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Pteropods in Southern Ocean ecosystems 总被引：1，自引：0，他引：1
To date, little research has been carried out on pelagic gastropod molluscs (pteropods) in Southern Ocean ecosystems. However, recent predictions are that, due to acidification resulting from a business as usual approach to CO2 emissions (IS92a), Southern Ocean surface waters may begin to become uninhabitable for aragonite shelled thecosome pteropods by 2050. To gain insight into the potential impact that this would have on Southern Ocean ecosystems, we have here synthesized available data on pteropod distributions and densities, assessed current knowledge of pteropod ecology, and highlighted knowledge gaps and directions for future research on this zooplankton group.Six species of pteropod are typical of the Southern Ocean south of the Sub-Tropical Convergence, including the four Thecosomes Limacina helicina antarctica, Limacina retroversa australis, Clio pyramidata, and Clio piatkowskii, and two Gymnosomes Clione limacina antarctica and Spongiobranchaea australis. Limacina retroversa australis dominated pteropod densities north of the Polar Front (PF), averaging 60 ind m−3 (max = 800 ind m−3) and 11% of total zooplankton at the Prince Edward Islands. South of the PF L. helicina antarctica predominated, averaging 165 ind m−3 (max = 2681 ind m−3) and up to >35% of total zooplankton at South Georgia, and up to 1397 ind m−3 and 63% of total zooplankton in the Ross Sea. Combined pteropods contributed <5% to total zooplankton in the Lazarev Sea, but 15% (max = 93%) to macrozooplankton in the East Antarctic. In addition to regional density distributions we have synthesized data on vertical distributions, seasonal cycles, and inter-annual density variation.Trophically, gymnosome are specialist predators on thecosomes, while thecosomes are considered predominantly herbivorous, capturing food with a mucous web. The ingestion rates of L. retroversa australis are in the upper range for sub-Antarctic mesozooplankton (31.2-4196.9 ng pig ind−1 d−1), while those of L. helicina antarctica and C. pyramidata are in the upper range for all Southern Ocean zooplankton, in the latter species reaching 27,757 ng pig ind−1 d−1 and >40% of community grazing impact. Further research is required to quantify diet selectivity, the effect of phytoplankton composition on growth and reproductive success, and the role of carnivory in thecosomes.Life histories are a significant knowledge gap for Southern Ocean pteropods, a single study having been completed for L. retroversa australis, making population studies a priority for this group. Pteropods appear to be important in biogeochemical cycling, thecosome shells contributing >50% to carbonate flux in the deep ocean south of the PF. Pteropods may also contribute significantly to organic carbon flux through the production of fast sinking faecal pellets and mucous flocs, and rapid sinking of dead animals ballasted by their aragonite shells. Quantification of these contributions requires data on mucous web production rates, egestion rates, assimilation efficiencies, metabolic rates, and faecal pellet morphology for application to sediment trap studies.Based on the available data, pteropods are regionally significant components of the Southern Ocean pelagic ecosystem. However, there is an urgent need for focused research on this group in order to quantify how a decline in pteropod densities may impact on Southern Ocean ecosystems. 相似文献
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A. V. Lozhkin P. M. Anderson N. A. Goryachev P. S. Minyuk A. Yu. Pakhomov T. B. Solomatkina M. V. Cherepanova 《Doklady Earth Sciences》2010,430(2):198-200
Investigation of Pernatoe Lake sediments in the south of Paramushir Island has enabled us to obtain the first continuous pollen
record of climate and vegetation changes in the north of the Kurile archipelago during the Holocene. Series of radiocarbon
datings of between 10 000 ± 40 and 2180 ± 40 years ago are evidence that the beginning of sediments accumulation, found after
borehole development, is related to the Early Holocene. Diatom analysis has shown several stages in the lake development:
raised bog on the border of the Pleistocene and Holocene, lagoon formation resulting from the sea level rise over 9–6 ky,
and freshwater lake formation 6 ky and up to the present. Climate warming during the period attributed to the boreal and Atlantic
periods of the Holocene is reflected by the dominance of Pinus pumila and Alnus serrulata assemblages in vegetation cover. Wide dune fields were formed in the Sea of Okhotsk and the Pacific shores of Paramushir
Island 5–4 ky. Strengthening of atmogenic processes is related to cooling of the climate and drying of some areas of the underwater
slope. 相似文献
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E. V. Ruban G. A. Alekseeva A. A. Arkharov E. I. Hagen-Thorn V. D. Galkin I. N. Nikanorova V. V. Novikov V. P. Pakhomov T. Yu. Puzakova 《Astronomy Letters》2006,32(9):604-607
We present the results of our visual and near-infrared spectrophotometric observations for 77 variable stars obtained during 1971–1991 in Chile, Armenia, and Bolivia. The quasi-monochromatic, extraatmospheric fluxes from the stars are given in absolute energy units (W m?2 m?1) at all wavelengths of the spectral range at 2.5-nm intervals. 相似文献
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Yu. V. Pakhomov 《Astronomy Letters》2012,38(2):101-116
The results of a comparative analysis of the elemental abundances in the atmospheres of 14 red giants with high Galactic space
velocities are presented. For almost all of the chemical elements considered, the their abundance trends with metallicity
correspond to those constructed for thick-disk dwarfs. In the case of sodium, the main factor affecting the [Na/Fe] abundance
in the stellar atmosphere for red giants is the surface gravity that characterizes the degree of development of the convective
envelope. The difference between the [Na/Fe] abundances in the atmospheres of thin- and thick-disk red giants has been confirmed. 相似文献
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Yu. V. Pakhomov 《Astronomy Letters》2013,39(1):54-64
The atmospheric parameters and elemental abundances for ten thick-disk red giants have been determined from high-resolution spectra by the method of model stellar atmospheres. The results of a comparative analysis of the [Na/Fe] abundances in the atmospheres of the investigated stars and thin-disk red giants are presented. Sodium in the atmospheres of thick-disk red giants is shown to have no overabundances typical of thin-disk red giants. 相似文献
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A. Atkinson V. Siegel E.A. Pakhomov M.J. Jessopp V. Loeb 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(5):727-740
Despite much research on Euphausia superba, estimates of their total biomass and production are still very uncertain. Recently, circumpolar krill databases, combined with growth models and revisions in acoustics have made it possible to refine previous estimates. Net-based databases of density and length frequency (KRILLBASE) yield a summer distributional range of ～19×106 km2 and a mean total abundance of 8×1014 post-larvae with biomass of 379 million tonnes (Mt). These values are based on a standardised net sampling method but they average over the period 1926–2004, during which krill abundance has fluctuated. To estimate krill biomass at the end of last century we combined the KRILLBASE map of relative krill density around Antarctica with an acoustics-derived biomass estimate of 37.3 Mt derived for the Scotia Sea area in 2000 by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). Thus the CCAMLR 2000 survey area contains 28% of the total stock, with total biomass of ～133 Mt in January–February 2000. Gross postlarval production is estimated conservatively at 342–536 Mt yr?1, based on three independent methods. These are high values, within the upper range of recent estimates, but consistent with the concept of high energy throughput for a species of this size. The similarity between the three production estimates reflects a broad agreement between the three growth models used, plus the fact that, for a given population size, production is relatively insensitive to the size distribution of krill at the start of the growth season. These production values lie within the envelope of what can be supported from the Southern Ocean primary production system and what is required to support an estimated predator consumption of 128–470 Mt yr?1. Given the range of recent acoustics estimates, plus the need for precautionary management of the developing krill fishery, our net-based data provide an alternative estimate of total krill biomass. 相似文献
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Using atmosphere models based on high-resolution spectra, we have derived the abundances of chemical elements in the atmospheres of seven classical barium stars and compared them with the elemental abundances of moderate barium stars and normal red giants. The behavior of elements up to the iron peak is the same in all three groups of giants, providing evidence that they have a common origin. The dependence of the anomalous abundances of s-process elements on stellar mass and metallicity is qualitatively similar for all three groups, probably indicating that a substantial role is played by the evolutionary phase of the stars. We conclude that the barium-star phenomenon and the overabundances of s-process elements in barium stars cannot be explained as a consequence of binarity alone. The extent to which the s-process elements are overabundant is affected by the mass, metallicity, and evolutionary phase of the given star, and any of these parameters may prove to be important in a specific object. 相似文献
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A. A. Boyarchuk Yu. V. Pakhomov L. I. Antipova M. E. Boyarchuk 《Astronomy Reports》2002,46(10):819-829
We used high-resolution spectra to compute model atmospheres to derive the atmospheric abundances of moderate barium stars. Comparing our results with analogous data for normal red giants, we find that the moderate barium stars appear to not differ systematically from normal red giants. Their chemical abundance anomalies show the same patterns and can be interpreted in terms of evolutionary effects: the evolutionary stage, mass, luminosity, and metallicity of the objects. 相似文献
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The non-LTE sodium abundance has been determined from the Na I 6154 and 6161 Å lines for 38 thin-disk stars (15 of them are Ba II stars), 15 thick-disk stars, 13 Hercules-stream stars, and 13 stars that cannot be attributed neither to the thick Galactic disk nor to the thin one. The Na I model atom has been constructed using the most accurate present-day atomic data. For the Na I 6154 and 6161 Å lines, the non-LTEabundance corrections are from ?0.06 to ?0.24 dex, depending on the stellar parameters. No differences in [Na/Fe] abundance between the thick and thin disks have been detected; the derived ratios are close to the solar ones. The existence of a [Na/Fe] overabundance in the Ba II stars has been confirmed. The Hercules-stream stars exhibit nearly solar [Na/Fe] ratios. The results obtained can be used to test the sodium nucleosynthesis models. 相似文献