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Steven P. Beukema R.V. Krishnamurthy N. Juyal N. Basavaiah A.K. Singhvi 《Quaternary Research》2011,75(3):597-604
Stable isotope analysis along with radiocarbon and luminescence dating of late Pleistocene lacustrine deposits at Burfu in the higher central Himalaya are used to interpret hydrologic changes in the lake basin. From 15.5 ka to ~ 14.5 ka the Burfu lake was largely fed by melting glaciers. A warming event at 14.5 ka suggests an enhanced monsoon and increased carbonate weathering. From ~ 13.5 ka to ~ 12.5 ka the isotopic data suggest large-amplitude climate variability. Following this, the isotope data suggest a short-lived, abrupt cooling event, comprising a ~ 300-yr intense cool period followed by a ~ 500-yr interval of moderate climate. A shift in isotope values at ~ 11.3 ka may signify a strengthening monsoon in this region. The inferred climatic excursions appear to be correlative, at least qualitatively, with global climatic events, and perhaps the Burfu lake sequence provides regional evidence of globally recorded excursions. This study also suggests a potential use of radiocarbon ages in specific environments as a paleoenvironmental proxy. 相似文献
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I. D. Williams J. van der Meer R. Dekker J. J. Beukema S. P. Holmes 《Journal of Sea Research》2004,52(4):1
Using data taken from three long-term monitoring programs, we modelled the population dynamics of 13 common macrozoobenthic species of the Balgzand, an approximately 50 km2 intertidal area in the Dutch part of the Wadden Sea. In order to identify likely interactions among species, while accounting as much as possible for other factors influencing population dynamics, models included both ‘environmental’ (water temperature, and phytoplankton concentration) and ‘biological’ (biomass of potentially interacting species) variables. This approach appeared to be effective at identifying certain types of interactions acting over relatively short time-frames, such as predation and competition for food. Among the species we considered, the strongest effects of this kind appeared to be from what we presume to be predation by Nephtys hombergii, and from competition for food among bivalves. Several of the strongest results of our analysis corroborated expectations derived from previous small-scale surveys or experimental studies, but there were also a number of highly significant results indicating possible interactions which were not immediately explicable, including the apparent positive effect of Macoma balthica on Arenicola marina, and the apparent negative effect of Nephtys hombergii on Mya arenaria. Our results also suggest that year to year changes in Cerastoderma edule and Arenicola marina populations did not have substantial and widespread influences on the population dynamics of the majority of other common infauna, which is not to deny the likely critical importance of recruitment effects and biogenic transformation of the intertidal environment by these species over longer time frames. Our modelling approach could be applied to other long-term data sets, and will become more useful as longer time series become available. 相似文献
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Consequences of the Sudden Removal of Nearly All Mussels and Cockles from the Dutch Wadden Sea 总被引：4，自引：0，他引：4
Abstract. Three successive years of recruitment failure, intensive fishery, and high rates of natural mortality eliminated all intertidal mussel beds and nearly all cockle beds from the Dutch Wadden Sea in the course of 1990. In late 1990 and early 1991, zoobenthic biomass and particularly bivalve stocks were unprecedentedly low. The following unusual events were noted:
It is concluded that the Wadden Sea ecosystem responded in an elastic way to the removal of two of its key species. The events are not seen as merely coincidental but are regarded as a chain of causes and effects. 相似文献
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Relatively high diatom and chlorophyll concentrations in the autumn of 1990 and an exceptionally early and dense spring bloom of diatoms in March 1991;
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Exceptionally early onset of rapid growth in the bivalve Macoma balthica in March 1991;
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Above-average weights of the soft parts of bivalves in the 1990/91 winter;
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Elevated mortality rates in bivalves that could serve as alternative prey for birds specialised on big bivalves (oystercatchers and eiders);
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Signs of food shortage in such birds: high mortality rates and emigration to other feeding areas;
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A rapid recovery of the benthos started in the summer of 1991, accelerated by an exceptionally high recruitment in some of the affected species.
It is concluded that the Wadden Sea ecosystem responded in an elastic way to the removal of two of its key species. The events are not seen as merely coincidental but are regarded as a chain of causes and effects. 相似文献
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