细菌细胞中类异戊二烯醌的分析

类异戊二烯醌是细菌质膜的成分,在电子传递和氧化磷酸化中起重要作用.甲基萘醌和泛醌是其中较为重要的两类化合物.这两种化合物的分析鉴定是研究细菌细胞中类异戊二烯醌组成构象的前提,在细菌化学分类的研究中具有十分重要的意义.本文参考了有关细菌类异戊二烯醌分析的文献,综述了甲基萘醌和泛醌的分析方法,其中包括:液-液萃取、薄层色谱(TLC)、高效液相色谱(HPLC)、紫外吸收光谱(UV)、质谱(MS)的定性鉴定及HPLC的定量分析.     

醌类图谱分析在环境微生物生态测定中的应用

近年来，随着人们对各种非培养微生物测定法的重视，醌类图谱分析作为微生物群体指标已在各种环境中得到了应用．首先是样品的分析测定技术得到了提高，如用硅胶柱代替薄层色谱．醌类图谱分析的特点是能够同时对应微生物生态评价的3个重要指标，即微生物群体结构、生物量及微生物多样性．在结合统计分析的基础上，在土壤、污泥及堆肥等不同环境样品及不同微生物反应过程中，已通过醌类图谱分析对这3个指标在微生物生态系中的变动进行了成功的评价．另外，对C-14同位素标记醌类图谱分析法及醌类图谱分析法在污染物降解中的应用等最新进展也进行了简介．图4表3参43     

植物根系分泌物分析及对湿地微生物群落的影响研究

植物是人工湿地的重要组成部分,其通过根系分泌物对湿地中的微生物群落结构产生影响。本研究分析了美人蕉（Canna indica）、茭白（Zizania caduciflora）、千屈菜（Lythrum salicaria Linn）等3种湿地植物的根系分泌能力及分泌物组成。3种植物的根系分泌物主要组成物质相似,均含有小分子有机酸、酚类、芳香族蛋白质,但各组成比例有所差异。分泌能力则随生长周期持续下降,千屈菜的分泌能力远强于美人蕉和茭白。本研究利用醌指纹研究人工湿地中微生物群落结构,结果发现不同湿地植物对湿地中微生物的组成和多样性产生显著影响。     

多形态多水平氮添加对温带森林土壤根系呼吸和微生物呼吸的影响

为阐明不同水平、不同形态的氮添加对土壤总呼吸、土壤微生物呼吸、根系呼吸的影响及微生物机制,本研究以温带森林土壤为研究对象,开展多形态(硝态氮(NaNO_3)、铵态氮((NH_4)_2SO_4)和混合态氮(NH_4NO_3))多水平(50 kg N·ha~(-1)·a~(-1)和150 kg N·ha~(-1)·a~(-1))的增氮控制实验.在施氮后的第7—9年,利用静态箱-气相色谱法研究土壤呼吸组分和磷脂脂肪酸方法研究微生物群落丰度和群落结构的改变.结果表明,氮添加显著提高了土壤硝态氮和铵态氮含量,而土壤pH平均降低0.85个单位.在施氮后的第7—9年,氮添加将会减弱土壤呼吸活动,高水平的氮添加效应强于低水平氮添加;就形态来说,(NH_4)_2SO_4起到促进效应,而NH_4NO_3则逐渐由促进效应转变成抑制效应,例如在2019年(施肥后第9年),高水平的(NH_4)_2SO_4施加分别提高土壤总呼吸和微生物呼吸的34.06%和37.95%,而高水平NH_4NO_3添加则分别抑制了土壤总呼吸和微生物呼吸的27.62%和31.70%.而高水平的(NH_4)_2SO_4添加对根系呼吸有促进作用,而高水平的NH_4NO_3则有抑制效应.微生物呼吸和细菌、真菌显著正相关,和真菌/细菌比值也呈正相关.总之,土壤呼吸各组分对氮添加的响应受氮素形态和水平的控制,特定森林土壤碳排放量对土壤氮基质响应具有多阶段性,微生物呼吸的降低反映了土壤有机质分解速度的降低,这有可能会进而促进土壤碳的积累,达到氮促碳汇的效果.     

城市大气颗粒物表面半醌自由基的测定及特征分析

采集上海市城区和郊区两个典型站位的大气颗粒物样品,通过二氯甲烷萃取分离并利用电子自旋共振波谱技术(ESR)分析测定吸附在颗粒物表面的稳定自由基.结果显示,测试样品的波谱特征表现为显著的三重信号峰,且g因子值均在2.00379—2.00395范围内,通过与醌类标准物质图谱比对,可以判断颗粒物表面至少吸附1种邻位半醌自由基.对自由基分布特征研究发现,自由基浓度的时空变化和粒径分布特征显著:闵行采样点的半醌自由基浓度远高于普陀采样点;在季节变化上表现为夏秋季半醌自由基浓度低于冬春季,其中春季最高,夏季最低;半醌自由基在不同粒径颗粒上的分布,呈现PM2.5>PM10>TSP的变化规律,说明自由基更容易富集在细颗粒上.     

黄淮海平原不同土地利用方式对土壤有机碳及微生物呼吸的影响

土壤是陆地生态系统最大的碳库,有机碳通过微生物分解作用向大气释放CO_2,土壤碳库的微小变化将会对大气CO_2浓度和全球碳循环产生巨大的影响。在当前人类活动频繁和土地利用与土地覆被变化的背景下,研究不同土地利用方式对土壤有机碳等理化性质和土壤微生物呼吸等功能的影响,可以阐明影响土壤碳汇功能的关键因子,为未来土地利用管理提供科学依据。以开封市为例,研究了黄淮海平原不同土地利用方式(包括弃耕地、草地、果园、农田和森林)下土壤湿度、pH值、铵态氮、硝态氮、总碳、总氮、有机碳、可溶性有机碳、微生物生物量碳氮、微生物呼吸及其温度敏感性的变化规律。研究结果表明,(1)森林土壤湿度、总碳、总氮、有机碳(1.48%)、微生物生物量碳氮含量显著高于其他土地利用方式,但其微生物呼吸(101.06 mg·kg~(-1)·d~(-1))和温度敏感性(1.18)最小。(2)农田土壤的总碳、总氮、有机碳、微生物生物量碳氮含量均次于森林且高于其他土地利用方式,微生物呼吸速率较大(128.55 mg·kg~(-1)·d~(-1))。(3)弃耕地、草地和果园土壤碳氮和微生物碳氮较小。(4)结构方程模型表明土地利用方式可以直接解释土壤有机碳积累的68%,且可通过土壤湿度间接地影响土壤有机碳和微生物呼吸。土壤有机碳和微生物呼吸分别被土壤湿度和硝态氮含量等因子解释了93%和54%。该研究表明森林生态系统利于土壤有机碳固持,其较小的微生物呼吸温度敏感性对应对未来全球气候变化具有重大意义;农田占地面积广大,农业经营中在保障粮食生产的同时要采取免耕或秸秆还田等措施充分发挥其碳汇作用。     

电子穿梭体介导土壤锑还原成矿的微生物机制

微生物锑还原成矿有助于降低土壤锑的生物有效性和移动性,是土壤锑污染修复的重要策略之一。电子穿梭体AQDS能够加速土壤富集菌群锑还原速率,可能与其促进微生物呼吸及细胞生长有关。理解电子穿梭体（ES）介导微生物锑还原过程与机制可为土壤锑污染控制提供关键理论支撑。醌类和黄素类电子穿梭体（AQDS和FMN）存在时可能改变微生物呼吸代谢中的电子传递过程,然而ES介导下的微生物锑还原过程及转录响应机制尚不清楚。利用锑污染稻田土壤分离的兼性厌氧锑还原细菌Mesobacillus jeotgali PS1作为研究对象,探究醌类和黄素类电子穿梭体（AQDS和FMN）对菌株PS1锑还原过程及关键功能基因转录活性的影响。结果表明,菌株PS1驱动Sb(Ⅴ)还原为Sb(Ⅲ)过程中水溶态Sb(Ⅲ)随培养时间先累积后下降,培养72 h后水溶态锑去除率为64%,生成十四面体方锑矿,表明菌株PS1驱动锑还原成矿有助于锑的钝化。两种ES能够加速细菌锑还原反应,而对胞外生成的方锑矿晶型没有影响。通过定量分析菌株PS1潜在功能基因转录表达活性,结果表明AQDS相比FMN更能促进菌株PS1细胞膜二甲基亚砜还原酶（DMSOR）基...     

氮沉降增加对贝加尔针茅草原土壤微生物群落结构的影响

土壤微生物是草原土壤生态系统的重要组成部分。为研究氮沉降增加对草原土壤微生物群落结构的影响,以内蒙古贝加尔针茅草原为研究对象,开展连续6年(2010—2015年)模拟氮沉降试验,以N计算,设置:N0(0 kg·hm~(-2))、N50(50kg·hm~(-2))、N100(100 kg·hm~(-2))、N150(150 kg·hm~(-2))和N300(300 kg·hm~(-2))5个处理,采用磷脂脂肪酸(PLFA)技术测定0~10 cm土壤特征微生物PLFA生物标记数量并探讨土壤微生物群落结构对氮沉降的响应。结果表明:随氮添加量增大,土壤微生物总PLFAs、细菌PLFAs、革兰氏阳性细菌PLFAs、革兰氏阴性细菌PLFAs和放线菌PLFAs含量呈先升高后降低的趋势,均以N100(100 kg·hm~(-2))处理最高。土壤微生物群落PLFA标记的主成分分析显示,不同氮添加下土壤微生物PLFA标记有显著差异。相关分析表明,土壤革兰氏阳性菌、放线菌PLFA含量、G~+/G~-与土壤p H值呈显著负相关,土壤微生物总PLFAs、土壤细菌PLFAs、革兰氏阳性菌PLFAs、革兰氏阴性菌PLFAs、放线菌PLFAs和饱和脂肪酸PLFAs含量均与土壤速效磷含量呈显著正相关。综合研究表明,连续6年氮添加改变了贝加尔针茅草原土壤微生物群落结构,土壤p H值和土壤速效磷含量是驱动这种变化的主要因素。     

致癌性卤代醌介导的脂质氢过氧化物分解的分子机制

卤代醌是许多卤芳香持久有机污染物的致癌代谢产物和饮用水消毒副产物.13-过氧羟基-9,11-十八碳二烯酸(13-HPODE)是最为广泛研究的内源性脂质过氧化物.众所周知,过渡金属离子可以催化分解13-HPODE,但尚不清楚卤代醌是否可以通过不依赖金属离子的途径促进其分解;若是如此,又有什么特异性和相似性?我们发现卤化醌如2,5-二氯-1,4-苯醌(DCBQ)可显著促进13-HPODE的分解.综合采用电子自旋共振-自旋捕获、HPLC-MS和GC-MS等分析方法,可检测到反应形成的脂质烷基自由基如戊烷基自由基、7-羧甲基自由基以及具有基因毒性的4-羟基-2-壬烯醛(HNE)等.在DCBQ和13-HPODE的反应中也能检测到两种氯醌-脂质烷氧基耦合物.我们认为卤代醌促进内源性脂质过氧化物13-HPODE分解生成活性脂质烷基自由基和基因毒性的HNE是通过一类新型的金属非依赖亲核取代与裂解机理来实现的,这也在一定程度上解释了其潜在的基因毒性和致癌性.     

不同林分密度油松天然林土壤理化性质及微生物量碳氮特征研究

为应对天然林退化和天然林生态系统的经营问题,探究以林分密度为调节因子的森林土壤响应,在关帝山林区油松(Pinus tabulaeformis)天然林区开展探索研究,通过样地调查及土壤采样分析,对不同林分密度(725-1 375 plant·hm~(-2))森林土壤理化性质及微生物碳氮特征规律进行分析研究,探明土壤属性对林分密度变化的响应机制,为森林质量精准提升及森林生态系统可持续经营提供理论依据。结果表明,(1)林分密度的变化间接影响土壤含水量(18.27%-34.27%)、容重(0.87-1.10 g·cm~(-3))、pH(6.86-7.13),总碳(15.26-29.44 g·kg~(-1))、全氮(0.92-2.14 g·kg~(-1))、全磷(0.20-0.30 g·kg~(-1))、微生物量碳(760.56-1 808.73mg·kg~(-1))、微生物量氮含量(134.84-257.59mg·kg~(-1)),除容重、pH值、全磷含量外,其他指标现随密度变化均呈先增后减的变化规律。(2)土壤属性指标垂直分布规律:土壤含水量、总碳、全氮、全磷、微生物量碳、微生物量氮含量随土层深度增加而下降,土壤容重和pH值却呈相反趋势;林分密度不改变总体格局,但随林分密度的变化,土壤垂直分异程度在中密度林分中(975-1 175 plant·hm~(-2))最小,更为均一稳定。(3)当油松天然林林分密度适中时,0-30cm深度的土壤水分、总碳、全氮、全磷、微生物量碳、微生物量氮含量保持在较高水平。综上,认为研究地区油松天然林适宜的保留密度为975-1 175 plant·hm~(-2)。     

Denitrification and the nitrogen budget of a reservoir in an agricultural landscape.

Denitrification is an important process in aquatic sediments, but its role has not been assessed in the N mass balance of upper-Midwestern (USA) reservoirs that receive large agricultural riverine N inputs. We used a 4400-ha reservoir to determine the role of denitrification in the N mass balance and effectiveness in reducing downstream transport of NO(3-)N. Sediment denitrification was (1) measured monthly (March 2002-March 2003) at eight sites in the Lake Shelbyville reservoir in central Illinois using the acetylene inhibition, chloramphenicol technique, (2) scaled to the overall reservoir and compared to N not accounted for in a mass balance, and (3) estimated indirectly using long-term (1981-2003) mass balances of N in the reservoir. Denitrification rates in the reservoir were high during spring and early summer of 2002, when maximum NO(3-)N concentrations were measured (10-14 mg NO(3-)N/L). We estimated that denitrification for the year was between 2580 and 5150 Mg N. Missing N from the mass balance was 3004 Mg N, suggesting that sediment denitrification was the sink. Areal rates of sediment denitrification in the reservoir ranged from 62 to 225 g N x m(-2) x yr(-1), with rates a function of both denitrification intensity (microg N x g dry mass x h(-1)) and the overall mass of sediment present. From 1981 to 2003 the average NO(3-)N inlet flux was 8900 Mg N/yr. About 58% of the total NO(3-)N input was removed, and annual NO(3-)N removed as a percentage of inputs was significantly related to reservoir retention time (average = 0.36 yr for the 23 years, range = 0.21-0.84 yr). By scaling denitrification in Lake Shelbyville to other reservoirs in Illinois, we estimated a sink of 48900 Mg N/yr. When combined with estimated in-stream denitrification, 60900 Mg N/yr was estimated to be removed by sediment denitrification. This reduces riverine export from Illinois to the Gulf of Mexico, where the flux during the 1990s was about 244000 Mg N/yr, and illustrates the importance of reservoir denitrification as an N sink in Midwestern agricultural landscapes.     

Increasing trend of primary NO2 exhaust emission fraction in Hong Kong

Despite the successful reduction in roadside NO( x ) levels, no such decrease has been detected in roadside NO(2) concentration in Hong Kong. One underlying cause could be the rising primary NO(2) fraction of the total emission of NO( x ). Primary NO(2) can be particularly detrimental to Hong Kong because a large fraction of the population are exposed to the traffic-related primary pollutants in the street canyons formed by congested high-rise buildings. In this study, hourly mean concentration data for roadside nitrogen oxides (NO( x )), nitrogen dioxide (NO(2)), and background ozone (O(3)) were used to estimate the mean primary NO(2) fraction from vehicle exhausts in Hong Kong. An overall increasing trend was observed for the primary NO(2) fraction (f-NO(2)) values in all the three roadside air monitoring sites. The primary NO(2) as a fraction of total NO( x ) (f-NO(2)) increased approximately from 2% in 1998 to 13% in 2008 in Hong Kong. The two particular periods of rising f-NO(2) coincided with the two implementation periods of the diesel retrofit programs for the light-duty vehicles and heavy-duty vehicles. Future vehicle emission control strategies should target not only total NO( x ) but also primary NO(2). Health benefit or disease burden estimates should be taken into account and updated in the process of policy planning and evaluation.     

Habitat-mediated foraging limitations drive survival bottlenecks for juvenile salmon

Realistic population models and effective conservation strategies require a thorough understanding of mechanisms driving stage-specific mortality. Mortality bottlenecks for many species occur in the juvenile stage and are thought to result from limitation on food or foraging habitat during a "critical period" for growth and survival. Without a way to account for maternal effects or to measure integrated consumption rates in the field, it has been virtually impossible to test these relationships directly. Hence uncertainties about mechanisms underlying such bottlenecks remain. In this study we randomize maternal effects across sites and apply a new method for measuring consumption integrated over weeks to months to test the hypothesis that food limitation drives early-season juvenile mortality bottlenecks in Atlantic salmon (Salmo salar). Using natural signatures of geologically derived cesium (133Cs), we estimated consumption rates of >400 fry stocked into six streams. Two to four weeks after stocking, consumption was extremely low across sites (0.005 g x g(-1) x d(-1)) and was predicted to be below maintenance rations (i.e., yielding negative energy balances) for the majority of individuals from five of six sites. However, consumption during this time was positively correlated with growth rates and survival (measured at the end of the growing season). In contrast, consumption rates increased in mid- (0.030 g x g(-1) x d(-1)) and late (0.035 g x g(-1) x d(-1)) seasons, but juvenile survival and consumption were not correlated, and correlations between growth and consumption were weak. These findings are consistent with predictions of a habitat-based bioenergetic model constructed using the actual stream positions of the individual fish in the present study, which indicates that habitat-based models capture important environmental determinants of juvenile growth and survival. Hence, by combining approaches, reducing maternal effects and controlling initial conditions, we offer a general framework for linking foraging with juvenile survival and present the first direct consumption-based evidence for the early season bottleneck hypothesis.     

Allometric exponents do not support a universal metabolic allometry

The debate about the value of the allometric scaling exponent (b) relating metabolic rate to body mass (metabolic rate = a x mass(b)) is ongoing, with published evidence both for and against a 3/4-power scaling law continuing to accumulate. However, this debate often revolves around a dichotomous distinction between the 3/4-power exponent predicted by recent models of nutrient distribution networks and a 2/3 exponent predicted by Euclidean surface-area-to-volume considerations. Such an approach does not allow for the possibility that there is no single "true" exponent. In the present study, we conduct a meta-analysis of 127 interspecific allometric exponents to determine whether there is a universal metabolic allometry or if there are systematic differences between taxa or between metabolic states. This analysis shows that the effect size of mass on metabolic rate is significantly heterogeneous and that, on average, the effect of mass on metabolic rate is stronger for endotherms than for ectotherms. Significant differences between scaling exponents were also identified between ectotherms and endotherms, as well as between metabolic states (e.g., rest, field, and exercise), a result that applies to b values estimated by ordinary least squares, reduced major axis, and phylogenetically correct regression models. The lack of support for a single exponent model suggests that there is no universal metabolic allometry and represents a significant challenge to any model that predicts only a single value of b.     

Lytic bacteriophages specific to Flavobacterium columnare rescue catfish, Clarias batrachus (Linn.) from columnaris disease

This investigation was aimed to find out appropriate strategy against antibiotic resistant bacterial fish pathogen, F. columnare. This pathogen was found persistently associated with fishes causing columnaris disease and ensuing mass mortality in hatchery and culture system of Sub - Himalayan region. Nine lytic F. columnare phages (FCP1 - FCP9) specific to its fifteen isolates were isolated from the water and bottom sediments of various geo-climatic regions of North India. The F. columnare phage FCP1 (made of hexagonal head and non contractile long tail belonging to family Podovariedae, a member of DNA virus) exhibited broader host range to lyse 9 out of 15 isolates of F. columnare. Therapeutic ability of FCP1 phage was assessed in C. batrachus inoculated intramuscularly (im) with virulent bacterial isolate FC8 and post inoculated (PI) with FCP1 phage (@ 10(8) : 10(6):: cfu : pfu) through intramuscular (im), immersion (bath) and oral (phage impregnated feed) treatment. Significant (p < 0.001) reduction (less than 10(-3) cfu ml(-1)) in host bacterium in the sera, gill, liver and kidney of challenged fishes was noted after 6 hr of phage treatment. Quantum of phage played a significant role in bringing down bacterial population as in the sera of dose 1 (@ 4.55 x 10(6) pfu ml(-1)) and dose 2 (@ 9.15 x 10(6) pfu ml(-1)) treated fishes mean log10 cfu value reduced by 3 logs (58.39%) and 5 logs (73.77%) at 96 hr, respectively. Phage treatment led to disappearance of gross symptoms, negative bacteriological test, detectable phage and 100% survival in experimentally infected C. batrachus. Result of this study provides evidence of profound lytic impact of FCP1 phage and represents its interesting therapeutic importance against antibiotic resistant F. columnare.     

Greenhouse gas fluxes in southeastern U.S. coastal plain wetlands under contrasting land uses

Whether through sea level rise or wetland restoration, agricultural soils in coastal areas will be inundated at increasing rates, renewing connections to sensitive surface waters and raising critical questions about environmental trade-offs. Wetland restoration is often implemented in agricultural catchments to improve water quality through nutrient removal. Yet flooding of soils can also increase production of the greenhouse gases nitrous oxide and methane, representing a potential environmental trade-off. Our study aimed to quantify and compare greenhouse gas emissions from unmanaged and restored forested wetlands, as well as actively managed agricultural fields within the North Carolina coastal plain, USA. In sampling conducted once every two months over a two-year comparative study, we found that soil carbon dioxide flux (range: 8000-64 800 kg CO2 x ha(-1) x yr(-1)) comprised 66-100% of total greenhouse gas emissions from all sites and that methane emissions (range: -6.87 to 197 kg CH4 x ha(-1) x yr(-1)) were highest from permanently inundated sites, while nitrous oxide fluxes (range: -1.07 to 139 kg N2O x ha(-1) x yr(-1)) were highest in sites with lower water tables. Contrary to predictions, greenhouse gas fluxes (as CO2 equivalents) from the restored wetland were lower than from either agricultural fields or unmanaged forested wetlands. In these acidic coastal freshwater ecosystems, the conversion of agricultural fields to flooded young forested wetlands did not result in increases in greenhouse gas emissions.     

Impact of different doses of lead on internal organs of quails

Lead (Pb) is the most ancient poison known to man. In the present study, amount of accumulation of Pb in liver, kidney, ovary and testes of rain quail was studied using different doses of lead. Spectrophotometric analysis of heavy metal treated organs was carried out to determine the amount of metal accumulation in these organs. LD50 value was 4 ppm. Dose of lead was given in three ranges of low, medium and high. It was observed that testes (< or =6.8 x 10(-6)) mgkg(-1)day(-1) and ovary (< or =7.5 x 10(-6)) mgkg(-1)day(-1), accumulated low amount from different doses when given continuously for 21 days. In contrast to this, liver (< or =9.2 x 10(-6)) mgkg(-1)day(-1) and kidney (< or =9.3 x 10(-6)) mgkg(-1)day(-1) accumulated the maximum amount of metal when treated for the same number of days. This study is quite unique and astonishing as the period for intoxication is short (21 days) as compared to the long ones (91 days and above). Our results show that generally metal accumulation is highest in liver, while it is low in gonad.     

Extremely high secondary production of introduced snails in rivers.

The functional importance of invasive animals may be measured as the degree to which they dominate secondary production, relative to native animals. We used this approach to examine dominance of invertebrate secondary production by invasive New Zealand mudsnails (Potamopyrgus antipodarum) in rivers. We measured secondary production of mudsnails and native invertebrates in three rivers in the Greater Yellowstone Area (Wyoming, USA): Gibbon River, Firehole River, and Polecat Creek. Potamopyrgus production was estimated by measuring in situ growth rates and multiplying by monthly biomass; native invertebrate production was estimated using size frequency and instantaneous growth methods. Mudsnail growth rates were high (up to 0.06 d(-1)) for juvenile snails and much lower for adult females (0.003 d(-1)). Potamopyrgus production in Polecat Creek (194 g x m(-2) x yr(-1)) was one of the highest values ever reported for a stream invertebrate. Native invertebrate production ranged from 4.4 to 51 g x m(-2) x yr(-1). Potamopyrgus was the most productive taxon and constituted 65-92% of total invertebrate productivity. Native invertebrate production was low in all streams. Based on a survey of production measures from uninvaded rivers, the distribution of secondary production across taxa was much more highly skewed toward the invasive dominant Potamopyrgus in the three rivers. We suggest that this invasive herbivorous snail is sequestering a large fraction of the carbon available for invertebrate production and altering food web function.     

Macroinvertebrate production and food web energetics in an industrially contaminated stream.

This study examines secondary production and periphyton-invertebrate food web energetics at two sites in an industrially contaminated, nutrient-enriched stream. Secondary production data and data from the literature were used to calculate potential amounts of mercury transferred from periphyton to chironomid larvae and into terrestrial food webs with emerging adults. The nutritional quality of periphyton was characterized using energy content, chlorophyll a, protein, ash-free dry mass (AFDM), and percentage of organic matter. Chironomid larvae (Orthocladiinae: Cricotopus spp.) comprised 96% of all macroinvertebrates collected from stones at the two sites. Cricotopus production was extremely high: production was 59.5 g AFDM x m(-2) x yr(-1) at the site upstream of a 1-ha settling basin and 32.4 g AFDM x m(-2) x yr(-1) at the site below the basin. Apparent differences in annual secondary production were associated with reduced organic content (i.e., nutritional quality) of the periphyton matrix under different loading of total suspended solids. The periphyton matrix at both sites was contaminated with inorganic (Hg(II)) and methyl (MeHg) mercury. The amount of Hg(II) potentially ingested by Cricotopus was calculated to be 49 mg Hg(II) x m(-1) x yr(-1) at the upstream site and 19 mg Hg(II)x m(-2) x yr(-1) at the downstream site. Mercury ingestion by Cricotopus at the downstream site was calculated to be 2% of the estimated annual deposition of particulate-bound Hg(II) to the stream bed. Emergence of adult Cricotopus was calculated to remove 563 microg Hg(II)x m(-2) x yr(-1) from the stream at the upstream site and 117 microg Hg(II) x m(-2) x yr(-1) at the downstream site, which amounted to 4.1 g Hg(II)/yr for the 2.1-km reach of stream included in this study. The ratio of metal export in emergence production to surface area for the study stream was 10 to 10(3) times higher than ratios calculated for lakes using data from the literature. This study is the first well-documented example of extremely high aquatic insect production in an industrially contaminated, nutrient-enriched stream, and it highlights the application of production measurements to examine the role of aquatic insect production in the trophic transfer of energy and persistent contaminants in aquatic food webs and into terrestrial food webs.     

Gas exchange in Paulownia species growing under different soil moisture conditions in the field

In order to evaluate their responses to drought, we determined the photosynthetic activity water potential, stomatal conductance, transpiration, water use efficiency photosynthetic photon flux density and leaf temperature of Paulownia imperialis, P. fortunei and P. elongata in three different soil moisture conditions in the field. Our results showed that P. imperialis had greater photosynthesis (8.86 micromol CO2 m(-2) s(-1)) and instantaneous water use efficiency (0.79 micromol CO2 mmol H2O(-1)) than either P. elongata (8.20 micromol CO2 m(-2) s(-1) and 0.71 micromol CO2 mmol H2O(-1)) or P. fortunei (3.26 micromol CO2 m(-2) s(-1) and 0.07 micromol CO2 mmol H2O(-1)). The rapid growth of Paulownia did not appear to be correlated with photosynthetic rates. Paulownia fortunei showed more transpiration (48.78 mmol H2O m(-2) s(-1)) and stomatal conductance (840 mmol m(-2) s(-1)) than P. imperialis (20 mmol H2O m(-2) s(-1) and 540 mmol m(-2) s(-1)) and P. elongata (20 mmol H2O m(-2) s(-1) and 410 mmol m(-2) s(-1)), which allowed these two Paulownia species to increase their tolerance to low soil moisture, and maintain higher water use efficiency under these conditions. According to our physiological gas exchange field tests, Paulownia imperialis does appear to be capable of successful growth in semiarid zones.