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581.
Maarten Blaauw Barbara Wohlfarth J. Andrés Christen Linda Ampel Daniel Veres Konrad A. Hughen Frank Preusser Anders Svensson 《第四纪科学杂志》2010,25(3):387-394
Several large abrupt climate fluctuations during the last glacial have been recorded in Greenland ice cores and archives from other regions. Often these Dansgaard–Oeschger events are assumed to have been synchronous over wide areas, and then used as tie‐points to link chronologies between the proxy archives. However, it has not yet been tested independently whether or not these events were indeed synchronous over large areas. Here, we compare Dansgaard–Oeschger‐type events in a well‐dated record from southeastern France with those in Greenland ice cores. Instead of assuming simultaneous climate events between both archives, we keep their age models independent. Even these well‐dated archives possess large chronological uncertainties that prevent us from inferring synchronous climate events at decadal to multi‐centennial time scales. If possible, comparisons between proxy archives should be based on independent, non‐tuned time‐scales. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
582.
The effect of forest litter on snow surface albedo has been subject to limited study, mainly in the hardwood‐dominated forests of the northeastern United States. Given the recent pine beetle infestation in Western North America and associated increases in litter production, this study examines the effects of forest litter on snow surface albedo in the coniferous forests of south‐central British Columbia. Measured changes in canopy transmittance provide an indication of canopy loss or total litterfall over the winter of 2007–2008. Relationships between percent litter cover, an index of albedo, snow depth, and snow ablation during the 2008 melt season are compared between a mature, young, and clearcut coniferous stand. Results indicate a strong feedback effect between canopy loss and subsequent enhanced shortwave transmittance, and litter accumulation on the snow surface from that canopy loss. However, this relationship is confounded by other variables concurrently affecting albedo. While results suggest that a relatively small percent litter cover can have a significant effect on albedo and ablation, further research is underway to extract the litter signal from that of other factors affecting albedo, particularly snow depth. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
583.
Abstract The frequency and directional wave‐modelling capability of the Ocean Data Gathering Program (ODGP) deep water spectral wave model is assessed through comparison with WAVEC data gathered at Hibernia. Both qualitative and quantitative analyses indicate better agreement with observations during storms and with the wind‐driven component of the wave spectra. There is statistically poor modelling of the swell. A coherence analysis on derived wave vectors indicates that the ODGP model does not simulate geophysical variability with time‐scales less than about 30 h for overall spectral energy and less than 24 h for wave energy of frequency greater than 0.6 rad s?1 (0.095 Hz). The signals associated with swell waves are incoherent at nearly all time‐scales. 相似文献
584.
The growing aquaculture industry is projected to feature ever more prominently in the lives and economies of rural coastal communities in Atlantic Canada and around the world. Both private industry and government have a responsibility to ensure employment opportunities created in aquaculture take place in healthy, safe environments. However, systematic occupational health and safety (OHS) research within this industry, an important prevention tool, is still in its infancy. With particular emphasis on marine aquaculture in Atlantic Canada, we provide a detailed outline of the structure of the industry from feed production through to processing, identify potential OHS hazards associated with each of these activities and make recommendations for future research and action. 相似文献
585.
A litter bag experiment was performed on a wrack-loaded beach in Hornsund (southern Spitsbergen) to study the decay rate of stranded macroalgae and their colonization by meiofauna. The average monthly loss of macroalgal dry mass was 45 ± 5%. The composition of the wrack-associated fauna was similar to those reported from other world regions. Nematodes composed of bacterivorous rhabditids and monhysterids were the numerically dominant taxon (>99% of the community). High nematode densities averaging 35,000 ind. per litter bag (6,500 ind g−1 dwt) indicate their skills for rapid colonization and successful exploitation of the short-lived habitat established on an Arctic beach. We suggest that stranded macroalgae may play a role as a potential hotspot for nematodes and microbial processes in the Arctic coastal ecosystem. It is also suggested that wrack position on the beach profile which resulted in different wrack-age and moisture content may affect the composition and diversity of the wrack-associated meiofauna. 相似文献
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588.
Melanie S. Adams Barbara Demmig-Adams Ruiqi Li Daniel Zarate Jingchun Li 《Marine Ecology》2020,41(6):e12618
Coral reefs’ high productivity has been attributed mainly to photosymbioses between the coral animal and algae of the family Symbiodiniaceae, with recognition that the host can increase algal photosynthesis by concentrating nutrients and enhancing the efficiency of light absorption. Here, we propose that an additional effect, consumption of carbohydrate by the host, may also enhance algal photosynthesis. We examine evidence from symbiosis between terrestrial plants and root fungi that indicates a link between carbohydrate consumption by the symbiotic partner and photosynthetic upregulation in the plant system. In addition, we review evidence from free-living algae manipulated to exude carbohydrate into the external medium, which was associated with strong upregulation of photosynthetic capacity. We offer suggestions on how host-induced carbohydrate release may increase photosynthesis rates in the symbionts in the intact photosymbiosis and how this relationship evolved. 相似文献
589.
Leptiminus, a Roman port city on the west coast of Tunisia, North Africa, exported olive oil and a garum fish paste to Rome. Excavations have uncovered many facilities including kilns and a potter's workshop, indicating an extensive ceramic industry. The vessels, manufactured at Leptiminus, included African red‐slip fineware, coarseware, and amphorae. A petrographic study of pottery sherds showed them to contain very similar temper, rounded aeolian sand grains and limestone, but varying in proportions to produce different textures. An investigation of the source of raw materials for the pottery found three distinct types of clay within a 50 km radius of Leptiminus: grey Miocene, brown Pliocene, and green Late Pliocene clay. Statistical analysis of trace element compositions, using induced neutron activation, of clays and sherds showed that the Pliocene brown clay was used to create all types of pottery. The specific clay horizon, used in Roman times, has apparently been removed by quarrying. However, a lateral continuation of this bed was found 7 m beneath the Leptiminus site 290. © 2002 Wiley Periodicals, Inc. 相似文献
590.
Samples from extremely acidic waters should be taken using the introduced syringe technique avoiding atmospheric contact to minimize CO2 evaporation from the samples. The syringe technique inclusive manual injection enables the determination of TIC in acid waters with high precision and accuracy. If a TOC analyser with a small sample volume is used, the vials should be filled directly inside the water sampler without air bubbles, covered with aluminium foil and transported at ambient water temperatures. If an autosampler is used, partial selection of the vials increases the stability of the results. Care should be taken that samples can be analysed within a short time. 相似文献