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1.
A total of 1504 larval and 31 pupal Simuliidae were caught from March 2000 to February 2001 at the Weidlingbach, a fourth order tributary of the Danube near Vienna, Austria, using a modified box sampler (sampling area = 2116 cm2) at 12 sampling stations from source to mouth. From the six species collected, Prosimulium tomosvaryi (Enderlein) and two species of the Simulium ornatum-group (S. trifasciatum Curtis and S. ornatum Meigen) accounted for 97.5% of the total. Based on head width, instars 1–7 were collected in the S. ornatum-group and instars 2–7 in P. tomosvaryi; from two of the remaining species [Simulium (Nevermannia) cryophilum (Rubzov) and S. (N.) vernum Macquart], only pupae were sampled. The S. ornatum-group was most abundant on coarse substrates (median = 55.9 mm) exposed to high water velocity (median = 55.9 cm/s; range = 9–83 cm/s); the latter was also true for P. tomosvaryi although it favoured smaller sediment grain sizes (median = 32.4 mm). Species richness and population density increased from source to mouth. At sampling sites near the source Simuliidae were completely lacking. In headwaters only P. tomosvaryi was present, whereas the S. ornatum-group and Simulium (Simulium) argyreatum Meigen was collected exclusively near the mouth.  相似文献   

2.
The Austrian blackfly fauna were analysed with regard to spatial (ecoregions, bioregions), vertical (altitude classes) and longitudinal zonation characteristics [stream order, biocoenotic (= fish) regions] on the basis of 2600 investigation sites. Of a total of 45 species recorded, Simulium ornatum, S. variegatum, S. argyreatum and S. reptans are the most common and most frequently distributed species, occurring in 60% of the investigated sites. Although the Austrian blackfly fauna seem to be quite well documented (on average one investigation site per 32 km2) the jackknife analyses indicates that there are still some fauna deficits. Whereas the species diversity of the main ecoregions is quite similar, the number of species differs clearly between the bioregions. Within the typological context of the Water Framework Directive, the Austrian Simuliidae confirm the bioregions as the most useful spatial units for river typology. A further optimisation in predicting a target list of blackfly species of a site can be achieved by subdividing the bioregions into either catchment area and altitude classes or into longitudinal zonation types (biocoenotic regions).  相似文献   

3.
肖茜  杨昆  洪亮 《湖泊科学》2018,30(4):1083-1096
以云贵高原湖泊近30 a来的TM、ETM~+和OLI遥感影像为数据源,采用归一化水体指数(NDWI)、改进归一化水体指数(MNDWI)、新型水体指数(NWI)、增强型水体指数(EWI)和自动水体提取指数5种水体指数提取了1985—2015年云贵高原10个湖泊表面水体面积,并对各种算法进行精度对比分析.针对湖泊各自特点采用不同的水体指数提取其表面水体面积,并进行水体面积变化时空分析.结果表明:云贵高原湖泊表面水体面积总体呈现先增加后缩减趋势,1985—1995年湖泊表面水体面积增加了30.86 km~2,1995—2015年湖泊水体表面面积减少了48.12 km~2,其中,面积变化最大的是杞麓湖与异龙湖.对云贵高原湖泊表面水体面积变化与该区域的年降水量、蒸发量、平均气温、流域植被覆盖面积和人类活动时空进行相关分析,结果表明:1)高原湖泊对区域气候变化的响应具有明显的空间差异性,云贵高原湖泊的表面水体面积与气候相关性较显著,气温升高引起蒸发加速,降水量下降,湖面不断缩小,与逐年上升的气温呈负相关,与逐年波动上升的蒸发量呈负相关,与逐年减少的降水量呈正相关;2)云贵高原湖泊各流域的植被覆盖面积与湖泊面积变化相关性较弱;3)人类活动是影响湖泊面积变化的重要因素,大肆围湖造田、围湖养殖以及旅游开发等人类活动直接导致云贵高原湖泊面积的锐减,并对湖泊生态环境产生重要影响.  相似文献   

4.
离散型湖泊水体提取方法精度对比分析   总被引：4，自引：2，他引：2  
基于卫星遥感的陆地水体提取方法多种多样,并且应用广泛.对于水体分布支离破碎的枯水期湖泊,准确的水体提取方法尚不明晰,直接影响湖泊水域面积的提取精度.以鄱阳湖湖区为研究对象,利用ALOS遥感影像,以2.5 m高分辨率全色波段融合影像非监督分类(ISODATA)得到的水体面积为参考值,分别使用归一化水体指数(NDWI)法、NDWIISODATA法和基于近红外(NIR)的ISODATA法提取了10 m分辨率的水体分布,分析了不同方法提取结果之间的差异性及产生原因.结果表明:3种方法均可以较好地提取出水体,但利用ISODATA法提取的水体细部信息更为明显,面积值较NDWI法更大;相对于近红外单波段而言,基于NDWI图像的ISODATA法提取水体的精度更高.纵观3种方法,基于NDWI图像的ISODATA法提取的水体精度最高,基于近红外波段的ISODATA法提取结果次之,NDWI阈值法的提取效果最差.研究结果对于离散型湖泊水体提取方法及数据源的选择等具有重要的借鉴和参考意义.  相似文献   

5.
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6.
安徽太平湖水库初级生产力时空分布及分析   总被引：1，自引：1，他引：0  
安徽太平湖是2014年国家列入的重点保护湖泊之一,鉴于其生物本底资料的缺乏,于2012年11月至2014年10月,从上游至下游选取H1、H2、H3、H4、H5共5个样点,采用黑白瓶法对太平湖的初级生产力进行为期2年的调查研究.结果显示,太平湖水柱毛初级生产力、水柱净初级生产力和水柱呼吸量的平均值分别为4.54±6.72、-1.82±7.77和6.50±7.62 g/(m2·d).时间分布上,水柱毛初级生产力出现3个峰值,分别在2012年11月、2013年5月和2014年7月,呼吸量在2013年7月份出现远高于其他月份的峰值,达到了16.04 g/(m2·d),水柱毛初级生产力季节变化表现为夏季秋季春季冬季.太平湖初级生产力存在显著的空间差异,水平分布上毛初级生产力与呼吸量的水平分布相似,湖心H3样点最小,下游的H4、H5样点较高;垂直分布显示,毛初级生产力主要贡献在表层和1SD层,并沿水深逐渐降低,呼吸量的垂直分布与毛初级生产力不同,最高值出现在1SD和2SD层,各层净初级生产力的值均较小,无明显峰值或谷值.研究表明,太平湖水库水柱的P/R系数小于1,但最高生产力层(表层)的P/R系数大于1.相关分析显示水柱毛初级生产力与温度和湖深呈显著正相关,与其它环境因子相关性不明显.  相似文献   

7.
Surface partial pressure of CO2 (pCO2), temperature, salinity, nutrients, and chlorophyll a were measured in the East China Sea (ECS; 31°30′–34°00′N to 124°00′–127°30′E) in August 2003 (summer), May 2004 (spring), October 2004 (early fall), and November 2005 (fall). The warm and saline Tsushima Warm Current was observed in the eastern part of the survey area during four cruises, and relatively low salinity waters due to outflow from the Changjiang (Yangtze River) were observed over the western part of the survey area. Surface pCO2 ranged from 236 to 445 μatm in spring and summer, and from 326 to 517 μatm in fall. Large pCO2 (values >400 μatm) occurred in the western part of the study area in spring and fall, and in the eastern part in summer. A positive linear correlation existed between surface pCO2 and temperature in the eastern part of the study area, where the Tsushima Warm Current dominates; this correlation suggests that temperature is the major factor controlling surface pCO2 distribution in that area. In the western part of the study area, however, the main controlling factor is different and seasonally complex. There is large transport in this region of Changjiang Diluted Water in summer, causing low salinity and low pCO2 values. The relationship between surface pCO2 and water stability suggests that the amount of mixing and/or upwelling of CO2-rich water might be the important process controlling surface pCO2 levels during spring and fall in this shallow region. Sea–air CO2 flux, based on the application of a Wanninkhof [1992. Relationship between wind speed and gas exchange over the ocean. Journal of Geophysical Research 97, 7373–7382] formula for gas transfer velocity and a set of monthly averaged satellite wind data, were −5.04±1.59, −2.52±1.81, 1.71±2.87, and 0.39±0.18 mmol m−2 d−1 in spring, summer, early fall, and fall, respectively, in the northern ECS. The ocean in this study area is therefore a carbon sink in spring and summer, but a weak source or in equilibrium with the atmosphere in fall. If the winter flux value is assumed to have been the mean of autumnal and vernal values, then the northern ECS absorbs about 0.013 Pg C annually. That result suggests that the northern ECS is a net sink for atmospheric CO2, a result consistent with previous studies.  相似文献   

8.
Phytoplankton size structure plays a significant role in controlling the carbon flux of marine pelagic ecosystems. The mesoscale distribution and seasonal variation of total and size-fractionated phytoplankton biomass in surface waters, as measured by chlorophyll a (Chl a), was studied in the Southern Yellow Sea using data from four cruises during 2006–2007. The distribution of Chl a showed a high degree of spatial and temporal variation in the study area. Chl a concentrations were relatively high in the summer and autumn, with a mean of 1.42 and 1.27 mg m−3, respectively. Conversely, in the winter and spring, the average Chl a levels were only 0.98 and 0.99 mg m−3. Total Chl a showed a clear decreasing gradient from coastal areas to the open sea in the summer, autumn and winter cruises. Patches of high Chl a were observed in the central part of the Southern Yellow Sea in the spring due to the onset of the phytoplankton bloom. The eutrophic coastal waters contributed at least 68% of the total phytoplankton biomass in the surface layer. Picophytoplankton showed a consistent and absolute dominance in the central region of the Southern Yellow Sea (>40%) in all of the cruises, while the proportion of microphytoplankton was the highest in coastal waters. The relative proportions of pico- and nanophytoplankton decreased with total biomass, whereas the proportion of the micro-fraction increased with total biomass. Relationships between phytoplankton biomass and environmental factors were also analysed. The results showed that the onset of the spring bloom was highly dependent on water column stability. Phytoplankton growth was limited by nutrient availability in the summer due to the strong thermocline. The combined effects of P-limitation and vertical mixing in the autumn restrained the further increase of phytoplankton biomass in the surface layer. The low phytoplankton biomass in winter was caused by vertical dispersion due to intense mixing. Compared with the availability of nutrients, temperature did not seem to cause direct effects on phytoplankton biomass and its size structure. Although interactions of many different environmental factors affected phytoplankton distributions, hydrodynamic conditions seemed to be the dominant factor. Phytoplankton size structure was determined mainly by the size-differential capacity in acquiring resource. Short time scale events, such as the spring bloom and the extension of Yangtze River plume, can have substantial influences, both on the total Chl a concentration and on the size structure of the phytoplankton.  相似文献   

9.
During the 22nd Chinese Antarctic Research Expedition (CHINARE-22), the atmospheric gas samples above the oceanic surface and near the surface were collected on the track for the scientific ship “Xuelong” and on Millor Peninsula of eastern Antarctica, respectively, using the Tedlar gas bags. Every day the sampling times were 10:00 and 22:00 (local time), respectively. In the laboratory, high-precision measurement of the isotopic compositions for N2O in these gas samples was conducted using Thermo Finnigan MAT-253 Isotopic Mass Spectrometer with a fully automated interface for the pre-GC concentration (PreCon) of trace gases. The temporal and spatial variations of δ 15N and δ 18O in atmospheric N2O were analyzed. The mean δ 15N and δ 18O-N2O values above the oceanic surface were (7.21±0.50)‰ and (44.52±0.52)‰, respectively. From 30°N to Antarctica, the δ 15N (6.05‰–7.88‰) linearly increased with the rate of about 0.01‰ with the latitude while the δ 18O (43.05‰–48.78‰) showed a large fluctuation. The δ 15N negatively correlated with air temperature and N2O concentration, and slightly positively correlated with δ 18O. The summertime variations of δ 15N and δ 18O-N2O appeared the same trend on Millor Peninsula of eastern Antarctica. They significantly positively correlated with each other and negatively with N2O concentration. The δ 15N and δ 18O-N2O at different sites averaged (7.42±0.35)‰ and (44.69±0.49)‰, respectively, slightly higher than those above the oceanic surface, significantly higher than those of atmospheric N2O in the low-latitude regions of Northern Hemisphere. The predominant factors affecting the spatial variations of δ 15N and δ 18O values were also discussed. The isotopic data given in this study can help to investigate the global and regional N2O budgets. Supported by the National Natural Science Foundation of China (Grant Nos. 40676005 and 40406001)  相似文献   

10.
Video equipment was used to record and to compare the behaviour of different blackfly species at two flow velocities 0.25 m s−1 and 1.35 m s−1. Simulium noelleri Friederichs, Simulium ornatum (complex) Meigen and Simulium variegatum Meigen were studied. Effects of flow velocity on larval locomotive activties were analysed. Looping activity and the time needed to attach for filter feeding again were affectet to some extend, depending on species and flow velocity. While in S. ornatum no differences were recorded in locomotive activity, larvae of S. noelleri and S. variegatum were less active at high flow velocities. Larvae of S. noelleri also moved over shorter distances when exposed to high flow velocities. Consequences of the differences in behavioural response to flow velocities are discussed with respect to drift and silk pad adhesion.  相似文献   

11.
The geopotential scale factor R o = GM/W o (the GM geocentric gravitational constant adopted) and/or geoidal potential Wo have been determined on the basis of the first year's (Oct 92 – Dec 93) ERS-1/TOPEX/POSEIDON altimeter data and of the POCM 4B sea surface topography model: R o °=(6 363 672.58°±0.05) m, W o °=(62 636 855.8°±0.05)m 2 s –2 . The 2°–°3 cm uncertainty in the altimeter calibration limits the actual accuracy of the solution. Monitoring dW o /dt has been projected.  相似文献   

12.
Sampling the sea bottom surface remains difficult because of the surface hydraulic shock due to water flowing through the gear (i.e., the bow wave effect) and the loss of epifauna organisms due to the gear’s closing mechanism. Slow-moving mobile epifauna, such as the ophiuroid Ophiothrix fragilis, form high-density patches in the English Channel, not only on pebbles like in the Dover Strait or offshore Brittany but also on gravel in the Bay of Seine (>5000 ind m−2). Such populations form high biomasses and control the water transfer from the water column to the sediment. Estimating their real density and biomass is essential for the assessment of benthic ecosystem functioning using trophic web modelling. In this paper, we present and discuss the patch patterns and sampling efficiency of the different methods for collecting in the dense beds of O. fragilis in the Bay of Seine. The large Hamon grab (0.25 m−2) highly under-estimated the ophiuroid density, while the Smith McIntyre appeared adequate among the tested sampling grabs. Nowadays, diving sampling, underwater photography and videos with remote operated vehicle appear to be the recommended alternatives to estimate the real density of such dense slow-moving mobile epifauna.  相似文献   

13.
戚美侠  王红萍  陈杰 《湖泊科学》2017,29(2):420-429
水生植物修复已经成为水体富营养化修复的重要手段,但其周期性的衰亡也给水体带来不容忽视的负效应.以府河流域丘陵地带农业区小水系自然生长的芦苇(Phragmites australis)和狭叶香蒲(Typha angustifolia)为研究对象,通过模拟实验,研究其冬季和春季腐烂分解过程的差异以及对水体营养盐水平的影响.结果表明,2种挺水植物的剩余干物质量整体上都呈现先快速下降再缓慢下降的趋势,芦苇和狭叶香蒲春季的分解速率分别为0.0251和0.0169 d~(-1),分别明显高于冬季分解速率(0.0027和0.0052 d~(-1));且腐烂分解速率与植物初始氮磷含量和氮磷比都有一定相关性.2种植物在冬季和春季磷的矿化速率都明显高于氮的矿化速率.实验水体的总氮和总磷浓度在腐解过程呈现初期迅速上升、中期迅速下降、后期缓慢下降的趋势.总体来看,芦苇和狭叶香蒲的腐烂分解受季节和初始氮磷浓度的影响较大,芦苇反应较香蒲更敏感且对水质的影响具有时效性.  相似文献   

14.
刘胜  陈宇炜 《湖泊科学》2017,29(6):1412-1420
于2014年10月到2015年5月鄱阳湖退水期,利用密闭箱—气相色谱法对鄱阳湖北部星子县洲滩两种代表性的植被群落——薹草(Carex cinerascens)和藜蒿(Artemisia selengensis)进行CO_2通量的对比观测,结果表明:薹草和藜蒿湿地的生态系统呼吸具有明显季节变化模式,其最小值均出现在冬季,最大值均出现在春季,平均值分别为3291.80和2581.89mg CO_2/(m~2·h),退水期薹草和藜蒿湿地累积的CO_2通量分别为213.71±2.27和176.39±11.48 t CO_2/hm~2.较高的生物量是薹草湿地CO_2通量高于藜蒿湿地的原因.5 cm土温是影响薹草和藜蒿湿地CO_2通量季节变化最重要的影响因子,藜蒿湿地生态系统呼吸的温度敏感性指数(Q10)高于薹草湿地.水分、植物生物量和湿地CO_2通量之间无显著相关性.  相似文献   

15.
The real area of contact during frictional sliding has been determined as a function of changing normal stress in triaxial experiments through the use of thermodyes. Utilizing the technique, described by Teufel and Logan in 1978, with saw-cut surfaces inclined 35° to the load axis, determinations were made for monolithologic sliding of Tennessee sandstone and Indiana limestone and dilithologic sliding of the same rocks. Confining pressures to 200 MPa were investigated at a constant shortening rate of 10–2 mm/sec and at room temperature. Direct measurements were made of single-asperity areas and the asperity density. The product of these measurements gives the percent area of real contact across the sliding surface. Single-asperity area and density are found to remain relatively constant during the displacement. Single-asperity areas are in the ranges of 0.4 to 6×10–2 mm2 for sandstone, 0.8 to 2×10–2 mm2 for limestone, and 0.2 to 24×10–2 mm2 for sandstone sliding against limestone. These values are smaller than the grain size of either rock. The values increase with increasing normal stress for both monolithologic and dilithologic sliding. In sandstone the asperity density increases from about 0.8 to 2.75 contacts per square millimeter in a logarithmic fashion. Monolithologic limestone has values of about 0.9 contacts per square millimeter and does not show significant change with increasing normal stress. The percent area of real contact increases in all cases, with average maximum values of 16% of the apparent area at a normal stress of 374 MPa in sandstone, 18% at 25 MPa in limestone, and 22% at 123 MPa in the dilithologic specimens. The normal stress recalculated for the real area of contact approaches the unconfined compressive strength for sandstone and limestone.  相似文献   

16.
阳振  史小丽  陈开宁  张民 《湖泊科学》2021,33(4):1043-1050
原位生长率是研究藻类生长、衰亡、种群演变、生产力估算,以及藻类对环境变化响应的重要指标,针对水华蓝藻原位生长率的测定,目前还缺乏成熟可靠的手段.本研究利用改进的原位培养法,根据培养前后藻蓝素浓度的变化,对巢湖东、中、西3个湖区水华蓝藻的原位生长率进行周年调查.结果表明,巢湖水华蓝藻的原位生长率变化范围在-1.16～0.69 d-1之间,表层的原位生长率最高,中层次之,底层大部分月份都为负值;原位生长率在空间分布上由高到低依次为西部湖区中部湖区东部湖区;在季节变化上,原位生长率春季(4 6月)相对较高,冬季(1 2月)相对较低.与环境因子进行相关分析后发现,原位生长率与溶解性总磷和温度正相关,这表明溶解性总磷和温度可能是影响巢湖水华蓝藻原位生长率的重要环境因子.  相似文献   

17.
冷季不同植物人工湿地处理生活污水的工程实例分析   总被引：2，自引：0，他引：2  
本实验以亚热带地区福建省永春县农村生活污水作为处理对象,选取10种湿地植物,构建具有不同植物类型的表面流人工湿地的实例工程,比较不同植物配置人工湿地的处理能力,以及湿地植物的生物量和植物体内氮、磷累积能力.研究结果表明,水龙和美人蕉人工湿地具有较高的铵态氮去除能力,去除率可分别达到76.7%和87.7%;两者同时也对总氮表现出较好的去除效果,尤其是美人蕉人工湿地在冬季节对总氮的去除率可维持在80.3%以上;2014年初冬季节实验结果表明,水龙还具有一定的总磷去除能力,去除率可达到69.0%.水龙和美人蕉具有较大的生物量,其单位面积干重可分别达到0.46和0.30 kg/m~2,又能较好地积累氮、磷元素,其体内氮含量可分别达到6.43和4.60 g/m~2,磷含量可分别达到0.50和1.01 g/m~2.综上所述,种植水龙和美人蕉的人工湿地总体处理效果较好,同时又能更多地积累氮、磷元素,且具有更大的生物量,可选为相对适宜用于处理生活污水的适合亚热带地区应用的人工湿地植物.  相似文献   

18.
The stability of cohesive and non-cohesive sediments in a mixed intertidal habitat within the Ria Formosa tidal lagoon, Portugal, was examined during two field campaigns as part of the EU F-ECTS project. The cohesive strength meter Mk III was used to determine critical erosion shear stress (τc) within a variety of different intertidal habitats and substrata, including Spartina maritima fields and Zostera noltii beds. The best predictor(s) for τc were derived from a range of properties measured for the surface sediments (chlorophyll a, colloidal carbohydrate, water, organic content, % fraction <63 μm, and seabed elevation). Pigment biomarkers were used to identify the dominant algal groups within the surface phytobenthic assemblage.Strong, seasonally dependent relationships were found between τc and habitat type, chl a, colloidal carbohydrate and bed elevation. Typically, critical erosion thresholds decreased seawards, reflecting a change from biostabilisation by cyanobacteria in the upper intertidal areas, to biostabilisation by diatoms on the bare substrata of the channel edges. In the late summer/early autumn, cyanobacteria were the main sediment stabilisers, and colloidal carbohydrate was the best bio-dependent predictor of τc across the entire field area. In the late winter/early spring, cyanobacterial activity was lower, and sediment stabilisation by Enteromorpha clathrata was important; the best predictor of τc was bed elevation. The implications and use of proxies for sediment stability are discussed in terms of feedback and sedimentation processes operating across the intertidal area.  相似文献   

19.
QC-estimates of Kachchh Basin in western India have been obtained in a high frequency range from 1.5 to 24.0 Hz using the aftershock data of Bhuj earthquake of January 26, 2001 recorded within an epicentral distance of 80 km. The decay of coda waves of 30 sec window from 186 seismograms has been analysed in four lapse time windows, adopting the single backscattering model. The study shows that Qc is a function of frequency and increases as frequency increases. The frequency dependent Qc relations obtained for four lapse-time windows are: Qc=82 f1.17 (20–50 sec), Qc=106 f1.11 (30–60 sec), Qc=126f1.03 (40–70 sec) and Qc=122f1.02 (50–80 sec). These empirical relations represent the average attenuation properties of a zone covering the surface area of about 11,000, 20,000, 28,000 and 38,000 square km and a depth extent of about 60, 80, 95, 110 km, respectively. With increasing window length, the degree of frequency dependence, n, decreases marginally from 1.17 to 1.02, whereas Q0 increases significantly from 82 to 122. At lower frequencies up to 6 Hz, Qc−1 of Kachchh Basin is in agreement with other regions of the world, whereas at higher frequencies from 12 to 24 Hz it is found to be low.  相似文献   

20.
张娇  陈莉琼  陈晓玲 《湖泊科学》2016,28(4):718-725
利用1999 2014年Landsat卫星遥感影像数据,采用浮游藻类指数(FAI)方法识别、提取洱海蓝藻水华信息,进而获取蓝藻水华时空分布数据,为进一步分析洱海蓝藻水华发生规律及监测预警提供参考.结果表明:1999 2014年洱海夏、秋季多次发生蓝藻水华,以小型水华为主(水华面积在10 km~2以内),大型水华现象主要发生在2003、2006、2013年,其中2006年水华面积最大,达到42 km~2.除近岸湖湾区域容易产生蓝藻堆积外,洱海蓝藻大型水华主要发生在洱海北部和中部区域,南部发生频次较少.近岸区域蓝藻堆积从春季开始,中心水域水华发生在夏末和秋季(8 11月),其中大型水华集中发生在10月左右.  相似文献   

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