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381.
Miguel Alvarez Cobelas María Verdugo Carmen Rojo 《Aquatic Sciences - Research Across Boundaries》1995,57(3):185-198
Coupling of multivariate methods and time series analysis can be ueful for studying dynamics of aquatic communities. This is demonstratred with a data set from the pelagic area of an oligo-mesotrophic lake in Central Spain during 61 consecutive days of Autumn overturn. Abiotic variables, phytoplankton species and their total biomass were traced. Species abundance and specific biomass were considered as indices of community structure and resource partitioning, respectively. Abiotic and algal data sets were subjected to factor analyses of cases separately. Atmospheric forcing and nitrogen could be considered as the main (2) driving variables of the abiotic matrix. The coupling of motile abilities and cell size was associated to the main factors of the community structure matrix whereas phosphorus limitation and species responses to buoyancy represented the main factors of the biomass matrix. Coordinates of the two first factors could be used to mimic the trajectories in the data space. Significant short term lags (1–4 days) were found in most time series. Lagged responses of atmospheric forcing and nitrogen on phytoplankton community structure and resource partitioning at scales of 1–7 days were also shown. Overall phytoplankton biomass did not show significant delayed responses, thereby suggesting that it might be resulting from the interplay of other non-studied factors. 相似文献
382.
本文报道了1991/1992年南极夏季在普里兹湾邻近海域浮游植物调查的研究结果。经鉴定共有浮游植物3门26属78种;其平均细胞丰度为120±174×105个/m3,密集区分布在62°S、78°~103°E,这一海域其细胞丰度在110×105~864×105个/m3之间。根据浮游植物种类组成和细胞丰度百分比的聚类分析,测区浮游植物群落中可划分为四个聚合类群:菱形藻(Nitzschia)与赖氏针杆藻(Synedrareinboldi)、长环毛藻(Corethroncriophilum)与翼根管藻(Rhizosoleniaala-ta)和翼根管藻与赖氏针杆藻占优势的聚合类群及由海冰习性的菱形藻与近岸性角刺藻(Chaetoceros)占优势组成的中山站近岸单一生态类群。文中还讨论了浮游植物丰度与环境因子的关系并对过去数年南极浮游植物的调查结果进行了比较 相似文献
383.
384.
We treat the ocean carbon cycle as a coupled physical-biogeochemical process. The interactions between mixed-layer dynamics
and growth of phytoplankton in the layer are discussed, and the formal relationship between phytoplankton accumulation and
new production is examined. A coupled biological-physical model is presented for studying the classical spring bloom in the
N. Atlantic, and possible differences in the mechanisms that drive the seasonal phytoplankton blooms in the N. Atlantic and
the Arabian Sea are discussed. Finally, recommendations are made for observational programs to improve our understanding of
the biologically-mediated carbon cycle in the Arabian Sea. 相似文献
385.
盘星藻烷烃生物标志物特征及其热演化试验的初步研究 总被引:6,自引:2,他引:6
本文以盘星藻作为典型样品,研究淡水水生单细胞藻类的烷烃生物标志特征及其热解生烃特征。实验结果表明,盘星藻生烃主要分成四大类:正烷烃、稀烃、无环类异戊二烯和二环萜类。nC17在正烷烃组分中占51.6%。检出一组C20的二环萜类同分异构体,其含量相当于正浣烃含量的97.1%。盘星藻热解生烃也以低碳数烃类为主,与高等植物来源的烃类相区别;甾烷C29/(C27+C28+C29)值为0.5左右,与海洋浮游生 相似文献
386.
387.
Some chemical and biological parameters were analysed at sixteen stations in the mangrove ecosystem, of the neighbouring Gautami-Godavari
(GG) river estuary and Kakinada (KKD) bay to understand the present status of water quality and the impact of external terrigenous
inputs during southwest (SW) monsoon in the study areas. High concentrations of nutrients in the mangrove ecosystem compared
to the bay and estuarine ecosystems reveal the importance of this zone as a source of nutrients to the adjacent coastal ecosystems.
Low Si:N:P (29:4:1) ratios in these ecosystems are due to the enrichment of these nutrients through external anthropogenic
inputs even after the utilization by phytoplankton in the biological cycle. The mean Chl b/Chla and Chl c/Chla ratios and high phaeopigments (Pp) concentrations compared to Chlb and high ratios of Chl a/Pp suggests the possibility of the potential growth of phytoplankton populations in lower light
intensity and low turbulent areas of these mangrove ecosystems. 相似文献
388.
Qianli XIE Peter Dillon Lewis Molot 《中国地球化学学报》2006,25(B08):204-204
In aquatic environment, iron redox reaction may occur through a) microbial activity and b) photo-chemistry. Iron chemistry plays a significant role in the health of aquatic ecosystems. For example, Fe^2+ is more mobile than Fe^3+. Iron can be bound to dissolved organic carbon (DOC), and when Fe^2+ is oxidized to Fe^3+ (biotically or abiotically), Fe is precipitated and induce co-precipitation of the DOC. Furthermore, iron is a major nutrient to aquatic organisms. Because Fe^2+ is more bioavailable than Fe^3+, iron redox chemistry can be a controlling factor in biological production, such as algae bloom which can be a public health concern. Experiments have shown that Fe redox reactions, biotically or abiotically, can generate significant Fe isotope fraction among different Fe species. Accordingly, analysis of Fe isotope composition of phytoplanktons can be a valuable tool in studying Fe dynamics in ecosystems. Precise measurement of Fe isotope, however, presents some challenges. Recent advances in mass spectrometry, specifically high resolution MC-ICP-MS, allow measurement of Fe isotopes free of interferences. 相似文献
389.
Abstract The Sagara oil field is located in the Neogene Kakegawa Basin, close to the Izu collision zone at the junction between the main Japanese Islands and the Izu–Bonin Arc. The Sagara oil field is one of the few oil fields situated in a forearc basin on the Pacific side of Japan and is present in a sedimentary basin with poor oil-generating potential. Several crude oils from Sagara oil field were investigated to infer their origin. Organic geochemical characteristics of Sagara oils showed the influences of light biodegradation, migration-contamination, and migration-fractionation. The maturity levels of Sagara oils evaluated based on abundant alkylnaphthalenes corresponded to 0.9–1.2% vitrinite reflectance. Sagara oils were characterized by significant amounts of higher plant biomarkers, a high pristane/phytane ratio and an absence of organic sulphur compounds, suggesting a siliciclastic source rock deposited under nearshore to fluvial–deltaic environments. Numerous faults and fractures in the active forearc basin provided excellent conduits and facilitated upward migration of light hydrocarbons generated at greater depth in the Kakegawa Basin. 相似文献
390.
原油中生物标志物的组成是成藏史的反映 总被引:11,自引:1,他引:10
油藏中原油的生物标志化合物不仅可以指示生油岩的类型,成熟度,而且可以映油藏的充注方向及成藏史,以济阳坳陷中的孤南洼陷和津洼陷为例,利用生物标志物化合物进行油源对比,区分现不同成因的原油,并确定了不同的成熟阶段,孤南洼陷的油田中有分别生成于沙一段和沙三段的原油,利津洼陷的油田中则是来自于少三段和沙四段的原油,它们各自的成熟度指示成藏的期次和时间,沙一段和沙四段生油岩形成咸水环境,开始生烃早,对应于R 相似文献