排序方式： 共有20条查询结果，搜索用时 46 毫秒
1.
Sauveur Belviso Grard Thouzeau Sabine Schmidt Marit Reigstad Paul Wassmann Elena Arashkevich Jacqueline Stefels 《Estuarine, Coastal and Shelf Science》2006,68(3-4):473
In April 1997 and 1998 the significance of sedimentation as a sink for epipelagic dimethylsulphoniopropionate (DMSP) production and as a source for marine sediments was reassessed using a newly designed sediment trap. The behaviour of the traps in immersion was monitored continuously and the collection efficiency was evaluated with 234Th measurements. Net DMS(P) fluxes were corrected for some physical and biological losses during the whole sedimentation process providing reliable estimates of gross DMSP fluxes. It is shown that daily losses by sedimentation account for between 0.1% and 16% of seawater particulate DMSP (DMSPp) standing stocks, and between 3% and 75% of daily DMSPp production. In the Malangen fjord we observed temporal increases of DMSP production and standing stocks which resulted also in increases of DMSP vertical fluxes and DMS(P) concentrations at the sediment surface. This result illustrates how tight the coupling can be between pelagos and benthos, and confirms that DMS(P) concentration in the sediment was a reliable diagnostic indicator of vertical export from overlying waters in Malangen fjord. In Ullsfjord, however, DMS(P) concentrations in the sediment were poorly indicators of Phaeocystis pouchetii export during the early stage of growth of a bloom. The high load of DMS(P) in Balsfjord's sediments could neither be attributed to local vertical sedimentation nor to short-term lateral advection of fresh DMSP-containing phytoplanktonic material, and provides indication that this tracer sometimes also can be misleading. The highest loads of DMS(P) in sediments and the fastest rates of sedimentation occurred in the Southern Bight of the North Sea. 相似文献
2.
C. Svensen D. Vili
i&#x; P. Wassmann E. Arashkevich T. Ratkova 《Estuarine, Coastal and Shelf Science》2007,71(3-4):381-390
The aim of this study was to investigate phytoplankton abundance, composition and vertical export in the highly stratified Krka estuary, Croatia. The estuary is stratified throughout the year, and an interface between fresh- and brackish water plays an important role in production and degradation of biogenic matter. Vertical export of particulate organic carbon (POC), phytoplankton carbon (PPC) and faecal pellet carbon (FPC) was studied by deploying sediment traps in the middle and lower reach of the estuary and in the adjacent coastal zone. Zooplankton faecal pellet (FP) production experiments were conducted to provide additional information on the potential contribution of FP to the total carbon flux. High suspended concentrations of POC, chlorophyll a and phytoplankton was found in the lower reaches of the Krka estuary, adjacent to a source of anthropogenic eutrophication. The fraction of organic detritus to the total POC flux was 61–69% inside the estuary but only 7% at the marine station. This indicates that the primary producers in the surface layer of the Krka estuary are decomposed in and below the interface and then settle as detritus to the bottom. Low sedimentation rates in the coastal zone outside the estuary revealed that the eutrophication does not spread out of the estuary. Mesozooplankton played a modest role in vertical flux regulation, due to their low abundance and dominance of smaller forms as well as low faecal pellet production rates. It is concluded that processes taking place at the freshwater-seawater interface are of major importance for the vertical carbon flux in the investigated area. 相似文献
3.
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
4.
Drits A. V. Pasternak A. F. Kravchishina M. D. Arashkevich E. G. Sukhanova I. N. Flint M. V. 《Oceanology》2019,59(5):669-677
Oceanology - The role of plankton in the vertical flux in the East Siberian Sea was studied in the 69 cruise of the RV “Akademik Mstislav Keldysh” in September 2017. Vertical fluxes... 相似文献
5.
S. Zervoudaki C. Frangoulis C. Svensen E. D. Christou E. Tragou E. G. Arashkevich T. N. Ratkova Ι. Varkitzi E. Krasakopoulou K. Pagou 《Estuaries and Coasts》2014,37(4):911-924
This work focuses on the direct measurement of the vertical flux of appendicularian houses in order to assess their importance as a component of vertical carbon flux in coastal areas. For this purpose, arrays of cylindrical sediment traps were deployed for 5 to 8 days at two depths in a coastal area of the northern Aegean Sea (inner Thermaikos Gulf) during spring. The data support the contention that resuspension was minimal. Fecal pellet (FP) production and grazing experiments with the dominant copepods (Acartia clausi) were conducted to provide additional information on the potential FP contribution to the total carbon flux. The magnitude of the vertical flux of particulate organic carbon (POC) ranged between 310 and 724 mg C m?2 day?1. The proportion of phytoplankton carbon in the POC vertical flux was up to 45 %. The contribution of zooplankton FPs to the total carbon never exceeded 5 %. On the contrary, appendicularian houses were an essential component of the biogenic carbon flux contributing up to 55.3 % of the total vertical carbon flux. Consequently, both phytoplankton and appendicularian houses contributed equally to the biogenic carbon flux exceeding 80 % of the total sinking POC. Taking into account the sinking speed of the particles and the environment in the area, all this carbon probably reaches the seafloor, thus indicating a strong pelagic–benthic coupling. 相似文献
6.
N. D. Romanova V. K. Chasovnikov E. G. Arashkevich S. A. Mosharov A. B. Nikishina A. V. Kostyleva N. E. Louppova 《Oceanology》2016,56(1):114-117
The water conditions and trophic status in the shelf-slope zone and bays of the northeastern Black Sea were evaluated on the basis of monitoring data from 2007–2014. It has been shown that the concentrations of nutrients and chlorophyll “a” in the studied area are at the level of the pristine period (of the late 1970s). The concentration of mineral nitrogen in the surface water layer varied from 0.19 to 5.64 μM. The concentration of phosphates differed from analytical zero to 0.56 μM. The concentration of chlorophyll “a” in different seasons ranged from 0.24 to 0.89 μg/L. The trophic index characterizes the status of the marine shelf ecosystem near Gelendzhik city as “excellent” even in the bays. Significant year-to-year differences in the index were not detected. The range between the values of the trophic index in the bays and open sea was low (3.7 and 3.2, respectively). 相似文献
7.
8.
A. F. Pasternak E. G. Arashkevich U. Grothe A. B. Nikishina K. A. Solovyev 《Oceanology》2013,53(5):547-553
Two copepod species, Calanus finmarchicus (a widespread North Atlantic species) and C. glacialis (an Arctic species), are dominant in the zooplankton of Arctic seas. We hypothesized that the anticipated warming in the Arctic might have different effects on the arctic and boreal species. The effect of temperature on egg production rate (EPR) in these species at temperatures of 0, 2.5, 5, 7.5, and 10°C under contrasting feeding conditions was assessed in 5-day-long experiments. The EPR of the fed C. finmarchicus increased with temperature over the entire tested range. On the contrary, the EPR of C. glacialis increased only in the range of 0–5°C and dropped with further temperature growth. The difference in the influence of temperature on reproduction of these two species is statistically significant. Feeding conditions have a considerable effect on the C. finmarchicus EPR. The EPRs of the female C. glacialis that fed or starved for 5 days displayed no significant difference. These results suggest that the C. finmarchicus EPR increases with temperature under favorable feeding conditions, whereas the C. glacialis EPR decreases at a temperature over 5°C independently of the feeding conditions. This allows for prediction of the shift in abundances of these two species in pelagic communities of Arctic seas in the case of a warming scenario. 相似文献
9.
Belevich T. A. Ilyash L. V. Arashkevich E. G. Flint M. V. 《Doklady Earth Sciences》2019,484(2):207-210
Doklady Earth Sciences - The abundance and biomass of picophytoplankton, the total concentration of chlorophyll a, and the contribution of the picofraction to chlorophyll a were studied in the... 相似文献