, and total acidity, and by positive ones – in NO3–. All statistically significant changing parameters of new snow, except NH4+, showed high temporal variability. In the old snow, trends of decreasing NO3– and total acidity and increasing pH with the depth in the snow cover, as well as a positive correlation between NO3– and NH4+ have been revealed, that is not typical for the new snow. It was shown that the ammonium content in the old snow was, on average, 2.8 times higher than in the new one. The influence of different natural and anthropogenic factors on the snow chemical composition on the Bolshevik Island is discussed. We show that the increase in the total acidity of snow up to 0.001–0.014 meq/l in November–June during the young ice formation and then freeze-up could be due to anthropogenic nitrogen and sulfur oxides in roughly equal proportions. However, the chemical composition of the studied snow corresponds to the zone of the ecological norm. We compared the chemical composition of snow on the Bolshevik Island with similar characteristics of precipitation in other background regions of the Russian Federation using data of the World Weather Watch of the World Meteorological Organization. It was revealed that the studied snow was more acidic, less mineralized, depleted in sulfates, ammonium, nitrates and contained low electrical conductivity. In comparison with the snow cover on the Golomyanny Island (Severnaya Zemlya), the studied old snow contained minimal amounts of basic ions and was more acidic.Впервые изучены особенности химического состава снежного покрова в период его накопления на о. Большевик (район научно-исследовательского стационара «Ледовая База «Мыс Баранова»). Зимой 2018/19 г. в свежем и слежавшемся снеге измерены удельная электропроводность, плотность, общая кислотность, pH, NH4+, NO3-, NO2-, PO43-, Si и, дополнительно, в слежавшемся снеге – Na+, К+, Ca2+, Mg2+, Cl- и SO42-. Найдены закономерности изменения параметров свежего и слежавшегося снега, обсуждается влияние морских и антропогенных факторов. Проведено сравнение химического состава снега о. Большевик с составом атмосферных осадков и снежного покрова в других фоновых районах Российской Федерации

Изменчивость гидрохимических характеристик поверхностных вод пролива Шокальского по результатам наблюдений на научно-исследовательском стационаре «Ледовая база Мыс Баранова» в 2018–2019 гг.

In connection with the progressing climate change in the Arctic, it is extremely important to conduct systematic long-term monitoring in the high-latitude Arctic. An important place in the network of monitoring stations is occupied by the research Station «Cape Baranov» Ice base», located on Severnaya Zemlya (in the area of the Shokalsky Strait). The article presents the results of hydrochemical observations at the Ice base from December 02, 2018 to July 15, 2019. 35 hydrochemical stations were operated from the ice of the strait in the seawater layer of 0–110 m. A significant temporal variability of the characteristics in the upper layer (0–10 m) has been recorded. Four phases of variability of the hydrochemical parameters (HP) have been identified. In December (phase 1) the HP values indicate the presence of surface waters, the origin of which we associate with the transformed river waters (TRW) of the Ob and Yenisei, coming from the Kara Sea. From January to mid-April (phase 2) the highest salinity levels and homogeneous HP are observed due to intensive vertical mixing of waters in the autumn-winter period. At the end of April — May (phase 3) there is a slight desalination of the surface layer in the Shokalsky Strait, with HP pointing to the presence of TRW. From June to July, 15 (4th phase), there is a sharp decrease in the salinity, an increase in oxygen and pH, as well as a drop in the concentration of all the biogenic elements. Such HPs indicate both additional desalination from ice and snow melting and the beginning of phytoplankton bloom. An estimation has been carried out of the proportion of TRW and waters formed during sea ice melting. The average integral proportion of TRW in the water column is ~ 4 %, and for melt water this indicator is close to zero. The influence of ice formation on the hydrochemical characteristics of the surface layers is most noticeable in the 1st and 3rd phases. During the period of strong desalination of the surface waters (May —July), the TRW proportion can reach 10 % or more. From July, the contribution of the melting of sea ice is comparable to that of TRW.В соответствии с программой систематического долгосрочного мониторинга климата Арктики на НИС «Ледовая база Мыс Баранова» в 2018–2019 гг. в проливе Шокальского выполнено наблюдение гидрохимических характеристик поверхностных вод и проведен анализ причин их временной изменчивости. Выделены 4 фазы изменчивости характеристик поверхностных вод, обусловленных влиянием речного стока, процессами вертикального перемешивания, образования и таяния льда и функционированием фитопланктона в весенне-летний период. Выполнена оценка доли речных и талых вод в составе поверхностного слоя вод пролива: доля речных вод в столбе воды составляет ~ 4 %, для талых вод этот показатель близок к нулю. В периоды сильного распреснения поверхностных вод (май — июль) доля речных вод достигает десяти и более процентов

Сравнительный анализ многолетних изменений в структурной организации зообентоса в условиях постоянного антропогенного воздействия (на примере Севастопольской бухты, Крым)

Представлены результаты бентосной съемки рыхлых грунтов Севастопольской бухты (2001 г.), являющейся одной из наиболее антропогенно нагруженных акваторий побережья Крыма. Дана характеристика количественного развития, выделены таксоны, определяющие особенности структурной организации комплексов макрозообентоса. Полученные результаты позволяют отнести Севастопольскую бухту к фаунистически богатым акваториям Крыма и Черного моря в целом. Использование методов многомерной статистики позволило выделить комбинации 7 – 8 ключевых абиотических переменных, из общего числа 32-х, включенных в анализ, которые наилучшим образом “объясняют” распределение бентоса. При этом, хлороформные битумоиды, традиционно относимые к наиболее значимым для зообентоса абиотическим факторам, по результатам нашего анализа не вошли в группу ключевых переменных для макробентоса. Сравнительный анализ материалов, полученных с 1928 по 2001 гг., позволил сделать заключение о многолетних тенденциях увеличения средней биомассы бентоса в бухте и изменения трофической структуры донных группировок в сторону преобладания детритофагов. Такие изменения можно рассматривать в качестве ответной реакции экосистемы в условиях роста органического обогащения прибрежных вод Крыма.The results of benthic survey of soft bottoms in the Sevastopol bay had been performed in 2001 are presented. This bay is under permanent technogenic impact and is being considered as one of the most polluted areas along the coastal part of Crimea. The peculiarities of quantitative development of macrobenthic assemblages were characterized, and taxa which define the structural organization of assemblages were distinguished. In spite of strong influence of technogenic pollution, Sevastopol bay can be attributed to faunistically rich areas of Crimean coast and the Black Sea at whole. Using the methods of multivariate statistical analysis, suites of 7 – 8 environmental variables (from the 32 ones considered in the analysis) that best explained the observed benthic spatial distribution pattern were identified. It was noted that chloroform-extracted bitumens, which traditionally are being attributed to the most important abiotic factors affecting to bottom communities, were not included into set of the most significant variables influencing on macrobenthos. Comparative analysis of materials which had been collected in extremely far-separated time periods (1928 – 2001) allowed revealing availability of long-term tendencies: increasing of average benthos biomass values in the bay; and change in trophic structure of benthos when detritus-feeders became prevail. Such alterations can be considered as one of the way of adaptive response of the bay’s ecosystem under growing of organic enrichment in Crimean coastal waters