排序方式： 共有70条查询结果，搜索用时 281 毫秒
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A. V. Drits M. D. Kravchishina A. F. Pasternak A. N. Novigatsky O. M. Dara M. V. Flint 《Oceanology》2017,57(6):841-854
The role of zooplankton in the vertical mass flux in the Kara and Laptev seas was studied during cruise 63 of the R/V Akademik Mstislav Keldysh in August–October 2015. Mass fluxes were estimated using sediment trap samples. The maximum values of the total vertical flux (19600 mg m?2 day?1) and particulate organic carbon (POC) flux (464 mg C m?2 day?1) were measured close to the Lena River Delta in the Laptev Sea. In the Kara Sea, the total flux (80–2700 mg m?2 day?1) and the POC flux (17–130 mg C m?2 day?1) were substantially higher than the estimates published earlier. The fecal pellet flux varied from 2 to 92 mg C m?2 day?1 and made up 4–190% of the total organic carbon flux. The mineral composition of fecal pellets largely mirrored that of suspended particulate matter. Clay minerals in the fecal pellets were more abundant than in particulate matter in the areas with noticeable freshwater impact. The flux of zooplankton carcasses varied from 0.1 to 66.4 mg C m?2 day?1 and made up 0.2–72% of total POC flux. The results are discussed in relation to the abundance and composition of zooplankton, the concentration and composition of suspended particulate matter, hydrophysical conditions, and methods of sample preparation for analysis. 相似文献
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Pautova L. A. Silkin V. A. Kravchishina M. D. Chultsova A. L. Lisitzin A. P. 《Doklady Earth Sciences》2020,490(1):46-50
Doklady Earth Sciences - This paper reports on a study of the phytoplankton calcium carbonate pump in the Norwegian and Barents seas in July–August 2017. Coccolithophores, a unique marine... 相似文献
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A. P. Lisitzin A. N. Novigatsky R. A. Aliev V. P. Shevchenko A. A. Klyuvitkin M. D. Kravchishina 《Doklady Earth Sciences》2015,465(2):1253-1256
A new approach using dispersed organic matter of the water column in sedimentation traps in comparison with the surface layer of the bottom sediments is applied for the study of marine sedimentation. This approach provides the opportunity for an in situ (by fluxes of sedimentary matter in the water column) study of modern sedimentation in the surface layers of the bottom sediments and tracing the changes in the environment and climate at a new technological level. This also allows us to choose the reverse task: to reconstruct the fluxes of the matter and chemical elements in ancient seas by the rates (or absolute masses) of sedimentation. 相似文献
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A. Yu. Lein I. I. Rusanov M. D. Kravchishina M. V. Ivanov 《Lithology and Mineral Resources》2012,47(4):281-293
Isotopic compositions of organic (δ13C-Corg) and carbonate (δ13C-Ccarb) carbon were analyzed in the particulate matter (hereafter, particulates) and sediments from the North and Middle Caspian basins. Isotopic composition of Corg was used for assessing proportions of the allochthonous and autochthonous organic matter in the particulates. Difference between the δ13C-Corg values in surface sediments and particulates is explained by the aerobic and anaerobic diagenetic transformations. Isotopic composition of Corg in sediments may be used as a tool for reconstructing the Quaternary transgressive-regressive history of the Caspian Sea. 相似文献
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A. Yu. Lein M. D. Kravchishina N. V. Politova A. S. Savvichev E. F. Veslopolova I. N. Mitskevich N. V. Ul’yanova V. P. Shevchenko M. V. Ivanov 《Lithology and Mineral Resources》2012,47(2):99-128
Complex biogeochemical studies including the determination of isotopic composition of Corg in both suspended particulate matter and surface horizon (0–1 cm) of sediments (more than 260 determinations of δ13C-Corg) were carried out for five Arctic shelf seas: White, Barents, Kara, East Siberian, and Chukchi. The aim of this study is
to elucidate causes that change the isotopic composition of particulate organic carbon at the water-sediment boundary. It
is shown that the isotopic composition of Corg in sediments from seas with a high river runoff (White, Kara, and East Siberian) does not inherit the isotopic composition
of Corg in particles precipitating from the water column, but is enriched in heavy 13C. Seas with a low river runoff (Barents and Chukchi) show insignificant difference between the value of δ13C-Corg in both suspended load and sediment because of a low content of the isotopically light allochthonous organic matter (OM)
in particulates. Complex biogeochemical studies with radioisotope tracers (14CO2, 35S, and 14CH4) revealed the existence of specific microbial filter formed from heterotrophic and autotrophic organisms at the water-sediment
boundary. This filter prevents the mass influx of products of OM decomposition into water column, as well as reduces the influx
of a part of OM contained in the suspended particulate matter from water into sediment. 相似文献
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M. D. Kravchishina A. Yu. Lein L. A. Pautova A. A. Klyuvitkin N. V. Politova A. N. Novigatsky V. A. Silkin 《Oceanology》2016,56(6):819-836
The features of the vertical distribution of chlorophyll a, particulate organic carbon and its isotopic composition, total suspended particulate matter (SPM), and the structure of the phytoplankton community in the Middle and South Caspian Sea in May–June 2012 are discussed. The subsurface chlorophyll a maximum (SCM) was found everywhere at depths of ~20 to 40–60 m. The position of this layer is confined to the depth of the seasonal thermocline, which is determined by the development of a cold-water (dark) phytocenosis. The genesis of this layer was studied. The increase in chlorophyll a concentration in this layer is caused by an abundance of phytoplankton or an increased concentration of this phytopigments per algal cell. The highest values of the studied organic compounds and phytoplankton biomass are revealed as close to the seasonal thermocline extending from the southern periphery of the Derbent Depression to the Apsheron Sill, which is determined by the bottom topography. The presence of chlorophyll a at depths exceeding 300 m (up to ≥1 mg/m3) was revealed. This was supported by findings of individual algal cells containing chlorophyll a and even their accumulations in the deep water layer. The most probable mechanisms responsible for the presence of these cells at the deep water level are discussed in the paper. The vertical distribution of the values of the organic carbon isotopic composition is primarily controlled by the vertical structure of phytoplankton and chlorophyll a in the water column up to ~500 m and by biogeochemical processes at the redox barrier (~600 m layer). The relative stability of chlorophyll a and the stability of pheophytin a in anaerobic environments were verified. A significant amount of weakly transformed chlorophyll a was found close the sea bottom. 相似文献