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41.
42.
Age verification of rubyfish (Plagiogeneion rubiginosum) was sought using the bomb radiocarbon chronometer procedure. Stable isotopes were investigated for life history characteristics. Radiocarbon (14C) and stable isotope (δ18O and δ13C) levels were measured in micro-samples from five otoliths that had been aged using a zone count method. All the core 14C measurements were ‘pre-bomb’ indicating ages of at least 45 years, and the 14C measurements across the otolith sections suggested that the zone-count ageing method described herein is not biased. Maximum estimated age was 100 years. There was no significant between-sex difference in the von Bertalanffy growth curves. The δ18O values indicated that rubyfish are near-surface as juveniles, and move deeper with age. Adults appear to reside in 600–1000 m; this is deeper than most trawl-capture data suggest, but not implausible, and has stock assessment implications. The δ13C values reflect fish metabolic rates, trophic feeding levels and oceanographic conditions. The stable isotopes record the environmental life history of each fish, and have value in distinguishing stocks and/or indicating vertical and latitudinal migratory patterns. 相似文献
43.
David R. Butler 《地球表面变化过程与地形》2012,37(8):876-882
Many beaver ponds in the Rocky Mountains, that have been described in the literature, are in‐channel ponds that are relatively small and short‐lived. This paper describes floodplain beaver ponds on low‐gradient deltas in glacial finger lakes in Glacier National Park, Montana. These ponds are distinctly larger, probably fed by hyporheic flow, and stable and long‐lived. Ponds examined were, with one exception, 44 years old. Glacial discharge is present in each valley where beaver ponds occupy low‐gradient deltas, and this discharge likely sustains pond water level over the course of the summer. As glaciers recede and disappear, deltaic beaver ponds dependent on hyporheic flow may be negatively affected. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
44.
David R. Butler 《自然地理学》2013,34(4):275-276
45.
Two adjacent beaver-pond sequences of seven ponds each were examined along the eastern boundary of Glacier National Park, Montana, to determine spatial patterns and amounts of sedimentation, both within individual ponds and along pond sequences. Dams and their associated ponds were categorized into two age groups, young versus old, based on dam morphology and surface vegetation. Old ponds contained significantly more sediment than did young ponds. However, hypothesized patterns of downstream reductions in coarse-grained sediment, both within a pond and along a sequence, were not observed, nor were there any discernible patterns in sediment texture across ponds. [Key words: beaver pond, sedimentation, Rocky Mountains, Montana.] 相似文献
46.
P.M. Butler 《Cretaceous Research》2012,33(1):135-145
‘Triconodonts’ are relatively rare in the new Purbeck Limestone Group mammal fauna, especially in comparison with the finds made in the nineteenth century in the same beds. However, besides some remains of the already known Triconodontidae, a new possible morganucodontan of uncertain familial affinities, Purbeckodon batei gen. et sp. nov., has been discovered, extending considerably the chronological range of the order while constituting another testimony to the vitality and diversity of Mesozoic mammals. 相似文献
47.
D. Rickard B. Hatton D. M. Murphy I. B. Butler A. Oldroyd A. Hann 《Aquatic Geochemistry》2011,17(4-5):545-566
Plasmid DNA was incubated at 25°C with aqueous solutions of dissolved Fe(II), S(-II), and nanoparticulate FeS with a mackinawite structure, FeSm. At ??0.1 mM total dissolved Fe(II) and S(-II), an increase in the proportion of the relaxed plasmid DNA occurs, through scission of the DNA backbone. In solutions where FeSm was precipitated, nanoparticulate FeSm binds to the DNA molecules. In solutions with concentrations below the FeSm solubility product, nicking of supercoiled pDNA occurs. Plasmid DNA appears to be a sensitive proxy for radical reactions. The reactant is proposed to be a sulfur-based radical produced from the iron-catalyzed decomposition of bisulfide, in a manner analogous to the Fenton reaction. This is further supported by experiments that suggest that sulfide free radicals are produced during the photolysis of aqueous solutions of polysulfides. Supercoiling of DNA affects nearly all DNA?Cprotein transactions so the observation of relaxation of supercoiled forms through reaction with FeS solutions has direct implications to biochemistry. The results of this experimentation suggest that genotoxicity in FeS-rich systems is a further contributory factor to the limited survival of organisms in sulfidic environments. Mutations resulting from the interactions of organisms and mobile elements, such as plasmids, in sediments will also be affected in sulfide-rich environments. 相似文献
48.
H.P. Jarvie P.M. Haygarth C. Neal P. Butler B. Smith P.S. Naden A. Joynes M. Neal H. Wickham L. Armstrong S. Harman E.J. Palmer-Felgate 《Journal of Hydrology》2008,350(3-4):215-231
This study examined stream water quality across a range of catchments which are representative of the key environments and land uses of rural south-west England. These catchments included: (a) an acidic upland headwater catchment, rising on the moorlands of Dartmoor, with low-intensity sheep rearing; (b) a headwater catchment rising on the weathered granite lower slopes of Dartmoor, with cattle farming; (c) a lowland headwater clay catchment with sub-surface drainage and high intensity livestock farming, fodder crop cultivation, and hard-standing/slurry storage; and (d) the main River Taw, a lowland river system receiving drainage from a range of tributaries, exemplified by the above catchment types. Variations in water chemistry and quality were observed along an upland–lowland transition, from headwater streams to the main river channel. Within the livestock-dominated headwater streams, total phosphorus (TP) was dominated by particulate phosphorus (PP). These PP concentrations appeared to be mainly linked to two sets of processes: (1) in-stream sediment precipitation with sorption/co-precipitation of phosphate and/or localised in-channel mobilisation of sediment (by cattle or channel-clearing operations) under low flow conditions, and (2) sediment erosion and transportation associated with near-surface runoff during storm events. Under baseflow conditions, in-stream and/or riparian processes played a significant role in controlling general nutrient chemistry, particularly in the headwater streams which were heavily impacted by livestock. 相似文献
49.
50.
Hori Yukari Gough William A. Butler Ken Tsuji Leonard J.S. 《Theoretical and Applied Climatology》2017,129(3-4):1309-1320
Theoretical and Applied Climatology - In northern Canada, winter roads are essential for communities. The duration of the winter road season depends on particular meteorological conditions. In this... 相似文献