Food webs and carbon flux in the Barents Sea   总被引：6，自引：3，他引：6  

Paul Wassmann  Marit Reigstad  Tore Haug  Bert Rudels  Michael L. Carroll  Haakon Hop  Geir Wing Gabrielsen  Stig Falk-Petersen  Stanislav G. Denisenko  Elena Arashkevich  Dag Slagstad  Olga Pavlova 《Progress in Oceanography》2006,71(2-4):232

Within the framework of the physical forcing, we describe and quantify the key ecosystem components and basic food web structure of the Barents Sea. Emphasis is given to the energy flow through the ecosystem from an end-to-end perspective, i.e. from bacteria, through phytoplankton and zooplankton to fish, mammals and birds. Primary production in the Barents is on average 93 g C m⁻² y⁻¹, but interannually highly variable (±19%), responding to climate variability and change (e.g. variations in Atlantic Water inflow, the position of the ice edge and low-pressure pathways). The traditional focus upon large phytoplankton cells in polar regions seems less adequate in the Barents, as the cell carbon in the pelagic is most often dominated by small cells that are entangled in an efficient microbial loop that appears to be well coupled to the grazing food web. Primary production in the ice-covered waters of the Barents is clearly dominated by planktonic algae and the supply of ice biota by local production or advection is small. The pelagic–benthic coupling is strong, in particular in the marginal ice zone. In total 80% of the harvestable production is channelled through the deep-water communities and benthos. 19% of the harvestable production is grazed by the dominating copepods Calanus finmarchicus and C. glacialis in Atlantic or Arctic Water, respectively. These two species, in addition to capelin (Mallotus villosus) and herring (Clupea harengus), are the keystone organisms in the Barents that create the basis for the rich assemblage of higher trophic level organisms, facilitating one of the worlds largest fisheries (capelin, cod, shrimps, seals and whales). Less than 1% of the harvestable production is channelled through the most dominating higher trophic levels such as cod, harp seals, minke whales and sea birds. Atlantic cod, seals, whales, birds and man compete for harvestable energy with similar shares. Climate variability and change, differences in recruitment, variable resource availability, harvesting restrictions and management schemes will influence the resource exploitation between these competitors, that basically depend upon the efficient energy transfer from primary production to highly successful, lipid-rich zooplankton and pelagic fishes.  相似文献   

Barium Geochemical Cycle in the Ocean     

Lein  A. Yu.  Kravchishina  M. D. 《Lithology and Mineral Resources》2021,56(4):293-308

Lithology and Mineral Resources - A model of the Ba geochemical cycle in the ocean is discussed based on a few own and published data. Barium ion reacts with the sulfate ion in various fluids (pore...  相似文献   

Hydrogen sulfide production in surface layers of sediments in the Atlantic Ocean (from radioisotope data)     

A. Yu. Lein  M. V. Ivanov 《Oceanology》2015,55(6):884-888

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Trophic structure of zooplankton in the Fram Strait in spring and autumn 2003     

Katarzyna Blachowiak-Samolyk  Slawek Kwasniewski  Katarzyna Dmoch  Haakon Hop  Stig Falk-Petersen 《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2716

The trophic structure of zooplankton was investigated in Fram Strait (north western Svalbard) in spring and autumn of 2003. Depth-stratified zooplankton samples were collected at 12 stations on the shelf (200 m), across the shelf-slope (500 m) and over deep water (>750 m), using a Multiple Plankton Sampler equipped with 0.180-mm mesh size nets.Higher zooplankton abundance and estimated biomass were found in the shelf area. Abundance and biomass were two times higher in August, when sea-surface temperature was higher than in May. Herbivores dominated numerically in May, and omnivores in August, suggesting a seasonal sequence of domination by different trophic groups. Cirripedia nauplii and Fritillaria borealis prevailed in spring, whereas copepod nauplii and Calanus finmarchicus were numerically the most important herbivores in autumn. Small copepods, Oithona similis and Triconia borealis, were the most numerous omnivorous species in both seasons, but their abundances increased in autumn. Chaetognatha (mainly Eukrohnia hamata) accounted for the highest abundance and biomass among predatory taxa at all deep-water stations and during both seasons. Regarding vertical distribution, herbivores dominated numerically in the surface layer (0–20 m), and omnivores were concentrated somewhat deeper (20–50 m) during both seasons. Maximum abundance of predators was found in the surface layer (0–20 m) in spring, and generally in the 20–50 m layer in autumn. This paper presents the first comprehensive summary of the zooplankton trophic structure in the Fram Strait area. Our goals are to improve understanding of energy transfer through this ecosystem, and of potential climate-induced changes in Arctic marine food webs.  相似文献   

Biogeochemical processes in the water column of the Caspian Sea in November 2008     

Lein  A. Yu.  Rusanov  I. I.  Klyuvitkin  A. A.  Kravchishina  M. D.  Zakharova  E. E.  Veslopolova  E. F.  Makkaveev  P. N.  Ivanov  M. V. 《Doklady Earth Sciences》2010,434(2):1381-1385

Doklady Earth Sciences -  相似文献   

Managing the water of Kilimanjaro: Water,peasants, and hydropower development     

Haakon Lein 《GeoJournal》2004,61(2):155-162

The furrow irrigation systems of Kilimanjaro were first described by European explorers coming to the area by the end of the 19th century. Although being impressed, the German and later the British colonial powers soon came to see the system as wasteful and in need of improvement. Despite several attempts to control water use among the ‘natives’ in the highlands, the furrow system has remained fairly intact and still plays a key role in the local farming systems. However, the utilisation of available water resources is still a highly controversial political issue and in this paper three major challenges to traditional water use are discussed: (i) hydropower development, (ii) construction of large-scale irrigation projects, and (iii) implementation of economic and institutional reforms. All this has led to renewed and intensified conflicts over the use of water on Kilimanjaro as well as in the Pangani river. At one level, the situation can be described as a conflict over access to a scarce resource. However, beyond this perception, the controversies over water are also based on more fundamental ideological conflicts and competing ways of thinking about both development and water management. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Isotopic-geochemical characteristics of the lost city hydrothermal field     

E. O. Dubinina  I. V. Chernyshev  N. S. Bortnikov  A. Yu. Lein  A. M. Sagalevich  Yu. V. Gol’tsman  E. D. Bairova  A. V. Mokhov 《Geochemistry International》2007,45(11):1131-1143

The isotopic (δD, δ¹⁸O, δ¹³C, and ⁸⁷Sr/⁸⁶Sr) and geochemical characteristics of hydrothermal solutions from the Mid-Atlantic Ridge and the material of brucite-carbonate chimneys at the Lost City hydrothermal field at 30°N, MAR, were examined to assay the role of the major factors controlling the genesis of the fluid and hydrothermal chimneys of the Lost City field. The values of δD and δ¹⁸O in fluid samples indicates that solutions at the Lost City field were produced during the serpentinization of basement ultramafic rocks at temperatures higher than 200°C and at relatively low fluid/rock ratios (<1). The active role of serpentinization processes in the genesis of the Lost City fluid also follows from the results of the electron-microscopic studying of the material of hydrothermal chimneys at this field. The isotopic (δ¹⁸O, δ¹³C, and ⁸⁷Sr/⁸⁶Sr) and geochemical (Sr/Ca and REE) signatures indicate that, before its submarine discharging at the Lost City field, the fluid filtered through already cold altered outer zones of the Atlantis Massif and cooled via conductive heat loss. During this stage, the fluid could partly dissolve previously deposited carbonates in veins cutting serpentinite at the upper levels of the Atlantis Massif and the carbonate cement of sedimentary breccias underlying the hydrothermal chimneys. Because of this, the age of modern hydrothermal activity at the Lost City field can be much younger than 25 ka.  相似文献   

Shear zones in porous sand: Insights from ring-shear experiments and naturally deformed sandstones   总被引：2，自引：1，他引：2  

Anita Torabi  Alvar Braathen  Fabrice Cuisiat  Haakon Fossen 《Tectonophysics》2007,437(1-4):37-50

In a high-resolution small-scale seismic experiment we investigated the shallow structure of the Wadi Araba fault (WAF), the principal fault strand of the Dead Sea Transform System between the Gulf of Aqaba/Eilat and the Dead Sea. The experiment consisted of 8 sub-parallel 1 km long seismic lines crossing the WAF. The recording station spacing was 5 m and the source point distance was 20 m. The first break tomography yields insight into the fault structure down to a depth of about 200 m. The velocity structure varies from one section to the other which were 1 to 2 km apart, but destinct velocity variations along the fault are visible between several profiles. The reflection seismic images show positive flower structures and indications for different sedimentary layers at the two sides of the main fault. Often the superficial sedimentary layers are bent upward close to the WAF. Our results indicate that this section of the fault (at shallow depths) is characterized by a transpressional regime. We detected a 100 to 300 m wide heterogeneous zone of deformed and displaced material which, however, is not characterized by low seismic velocities at a larger scale. At greater depth the geophysical images indicate a blocked cross-fault structure. The structure revealed, fault cores not wider than 10 m, are consistent with scaling from wear mechanics and with the low loading to healing ratio anticipated for the fault.  相似文献   

Chlorophyll a in suspended particulate matter of the Caspian Sea as an indicator of biogenic sedimentation conditions     

M. D. Kravchishina  A. A. Klyuvitkin  L. A. Pautova  N. V. Politova  A. Yu. Lein  A. P. Lisitzin 《Doklady Earth Sciences》2015,465(1):1200-1205

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Energy sources for diagenesis: Evidence from the Black Sea     

A. Yu. Lein  I. I. Rusanov  G. A. Pavlova  O. M. Dara  Z. I. Verkhovskaya  E. E. Zakharova  S. K. Yusupov  M. V. Ivanov 《Lithology and Mineral Resources》2011,46(2):135-150

Complex investigations of recent and Drevnechernomorian (ancient Black Sea) sediments from the outer shelf, continental slope, and deep-water basin of the Russian Black Sea sector have been carried out using samples collected during cruise of the R/V Professor Shtokman organized by the Institute of Oceanology of the Russian Academy of Sciences (March 2009) and expedition of “YUZHMORGEO” (summer 2006). Rates of the main anaerobic processes during diagenesis (sulfate reduction, dark CO₂ fixation, methanogenesis, and methane oxidation) were studied for the first time in sediment cores of the studied area. Two peaks in the rate of microbial processes and two sources of these processes were identified: the upper peak near the water-sediment contact is related to the solar energy (OM substrate of the water column) and the lower peak at the base of the Drevnechernomorian sediments with high(>1000 μM) methane concentration related to the energy of anaerobic methane oxidation. The neogenic labile OM formed during this process is utilized by other groups of microorganisms. According to experimental data, the daily rate of anaerobic methane oxidation is many times higher than that of methanogenesis, which unambiguously indicates the migration nature of the main part of methane.  相似文献