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A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization 总被引:63,自引:0,他引:63
Boyd PW Watson AJ Law CS Abraham ER Trull T Murdoch R Bakker DC Bowie AR Buesseler KO Chang H Charette M Croot P Downing K Frew R Gall M Hadfield M Hall J Harvey M Jameson G LaRoche J Liddicoat M Ling R Maldonado MT McKay RM Nodder S Pickmere S Pridmore R Rintoul S Safi K Sutton P Strzepek R Tanneberger K Turner S Waite A Zeldis J 《Nature》2000,407(6805):695-702
Changes in iron supply to oceanic plankton are thought to have a significant effect on concentrations of atmospheric carbon dioxide by altering rates of carbon sequestration, a theory known as the 'iron hypothesis'. For this reason, it is important to understand the response of pelagic biota to increased iron supply. Here we report the results of a mesoscale iron fertilization experiment in the polar Southern Ocean, where the potential to sequester iron-elevated algal carbon is probably greatest. Increased iron supply led to elevated phytoplankton biomass and rates of photosynthesis in surface waters, causing a large drawdown of carbon dioxide and macronutrients, and elevated dimethyl sulphide levels after 13 days. This drawdown was mostly due to the proliferation of diatom stocks. But downward export of biogenic carbon was not increased. Moreover, satellite observations of this massive bloom 30 days later, suggest that a sufficient proportion of the added iron was retained in surface waters. Our findings demonstrate that iron supply controls phytoplankton growth and community composition during summer in these polar Southern Ocean waters, but the fate of algal carbon remains unknown and depends on the interplay between the processes controlling export, remineralisation and timescales of water mass subduction. 相似文献
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Chlorodimeform and its effect on monoamine oxidase activity in the cattle tick, Boophilus microplus.
The action of the acaricide, chlorodimeform and its metabolite. N-desmethylchlorodimeform, on the activity monoamine oxidase (MAO) from the cattle tick, Boophilus microplus, were studied. Both compounds were found to be potent in vitro and in vivo inhibitors of the enzyme. However the inhibition of MAO does not seem to be related to the toxic action of the acaricide. 相似文献
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Summary The action of the acaricide, chlorodimeform and its metabolite, N-desmethylchlorodimeform, on the activity monoamine oxidase
(MAO) from the cattle tick,Boophilus microplus, were studied, Both compounds were found to be potent in vitro and in vivo inhibitors of the enzyme. However the inhibition
of MAO does not seem to be related to the toxic action of the acaricide. 相似文献
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Exposure of rare-earth films to hydrogen can induce a metal-insulator transition, accompanied by pronounced optical changes. This 'switchable mirror' effect has received considerable attention from theoretical, experimental and technological points of view. Most systems use polycrystalline films, but the synthesis of yttrium-based epitaxial switchable mirrors has also been reported. The latter form an extended self-organized ridge network during initial hydrogen loading, which results in the creation of micrometre-sized triangular domains. Here we observe homogeneous and essentially independent optical switching of individual domains in epitaxial switchable mirrors during hydrogen absorption. The optical switching is accompanied by topographical changes as the domains sequentially expand and contract; the ridges block lateral hydrogen diffusion and serve as a microscopic lubricant for the domain oscillations. We observe the correlated changes in topology and optical properties using in situ atomic force and optical microscopy. Single-domain phase switching is not observed in polycrystalline films, which are optically homogeneous. The ability to generate a tunable, dense pattern of switchable pixels is of technological relevance for solid-state displays based on switchable mirrors. 相似文献
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大叶白麻叶化学成分的研究 总被引:1,自引:0,他引:1
从大叶白麻[poacynumhendersonii(Hookf)woodson]叶中分得2个木脂素类化舍物,经理化常数测定和光谱分析,分别鉴定为(-)-丁香脂素[(-)-Syringaresino1]和( )-松脂素-4-O-β-D-葡萄糖甙[( )-Pinoresionol-4-0-β-D-glucopyranoside]. 相似文献
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