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- Jacoby, Charles A., et al.
(författare)
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Vertical distribution, behavior, chemical composition and metabolism of Stauroteuthis syrtensis (Octopoda : Cirrata) in the northwest Atlantic
- 2009
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Ingår i: Aquatic Biology. - : Inter-Research Science Center. - 1864-7782 .- 1864-7790. ; 5:1, s. 13-22
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Tidskriftsartikel (refereegranskat)abstract
- The cirrate octopod Stauroteuthis syrtensis is a mesopelagic species commonly collected in the North Atlantic. Individuals were observed at depths > 600 m and typically within 100 m of the bottom in three similar to 900 m deep canyons indenting the southern edge of Georges Bank. When first sighted, most octopods were floating passively with their webbed arms gathered into a small ball. When disturbed, they expanded their webs to form a 'balloon' shape, swam slowly by Sculling their fins, pulsed their webs like medusae and, in some cases, streamlined their arms and webs and moved away smoothly by rapidly sculling their fins. The bodies of 9 octopods comprised 92 to 95 % water, with tissue containing 9 to 22 % carbon (C) and 2 to 4 % nitrogen (N). These values were similar to those reported for medusae and ctenophores. Oxygen (O(2)) consumption rates of 4.6 to 25.8 mu mol 02 g(-1) C h(-1) were within ranges reported for medusae, ctenophores, and deep-water cephalopods. The stomachs of S. syrtensis, dissected immediately after capture, contained only the calanoid copepod Calan us finmarchicus. Calculations indicated that S. syrtensis need 1.3 to 30.1 ind. d(-1) of C. finmarchicus to meet their measured metabolic demand. Excretion rates (0.3 to 12.4 mu g NH(4)(+) g(-1) C h(-1) and 0.06 to 4.83 mu g PO(4)(3-) g(-1) C h(-1)) were at least an order of magnitude lower than rates reported for other octopods or gelatinous zooplankters. O:N ratios (11 to 366) suggested that S. syrtensis catabolized lipids, which may be supplied by C. finmarchicus. Vertical distribution, relatively torpid behavior and low metabolic rates characterized S. syrtensis as a benthopelagic and relatively passive predator on copepods.
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- Jacoby, Wolfgang R., et al.
(författare)
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Temporal Gravity Variations near Shrinking Vatnajokull Ice Cap, Iceland
- 2009
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Ingår i: Pure and Applied Geophysics. - : Springer Science and Business Media LLC. - 0033-4553 .- 1420-9136. ; 166:8-9, s. 1283-1302
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Tidskriftsartikel (refereegranskat)abstract
- Repeated gravity measurements were carried out from 1991 until 1999 at sites SE of Vatnajokull, Iceland, to estimate the mass flow and deformation accompanying the shrinking of the ice cap. Published GPS data show an uplift of about 13 +/- A 5 mm/a near the ice margin. A gravity decrease of -2 +/- A 1 mu Gal/a relative to the Hofn base station, was observed for the same sites. Control measurements at the Hofn station showed a gravity decrease of -2 +/- A 0.5 A mu Gal/a relative to the station RVIK 5473 at Reykjavik (about 250 km from Hofn). This is compatible, as a Bouguer effect, with a 10 +/- A 3 mm/a uplift rate of the IGS point at Hofn and an uplift rate of similar to 20 mm/a near the ice margin. Although the derived gravity change rates at individual sites have large uncertainties, the ensemble of the rates varies systematically and significantly with distance from the ice. The relationship between gravity and elevation changes and the shrinking ice mass is modelled as response to the loading history. The GPS data can be explained by 1-D modelling (i.e., an earth model with a 15-km thick elastic lithosphere and a 7 center dot 10(17) Pa center dot s asthenosphere viscosity), but not the gravity data. Based on 2-D modelling, the gravity data favour a low-viscosity plume in the form of a cylinder of 80 km radius and 10(17) to 10(18) Pa center dot s viscosity below a 6 km-thick elastic lid, embedded in a layered PREM-type earth, although the elevation data are less well explained by this model. Strain-porosity-hydrology effects are likely to enhance the magnitude of the gravity changes, but need verification by drilling. More accurate data may resolve the discrepancies or suggest improved models.
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- Juday, G.P, et al.
(författare)
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Chapter 14: Forests, Land Management and Agriculture
- 2005
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Ingår i: The Arctic Climate Impact Assessment - The Scientific Report. - Cambridge : Cambridge University Press. - 0521865093 ; , s. 781-862
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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