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1.
Correlations between guillemots (including Common Guillemots Uria aalge and Brünnich's Guillemots U. lomvia) and their prey (divided into five prey categories, capelin Mallotus villosus , herring Clupea harengus , polar cod Boreogadus saida , plankton, and a mixture of other prey species) at two depths (10-100 m and 100-200m) were estimated along an extended transect of 3,060 nautical miles (5,667 km) in the Barents Sea in April/May 1986. Spatial concordance was highest during daylight hours when the largest number of birds were seen on water (presumably feeding birds). Capelin was the single prey category which was most often associated with birds but no single prey category could alone explain the distribution of birds. Although only a small fraction of guillemots could be identified to species, there was some evidence that capelin were of greater importance to Common than to Brünnich's Guillemots. Overall correlation between birds and total prey density was statistically significant at the smallest scale of 5 nautical miles (n.m.). The removal of herring from the calculations increased the strength of the correlation. The depth at which prey was located had little effect on the distribution of birds. The correlation between birds and prey was scale dependent, and reached a maximum at 90 n.m., although there seemed to be some upper threshold in the coefficient at c. 40 n.m. Numerical concordance (including only 5 n.m. periods where both prey and birds were present) was significant at the 5 n.m. scale but was higher for high density than for low density prey patches. The results are discussed in relation to the few similar studies in other oceans and in relation to the severe reduction of important prey species in the Barents Sea. 相似文献
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Palynology in a polar desert, eastern North Greenland 总被引：2，自引：0，他引：2
SVEND FUNDER NIELS ABRAHAMSEN 《Boreas: An International Journal of Quaternary Research》1988,17(2):195-207
A pollen diagram from a lake in a polar desert in eastern North Greenland records the regional vegetation history back to c. 7,000 years calBP (6,000 years convBP) in this extreme environment, which presents the coldest thermal regime where vascular plants can grow. The diagram shows that polar desert developed from sparse high arctic tundra at c. 4,300 years calBP (3,900 years convBP), owing to reduced summer heat. Also adjacent parts of high arctic Greenland, Canada and Svalbard suffered environmental decline, and polar deserts - presently restricted to a narrow fringe of land at the shores of the Arctic Ocean - were even more restricted before this time. Like other arctic vegetation types, polar desert is highly sensitive to summer temperatures, and its southern limit coincides with the isotherm for mean July temperatures of 3.5C. A comparison with the Northwest European ice-age pollen record shows no evidence of summers as cold as those now prevailing in the extreme north, and the results support the contention that the present Arctic and the ice-age mid-latitude environments are not identical. 相似文献
3.
The distributional patterns of Barents Sea harp seals (Phoca groenlandica) throughout the year are presented based on existing literature and recent Norwegian and Russian field observations. The harp seals breed in February-March in the White Sea. Moulting occurs during April to June in the White Sea and southern Barents Sea. Feeding.behaviour is closely related to the configuration and localisation of the drifting sea-ice during summer and autumn (June-October) when the seals follow the receding ice edge, retiring gradually northwards and northeastwards in the Barents Sea. The southward movement of the population in autumn probably takes place in November prior to the advance of the ice edge, and is likely related to food-search. Apparently, most Barents Sea harp seals seems to concentrate at the southern end of their range in winter and spring. 相似文献
4.
ABSTRACT Permian aeolian sediments on the island of Arran are divisible into dune (including draa) and interdune deposits. Both types display a distinctive and unusually wide variation in grain size. The dominant features of the dune deposits are grainfall lamination, sandflow lamination, and inverse graded lamination associated with ripple-form lamination and normal graded lamination. The flat-lying aeolian interdune deposits are characterised by granule and sand ripples, horizontal lamination in coarse sand and granules, plane bed lamination and inverse graded lamination. Associated structures include ripple-form lamination and deflation lags. Three types of trace fossil associated with completely bioturbated horizons occur in some low-angle dune and interdune deposits.
The aeolian facies interfinger with alluvial fan deposits giving rise to three recognizable facies belts. Marginal aeolian deposits are associated with fluvial conglomerates and are dominated by interdune deposits and occasionally very thin barchan deposits (set height 3-37 cm). Intermediate aeolian deposits are characterized by interbedded crescentic dune, small draa (dune set height 5 cm-4.5 m) and interdune deposits, and rare fluvial and lake sediments. Basinal aeolian deposits are dominated by draa deposits (dune set height 0.2-28 m) associated with rare interdune sediments. Transverse dunes and draas were moved by north-eastern palaeowinds towards the foot of the alluvial fans. The aeolian sediments were deposited in a fault-bounded desert basin. 相似文献
The aeolian facies interfinger with alluvial fan deposits giving rise to three recognizable facies belts. Marginal aeolian deposits are associated with fluvial conglomerates and are dominated by interdune deposits and occasionally very thin barchan deposits (set height 3-37 cm). Intermediate aeolian deposits are characterized by interbedded crescentic dune, small draa (dune set height 5 cm-4.5 m) and interdune deposits, and rare fluvial and lake sediments. Basinal aeolian deposits are dominated by draa deposits (dune set height 0.2-28 m) associated with rare interdune sediments. Transverse dunes and draas were moved by north-eastern palaeowinds towards the foot of the alluvial fans. The aeolian sediments were deposited in a fault-bounded desert basin. 相似文献
5.
What determines the distribution of seabirds at sea? 总被引：1，自引：0，他引：1
6.
Heat conservation during cold exposure in birds (vasomotor and respiratory implications) 总被引：1，自引：0，他引：1
The mechanisms by which peripheral circulation and respiration serve in maintaining thermal homeostasis in birds living in cold climates are reviewed. Three types of arteriovenous heat exchanger (an elaborate , a simple rete , and a venae comitantes system) are found in the legs of birds. The anatomical differences between the different types of A-V associations are described, and the regulation of peripheral blood flow, in respect to maximal heat conservation and prevention of tissue damage, is discussed. A nasal temporal counter current heat exchanger, lowering the temperature of the expired air to values considerably below the body temperature, is the most important mechanism for minimizing the respiratory heat and water loss. In addition, a decreased ventilatory requirement, caused by a changed respiratory pattern and an increased parabronchial oxygen extraction, lowers the amount of air ventilated relative to the amount of oxygen uptake. Thus, the relative loss of heat and water is reduced. 相似文献
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Ship-following Kittiwakes Rissa tridactyla were caught and dye-marked with picric acid on three occasions from a ship trawling in the Barents Sea in August 1986. The ship trawled regularly every 20-30 nautical miles and most of the trawl contents were fed to the birds accompanying the ship. Kittiwakes followed the ship for an average of 480-591 min. Between trawl-stations the birds rested on lifeboats and on the rail of the ship, and resting birds showed aggressive behaviour towards neighbours and intruders. The mean departure rate ranged from 4.2 to 5.1% per hour, and the turnover rate was 32 hours. It is obvious that the Kittiwakes behaved opportunistically and had adapted to exploit the waste from the commercial fisheries in the area. 相似文献
9.
Two-dimensional seismic modelling has been undertaken on an overall progradational succession of sloping mudstone and sandstone units from the Palaeogene of Spitsbergen. The modelling shows that the main geometric features of the section would be resolved at 1500 m depth (with frequencies below 60 Hz, which is common in seismic data at these depths). However, interference between the base and top of lithological units gives lateral amplitude variations and discrepancies between the seismic image and the geometrical model. This is particularly prominent in low-frequency models. Terminations of reflectors, resembling toplap and onlap, may be interpreted, but are artefacts of the general convergence of lithological units present in the geometrical model. The geological section causes a seismic pattern resembling sigmoid progradational seismic facies. Two-dimensional seismic modelling is an efficient tool in bridging the gap between outcrop observations and subsurface data. Hence, modelled outcrop sections are important as reference points' for improved seismic stratigraphic interpretation. 相似文献
10.
A total of 138 walruses ( Odobenus rosmarus rosmarus ), including 21 cow/calf pairs, were observed during a ship-board survey in the southeastern Barents and Pechora seas 5-17 February 1993. The observations confirm these areas as wintering and nursery grounds for the species. 相似文献