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51.
Kurt Jax 《Hydrobiologia》1996,333(3):201-208
The sulfate reduction rate was measured for almost four years in the profundal sediments of Lake Kizaki, a mesotrophic lake
in central Japan. The rate was generally highest in the surface layer and decreased with depth. Seasonally, sulfate reduction
tended to be high in spring and summer, and then to decrease until the end of stratification (December) in spite of a constant
in situ temperature of around 6 °C, although fluctuations were found in every year. The rate also fluctuated greatly according to
year. The maximum rate of sulfate reduction was 0.33 mmol m−2 d−1 in May, 1990, and the minimum was 0.004 mmol m−2 d−1 in March, 1993. These relatively low rates, compared with those reported for freshwater sediments, seem to be due to low
concentrations of sulfate in the sediments (5–23 μmol l−1 in the surface layer). The rate was highly correlated with the concentration of sulfate in the sediments. The addition of
sulfate stimulated sulfate reduction in all sediment samples tested, but adding lactate did not. Therefore, sulfate reduction
should be limited mainly by the supply of sulfate. Measurements of sulfate reduction rates at different concentrations of
added sulfate revealed a low concentration of half-saturation constant as low as 12 μmol l−1. 相似文献
52.
Spatial variability in nutrient concentrations in the intertidal sediments and pore waters has been studied along downshore
transects and in core profiles at three locations in the Shannon estuary on the west coast of Ireland. The parameters measured
were N, as Kjeldahl N, NO3, NO2, and NH3, and P as total P and PO4 along with a range of other environmental variables such as salinity and sediment organic content.
The concentrations of all nutrients varied with season, but winter values were generally low in comparison with polluted mainland
european estuaries. There was a great deal of variation in nutrient concentrations along the transects, and coefficients of
variability of up to 153% (NH3), 173% (NO3), 129% (NO2) and 117% (PO4) were found. Overall, there was little evidence of any trends in concentration in any of the nutrients from the top to the
bottom of the transects, although it was occasionally possible to link particular instances to local conditions such as the
presence of the channel or a stream.
Sediment core profiles showed typical patterns, with NO3 concentrations for example being highest in surface sediments, while NH3 and PO4 concentrations increased with depth. Rather surprisingly perhaps, NO3 could still be detected on occasion at depths of up to 20 cm, well below the Redox Potential Discontinuity (RPD) and the
limit of oxygen penetration which oxygen microelectrodes had measured as being within a few mm of the surface. This was ascribed
to the activities of the macrofauna, in that the oxidised sediment which lined the burrows could clearly be seen in some cores.
This study not only shows that nutrient distributions along estuarine gradients are linked to physicochemical factors such
as oxygenation and freshwater/marine influence, but also that sediment instability, through random physical events such as
storms, and macrofaunal activity play an important role and that these latter factors deserve closer attention. 相似文献
53.
悬浮泥沙不仅影响水体的生态状况,而且对河口地貌及岸线的演变起到重要作用。高光谱技术可用于船载、机载及星载的光学传感器上,被认为是监测光学复杂水体的有效工具。为研究高光谱技术在河口悬浮泥沙监测应用中的可行性,于2004年5月及2006年8月,在珠江口进行了两个航次的现场水质采样及同步光谱测量。测量的原始遥感反射率光谱的分辨率为0.38nm,处理成为10nm的带宽,并进一步处理成导数光谱。以悬浮颗粒物(SPM)表征悬浮泥沙,分析了SPM和各光谱间的相关性。结果显示,一阶导数光谱,特别是605nm,可用于河口水体的SPM估算。该研究结果可应用到光学复杂河口水体的悬浮泥沙现场监测,并且对Hyperion及环境1号等卫星成像高光谱数据有潜在的应用价值。 相似文献
54.
Using ethane as a marker for peroxidative damage to membranes by reactive oxygen species (ROS) we examined the injury of rice
seedlings during submergence in the dark. It is often expressed that membrane injury from ROS is a post-submergence phenomenon
occurring when oxygen is re-introduced after submergence-induced anoxia. We found that ethane production, from rice seedlings
submerged for 24–72 h, was stimulated to 4–37 nl gFW−1, indicating underwater membrane peroxidation. When examined a week later the seedlings were damaged or had died. On de-submergence
in air, ethane production rates rose sharply, but fell back to less than 0.1 nl gFW−1 h−1 after 2 h. We compared submergence-susceptible and submergence-tolerant cultivars, submergence starting in the morning (more
damage) and in the afternoon (less damage) and investigated different submergence durations. The seedlings showed extensive
fatality whenever total ethane emission exceeded about 15 nl gFW−1. Smaller amounts of ethane emission were linked to less extensive injury to leaves. Partial oxygen shortage (O2 levels <1%) imposed for 2 h in gas phase mixtures also stimulated ethane production. In contrast, seedlings under anaerobic
gas phase conditions produced no ethane until re-aerated: then a small peak was observed followed by a low, steady ethane
production. We conclude that damage during submergence is not associated with extensive anoxia. Instead, injury is linked
to membrane peroxidation in seedlings that are partially oxygen deficient while submerged. On return to air, further peroxidation
is suppressed within about 2 h indicating effective control of ROS production not evident during submergence itself. 相似文献
55.
Using a polyclonal antibody against the mate recognition pheromone (MRP) of Brachionus rotundiformis Koshiki strain, we investigated the behavioral reproductive isolation and the similarity of MRP among geographically and temporally isolated B. rotundiformis strains. Males of the Koshiki strain did not discriminate in mating attempts among females of the Koshiki strain and those of conspecific allopatric strains from Hamana, Fiji, Thailand and Spain. Likewise, Koshiki males attempted mating with statistically indistinguishable frequency with Koshiki females and B. plicatilis strains. However, copulation was not consummated between Koshiki males and B. plicatilis females. The amount of anti-MRP binding to three allopatric B. rotundiformis strains was similar to that of the Koshiki strain, but binding to Hamana and the B. plicatilis strain was significantly lower. Four temporally separated B. rotundiformis populations were hatched from resting eggs collected from 0, 5, 10 and 15 cm depth in the sediment of Kai-ike pond in Koshiki island, Japan. Sediment age was determined using the 210Pb method, allowing us to estimate that resting eggs from 15 cm depth were produced 65 years ago. Results of mating assays and anti-MRP binding showed that no behavioral reproductive isolation exists among the four temporally isolated Koshiki strains. B. rotundiformis appears to be reproductively isolated from B. plicatilis, but heterospecific matings are still attempted between B. plicatilis and B. rotundiformis, suggesting that the MRP remains sufficiently similar to elicit circling behavior. 相似文献
56.
57.
【目的】初步探究海洋线虫与微生物的相互作用对碳、氮循环的影响。【方法】利用16S r RNA和18S r RNA基因高通量测序方法,对33个近岸沉积物样品中细菌、古菌和真核生物的多样性进行调查;对海洋线虫与细菌、海洋线虫与古菌的共现性进行网络分析,并采用Spearman统计学方法,识别出与海洋线虫共现性呈显著相关性的微生物种类。【结果】在夏季,红树林和潮间带泥滩样品中线虫OTU平均相对丰度基本呈随深度增加而递减趋势;冬季的红树林样品中发现相类似变化规律,只有在冬季潮间带泥滩样品中线虫OTU平均相对丰度在深层较高于表层。相对丰度最高的海洋线虫隶属于单宫目(47%)、色矛目(19%)、刺嘴目(16%)和垫刃目(9%),它们与热源体古菌、深古菌、γ-和δ-变形菌等微生物有显著正/负相关关系。【结论】在香港米埔湿地沉积物中,与相对丰度最高的5种线虫显著相关的几大类微生物均在碳、氮、硫等元素循环方面起十分重要的作用,暗示海洋线虫与微生物潜在的相互作用对元素地球化学循环具有重要影响。研究结果有助于深入了解线虫在生态系统中未被揭示的生态功能,有助于更清晰地认识海洋线虫在底栖生态系统中所扮演的角色。 相似文献
58.
湘西河流表层沉积物重金属污染特征及其潜在生态毒性风险 总被引:14,自引:0,他引:14
花垣河和峒河是湘西地区受到锰矿和铅锌矿生产影响严重的两条河流。通过表层沉积物采样分析了Cd、Pb、Cu、Ni、Cr、Zn和Mn的总量,根据BCR连续提取程序分析沉积物样品中重金属的地球化学赋存形态,采用内梅罗指数法和地积累指数法评价了沉积物重金属污染特征,根据重金属的富集程度探讨了重金属污染来源,采用淡水生态系统沉积物质量基准(SQGs,TEL/PEL)和毒性单位评价了花垣河和峒河沉积物中重金属元素的生态毒性风险。结果表明,花垣河和峒河绝大多数位点的表层沉积物中Cd、Pb、Cu、Ni、Cr、Zn和Mn的总量高于参照点,形成严重的复合污染,花垣河沉积物中重金属的污染水平明显高于峒河,但沿程变化规律不明显,而峒河沉积物中重金属的沿程变化较有规律,即上游含量低,中下游含量较高。两条河流表层沉积物中富集程度居前列的均为Cd、Pb、Zn和Mn。花垣河和峒河沉积物重金属污染主要来源于矿业生产所产生废渣和废水的点排放。在花垣河和峒河的大多数位点,Cd、Pb和Mn的形态具有共同特征,其生物可利用态均较大程度地超过生物不可利用态,而且Mn和Cd的生物可直接利用态所占比例远高于其它重金属,而Cu和Cr的生物可直接利用态所占比例很低。花垣河沉积物中Cd、Pb和Zn在所有位点极大地超过PEL,在峒河中下游,Cd、Pb、Ni和Zn超过PEL,具有较大的潜在生物毒性。除上游S1位点外,花垣河的其余各位点都具有明显的急性毒性,峒河中下游各位点具有明显的急性毒性,这些河段需要重点治理。 相似文献
59.
北京城区道路沉积物污染特性 总被引:3,自引:0,他引:3
为了解城市道路沉积物污染物的浓度水平及可能造成的生态环境危害,在北京城区的生活区、文教区、交通干线和公园绿地这四种功能区的道路沉积物进行了取样监测,并分析了道路沉积物中总氮(TN)、总磷(TP)、重金属铜(Cu)、铬(Cr)、铅(Pb)、锌(Zn)和有机质(TOC)的污染特性.研究结果表明,各类功能区道路沉积物中TN、TP和TOC的含量较高.交通干线、文教区、生活区和公园绿地道路沉积物TN均值分别为0.1009、0.1440、0.1071、0.0974mg/kg,文教区道路沉积物的TN显著高于其他类型道路沉积物;TP均值分别为0.0695、0.0729、0.0665、0.0608mg/kg,以文教区最高,但未达显著水平.交通干线和文教区道路沉积物TOC浓度显著高于生活区和公园绿地,交通干线、文教区和生活区道路沉积物重金属的含量高于公园绿地.主要原因可能是人类活动和车辆交通量的影响.四类功能区氮主要以可溶态赋存,磷主要以颗粒态赋存在沉积物中,并且交通干线道路沉积物中溶解态磷比例最低.溶解态的重金属占总量的比例均较低,只有溶解态Cu达到5%以上,表明重金属主要赋存在颗粒态存在的沉积物中.道路沉积物或者外界带入的固体物质是地表径流污染物的重要来源,研究结果为城市地表污染控制提供重要参考. 相似文献
60.
The biogeochemistry of nitrogen in freshwater wetlands 总被引:12,自引:7,他引:12
William B. Bowden 《Biogeochemistry》1987,4(3):313-348
The biogeochemistry of N in freshwater wetlands is complicated by vegetation characteristics that range from annual herbs to perennial woodlands; by hydrologic characteristics that range from closed, precipitation-driven to tidal, riverine wetlands; and by the diversity of the nitrogen cycle itself. It is clear that sediments are the single largest pool of nitrogen in wetland ecosystems (100's to 1000's g N m-2) followed in rough order-of-magnitude decreases by plants and available inorganic nitrogen. Precipitation inputs (< 1–2 g N m-2 yr-1) are well known but other atmospheric inputs, e.g. dry deposition, are essentially unknown and could be as large or larger than wet deposition. Nitrogen fixation (acetylene reduction) is an important supplementary input in some wetlands (< < 1–3 g N m-2 yr-1) but is probably limited by the excess of fixed nitrogen usually present in wetland sediments.Plant uptake normally ranges from a few g N m-2 yr-1 to 35 g N m-2 yr-1 with extreme values of up to 100g N m-2 yr-1 Results of translocation experiments done to date may be misleading and may call for a reassessment of the magnitude of both plant uptake and leaching rates. Interactions between plant litter and decomposer microorganisms tend, over the short-term, to conserve nitrogen within the system in immobile forms. Later, decomposers release this nitrogen in forms and at rates that plants can efficiently reassimilate.The NO3 formed by nitrification (< 0.1 to 10 g N m-2 yr-1 has several fates which may tend to either conserve nitrogen (uptake and dissimilatory reduction to ammonium) or lead to its loss (denitrification). Both nitrification and denitrification operate at rates far below their potential and under proper conditions (e.g. draining or fluctuating water levels) may accelerate. However, virtually all estimates of denitrification rates in freshwater wetlands are based on measurements of potential denitrification, not actual denitrification and, as a consequence, the importance of denitrification in these ecosystems may have been greatly over estimated.In general, larger amounts of nitrogen cycle within freshwater wetlands than flow in or out. Except for closed, ombrotrophic systems this might seem an unusual characteristic for ecosystems that are dominated by the flux of water, however, two factors limit the opportunity for N loss. At any given time the fraction of nitrogen in wetlands that could be lost by hydrologic export is probably a small fraction of the potentially mineralizable nitrogen and is certainly a negligible fraction of the total nitrogen in the system. Second, in some cases freshwater wetlands may be hydrologically isolated so that the bulk of upland water flow may pass under (in the case of floating mats) or by (in the case of riparian systems) the biotically active components of the wetland. This may explain the rather limited range of N loading rates real wetlands can accept in comparison to, for example, percolation columns or engineered marshes. 相似文献