The role of sediments in the phosphorus cycle in Lake Lugano. II. Seasonal and spatial variability of microbiological processes at the sediment-water interface   总被引：1，自引：1，他引：0  

Maja A. Lazzaretti  Kurt W. Hanselmann  Helmut Brandl  Daniel Span  Reinhard Bachofen 《Aquatic Sciences - Research Across Boundaries》1992,54(3-4):285-299

P, Fe, Mn, and S species were analyzed in water samples from the sediment-water interface collected at four seasonally different times during the course of a year at two sampling sites in the southern basin of Lake Lugano (Lago di Lugano). The results reveal the strong influence of the biogeochemical processes in the sediment on the chemical composition of the lake water above. Consumption of oxygen and nitrate under oxic to microoxic conditions in the water column as well as sequential release of reduced manganese and iron under anoxic conditions was observed as a direct or indirect consequence of microbially mediated degradation of organic matter. The seasonal pattern observed for the release and the retainment of dissolved reduced iron and manganese correlates well with the one for dissolved phosphate. Iron, manganese and phosphorus cycling are coupled tightly in these sediments. Both sediment types act as sinks for hydrogen sulfide and sulfate. An inner-sedimentary sulfur cycle is proposed to couple iron, manganese and phosphorus cycling with the degradation of organic matter. Nutrient cycling at the sediment-water interface might thus be driven by a microbially regulated electron pumping mechanism. The results contribute to a better understanding of the role of sediment processes in the lake's internal phosphorus cycle and its seasonal dynamics.  相似文献   

氧同位素在海洋磷酸盐研究中的应用     

陈法锦  黄亚楠  曾珍 《矿物岩石地球化学通报》2014,33(6)

海洋中磷酸盐的氧同位素组成不但记录现代海水磷循环的信息(磷酸盐的来源和生物地球化学作用),还记录古环境的信息。因此,利用氧同位素研究海洋磷酸盐正日益受到国内外研究人员的重视。本文综述了利用磷酸盐氧同位素研究方法及其在现代海洋环境与古海洋的应用进展,展示了中国海洋磷酸盐氧同位素研究现状,提出了今后的研究方向。  相似文献   

气候变暖下干旱对森林生态系统的影响     

周国逸  李琳  吴安驰 《南京气象学院学报》2020,12(1):81-88

人类活动显著影响着全球大气循环格局,全球平均温度升高导致干旱事件发生幅度、频度和持续时间增加,这对森林生态系统带来更多的是负面影响.本文基于已有研究,系统总结了干旱事件对森林生态系统地理分布格局、群落结构重建、植物生长和生理特性、死亡和灭绝、植物生产力以及碳循环功能的影响及其机理,并对未来干旱事件对森林生态系统长期效应以及在不同时间尺度上作用机理的研究提出建议.本研究对开展全球变化背景下森林生态系统对干旱事件响应机制的研究具有重要指导意义.  相似文献   

龙门山前陆褶皱冲断带的平衡剖面分析   总被引：49，自引：10，他引：39       下载免费PDF全文

陈竹新  贾东  张惬  魏国齐  李本亮  魏东涛  沈扬 《地质学报》2005,79(1):38-45

对龙门山前陆褶皱冲断带形成的正反转构造过程有过许多分析 ,但明显缺乏直接的证据和定量的分析。本文在地层资料分析的基础上 ,借助平衡剖面分析验证龙门山形成的正反转构造过程 :志留纪至中三叠世受多条倾向北西的同沉积断裂控制 ;晚三叠世以来遭受北西—南东向挤压、抬升和剥蚀 ,形成逆冲推覆构造。在晚三叠世和新生代的两期板块碰撞的影响下 ,龙门山产生了两期褶皱冲断作用 ,但在南、北两段表现出显著不同的变形过程。龙门山北段表现为复杂的逆冲推覆构造 ,能明确划分出两期构造变形 ,晚三叠世的变形强烈 ,缩短率达 31.7% ;而新生代的变形较弱 ,缩短率仅为 10 .5 %。南段则表现出基底卷入的叠瓦状冲断的特点 ,主要体现新生代的构造变形 ,晚三叠世的构造变形基本上被改造 ,南段整体缩短率达 2 6 .2 %。  相似文献   

Deglaciation and catchment ontogeny in coastal south‐west Greenland: implications for terrestrial and aquatic carbon cycling     

Melanie J. Leng  Bernd Wagner  N. John Anderson  Ole Bennike  Ewan Woodley  Simon J. Kemp 《第四纪科学杂志》2012,27(6):575-584

Here we present Holocene organic carbon, nitrogen, sulphur, carbon isotope ratio and macrofossil data from a small freshwater lake near Sisimiut in south‐west Greenland. The lake was formed c. 11 cal ka BP following retreat of the ice sheet margin and is located above the marine limit in this area. The elemental and isotope data suggest a complex deglaciation history of interactions between the lake and its catchment, reflecting glacial retreat and post‐glacial hydrological flushing probably due to periodic melting of local remnant glacial ice and firn areas between 11 and 8.5 cal ka BP. After 8.5 cal ka BP, soil development and associated vegetation processes began to exert a greater control on terrestrial–aquatic carbon cycling. By 5.5 cal ka BP, in the early Neoglacial cooling, the sediment record indicates a change in catchment–lake interactions with consistent δ¹³C while C/N exhibits greater variability. The period after 5.5 cal ka BP is also characterized by higher organic C accumulation in the lake. These changes (total organic carbon, C/N, δ¹³C) are most likely the result of increasing contribution (and burial) of terrestrial organic matter as a result of enhanced soil instability, as indicated by an increase in Cenococcum remains, but also Sphagnum and Empetrum. The impact of glacial retreat and relatively subdued mid‐ to late Holocene climate variation at the coast is in marked contrast to the greater environmental variability seen in inland lakes closer to the present‐day ice sheet margin. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Evaluation of nitrogen cycling associated with agricultural production and environmental load in a mountain region,in Hokkaido,Japan     

Lei Liang  Datian Jin  Ning Hu 《山地科学学报》2008,5(2):130-139

This study examined the nitrogen cycling associated with agricultural production and environmental load in central Hokkaido. The nitrogen （N） budget analysis model offers a new set of tools for evaluating N cycling in agro-ecosystems. The cycling index （CI） is a useful tool for estimating optimal N flows in farmlands. The fertilization index （FI） is a useful indicator for characterizing the N flows related to farms. Using these parameters, we analyzed all farm systems to estimate the optimal N cycling for minimizing N pollution in groundwater and maximizing agricultural production in mountain regions of Japan. The results showed that the critical N application rate （chemical fertilizer ＋ manure） was 143.3 kg N ha^-1 y^-1. The critical inter-system input （chemical fertilizer N, imported food and feed N, and natural supplied N） was 169.2 kg N ha^-1y^-1.  相似文献   

Quantifying nitrogen cycling beneath a meander of a low gradient,N‐impacted,agricultural stream using tracers and numerical modelling     

Stephen J. Van der Hoven  Nicholas J. Fromm  Eric W. Peterson 《水文研究》2008,22(8):1206-1215

In watersheds impacted by nitrate from agricultural fertilizers, nitrification and denitrification may be decoupled as denitrification in the hyporheic zone is not limited to naturally produced nitrate. While most hyporheic research focuses on the 1–2 m of sediment beneath the stream bed, there are a limited number of studies that quantify nitrogen (N) cycling at larger hyporheic scales (10s of metres to kms). We conducted an investigation to quantify N cycling through a single meander of a low gradient, meandering stream, draining an agricultural watershed. Chemistry (major ions and N species) and hydrologic data were collected from the stream and groundwater beneath the meander. Evidence indicates that nearly all the shallow groundwater flowing beneath the meander originates as stream water on the upgradient side of the meander, and returns to the stream on the downgradient side. We quantified the flux of water beneath the meander using a numerical model. The flux of N into and out of the meander was quantified by multiplying the concentration of the important N species (nitrate, ammonium, dissolved organic nitrogen (DON)) by the modelled water fluxes. The flux of N into the meander is dominated by nitrate, and the flux of N out of the meander is dominated by ammonium and DON. While stream nitrate varied seasonally, ammonium and DON beneath the meander were relatively constant throughout the year. When stream nitrate concentrations are high (>2 mg litre^?1), flow beneath the meander is a net sink for N as more N from nitrate in stream water is consumed than is produced as ammonium and DON. When stream nitrate concentrations are low (<2 mg litre^?1), the flux of N entering is less than exiting the meander. On an annual basis, the meander hyporheic flow serves as a net sink for N. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

南极普里兹湾碳循环研究进展          下载免费PDF全文

张凡  高众勇孙恒 《极地研究》2013,25(3):284-293

普里兹湾是南大洋碳循环研究典型代表海区,也是中国历次南大洋考察的重点调查区域。从初级生产力、营养盐、叶绿素、海-气CO₂通量、真光层颗粒有机碳（POC）输出通量,净群落生产力（NCP）等方面综合阐述了其碳循环特征。生物泵运转效率和海冰过程是碳吸收的主要控制因素。普里兹湾总体上可以从陆坡划界,分为湾内和湾外两大部分。两者碳循环特征差异显著。湾内碳循环过程活跃,是南大洋夏季的高生产力区域。湾外则表现出高营养盐、低叶绿素（HNLC）特征,初步认为存在Fe限制。总体上,溶解有机碳（DOC）、POC、营养盐、叶绿素、二氧化碳分压（pCO₂）等存在从湾内向湾外随纬度递增或递减的规律。海冰消长对碳循环过程影响剧烈。夏季融冰造成的冰藻释放、水体垂直稳定性增加是提高生物生产力的首要原因。总体上普里兹湾的碳循环受各种生物、物理过程及其耦合作用控制,对南大洋碳循环机制研究有重要意义。  相似文献   

黔南晚石炭世旋回珊瑚礁群落演化研究     

常洪伦  宋晓东  王艳敏 《吉林地质》2012,(3):23-27

发育于黔南地区的扁坪—岩板寨晚石炭世旋回珊瑚礁由3个旋回组成,每个旋回都具有较高的生物含量和生物多样性。根据生物的丰度和功能可识别出叶状藻-"不明管状物"群落、Ivanovia cf.manchurica群落、Tubiphytes群落和Fomitchevella群落。旋回珊瑚礁的演化过程可划分为6个阶段。分析表明,礁体形成过程中曾一度出现了高能的环境,第二、三旋回经历了迅速的环境变化。  相似文献   

Foraging across ecosystems: diet diversity and social foraging spanning aquatic and terrestrial ecosystems by an invertebrate     

Mark E. Laidre 《Marine Ecology》2013,34(1):80-89

Ecosystems are fundamentally connected to one another, although empirical documentation of the links between them, especially the links between marine and terrestrial ecosystems, has been limited. This study examined the foraging behavior and ecology of an understudied invertebrate, the hermit crab Coenobita compressus, which is remarkably abundant at the nexus of marine, terrestrial, and freshwater ecosystems. Data collected between 2008 and 2011 in the Osa Peninsula of Costa Rica revealed that C. compressus plays a generalist scavenger role across ecosystems. Beach almond fruits (Terminalia catappa) were a staple of the crabs’ diet, but the crabs also commonly consumed a variety of other fruit species and various parts of plants (nuts, seeds, flowers, husk, stems, buds) as well as algae, fungus, animal feces, and the carcasses of insects, jellyfish, conspecifics, other crustacean species, freshwater and saltwater fish, sea turtles (eggs and adults), and mammals. The crabs fed on these resources in prominent social aggregations, also forming such aggregations as they exchanged the aquatically derived gastropod shells that they use as homes while roaming the land. The size of the crabs’ aggregations around plant versus animal resources and around terrestrial versus aquatic resources did not differ, underscoring the species’ generalist foraging behavior. Broadly, these results suggest that C. compressus has one of the most diverse diets of any crustacean and plays a critical role in recycling organic matter and nutrients. This species might also mediate the passage of resources across different ecosystems, although further research is needed to explore this possibility.  相似文献