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影响萼花臂尾轮虫种群增长的生态学因子的研究:温度和饵料密度的影响 总被引:11,自引:0,他引:11
本文研究了在5个温度梯度和4个饵料密度的20个试验组合下,萼化臂尾轮虫(Brachionuscalyciflorus)的种群增长规律。结果表明,该轮虫实验种群的最适温度范围是28—32℃,临界高温是36-40℃;最适饵料密度是45-65×106个/ml。这两个生态因子的最佳组合是温度32℃,饵料密度为65×106个/ml,此时,种群达最大密度3.4×103个/ml。 相似文献
33.
High-resolution measurements of chromophoric dissolved organic matter in the Mississippi and Atchafalaya River plume regions 总被引:4,自引:0,他引:4
Chromophoric dissolved organic matter (CDOM) was measured in the spring and summer in the northern Gulf of Mexico with the ECOShuttle, a towed, instrumented, undulating vehicle. A submersible pump mounted on the vehicle supplied continuously flowing, uncontaminated seawater to online instruments in the shipboard laboratory and allowed discrete samples to be taken for further analysis. CDOM in the northern Gulf of Mexico was dominated by freshwater inputs from the Mississippi River through the Birdfoot region and to the west by discharge from the Atchafalaya River. CDOM was more extensively dispersed in the high-flow period in the spring but in both time periods was limited by stratification to the upper 12 m or so. Thin, subsurface CDOM maxima were observed below the plume during the highly stratified summer period but were absent in the spring. However, there was evidence of significant in situ biological production of CDOM in both seasons.The Mississippi River freshwater end member was similar in spring and summer, while the Atchafalaya end member was significantly higher in the spring. In both time periods, the Atchafalaya was significantly higher in CDOM and dissolved organic carbon (DOC) than the Mississippi presumably due to local production and exchange within the coastal wetlands along the lower Atchafalaya which are absent along the lower Mississippi. Nearshore waters may also have higher CDOM due to outwelling from coastal wetlands. High-resolution measurements allow the differentiation of various water masses and are indicative of rapidly varying (days to weeks) source waters. Highly dynamic but conservative mixing between various freshwater and marine end members apparently dominates CDOM distributions in the area with significant in situ biological inputs (bacterial degradation of phytoplankton detritus), evidence of flocculation, and minor photobleaching effects also observed. It is clear that high-resolution measurements and adaptive sampling strategies allow a more detailed examination of the processes that control CDOM distributions in river-dominated systems. 相似文献
34.
A Stable Carbon Isotope Study of the Food-web in a Freshwater-deprived South African Estuary, with Particular Emphasis on the Ichthyofauna 总被引:1,自引:0,他引:1
The importance of macrophytes as food sources for estuarine nekton is unclear. Previous carbon isotope investigations in the macrophyte-dominated, freshwater-deprived Kariega Estuary showed that the bivalveSolen cylindraceusdid not utilize the dominant estuarine macrophytes found within the estuary as a primary food source. This finding prompted questions as to what the nekton of this estuary utilize as primary energy sources. δ13C analyses of the principal autochthonous and allochthonous primary carbon sources, as well as the dominant invertebrate and fish species, indicate that there are two main carbon pathways within the Kariega Estuary. The littoral community, which incorporates the majority of crustaceans, gobies, mullet and a sparid, utilizes δ13C enriched primary food sources namelySpartina maritima,Zosteracapensis and epiphytes. The channel fauna, which includes the zooplankton, zooplanktivorous and piscivorous fish, utilizes a primary food source depleted in δ13C, which is most likely a mixture of phytoplankton, terrestrial plant debris and C4macrophyte detritus. The C3saltmarsh macrophytesSarcocornia perennisandChenolea diffusa, as well as benthic microalgae, appear to be less important as primary food sources to the nekton of the Kariega Estuary. 相似文献
35.
研究外荷载为长期非平稳随机过程。考虑长期荷载的特性 ,采用 1个概率谱密度函数来反映长期非平稳随机荷载及其特征 ;概率谱密度函数是基于大量的一般谱密度函数的统计特性获得。以延长结构的抗疲劳使用寿命为目标函数 ,提出了调谐质量减振阻尼器的优化设计方法 ,这在实际工程中有着极为广阔的应用前景。本文旨在从理论上发展长期非平稳随机荷载作用下调谐质量减振阻尼器的优化设计方法 ;文中采用长期波浪实测数据 ,给出了 1个数值算例说明整个设计过程。 相似文献
36.
Qualitative and quantitative composition of meiobenthos was studied in Amursky Bay (Peter the Great Bay, the East Sea). Ten
taxonomic groups were found, where nematodes were dominant. Density of meiobenthos in ground sediments of the Bay were not
uniform, and the average density was measured at 126.4±62.3 ind. m-2. 56 species of nematodes were detected, and dominant species wereSabatieria palmaris, Paracanthonchus macrodon, Sphaerolaimus limosus, S. gracilis andOncholaimium ramosum. Five taxocenes of nematodes were allocated based on the results of cluster analysis and species domination according to density.
Low diversity in species composition of nematodes was noted in the northwestern part of the Bay, which is a zone of desalination,
and in the eastern part, which is exposed to household drains. 相似文献
37.
Katsumi Matsumoto 《Journal of Oceanography》2006,62(6):887-902
Iron fertilization of nutrient-rich surface waters of the ocean is one possible way to help slow the rising levels of atmospheric
CO2 by sequestering it in the oceans via biological carbon export. Here, I use an ocean general circulation model to simulate
a patch of nutrient depletion in the subpolar northwest Pacific under various scenarios. Model results confirm that surface
fertilization is an inefficient way to sequester carbon from the atmosphere (Gnanadesikan et al., 2003), since only about 20% of the exported carbon comes initially from the atmosphere. Fertilization reduces future production
and thus CO2 uptake by utilizing nutrients that would otherwise be available later. Effectively, this can be considered as leakage when
compared to a control run. This “effective” leakage and the actual leakage of sequestered CO2 cause a significant, rapid decrease in carbon retention (only 30–45% retained after 10 years and less than 20% after 50 years).
This contrasts markedly with the almost 100% retention efficiency for the same duration using the same model, when carbon
is disposed directly into the northwest Pacific (Matsumoto and Mignone, 2005). As a consequence, the economic effectiveness
of patch fertilization is poor in two limiting cases of the future price path of carbon. Sequestered carbon in patch fertilization
is lost to the atmosphere at increasingly remote places as time passes, which would make monitoring exceedingly difficult.
If all organic carbon from one-time fertilization reached the ocean bottom and remineralized there, acidification would be
about −0.05 pH unit with O2 depletion about −20 μmol kg−1. These anomalies are probably too small to seriously threaten deep sea biota, but they are underestimated in the model because
of its large grid size. The results from this study offer little to advocate purposeful surface fertilization as a serious
means to address the anthropogenic carbon problem. 相似文献
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