Particulate matter fluxes in the southern and central Kara Sea compared to sediments: Bulk fluxes, amino acids, stable carbon and nitrogen isotopes, sterols and fatty acids (original) (raw)
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A contemporary sediment and organic carbon budget for the Kara Sea shelf (Siberia)
Marine Geology, 2005
It has recently been realized that the Arctic undergoes drastic changes, probably resulting from global change induced processes. This acts on the cycling of matter and on biogenic elements in the Arctic Ocean having feedback mechanisms with the global climate, for example by interacting with atmospheric trace gas concentration. A contemporary budget for biogenic elements as well as suspended matter for the Arctic Ocean as a baseline for comparison with effects of further global change is, thus, needed. Available budgets are based on the late Holocene sedimentary record and are therefore quiet different from the present which has already been affected by the intense anthropogenic activity of the last centuries.
Marine Geology, 2004
The Ob and Yenisei Rivers account for more than one-third of the total fresh water supply to the Arctic Ocean. In the past, their sediment load and particulate organic carbon (POC) discharge into the Kara Sea has been measured at stations in the hinterland far south of the estuaries. Suspended matter has been sampled in the estuaries and southern Kara Sea within the framework of the joint Russian -German ''SIRRO'' program (Siberian River Run-Off), allowing a reliable new estimate of fluxes from the rivers into the Kara Sea. Our estimates of annual supplies of sediment (3.76 Â 10 6 t), particulate organic carbon (0.27 Â 10 6 t) and particulate nitrogen (PN) (0.027 Â 10 6 t) from the Ob River to the Kara Sea are lower than earlier estimates from the northernmost gauging station in the hinterland due to deposition of particulate matter in the Ob Bay. On the other hand, our estimates of the Yenisei's annual sediment (5.03 Â 10 6 t), particulate organic carbon (0.57 Â 10 6 t) and particulate nitrogen (0.084 Â 10 6 t) supplies to the Kara Sea are probably too high, as they suggest a pure bypass system in the investigated area. We differentiate between an area of recent deposition in the south of the Kara Sea and an area of recent organic matter degradation further north. D
Global Biogeochemical Cycles, 2004
1] Surface sediments were collected during the 2000 TransArctic Expedition along the Siberian Arctic coastline, including the Ob, Yenisey, Khatanga, Lena, and Indigirka estuaries. Sediments were characterized for elemental composition (total organic carbon, TOC, black carbon, BC, and total N, as well as major and trace elements), isotopic signature (d 13 C, d 15 N, D 14 C, e Nd , 87 Sr/ 86 Sr), and organic molecular composition to better understand river export variations over the large spatial scale of the Siberian Arctic. On average, 79 ± 9% of the total C in sediments was organic while 21 ± 9% was inorganic. BC made up 9 ± 4% of the TOC pool, with a general increasing trend from west to east along the Siberian coast. The combined Nd-and Sr-isotopes (e Nd and 87 Sr/ 86 Sr) were used to define two distinct sediment sources between east and west Siberian regions with the Khatanga River as a boundary. Data from pyrolysis-GC/MS of the sedimentary organic carbon (SOC) indicated an increase in the freshness of the organic matter from west to east on the Siberian Arctic coast, with increasing relative abundance of furfurals (polysaccharides) with respect to nitriles. Values for the d 13 C of SOC ranged from À27.1% (mostly terrigenous) to À23.8%, while d 15 N increased from east to west (3.1 to 5.2%) with a significant correlation with C/N ratio. Values for the D 14 C of SOC ranged from À805 to À279%, with a consistent trend increasing from the east (Indigirka River) to the west (Ob River). These D 14 C values corresponded to a 14 C age of 2570 ± 30 yBP in the Ob estuary and 13,050 ± 50 yBP in the Indigirka estuary. Most importantly, D 14 C values were significantly correlated with the ratio of BC/TOC (R 2 = 0.91, n = 6), consistent with the distribution pattern of increasing permafrost zone from the west to the east along the Siberian coast. Together, our results suggest that older OC was derived from the release of recalcitrant BC during permafrost thawing and riverbank and coastal erosion, likely enhanced by ongoing environmental changes in the northern ecosystem.
2010
The circum-Arctic region contains approximately half of the global belowground organic carbon (OC) pool, more than twice as much as CO2-C currently in the atmosphere. These massive carbon stocks are freeze-locked in the least disturbed permafrost region of the Northern Hemisphere: the East Siberian Arctic, now subjected to the strongest climate warming in the world. Our knowledge is still waning on the fate and degradation status of the terrestrial organic carbon, remobilized through rivers and through eroding coasts. During the ship-based ISSS-08 research expedition onboard the Yakob Smirnitskiy in late summer 2008 we explored the coastal and shelf areas of the East Siberian Sea. We collected surface water particulate OC (POC) and surface sediment OC (SOC) along an off-river transect (500 km long) in the Kolyma paleoriver canyon. Bulk geochemical and molecular analyses were performed to obtain detailed information on origin, and relative importance of degradation and transport of v...
Zooplankton impact on the organic matter flux of Siberian Arctic seas
Doklady Biological Sciences, 2017
Role of zooplankton in the organic matter flux was studied in the Kara and Laptev seas using sediment traps in the course of voyage 63 of the Academician Mstislav Keldysh research vessel in August-October 2015. The values of the total flux and that of organic matter were at least an order of magnitude higher than those obtained before the 2000s. A hypothesis is proposed on an increasing influence of the river runoff on the Kara Sea area under climatic changes. Zooplankton contribution into C org flux varied broadly, averaging 50%. The highest flux values and contribution of zooplankton in them (up to 96%) were recorded in the frontal (gradient) zones.
The Plankton Community of the Kara Sea in Early Spring
The almost complete absence of information about the state of the Kara Sea plankton community in early spring prevents reconstruction of the seasonal cycle for the ecosystem of this basin and assessment of the effect of current climate changes in the Arctic. Studies performed during March 29-April 08, 2016 on the vessel Noril'skii nikel' yielded data that to a certain degree fill this gap. Samples for assessing the plankton structural and production characteristics were taken at 27 stations (figure) and hydrophysical, hydrochemical, and productivity parameters were recorded in the sea surface layer. The following characteristics were measured: temperature, conductance, illumination, alkalinity, and the concentrations of oxygen, silicon, phosphates, nitrates, total suspended solid material, and suspended and dissolved organic carbon. The spectral distribution of fluorescence and its intensity were recorded for colored dissolved organic matter. The species composition; abundance; and biomass of the autotrophic and heterotrophic picoplankton, nanoplankton, and microplankton; chlorophyll a concentration; assimilation number; primary and bacterial production; concentrations of virioplankton and bacterioplankton in water; and abundance of viruses associated with bacterial cells were determined. Total samples of zooplankton from the sea bottom to surface were collected at two stations.
Journal of Marine Systems, 2014
Primary production and fundamental environmental factors were measured during September-October 1993 in the Kara Sea. Relationships between the depth-integrated primary production (PP int ), the surface chlorophyll a (Chl 0 ) concentration and the maximum chlorophyll specific carbon rate within water column (P b opt ) had shown that only 12% of PP int variability were determined by Chl 0 and there were strong correlations between PP int and P b opt (R 2 = 0.64). Thus, in the autumn PP int values were largely influenced by the phytoplankton assimilation activity. At the end of a vegetative season high (close or above 1 mg m −3 ) values of Chl 0 were not an index of phytoplankton productivity within photosynthetic layer where the organic matter synthesis rate was low which testifies the lack of correlation between Chl 0 and PP int (R 2 = 0.12) and between Chl 0 and depth-integrated chlorophyll a (chl a) (R 2 = 0.22). This conclusion is based on the low assimilation activity within water column and small thickness of the photosynthetic layer. The latter corresponds to low insolation and water transparency. The lack of correlation between surface and depth-integrated productivity parameters is the challenge for satellite PP int estimations. In turn PP int and P b opt depended mainly on photosynthetically available radiation (PAR) and weakly related to the nitrogen and phosphorus concentrations. At the end of a vegetative season PAR level, apparently, should be considered as the main factor for primary production in the Kara Sea. Comparison between the integrated primary production from shipboard in September and the simulated evaluations of productivity (PP models) suggests that PP models overestimate the in situ PP int by a factor of 3-7 in the different Kara Sea regions. Improving of Kara Sea primary production estimations implies the development of regional satellite chl a algorithm and local primary production model considering specific features of PP in this Arctic Ocean region. (A.B. Demidov), mosharov@ocean.ru (S.A. Mosharov), makkaveev55@mail.ru (P.N. Makkaveev).
Spaceborne quantitative assessment of dissolved organic carbon fluxes in the Kara Sea
Advances in Space Research, 2012
An advanced algorithm for retrieval of phytoplankton chlorophyll (CHL) and dissolved organic carbon (DOC) concentrations from MERIS images of the Kara Sea is presented. The supply of DOC of terrestrial origin into the Kara Sea is numerically assessed from satellite data on DOC and historical records of river discharge rates. It exceeds the historical in situ values only by 25%. Satellite data on CHL were exploited for calculating the phytoplankton columnar biomass and the total phytoplankton biomass in the Kara Sea. Remote sensing and in situ data were used to calculate the value of the coefficient (K PH ) for calculation from phytoplankton biomass of autochthonous production of DOC. K PH proved to be 142 ± 8 gC/gPH/month and exhibited only slight interannual variations. The coefficient K PH was employed for the first time to evaluate the production of autochthonous DOC in the Kara Sea and to correct the value of the allochthonous DOC flux initially retrieved from space across the Kara Sea.