Microphytobenthic biomass and species composition in intertidal flats of the Nakdong River estuary, Korea   总被引：1，自引：0，他引：1  

GuoYing Du  Moonho Son  Misun Yun  Soonmo An  Ik Kyo Chung   《Estuarine, Coastal and Shelf Science》2009,82(4):663-672

Intertidal microphytobenthos (MPB) were investigated monthly from August 2006 to March 2008 at four different sites in the sand flats of Nakdong River estuary, Korea. Samples of surface sediment (ca. 1 cm) were collected, and chlorophyll a was extracted as biomass estimation. Species identification and enumeration were carried out by light microscopy, assisted where necessary by scanning electronic microscopy. Biomass varied between 0.47 and 16.58 μg cm⁻³, abundance changed from 5.25 to 414.75 × 10³ cells cm⁻³, while the Shannon diversity indexes ranged between 0.69 and 2.35 H′. Thirty-nine MPB taxa were identified, primarily composed of epipelic diatoms, among which Amphora and Navicula were the most abundant genera. Based on the biomass, abundance, species composition and their dynamics, MPB assemblages of sampling sites were grouped into three distinct communities corresponding to their sediment composition characteristics. Multivariate correlation analysis revealed that biomass was positively related to mud and very fine sand, negatively related to fine and medium sand, but not significantly related to environmental factors such as pore water nutrients, light intensity and salinity, which fluctuated rapidly during emersion period. Cluster analysis corroborated the division of MPB communities according to site types on seasonal scales, and also showed seasonality between sites by cluster of all summer groups. Principal component analysis identified that variability in species composition was significantly affected by mud, very fine sand, fine sand, light intensity, and sediment temperature. This study suggests that sediment composition plays an important role in the functioning of intertidal MPB communities in estuarine ecosystems.  相似文献   

Effects of iron limitation on intracellular cadmium of cultured phytoplankton: Implications for surface dissolved cadmium to phosphate ratios     

Erin S. Lane  David M. Semeniuk  Robert F. Strzepek  Jay T. Cullen  Maria T. Maldonado   《Marine Chemistry》2009,115(3-4):155-162

This study compares intracellular Cd content (Cd:C) of cultured marine phytoplankton grown under various Fe levels, with estimated particulate Cd:P ratios derived from regression slopes of Cd versus PO₄³⁻ relationships from a global dataset. A 66-fold difference in Cd:C ratios was observed among the seven species grown under identical Fe concentrations, with oceanic diatoms having the highest Cd quotas and prymesiophytes the lowest. Interestingly, all species significantly increased their Cd:C ratios under Fe-limitation (on average 2-fold). The global data set also showed that the mean estimated Cd:P ratio of surface water particulates in HNLC (high nutrient low chlorophyll) regions were approximately 2-fold higher than non-HNLC regions. A sequence of events are proposed to explain high Cd:P ratios in HNLC waters. First, the seasonal relief from Fe-limitation in HNLC regions leads to blooms of large chain forming diatoms with high intrinsic Cd:P ratios. These large blooms may, in theory, deplete surface water CO₂ and Zn concentrations, which ultimately, would result in increased Cd uptake. Eventually these blooms will run out of Fe, which has been shown to further increase intercellular Cd via growth biodilution and increased Cd uptake through non-specific Fe(II) transporters. Ultimately, Fe-limited diatoms with enhanced Cd quotas will sink out of surface waters leading to pronounced regional differences in Cd:P ratios between HNLC and non-HNLC waters in the global ocean.  相似文献   

Enceladus' plume: Compositional evidence for a hot interior     

Dennis L. Matson  Julie C. Castillo  Torrence V. Johnson 《Icarus》2007,187(2):569-573

The combined observations of Saturn's moon Enceladus by the Cassini CAPS, INMS and UVIS instruments detected water vapor geysers in which were present molecular nitrogen (N₂), carbon dioxide (CO₂), methane (CH₄), propane (C₃H₈), acetylene (C₂H₂), and several other species, together with all of the decomposition products of water. We propose that the presence of N₂ in the plume indicates thermal decomposition of ammonia, and hence high temperatures in the interior of the moon (e.g., 500 to 800 K). Such an environment also appears to be suitable for the production of methane (CH₄) from carbon monoxide (CO), or carbon dioxide (CO₂). The presence of C₂H₂ and C₃H₈ strongly suggest that catalytic reactions took place within a very hot environment. The internal environment of Enceladus is inferred to be or have been favorable for aqueous, catalytic chemistry. This permits the synthesis of many complex organic compounds that could be detected in future Cassini observations.  相似文献   

氮、磷对大亚湾大鹏澳海区浮游植物群落的影响Ⅱ种类组成   总被引：1，自引：0，他引：1  

朱艾嘉  黄良民  林秋艳  许战洲 《热带海洋学报》2009,28(6):103-111

根据2005年4－5月（春季）、8月（夏季）和11月（秋季）对大亚湾大鹏澳海区表层的现场调查结合营养盐加富实验，探讨了不同季节氮（NO3－或脲氮 (urea)）和无机磷（PO43－）营养元素对浮游植物种类组成的潜在影响。大鹏澳海区浮游植物优势种有明显季节变化，秋季种类组成的平面变化最明显。春季浮游植物平均细胞密度最高但多样性指数最低。实验结果显示，春季至夏季浮游植物优势种翼根管藻模式变型Rhizosolenia alata f. genuina、丹麦细柱藻Leptocylindrus danicus和绕孢角毛藻Chaetoceros cinctus之间的演替可能受氮、磷条件变化的控制。夏季优势种菱形海线藻Thalassionema nitzschioides和威氏海链藻Thalassiosira weissflogii之间的演替可能受营养条件外的因素控制。尽管磷被认为是该海区浮游植物生长的主要限制因子，但夏季无机氮磷比值较高的实验组中未出现磷限制现象，无机氮磷比值的变化对浮游植物种类组成也没有显著影响，而秋季氮对浮游植物种类组成有较明显的潜在影响。  相似文献   

Influence of neutral transport on ion chemistry uncertainties in Titan ionosphere     

N. Carrasco  E. Hbrard  M. Banaszkiewicz  M. Dobrijevic  P. Pernot 《Icarus》2007,192(2):519-526

Models of Titan ionospheric chemistry have shown that ion densities depend strongly on the neutral composition. The turbulent diffusion transport conditions, as modeled by eddy coefficients, can spectacularly affect the uncertainty on predicted neutral densities. In order to evaluate the error budget on ion densities predicted by photochemical models, we perform uncertainty propagation of neutral densities by Monte Carlo sampling and assess their sensitivity to two turbulent diffusion profiles, corresponding to the extreme profiles at high altitudes described in the literature. A strong sensitivity of the ion density uncertainties to transport is observed, generally more important than to ion–molecule reaction parameters themselves. This highlights the necessity to constrain eddy diffusion profiles for Titan ionosphere, which should progressively be done thanks to the present and future measurements of the orbiter Cassini.  相似文献   

Ion chemistry and N-containing molecules in Titan's upper atmosphere     

V. Vuitton  R.V. Yelle 《Icarus》2007,191(2):722-742

High-energy photons, electrons, and ions initiate ion-neutral chemistry in Titan's upper atmosphere by ionizing the major neutral species (nitrogen and methane). The Ion and Neutral Mass Spectrometer (INMS) onboard the Cassini spacecraft performed the first composition measurements of Titan's ionosphere. INMS revealed that Titan has the most compositionally complex ionosphere in the Solar System, with roughly 50 ions at or above the detection threshold. Modeling of the ionospheric composition constrains the density of minor neutral constituents, most of which cannot be measured with any other technique. The species identified with this approach include the most complex molecules identified so far on Titan. This confirms the long-thought idea that a very rich chemistry is actually taking place in this atmosphere. However, it appears that much of the interesting chemistry occurs in the upper atmosphere rather than at lower altitudes. The species observed by INMS are probably the first intermediates in the formation of even larger molecules. As a consequence, they affect the composition of the bulk atmosphere, the composition and optical properties of the aerosols and the flux of condensable material to the surface. In this paper, we discuss the production and loss reactions for the ions and how this affects the neutral densities. We compare our results to neutral densities measured in the stratosphere by other instruments, to production yields obtained in laboratory experiments simulating Titan's chemistry and to predictions of photochemical models. We suggest neutral formation mechanisms and highlight needs for new experimental and theoretical data.  相似文献   

柴达木盐湖化工科学研究联合基金实施概况   总被引：1，自引：1，他引：0  

李积升  年洪恩 《盐湖研究》2018,26(2):81-85

对2014~2017年国家自然科学基金委员会—青海省人民政府柴达木盐湖化工科学研究联合基金申报与资助项目进行分析,重点研究联合基金实施概况,指出实施成效及存在的问题,并提出解决相关问题的发展建议,通过对联合基金资助和实施结果进行探讨,不断总结经验,优化模式,更好地为柴达木盐湖化工科学研究联合基金创新发展提供制度保障和参考依据。  相似文献   

自动气象站采集器通道及合成误差分析          下载免费PDF全文

张天华  郭瑞宝 《气象与环境科学》2018,41(2):120-125

数据采集器通道误差是自动气象站观测系统误差来源的重要组成部分,直接影响自动站各要素观测数据的准确性,其与温、湿、压、风等各气象要素传感器误差的合成构成了自动气象站误差。在稳定的实验室环境条件下,利用高精度测量仪表,通过对多台CAWS600型采集器进行精确测量,得到自动站采集器各气象要素通道误差的校准数据。对温、湿、压、风等要素的自动测量系统(传感器和采集器)误差分析结果表明,自动站误差等于传感器误差与采集器通道误差之和。此外,采集器各主要通道的误差存在一定的分布规律:有10台采集器气温通道误差≤0.1℃,主要分布在-0.1~0.1℃,所占比例为77%;有3台采集器通道误差0.15℃而≤0.20℃,所占比例为23%。在600-1090 h Pa量程内,气压通道误差主要分布在-0.10~0.10 h Pa;风向、湿度通道误差较小,误差值相近,方向较一致,风向通道误差≤1°,湿度通道误差≤1%。  相似文献   

地球化学组成揭示的杜蒙沙地化学风化和沉积再循环特征及其对风尘物质贡献的指示   总被引：1，自引：0，他引：1  

袁方  谢远云  詹涛  康春国  迟云平  马永法 《地理科学》2017,37(12):1885-1893

对杜蒙沙地的河流冲积砂、河漫滩泥质粉砂、沙质古土壤和风成沙等不同类型沉积物进行了采样（27组）,对这些样品的细颗粒组分（<63 μm）进行了常量元素、微量元素、稀土元素（REE）和Sr-Nd同位素比值等地球化学分析,就杜蒙沙地的化学风化、沉积再循环特征及其对风尘物质的贡献等展开了讨论。结果显示,杜蒙沙地的地球化学组成表现出空间的均一性,低的化学蚀变指数CIA（48~56,平均52）及A-CN-K和A-CNK-FM图解均表明了杜蒙沙地仅遭受了低级的化学风化程度。沙地的成分成熟度较低,大部分河流沉积物表现出初次循环沉积特征,系大兴安岭东侧中酸性岩浆母岩风化剥蚀的产物经嫩江搬运堆积形成;古土壤表现出与河流沉积物相同的初次循环特征,表明古土壤的成土母质是河流沉积物,这与野外地层出露情况一致;风成沙表现出再循环沉积特征,系河流沉积物就地起沙搬运堆积形成。不活动元素比值、REE和Sr-Nd同位素比值等物源判别图解,结合植被和地貌状况,一致表明杜蒙沙地与东北平原中东部的风尘物质没有地球化学亲缘关系,其对该地区（甚至下风向更远地区）的大气风尘的贡献很小。  相似文献   

Application of partial least squares regression and WetSpa model to determine factors controlling sediment yield in Chardavol watershed,Iran     

Hossein Zeinivand 《国际地球制图》2017,32(4):386-400

This paper examines the effects of watershed complexity in terms of physiography and land use on the specific sediment yield of the Chardavol watershed (1012.946 km²) in Iran. First, specific sediment yield was simulated using spatially distributed hydrological WetSpa model, then the influential factors such as morphometric variables, land-use composition and pattern and soil properties of the watershed were calculated at the sub-watershed scale. Due to the inter-reliant of these watershed characteristics, a partial least squares regression (PLSR) was used to illustrate the relationship between the specific sediment yield and data of 15 selected watershed characteristics. The results showed that the land-use composition and soil properties had the maximum effects on the specific sediment yield and clarified 79% of the variation in the specific sediment yield. Regarding the availability of digital spatial database over the watershed, this simple PLSR procedure could be applied in different watersheds.  相似文献