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101.
本文结合形态学特征和线粒体COI基因分子数据,记述了采集于我国山东省的冠蜂科一新记录种:环足施氏冠蜂Schlettererius cinctipes (Cresson, 1880),详细描述了该种的形态特征,并提供鉴定特征图以及COI序列。通过与来自于北美、日本和澳洲的环足施氏冠蜂的COI序列对比,相似度达到99.79%。虽然环足施氏冠蜂在我国的寄主未能明确,但由于该蜂从松幽天牛Asemum amurense Kraatz, 1879为害的松木中羽化出来,能为其寄主的确定提供参考。研究标本分别保存在华南农业大学膜翅目标本室(SCAU)和山东省林业科学研究院林业有害生物标本室。 相似文献
102.
Large amounts of labile organic carbon in permafrost soils of northern Alaska 总被引:1,自引:0,他引:1 下载免费PDF全文
Carsten W. Mueller Janet Rethemeyer Jenny Kao‐Kniffin Sebastian Löppmann Kenneth M. Hinkel James G. Bockheim 《Global Change Biology》2015,21(7):2804-2817
Permafrost‐affected soils of the northern circumpolar region represent 50% of the terrestrial soil organic carbon (SOC) reservoir and are most strongly affected by climatic change. There is growing concern that this vast SOC pool could transition from a net C sink to a source. But so far little is known on how the organic matter (OM) in permafrost soils will respond in a warming future, which is governed by OM composition and possible stabilization mechanisms. To investigate if and how SOC in the active layer and adjacent permafrost is protected against degradation, we employed density fractionation to separate differently stabilized SOM fractions. We studied the quantity and quality of OM in different compartments using elemental analysis, 13C solid‐phase nuclear magnetic resonance (13C‐NMR) spectroscopy, and 14C analyses. The soil samples were derived from 16 cores from drained thaw lake basins, ranging from 0 to 5500 years of age, representing a unique series of developing Arctic soils over time. The normalized SOC stocks ranged between 35.5 and 86.2 kg SOC m?3, with the major amount of SOC located in the active layers. The SOC stock is dominated by large amounts of particulate organic matter (POM), whereas mineral‐associated OM especially in older soils is of minor importance on a mass basis. We show that tremendous amounts of over 25 kg OC per square meter are stored as presumably easily degradable OM rich in carbohydrates. Only about 10 kg OC per square meter is present as presumably more stable, mineral‐associated OC. Significant amounts of the easily degradable, carbohydrate‐rich OM are preserved in the yet permanently frozen soil below the permafrost table. Forced by global warming, this vast labile OM pool could soon become available for microbial degradation due to the continuous deepening of the annually thawing active layer. 相似文献
103.
104.
Effects of hydrodynamics on phosphorus concentrations in water of Lake Taihu,a large,shallow, eutrophic lake of China 总被引:4,自引:0,他引:4
Guangwei Zhu Boqiang Qin Guang Gao Lu Zhang Liancong Luo Yunlin Zhang 《Hydrobiologia》2007,581(1):53-61
To understand the effect of hydrodynamical process on water phosphorus concentration, wind, wave, and several water quality
indices were observed in Meiliang Bay, a shallow and eutrophic bay locates in north of Lake Taihu. During the 7 day observation
period, wind speed and significant wave height were recorded more than 3 h per day, and water samples were collected in five
water-depth layers once a day. Hydrodynamical disturbance had no significant correlationship with the water quality at the
top layer when the significant wave height was smaller than 30 cm, but it significantly increased suspended solids (SS) concentration
of the bottom water layer. Concentrations of nutrients showed no positive correlationship with SS concentration in the water
body. Intensive sediment resuspension may not have occurred when the hydrodynamic stress on sediment was only a little higher
than the critical stress for sediment resuspension. A new method for confirming the critical stress for intensive sediment
resuspension and nutrient release still needs to be developed. The range of the water quality indices was quite high during
the seven days of observation. High variation seems to be a common character of large shallow lakes like Taihu. 相似文献
105.
Jin Zeng Liuyan Yang Jiayun Li Yi Liang Lin Xiao Lijuan Jiang Dayong Zhao 《World journal of microbiology & biotechnology》2009,25(2):225-233
Vertical distribution of bacterial community structure was investigated in the sediments of two eutrophic lakes of China,
Lake Taihu and Lake Xuanwu. Profiles of bacterial communities were generated using a molecular fingerprinting technique, denaturing
gradient gel electrophoresis (DGGE) followed by DNA sequence analysis, and the results were interpreted with multivariate
statistical analysis. To assess changes in the genetic diversity of bacterial communities with changing depth, DGGE banding
patterns were analysed by cluster analysis. Distinct clusters were recognized in different sampling stations of Lake Taihu.
Canonical correspondence analysis (CCA) was carried out to infer the relationship between environmental variables and bacterial
community structure. DGGE samples collected at the same sampling site clustered together in both lakes. Total phosphorus,
organic matter and pH were considered to be the key factors driving the changes in bacterial community composition. 相似文献
106.
Methane emission and rhizospheric CH4 oxidation were studied in stands of Equisetum fluviatile, a common cryptogam in boreal lakes. The experiment was performed in mesocosms with organic sediment or sand bottoms under natural variation of temperature and light using the light-oxic – dark-anoxic chamber (LO/DA) technique. Net CH4 emission from the organic sediment during the growing season varied between 3.4 and 19.0 mg m–2 h–1, but from sand the net CH4 emission was only 3–10% of that measured from the organic sediment. In the organic sediment net CH4 emission was very significantly correlated with sediment temperature (r2 = 0.92). In the sand mesocosms the variation of net CH4 emission was better correlated with the shoot biomass than with sediment temperature variation during the growing season, indicating that methanogens were severely limited by substrate availability and were probably dependent on substrates produced by E. fluviatile. The proportion of the methane oxidized of the potential CH4 emission in summer did not differ significantly between the bottom types. The net CH4 emission during the growing season as a proportion of the seasonal maximum of the shoot biomass was significantly higher in the organic sediment mesocosms (6.5%) than in sand (1.7%). The high CH4 emissions observed from dense well-established E. fluviatile stands in the field appear to be more related to temperature-regulated turnover of detritus in the anaerobic sediment and less to CH4 oxidation and seasonal variation in plant growth dynamics 相似文献
107.
We used simple statistics (e.g. mean temperature, degree days, cumulative volume days) to describe present thermal habitats for cool water (yellow perch, Perca flavescens) and cold water (lake trout, Salvelinus namaycush) fish of a small boreal lake. We then modelled changes in the vertical and temporal extent of these habitats under various scenarios of climatic change that included increases in air temperature of 2°C, 4°C, and 9°C, and positive and negative deviations from present levels of 10% in solar radiation and relative humidity, and 20% in wind speed and the lake water extinction coefficient. Model simulations indicated pronounced changes in the temporal and vertical availability of fish thermal niche space. These changes were mainly driven by the large increases in mean mixed layer temperatures that corresponded to 85% of the increases in air temperature, but, in particular, changes in light attenuation also resulted in some non-linear, unexpected effects in the distribution and seasonal availability of thermal niche space. As expected, classical lake trout thermal habitat (5–15°C) was progressively reduced and almost disappeared in littoral areas in spring and early summer. Perch thermal niche space expanded for air temperature increases of up to 4°C, but largely disappeared for the 9°C increase. We discuss changes in thermal habitat with regard to the life history of lake trout and yellow perch, and include other determinants of fish habitat to evaluate the potential of these species for long-term ecological success under climatic warming. 相似文献
108.
Helen Michels Susanne Lildal Amsinck Erik Jeppesen Luc De Meester 《Hydrobiologia》2007,594(1):117-129
In shallow temperate lakes, zooplankton populations may exhibit diel horizontal migration (DHM) and move towards macrophytes
during the day to avoid fish. Using a natural Daphnia magna population, we undertook an experimental investigation aimed to describe the genetic variation for DHM and to study whether
an adaptive micro-evolutionary response occurred to changes in macrophyte coverage and fish predation pressure through time.
Twenty-seven D. magna clones were hatched from ephippia in the sediment of shallow Lake Ring, Denmark. This lake was eutrophied during the 20th
century and was subject to restoration measures in the 1970s. The DHM behaviour of the clones was observed both in the presence
and absence of fish kairomone. Significant interclonal variation in DHM behaviour occurred in both treatments. To study the
micro-evolutionary response of the Lake Ring D. magna population, two approaches were used. First, we compared the DHM behaviour of clones derived from ephippia collected at different
depths. A comparison was conducted between clones resurrected from the period of eutrophication (1960–1980) and from the period
of recovery (1986–2000). A significant treatment (presence and absence of fish kairomone) × period interaction effect was
identified, suggesting a significant micro-evolutionary response for DHM behaviour. The D. magna clones exhibited a significantly stronger horizontal migration response during the period of eutrophication than in the recovery
phase. Second, clonal means, representing the influence of the genotype on the trait, were correlated with environmental conditions
(macrophyte cover, fish predation pressure and Secchi depth). The results of this analysis also suggest that a micro-evolutionary
response by Daphnia has occurred in reaction to changes in fish predation pressure. In periods with high fish predation pressure, Daphnia migrated more strongly towards the plants.
Guest editor: Piet Spaak
Cladocera: Proceedings of the 7th International Symposium on Cladocera 相似文献
109.
The molecular diversity of the methanogenic community in a hypereutrophic freshwater lake determined by PCR-RFLP 总被引:1,自引:0,他引:1
Whitby C Earl J Lanyon C Gray S Robinson J Meadows J Edwards C 《Journal of applied microbiology》2004,97(5):973-984
AIMS: To combine database-held sequence information with a programme of experimental molecular ecology to define the methanogenic community of a hypereutrophic lake by a PCR-restriction fragment length polymorphism (RFLP) analysis. METHODS AND RESULTS: Methanogen diversity in a hypereutrophic freshwater lake was analysed using 16S rDNA PCR-RFLP. Database-held 16S rRNA gene sequences for 76 diverse methanogens were analysed for specific restriction sites that permitted unequivocal differentiation of methanogens. Restriction digestion and agarose gel electrophoresis of the 16S rDNA from selected methanogen pure cultures generated observed restriction profiles that corroborated the expected patterns. This method was then tested by analysing methanogen diversity in samples obtained over 1 year from sediment and water samples taken from the same sampling site. CONCLUSIONS: Restriction analysis of the 16S rRNA gene sequences from 157 methanogen clones generated from lakewater and sediment samples showed that over 50% were similar to Methanoculleus spp. Furthermore, a total of 16 RFLP types (1-16) were identified, eight of which contained no cultured representative archaeal 16S rRNA gene sequences. SIGNIFICANCE AND IMPACT OF THE STUDY: This RFLP strategy provides a robust and reliable means to rapidly identify methanogens in the environment. 相似文献
110.
巢湖西半湖富营养化时空变化趋势与成因分析 总被引:2,自引:0,他引:2
收集整理了巢湖西半湖6个国控监测点1983~2008年(26年)主要富营养化指标TP、TN、CODmn、Chla的监测数据,计算了6个监测点和西半湖总体26年的综合营养状态指数(∑TLI图示)时空变化情况。并用Spearm an秩相关系数分析检验了西半湖总体和6个监测点26年∑TLI年变化趋势。结果表明:按总平均∑TLI排列,6个监测点富营养化由重到轻依次为:南淝河入湖区(66.64)〉塘西(64.93)〉十五里河入湖区(63.35)〉派河入湖区(61.38)〉新河入湖区(59.51)〉西半湖湖心(59.18);在显著水平0.05和0.01各点∑TLI均有上升趋势,其中十五里河入湖区(R=0.715)、新河入湖区(R=0.824)和西半湖湖心(R=0.811)以及西半湖总体(R=0.512)∑TLI有显著上升趋势,而南淝河入湖区(R=0.192)、塘西(R=0.045)和派河入湖区(R=0.325)上升趋势均不显著。最后在上述研究的基础上,对巢湖西半湖富营养化时空变化的成因进行了简要分析。 相似文献