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1.
This study compares the marker pigment composition in three different lake compartments: the water column; the surface sediment
biofilm (0–0.5 cm), where production and main degradation processes take place; and the deep sediment (15–17 cm), where the
signal is finally stored and marker pigments are used as a proxy in paleolimnological studies. The aim was to evaluate which
marker pigments better record in the sediment the relative contributions of planktonic and benthic production in high mountain
lakes, taking into account the differential preservation existing among pigments. A survey of 82 high mountain lakes distributed
along the major environmental gradients was carried out in the Pyrenees. Comparison of pigments between the three compartments
revealed that both water column and sediment biofilm signals could be distinguished in old sediment layers, despite the observation
that some of the most characteristic carotenoids that appeared frequently and in high concentrations in the water column were
already less common or even absent from the sediment biofilm. In the shallowest lakes, pigment composition in the sediment
biofilm was typical of photosynthetically active communities and their deep sediment samples were characterised by a substitution
of fucoxanthin by diatoxanthin as the dominant diatom marker pigment. However, in the deepest lakes the pigment composition
of the sediment biofilm and deep sediment was similar, characterised by marker pigments of mainly planktonic algal groups
and pheophytins, which are typical pigments of decaying communities. Results are discussed in terms of how pigment source
(planktonic or benthic) and pigment type (lability of molecule) interact to shape pigment composition in the sediment record
of high mountain lakes. 相似文献
2.
荒漠草原2种植物群落土壤微生物及土壤酶特征 总被引：7，自引：2，他引：5
测定和分析了甘肃省金昌市金川区荒漠草原土壤微生物数量、微生物生物量和土壤酶活性。结果表明：同层土壤3大类微生物（真菌、细菌和放线菌）数量、土壤微生物量碳和氮含量及4类土壤酶（蔗糖酶、脲酶、磷酸酶和过氧化氢酶）活性均表现为盐爪爪（Kalidium foliatum）群落大于骆驼刺（Alhagi sparsifolia）群落,而土壤微生物量磷含量相反;同一植物群落,不同层土壤微生物数量（除骆驼刺群落中的真菌亚表层最高外）、土壤微生物量碳、氮、磷含量及土壤酶活性（除骆驼刺群落中脲酶呈现高-低-高-低趋势外）均呈现随土层的加深而降低的趋势;金川区荒漠草原不同植物群落不同空间层次土壤微生物数量、微生物生物量和各种酶之间有不同程度的相关性。 相似文献
3.
Ana M. Aguilar-Islas Robert Rember Shigeto Nishino Takashi Kikuchi Motoyo Itoh 《Polar Science》2013,7(2):82-99
The concentration of dissolved iron (DFe) and suspended leachable particulate iron (LPFe) in the water column of the western Beaufort Sea were investigated during the late summer of 2010. Elevated concentrations of surface DFe (0.49–1.42 nM) were similar to those reported in resent studies, likely reflecting input from melting sea ice and river discharge. The rapid decrease in DFe (5.20–0.48 nM) and LPFe (88.2–1.83 nM) values observed from inshore to offshore in Pacific influenced waters, suggest scavenging processes limit the input of DFe from the shelf to the deep basin. However, frequent eddies found in this region are likely important in promoting lateral advection, as suggested by higher surface DFe concentrations at an offshore station in the vicinity of a warm-core eddy. Within the Atlantic layer, relatively homogeneous DFe (0.69–0.80 nM) and LPFe (1.18–2.13 nM) concentrations were observed at all the stations, reflecting a balance in the interplay between input and removal processes within this watermass. An input of DFe east of the Lomonosov Ridge was inferred by comparing DFe values within the core of Atlantic water between the Eastern and Western Arctic. 相似文献
4.
A late Pleistocene and Holocene mineral magnetic record from sediments of Lake Aibi,Dzungarian Basin,NW China 总被引：1，自引：0，他引：1
Alina Tudryn Piotr Tucholka Elisabeth Gibert Francoise Gasse Keiquin Wei 《Journal of Paleolimnology》2010,44(1):109-121
We studied mineral magnetic properties of a 6-m-long, late Pleistocene through Holocene sediment sequence from Lake Aibi in
Dzungaria (Zunggary, Junggar), northern Xinjiang, China. Results were used to infer environmental changes and are compared
with previously studied cores from Lake Manas. Both water bodies occupy the deepest parts of the Dzungarian Basin and are
remnants of large Holocene lakes. During the Late Pleistocene, the magnetic mineralogy in both lakes was dominated by detrital,
iron oxide minerals. Oxic conditions, which dominated during sedimentation and early diagenesis, persisted over the Pleistocene–Holocene
transition. Later, during the middle Holocene, lake bottom conditions enabled authigenic formation of iron sulphide minerals
such as pyrite (FeS2) in Lake Aibi, and pyrite and greigite (Fe3S4) in Lake Manas. This iron sulphide mineralogy suggests increased biological activity in stagnant, anoxic bottom waters. Anoxic
bottom conditions started about 9.8 cal kyr BP in Lake Manas and at about 7.2 cal kyr BP in Lake Aibi. A short dry event recorded
in Lake Manas between 6.8 and 5.2 cal kyr BP is not clearly observed in Lake Aibi. In the late Holocene, i.e. the last 2.8 cal
kyr, sediments of both lakes are again characterised by iron oxides, suggesting well-mixed, shallow water bodies. For this
recent period, it seems that the detrital material in the two lakes had a common origin. Magnetic properties of sediments
in Lakes Aibi and Manas show broadly similar environmental evolution during the late Pleistocene and Holocene. Nevertheless,
despite the close proximity of the two lakes (~200 km) in the same basin, they display some different magnetic properties
and record environmental changes at different times. 相似文献
5.
采用微生物宏基因组学微阵列GeoChip 5.0技术，选择腾格里沙漠东南缘沙坡头地区不同年代人工固沙植被区的生物土壤结皮（BSC）为对象，分析BSC演替过程中参与铁代谢的功能微生物组成及其功能基因变化特征，研究微生物铁代谢对BSC演替的响应及调控。结果表明：真菌参与铁吸收和转运过程，古菌参与铁转运和贮存过程，细菌则在铁代谢吸收、转运和贮存过程中均起主要调控作用。门水平上，BSC铁代谢功能微生物组成变化对演替的响应不敏感，BSC铁代谢微生物主要为变形菌门（Proteobacteria）。BSC铁代谢功能基因多样性的显著提高和三类铁代谢过程基因信号强度达到最高水平需要经过61 a的演替。调控BSC铁吸收过程的主要功能基因为亚铁氧化酶编码基因iro；调控原核生物铁转运过程的主要功能基因，为羟基苯甲酰丝氨酸铁外膜转运体编码基因cirA和Fe（Ⅱ）转运蛋白编码基因feoB，真菌铁转运过程主要依靠含铁细胞转运体和铁氧化酶高亲和力的作用；调控铁贮存过程的主要功能基因为固定相类核蛋白编码基因dps。在BSC演替阶段末期，上述铁代谢功能基因强度的显著增加促进了微生物的铁代谢潜能。干旱、半干旱荒漠生态系统植被恢复过程中微生物铁代谢潜能的恢复需要较长时间。 相似文献
6.
Primary production in Lake Hayward, Western Australia, is dominated by benthic microbial communities, with limited planktonic
primary production. This study investigated the question of howArtemia, commonly regarded as simple, obligate, non-selective filter feeders, were able to survive in this system. Bacteria (heterotrophic
and autotrophic, filamentous and unicellular) were the major components in the diet of theArtemia in Lake Hayward. These bacteria were derived from bacterial aggregates in the water column and also from benthic mat material
(both still attached to the substrate and from pieces floating in the water column). Benthic diatoms were a substantial dietary
component of animals living in the unstratified shallow regions. Photosynthetic eukaryotic nanoplankton comprised a minor
component of the diet of thisArtemia population. Gut contents of a large number of animals and the results of a simple laboratory test indicated that these animals
utilise substrate-bound food resources. The results of the present study raises the question of the ecological significance
of surface grazing by brine shrimps in other shallow, benthos dominated saline systems. 相似文献
7.
Sulfur-deficiency has been observed in arid and semi-arid soils. To explore sulfur cycling in arid soils, four (4) arid soils collected from the Southwestern United States were tested for 12 chemical constituents and moisture content, and soil microbial communities were assayed for the ability to utilize a set of 31 organic substrates using EcoPlates™. Soils were cultured for the presence of sulfur-utilizing bacteria using thiosulfate as the sulfur source. The densities of thiosulfate-utilizing bacterial populations were determined using viable plate counts and differential media. Results showed that the soils contained high amounts of sulfate, calcium and other minerals. Active soil microbial communities utilized 24–31 organic substrates. The density of thiosulfate-utilizing bacterial populations ranged from 105 colony forming units per gram (cfu g−1) to greater than 106 cfu g−1. Regression analyses showed that there were no statistically significant correlations between the density of thiosulfate-reducing bacteria and other tested variables. However, the high density of sulfur-related bacteria and high organic substrate utilization by the microorganisms suggests that these organisms may be important in sulfur and carbon cycling in these soils. 相似文献
8.
含铬废水具有有机物含量高,难降解物质浓度高,色度大,悬浮物多,水质、水量变化大,含有微量毒性物质等特点。本文探讨了在不同参数条件下,硫酸亚铁、铁、硫化亚铁三种还原剂对含铬废水处理效果的影响,实验表明:硫酸亚铁具有明显的优越性,在同等条件下其去除率达到99%以上。 相似文献
9.
Bacterial dominance of phototrophic communities in a High Arctic lake and its implications for paleoclimate analysis 总被引：1，自引：1，他引：0
Dermot Antoniades Julie Veillette Marie-Josée Martineau Claude Belzile Jessica Tomkins Reinhard Pienitz Scott Lamoureux Warwick F. Vincent 《Polar Science》2009,3(3):147-161
The phototrophic communities in meromictic, perennially ice-covered Lake A, on Ellesmere Island in the Canadian High Arctic, were characterized by pigment analysis using high performance liquid chromatography. Samples were taken to determine the vertical changes down the water column as well as a variation between years. These analyses showed that Lake A had distinct phototrophic communities in its oxic and anoxic layers. The pigment analyses indicated that phototrophic biomass in the upper, oxic waters was dominated by picocyanobacteria, while in the lower, anoxic layer photosynthetic green sulphur bacteria were dominant. Interannual variation in pigment concentrations was related to the penetration of photosynthetically active radiation in the water column, suggesting that light availability may be limiting the net accumulation of photosynthetic bacterial biomass in Lake A. Pigment analysis of the surface sediments indicated that deposition was dominated by the photosynthetic sulphur bacterial contribution. The sedimentary record of bacterial pigments in polar meromictic lakes offers a promising tool for the reconstruction of past changes in ice cover and therefore in climate. 相似文献
10.
采用表面荧光显微分析方法对2014年夏季中国第6次北极科学考察期间采集于加拿大海盆7个海冰站位的融池、冰芯和冰下海水样品进行了细菌和原生生物群落分析。结果表明,上述3类生境中的第一优势类群均为细菌(不包括ICE07站位出现水华融池的统计),分别占总生物量的42.8%、37.8%和50.7%;第二优势类群均为鞭毛虫,分别占总生物量的40.2%、34.3%和37.5%。包含细菌、鞭毛虫和纤毛虫在内的异养生物在总生物量中占有优势,显示微食物环在其中起着重要作用。在北冰洋夏季快速融冰的背景下,3类生境总体上缺少快速生长的条件,总生物量偏低。其中ICE07站位出现融池水华和冰表自养鞭毛藻高值,推测合适的藻种和营养盐的额外补充共同促成了该站位冰表(融池)藻华的形成。 相似文献
11.
The electrical resistivity imaging (ERI) technique has been used to calibrate existing successful and dry borehole drilling
locations in the Cape Coast Granitoid Complex of the Central Region of Ghana. The area has a low groundwater potential and
most of the communities do not have access to potable water. Surface water is generally expensive to treat and is therefore
not considered as a good water supply option in such rural and dispersed communities where incomes are low. Supply of water
to communities from existing boreholes is inadequate. Therefore, there was the need to construct more boreholes to increase
access to potable water to meet coverage targets. Results show that the ERI technique is capable of detecting shallow bowl-shaped
conductive zones up to 75 m represented by low resistivity values mainly due to weathered granitoids and/or fractures within
the granitoids. Resistivity values typically less than 500 Ω-m obtained between depths of 10–50 m on model resistivity sections
accounted for about 80% of successful productive boreholes. Resistivity values in the range 500–1,500 Ω-m represented marginally
successful borehole locations which could be suitable for hand-pump installation and values greater than 1,500 Ω-m were confirmation
for dry borehole locations. 相似文献
12.
《The Australian geographer》1995,26(1):71-86
The upper Nepean River has been progressively regulated for water supply to Sydney and Wollongong since 1886 by the Upper Nepean Water Supply Scheme which consists of four large dams, two small dams and two diversion weirs. Secular rainfall changes produced periods of high rainfall and large floods (flood‐dominated regimes) between 1857 and 1900 and 1947 and the present, and an intervening period (1901–46) of low rainfall and small floods (drought‐dominated regime). Upstream impoundment and flow regulation significantly reduced flood magnitudes for most return periods during both types of flood regimes. The probability distribution of mean daily flows was also changed significantly by flow regulation such that during the drought‐dominated regime, the high and low frequency flows were reduced substantially but the moderate frequency flows were increased due to dam releases; the change from a regulated drought‐dominated regime to a regulated flood‐ dominated regime resulted in a substantial increase in discharge for most durations; and increased water diversions to Wollongong during the current flood‐dominated regime produced a marked downward shift in the whole flow duration curve. Nepean Dam reduced downstream suspended sediment yields by two orders of magnitude because it traps in excess of 99 per cent of the inflowing suspended sediment load. Streamflow releases are urgently required from the two diversion weirs to improve downstream water quality and to ensure the viability of the resident ‘potentially threatened’ eastern Macquarie perch (Macquaria nov. sp.). 相似文献
13.
Microcoleus vaginatus isolated from a desert algal crust of Shapotou was cultured in BG-11 medium containing 0.2 mol l−1 NaCl or 0.2 mol l−1 NaCl plus 100 mg l−1 sucrose, extracellular polymeric substances (EPS) or hot water-soluble polysaccharides (HWP), respectively. Photosynthetic oxygen evolution rates, photosystem II activity (Fv/Fm) and dark respiration of NaCl-stressed cells were enhanced significantly by the added sucrose or EPS under salt stress conditions (0.2 mol l−1 NaCl). Compared with cells treated with salt alone, sodium contents in cells reduced significantly; the content of cellular total carbohydrate did not change, and intracellular sucrose, water-soluble sugar increased significantly following the addition of exogenous carbohydrates. Sucrose synthase (SS) activity of NaCl-stressed cells increased following the addition of sucrose, and sucrose phosphate synthase (SPS) activity of NaCl-stressed cells increased following the addition of exogenous sucrose, EPS or HWP compared with cells stressed with NaCl only. The results suggested that the extruded EPS might be re-absorbed by cells of M. vaginatus as carbon source, they could increase salt tolerance of M. vaginatus through the changes of carbohydrate metabolism and the selective uptake of sodium ions. 相似文献
14.
北冰洋夏季海冰覆盖面积在2012年达到低值。为了了解海冰变化对浮游动物群落的影响, 利用夏季西北冰洋22个站位的网采样品, 通过种类组成和丰度研究了群落的类型、结构和地理分布, 探讨了其分布特征与环境因子的关系。根据记录到的54种(类)浮游动物, 21站位可以划分成在地理上基本隔离的三个浮游动物群落: 楚科奇海南部群落, 藤壶幼体数量占优, 站位丰度百分比在56.6%—79.8%之间, 桡足类次之(18.0%—42.2%), 同时还含有少量的白令海种类;楚科奇海中北部群落以广布性桡足类占绝对优势(62.3%—96.8%), 藤壶幼体次之(0—30.9%);深海群落浮游动物的丰度极低, 组成上以桡足类为主(71.6%—89.8%), 且多数是体型较大极地种。楚科奇海陆坡边缘的M06站丰度较高但是种类组成与深海站位相似, 没有归入任何群落。两个浅水群落优势种都是北极哲水蚤(Calanus glacialis)、伪哲水蚤类(Pseudocalanus sp.)、圆胃住囊虫(Oikopleur vanhoffeni)以及藤壶幼体(Barnacle larva), 但优势度各异。深海群落优势种较多, 北极哲水蚤(Calanus glacialis)、极北哲水蚤(Calanus hyperboreus)、细长长腹水蚤(Metridia longa)以及北极拟真刺水蚤(Paraeuchaeta glacialis)等体型较大的桡足类优势度较高, 体型较小的矮小微哲水蚤(Microcalanus pygmaeus)、长腹剑水蚤(Oithona similis)优势度相对较低。与群落类型按维度和深度的变化趋势一致, 统计分析显示表层温度和表层盐度是最重要的影响因子。与海冰覆盖面积较高的2003年相比, 群落类型和地理分布没有显著变化, 但是楚科奇海浮游动物丰度增加了1—2倍, 深海群落丰度降低而组成上大型种类比例升高。 相似文献
15.
The effects of elevated atmospheric carbon dioxide [CO2] on microbial communities in arid rhizosphere soils beneath Larrea tridentata were examined. Roots of Larrea were harvested from plots fumigated with elevated or ambient levels of [CO2] using Free-Air CO2 Enrichment (FACE) technology. Twelve bacterial and fungal rRNA gene libraries were constructed, sequenced and categorized into operational taxonomical units (OTUs). There was a significant decrease in OTUs within the Firmicutes (bacteria) in elevated [CO2], and increase in Basiomycota (fungi) in rhizosphere soils of plots exposed to ambient [CO2]. Phylogenetic analyses indicated that OTUs belonged to a wide range of bacterial and fungal taxa. To further study changes in bacterial communities, Quantitative Polymerase Chain Reaction (QPCR) was used to quantify populations of bacteria in rhizosphere soil. The concentration of total bacteria 16S rDNA was similar in conditions of enriched and ambient [CO2]. However, QPCR of Gram-positive microorganisms showed a 43% decrease in the population in elevated [CO2]. The decrease in representation of Gram positives and the similar values for total bacterial DNA suggest that the representation of other bacterial taxa was promoted by elevated [CO2]. These results indicate that elevated [CO2] changes structure and representation of microorganisms associated with roots of desert plants. 相似文献
16.
SIMON J. COOK PETER G. KNIGHT DEBORAH A. KNIGHT RICHARD I. WALLER 《Geografiska Annaler: Series A, Physical Geography》2012,94(3):351-362
Debris in basal ice produced by glaciohydraulic supercooling is typically characterized by high proportions of silt. A prominent hypothesis for this silt‐dominance is that frazil ice growing in supercooled water preferentially traps silt from sediment‐laden water percolating through it. It has therefore been suggested that silt‐dominance may be diagnostic of glaciohydraulic supercooling. The aim of our work is to test this hypothesis that freezing sediment‐laden supercooled water necessarily produces ice dominated by silt. We do this by simulating two freezing processes under laboratory conditions: (1) percolation of sediment‐laden water through frazil ice; (2) turbulent supercooling and subsequent freezing of sediment‐laden water. In experiments repeated using different particle sizes (sand, silt and clay in individual experiments) both processes entrained sand most effectively and silt least effectively. In experiments using a sediment mixture dominated by medium to coarse silt, both processes produced ice facies dominated by particle sizes between fine sand and coarse silt. These results suggest that silt‐dominance should therefore not be expected for supercooled freeze‐on, and is not a reliable diagnostic signature for supercooling. The silt‐dominated character of basal ice types associated with supercooling may result from other controls such as a silt‐dominated sediment supply or subglacial water flow rates, rather than the freezing process. 相似文献
17.
应用PCR-DGGE技术研究了连续2年氮素、水分添加处理对贝加尔针茅草原土壤氨氧化细菌(AOB)16S r RNA基因和古菌(AOA)amo A基因遗传多样性的影响。结果表明,土壤硝化势在水分添加低氮(N30)和非水分添加高氮(N300)处理下较对照显著升高(P0.05),在水分添加高氮(N200、N300)处理下较对照急剧下降(P0.05)。不同处理下氨氧化细菌的群落结构变化较氨氧化古菌敏感,氮素添加显著改变了氨氧化微生物的群落结构,在高氮素处理下,氨氧化细菌的多样性指数有下降的趋势,而古菌的多样性则有升高的趋势,表明氨氧化古菌在高氮素下生长比较活跃。发育树分析的结果表明,非水分添加处理下,氨氧化细菌的群落由亚硝化螺菌属的Cluster 1、Cluster 3和Cluster 4组成,水分添加处理下由亚硝化螺菌属Cluster 3、Cluster 4和亚硝化单胞菌属的Cluster 6组成,而氨氧化古菌群落在水分添加处理下主要由泉古菌门的Cluster 1、Cluster 2和water lineage组成,在非水分添加处理下主要由泉古菌门的Cluster 1、Cluster 2和Cluster 5组成,两种水分输入机制下,氨氧化微生物群落的不同组成说明,水分在调节氨氧化微生物群落结构方面有重要作用。此外,氨氧化细菌群落多样性与全氮,NH4+和NO3-的含量呈显著负相关,而古菌群落与其呈显著正相关,说明氨氧化细菌与古菌对氮素和水分添加有不同的且互补的反应机制。 相似文献
18.
《Basin Research》2018,30(Z1):513-531
Barremian‐Aptian sedimentary successions along the northern Arabian margin have been described as a transition from a siliciclastic to a carbonate‐dominated marine environment, deposited upon a low‐relief shelf or platform formed as a consequence of continuous regional subsidence. A long (360 m) core from northern Israel offers a unique look at this transition, providing valuable insights for the palaeoceanography, geometry and ventilation conditions that lead to Oceanic Anoxic Event 1 (OAE1) in this region. Results from high‐resolution elemental, mineralogical, sedimentological and petrophysical analyses carried out revealed the emplacement of abundant mass‐transport deposits (MTDs) during the Late Barremian and the Aptian. The transplanted units are characterized by fine grained calcareous shales with elevated organic matter, sulphur and iron contents. The scarcity or absence of bioturbation in the disturbed sequences provides a hint to the sediment/water interface conditions. However, a decrease in sulphur and iron occurring at the contact between the shales and the MTDs is explained as increased oxic conditions at the sediment‐water interface as a result of turbulence and mixing associated with the descending sediment masses. Such recurrent events ventilation of the low‐energy basinal environment during the Late Barremian and Aptian, predate the wide‐scale establishment of OAE1 in the northern Arabian margin. Moreover, the identification of coarse‐grained MTDs within deep‐water calcareous sediments indicates a much steeper gradient of the northern Arabian margin, challenging previous studies. 相似文献
19.
20.
Abundance,biomass and composition of spring ice algal and phytoplankton communities of the Laptev Sea(Arctic) 
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下载免费PDF全文 <正> Abundance,biomass and composition of the ice algal and phytoplank-ton communities were investigated in the southeastern Laptev Sea in spring 1999.Diatoms dominated the algal communities and pennate diatoms dominated the dia-tom population.12 dominant algal species occurred within sea ice and underlyingwater column,including Fragilariopsis oceanica,F.cylindrus,Nitzschiafrigida,N.promare,Achnanthes taeniata,Nitzschia neofrigida,Naviculapelagica,N.vanhoef fenii,N.septentrionalis,Melosira arctica,Clindrothecaclosterium and Pyrarnimonas sp.The algal abundance of bottom 10 cm sea icevaried between 14.6 and 1562.2×10~4 ceils l~(-1)with an average of 639.0×10~4cells l~(-1),and the algal biomass ranged from 7.89 to 2093.5μg C l~(-1)with an av-erage of 886.9μg C l~(-1),which were generally one order of magnitude higherthan those of sub-bottom ice and two orders of magnitude higher than those ofunderlying surface water.The integrated algal abundance and biomass of lower-most 20 cm ice column were averagely 7.7 and 12.2 times as those of upper 20 mwater column,respectively,suggesting that the ice algae might play an importantrole in maintaining the coastal marine ecosystem before the thawing of sea ice.Icealgae influenced the phytoplankton community of the underlying water column.However,the“seeding”of ice algae for phytoplankton bloom was negligible be-cause of the iow phytoplankton biomass within the underlying water column. 相似文献