Benthic macrofauna and productivity regimes in the Barents Sea — Ecological implications in a changing Arctic

Benthic faunal assemblages were analysed from 47 stations in the central and southern parts of the Barents Sea, together with sedimentary and water column parameters, daily ice records and modelled integrated primary productivity. Sampling spanned areas influenced by Atlantic Water (AW) to those lying under Arctic Water (ArW), and included stations with mixed water masses. Ice cover suppressed water column productivity in the northern areas. Three main faunal groups were identified, based on similarity of numerical faunal composition. The northern and southern faunal groups were separated by the northernmost penetration of AW in the bottom water and the third group, the Hopen group, was influenced by modified bank water. Faunal abundances were significantly higher within the southern faunal group relative to the northern group, but the numbers of taxa present were similar. The particularly rich fauna of the Hopen group reflected sediment heterogeneity and tight pelagic–benthic coupling. These results suggest that a retreat and thinning of the ice cover in the Barents Sea likely will result in the northern parts of the Barents Sea becoming more Atlantic in character, with a higher productivity at the sea floor.     

Geographical analysis of the changes in the demographic situation in Russia for the last 150 years

We present the results derived from reconstructing, for the first time, the time series of some demographic indices of Russia’s regions for the last 150 years. The problem posed for analysis was resolved through the use of extensive, officially published statistical data sets as gathered by these authors at the microlevel (uyezds, and districts) and referred within the contemporary boundaries of the subjects of the Russian Federation using economic-statistical methods and geoinformation technologies.     

Spectrum of quasi-wave disturbances in the topside daytime ionosphere according to the data of radiosounding onboard the Intercosmos-19 satellite

Quasi-wave disturbances in the topside daytime ionosphere, related to auroral activity, have been detected using the data of radiosounding onboard the Intercosmos-19 satellite on April 28, 1979. A disturbance was caused by an abrupt enhancement of the eastward electrojet, which was not reflected in the variations in the AE and AU indices. According to the estimates, the period of electron density disturbances was about 0.5 h, the velocity was 350 m/s, and the length along the meridian was several hundreds of kilometers, which corresponds to medium-scale traveling ionospheric disturbances (TIDs). The disturbance amplitude was only 30 km in the hmF2 variations and 0.20–0.25 MHz in the foF2 variations but increased to 0.25–0.30 MHz in the plasma frequency variations at satellite altitudes of 520–580 km with increasing altitude. It is impossible to register so weak short-period variations during ground-based sounding. The method for detecting disturbance spatial characteristics has been proposed. The disturbance spectrum including three quasiperiodic structures has been revealed using this method. The optimal estimates have been made for the trend, described by the polynomial of the third degree, and for the expansion of the residuals in terms of three harmonics.     

Calculation of atmospheric electric fields penetrating from the ionosphere

The spatial distributions of electric fields and currents in the Earth’s atmosphere are calculated. Electric potential distributions typical of substorms and quiet geomagnetic conditions are specified in the ionosphere. The Earth is treated as a perfect conductor. The atmosphere is considered as a spherical layer with a given height dependence of electrical conductivity. With the chosen conductivity model and an ionospheric potential of 300 kV with respect to the Earth, the electric field near the ground is vertical and reaches 110 Vm⁻¹. With the 60-kV potential difference in the polar cap of the ionosphere, the electric field disturbances with a vertical component of up to 13 V m⁻¹ can occur in the atmosphere. These disturbances are maximal near the ground. If the horizontal scales of field nonuniformity are over 100 km, the vertical component of the electric field near the ground can be calculated with the one-dimensional model. The field and current distributions in the upper atmosphere can be obtained only from the three-dimensional model. The numerical method for solving electrical conductivity problems makes it possible to take into account conductivity inhomogeneities and the ground relief.     

Food webs and carbon flux in the Barents Sea

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.     

Correction of Electron Density Profiles in the Low Ionosphere Based on the Data of Vertical Sounding with the IRI Model

The method of correcting the daytime vertical profiles of electron plasma frequency in the low ionosphere from International Refererence Ionosphere (IRI) model in accordance with the measured data of the virtual heights and absorption of signal radiowaves (method А1) reflected from the bottom of E-region at vertical sounding (VS) is presented. The method is based on the replacement of the IRI model profile by an approximation of analytical dependence with parameters determined according to VS data and partially by the IRI model. The method is tested by the results of four joint ground-based and rocket experiments carried out in the 1970s at midlatitudes of the European part of Russia upon the launches of high-altitude geophysical rockets of the Vertical series. It is shown that the consideration of both virtual reflection heigths and absorption makes it possible to obtain electron density distributions that show the best agreement with the rocket measurements made at most height ranges in the D- and E-regions. In additional, the obtained distributions account more adequately than the IRI model for the contributions of D- and E-regions to absorption of signals reflected above these regions.     

Composition and distribution of sublittoral zoobenthos in Kemskaya Bay of the White Sea

Data on the distribution of the zoobenthos in Kemskaya Bay (the Kem’ River estuary and the White Sea), which is subject to the strong influence of the river discharge, are presented. The number of species at the sampling stations varied from 4 to 65. The density of the communities and the zoobenthos biomass ranged from 342 ± 68 to 4293 ± 96 ind./m² and from 0.418 ± 0.081 to 1975.22 ± 494.36 g/m², respectively. The Shannon index values varied between 1.19 to 4.7 bit/ind. At the upper part of the estuary, detritivores dominated, while, in the central part and at outlets, sestonophages prevailed. The changes in the quantitative indices of the zoobenthos along the gradient of the water salinity were traced, and the relations of these indices with seven more environmental factors were revealed. It was found that the species composition, the biodiversity, and the trophic structure of the zoobenthos significantly correlate with some of the above mentioned parameters. Multiple regression analysis was used to assess the combined effect of the factors, and it revealed which of them play a determining role in Kemskaya Bay: for the species composition, these are the depth, the water color, and the content of total suspended matter; for the number, these are the contents of pelite and C_org in the bottom sediments. The biomass depends on the water salinity, the water chromaticity, and the C_org contents in the sediments and suspended matter. The Shannon index value is determined by the water color, the C_org contents in the sediments, and the pelite content. The calculations of the ecological stress values revealed two zones with an unstable state of the zoobenthos.     

Reconstruction of Electron-Density Height Profiles Based on Vertical Sounding Data under Multistratification of the E Region

Geomagnetism and Aeronomy - A method is proposed for the determination of the height profiles of the electron-plasma frequency based on vertical-sounding ionograms with allowance for additional...     

Identification of new cataclysmic variables in the 1RXS and USNO-B1.0 catalogs

As a result of applying the original optical variability search method on publicly available data, we have found eight new cataclysmic variables and two possible Optically Violent Variable quasars among the previously unidentified X-ray sources in the ROSAT catalog. We describe the search method and present the characteristics of the newly identified variable stars. The obtained results demonstrate the large potential of the concept of Virtual Observatory for identifying new objects of astrophysical interest.     

New cataclysmic variable 1RXS J073346.0+261933 in Gemini

In the course of our search for the optical identifications of ROSAT X-ray sources, we have found a highly variable object with a very unusual behavior on long time scales, rare color indices, and a high X-ray-to-optical flux ratio. We present the archival light curve from the Catalina Sky Survey, optical spectroscopy from RTT150, and time-resolved photometry from the Astrotel-Caucasus telescope. The object appears to be a magnetic cataclysmic variable (a polar) with an orbital period P = 3.20 h.