典型草地土壤好氧甲烷氧化的微生物生态过程

【目的】针对我国甘肃三个典型生态区草地土壤(玛曲MQ、临泽LZ和环县HX),研究其甲烷氧化潜力、甲烷氧化菌(methane-oxidizingbacteria,MOB)丰度及可能存在的群落分异规律。【方法】通过原位分析、室内高浓度甲烷模拟培养三种典型土壤及实时荧光定量、高通量测序的方法研究甲烷氧化菌标靶基因pmoA序列的组成及其丰度变化规律。【结果】三种典型草地土壤的原位甲烷氧化菌的丰度存在显著差异,表现为MQ>HX>LZ,其数量范围为为0.18–6.86×10^7g/d.w.s.;甲烷氧化潜力也表现出类似规律,其通量为109–169mg/(m^2·h);甲烷氧化潜力与原位土壤中甲烷氧化菌丰度有正相关。三种草地土壤甲烷氧化菌存在明显的空间异质性,采用高通量测序的方法,发现三种草地原位土壤中的优势类群为USCγ(Upland Soil Cluster gamma,USCγ);然而,室内高浓度甲烷氧化过程中,传统的甲烷氧化菌均发生明显增加,MQ土壤中TypeⅡ的Methylocystis为优势类群,而LZ和HX土壤的优势类群均为TypeⅠ型Methylosarcina。【结论】这些研究结果表明,我国甘肃典型草地土壤中也存在难培养的大气甲烷氧化菌和经典的可培养甲烷氧化菌,这些微生物极可能氧化极低浓度的大气甲烷,也可能利用闭蓄于土壤中的高浓度甲烷生长。未来应采用先进技术原位观测大气甲烷氧化过程并分离相应微生物类群,研究草地土壤甲烷氧化菌地理分异规律及其环境驱动机制。     

哈密露天煤矿不同环境介质微生物群落特征分析

【背景】干旱区露天煤矿开采过程中产生的粉尘颗粒物加剧了土壤生态环境的恶化和矿区空气质量的下降,针对煤矿区土壤和粉尘颗粒物的微生物群落组成的研究鲜有报道。【目的】研究新疆哈密南湖乡露天煤矿土壤、粉尘及大气PM_2.5颗粒物中的微生物群落结构和多样性特征,并预测潜在的功能类群。【方法】采用高通量测序技术,对煤矿露天采坑区和电厂粉煤灰堆放区的土壤、粉尘及大气PM_2.5颗粒物的微生物真菌及细菌群落组成进行比对分析。【结果】矿区优势真菌类群来自子囊菌门(Ascomycota)和担子菌门(Basidiomycota),优势细菌类群来自变形菌门(Proteobacteria)和放线菌门(Actinobacteria)。真菌和细菌群落的丰富度及α多样性在整个矿区内无显著性差异,大气PM_2.5颗粒物的细菌群落生态位宽度显著大于露天采坑区和粉煤灰区。矿区内的土壤和PM_2.5颗粒物样本中均发现了一些丰度差异显著的功能类群,真菌特征功能类群为腐生营养型类群,细菌特征功能类群主要包括甲烷营养型类群、几丁质酶类细菌类群等。【结论】露天煤矿区粉尘可能对区域内土壤和PM_2.5颗粒物的微生物群落结构产生重要影响,具有煤组分降解功能的特定微生物类群可能是维持矿区土壤生态安全的重要微生物学机制之一。     

氮沉降对温带森林土壤甲烷氧化菌的影响

大量研究显示氮沉降影响森林甲烷吸收量,但其中的微生物驱动机制仍缺乏研究。基于长白山典型温带森林长期氮沉降模拟实验平台样地,采用定量PCR和克隆测序技术,研究了长期施加不同形态氮((NH_4)_2SO_4、NH_4Cl和KNO_3)处理下森林土壤甲烷氧化菌的数量和群落组成随季节变化的特征。结果表明,夏季,森林土壤甲烷氧化菌pmo A基因丰度在不同施氮处理之间无显著性差异(每克干土1.54×10~6-3.20×10~6拷贝数);秋季,pmo A基因丰度在施加NH_4Cl和(NH_4)_2SO_4处理小区(每克干土1.93×10~5-7.6×10~5拷贝数)与对照(每克干土(4.03×10~6±1.2×10~6)拷贝数)相比有所降低,尤其在(NH_4)_2SO_4处理小区(每克干土(4.61×10~5±2.61×10~5)拷贝数)显著降低;无论夏季还是秋季,施加不同形态氮处理土壤甲烷氧化菌均以Type I型为主(相对丰度在70.6%-85.4%之间),并以Methylobacter-group(Type I)为优势类群,占Type I型的55.1%-91.7%;Methylobacter-group(Type I)的相对丰度在夏季不同形态氮处理土壤样品中无显著差异,但秋季样品中在施加(NH_4)_2SO_4(52.7%±6.5%)和NH_4Cl(56.1%±8.9%)的处理显著低于对照土壤(77.0%±2.9%),Methylococcus-group(Type I)的相对丰度则在(NH_4)_2SO_4和NH_4Cl处理土壤呈增加的趋势。这些结果表明铵态氮肥添加对温带森林土壤甲烷氧化菌的生长具有抑制作用并导致其群落结构发生改变,受夏季温度和水分的影响,这种抑制作用在秋季表现更明显,而NO_3~--N添加对土壤甲烷氧化菌的群落组成和丰度无显著影响。这些结果解释了以往观测到的施铵态氮肥显著降低秋季温带林地土壤甲烷净吸收量,而在夏季无显著影响的观测结果,解释了长期氮沉降影响森林土壤甲烷吸收的微生物机制。     

3 次连续重复提取DNA 能较好反映土壤微生物丰度

【目的】研究同一个土壤需要反复提取几次才能在最大程度上反映土壤微生物的丰度,探讨风干土壤代替新鲜土壤用于微生物丰度研究的可行性。【方法】针对两种理化性质具有较大差异的旱地和稻田新鲜土壤及其风干土壤,分别对土壤微生物进行5次连续裂解提取DNA。通过实时荧光定量PCR技术分析连续反复提取对土壤古菌和细菌16S rRNA gene数量、氨氧化古菌和细菌功能基因amoA数量的影响。【结果】3次连续提取DNA占5次提取DNA总量的76%以上,氨氧化古菌、氨氧化细菌、古菌和细菌4类微生物的3次连续提取最低回收率为77.5%;与新鲜土壤相比,风干处理导致氨氧化古菌、氨氧化细菌、古菌、细菌的数量分别降低84.3%、81.2%、12.5%和90.3%,然而,2种土壤风干过程中主要微生物类群的数量变化规律基本一致,表明土壤微生物对风干处理的响应可能受土壤类型的影响较小。【结论】土壤微生物连续3次裂解能较好反映微生物丰度。与新鲜土壤相比,风干过程显著降低了土壤微生物丰度,然而,通过风干土壤中微生物丰度的变化趋势反映新鲜土壤中微生物数量变化规律具有一定的可行性。     

青藏高原淡水湖普莫雍错和盐水湖阿翁错湖底沉积物中细菌群落的垂直分布

【目的】湖泊沉积物中存储着大量独特的微生物,这些微生物在湖泊生态系统生物地球化学循环中扮演着非常重要的角色。然而,很少有研究报道微生物群落在湖泊沉积物中的垂直分布。本文比较研究青藏高原淡水湖普莫雍错和盐水湖阿翁错沉积物在不同深度下细菌的丰度和群落结构。【方法】利用定量PCR(q PCR)和变性梯度凝胶电泳(DGGE)技术分别测定细菌群落的丰度与群落结构。【结果】定量PCR结果显示,湖泊沉积物中细菌丰度均随深度增加而降低,盐水湖阿翁错和淡水湖普莫雍错的细菌丰度分别从1011数量级降到108数量级,从1012数量级降到1010数量级。在相对应的沉积物层,淡水湖沉积物的细菌丰度比盐水湖高1-2个数量级。变性梯度凝胶电泳(DGGE)指纹图谱的分析表明,淡水湖沉积物细菌群落的DGGE条带数(丰富度)显著高于盐水湖(P=0.014);淡水与盐水湖泊沉积物细菌群落结构明显不同,同时在同一湖泊沉积物中上层(0-6 cm)和下层(7-20 cm)细菌群落结构也呈明显分异。系统发育分析表明,盐水湖阿翁错沉积物特有菌门为Gamma-变形菌、拟杆菌门、蓝细菌和栖热菌门,而淡水湖普莫雍错沉积物中特有菌门为Delta-和Beta-变形菌、酸杆菌和绿弯菌门。【结论】青藏高原淡水与盐水湖泊沉积物细菌丰度与群落结构具有明显的差异;同时,细菌群落结构在沉积物的不同深度也表现出差异。这些结果可为进一步阐明青藏高原湖泊生态系统中微生物对气候环境变化的响应提供科学依据。     

顺北典型油气藏上方土壤甲烷氧化菌菌群特征及其勘探意义

【目的】甲烷氧化细菌(MOB)长期以来一直被用作石油和天然气勘探的重要油气指示菌,其仅能利用甲烷作为唯一碳源。根据甲烷氧化菌菌群特征结合地质剖面可以较好地预测深部油气藏,为石油勘探提供良好的数据支撑。由于传统平板培养法只能针对可培养甲烷氧化菌,方法具有一定局限性。【方法】本文采用分子生物学技术结合地球化学烃类指标研究了顺北典型油气藏上方土壤中甲烷氧化菌的分布。【结果】研究结果显示,油气田上方pmoA基因拷贝数与酸解烃含量具有一定的正相关性,且油气区比背景区高0.5–2个数量级。16SrRNA基因高通量测序和pmoA基因的克隆文库结果显示顺北油藏上方土壤中甲烷氧化菌主要以I型为主,水平剖面中甲烷氧化菌随着离油田距离增加存在I型向II型演变的现象,且Methylomonassp.在背景区与油气区的丰度有较大差异,具有良好的油气指示潜力。【结论】综上所述,长期微渗透过程中甲烷氧化菌(MOB)的菌群特征对预测深层油藏具有一定的指示作用,结合地质剖面和地表烃类可以有效预测有利油藏区域。     

不同时期艾比湖湿地盐角草群落土壤固氮微生物的多样性分析

【目的】研究新疆艾比湖湿地不同季节盐角草根际和非根际土壤固氮微生物的多样性和丰富度与环境因子的相关性,以期探究在荒漠化和盐渍化不断严重的艾比湖湿地中随着季节变化的固氮微生物群落对恢复生态功能起到的潜在作用,为后续的湿地保护和退化恢复工作提供理论支持和数据基础。【方法】应用Illumina HiSeq PE250测序技术,分析6个土壤样本固氮微生物的多样性,结合相关的理化因子并利用RDA分析法探究土壤理化性质和固氮微生物菌落结构及丰富度的相关性。【结果】艾比湖湿地盐角草植物根际土壤的固氮微生物多样性高于非根际土壤,7月的土壤固氮微生物多样性高于10月和4月的土壤。土杆菌属(Geobacter)、假单胞菌属(Pseudomonas)、固氮菌属(Azotobacter)和慢生根瘤菌属(Bradyrhizobium)等为盐角草根际和非根际土壤中的共同优势菌属。这些固氮微生物优势菌属隶属于变形菌门(Proteobacteria)和蓝藻门(Cyanobacteria),且相对丰富度占比为85%和10%,其余各菌门共占比较少,仅为5%。土壤中固氮微生物的优势菌群与碱解氮(AN)、全氮(TN)、速效钾(AK)和有效磷(TP)呈显著相关。【结论】随着时间的推移土壤样本中固氮微生物的多样性和群落结构也发了改变,同一时期植物根际与非根际土壤中固氮微生物的群落结构并不相同。土壤的环境因子与固氮细菌的群落结构和丰富度的相关性研究可以为艾比湖湿地的退化恢复提供数据基础和理论支持。     

辉腾锡勒草原干涸湖泊中氨氧化微生物群落结构分析

【目的】以内蒙古辉腾锡勒草原九十九泉湿地为对象,研究湖泊干涸过程中氨氧化微生物的群落结构及其变化。【方法】通过MPN-PCR定量测定氨氧化古菌(AOA)和氨氧化细菌(AOB)的数量;构建amoA基因克隆文库,进行系统发育分析;结合土壤环境因子,探讨湿地退化过程中影响氨氧化微生物的潜在因素。【结果】依湖泊湿地退水梯度的不同样点中,有75%的样点AOB的数量高于AOA,AOB与AOA的数量比率为0.3-18.1。从湖心到湖岸草原带,AOA和AOB的数量有明显增加,但生物多样性呈降低趋势,二者没有呈现正相关。研究发现,AOB的数量与土壤中NH 4+-N的变化存在良好响应。系统发育分析显示,退化湖泊湿地AOA克隆序列均来自于泉古菌门(Crenarchaeota);AOB的amoA基因的克隆序列大部分与亚硝化单胞菌属(Nitrosomonas)有一定同源性,较少部分与亚硝化螺菌属(Nitrosospira)有一定同源性。【结论】湖泊退水过程增加了湿地土壤氨氧化微生物的数量,而氨氧化微生物的种群丰度有所降低。AOA和AOB群落对湖泊湿地的退化过程做出了响应,其中AOB的响应较为明显,氧化条件和土壤铵浓度的改变可能是促成这种响应的重要原因。     

好氧甲烷氧化耦合反硝化极限脱氮系统的效能及应用

【目的】探究甲烷浓度、温度和氮浓度对好氧甲烷氧化耦合反硝化(AME-D)极限脱氮系统的影响,分析该系统微生物群落结构,并对贵阳某污水处理厂尾水进行应用研究。【方法】采用阶段性实验研究甲烷浓度、温度和氮浓度对系统脱氮效能的影响,通过16SrRNA基因测序技术分析系统中微生物群落结构,利用共焦显微拉曼光谱仪分析实际废水水质变化特征。【结果】甲烷进气比为3%、温度为30°C、氮浓度为20 mg/L时脱氮效果最好,系统的总氮、氨氮和硝酸盐氮平均去除率分别为93.66%、96.13%和92.25%;系统中的主要甲烷氧化菌分别为Methylosarcina(1.84%)、Methylovulum(0.01%)和Crenothrix(0.14%),以及兼性甲烷氧化菌属Methylocystis(1.9%),主要的亚硝化菌为Nitrosomonas(0.008%),硝化菌为Nitrospira (0.42%),反硝化菌为Hyphomicrobium (1.19%)和Pseudomonas (0.61%);采用该系统处理贵阳某污水处理厂尾水时,出水总氮平均浓度达到0.96mg/L,能达到极限脱氮的目的,拉曼光谱分析显示系统对硝酸盐氮和亚硝酸盐氮有较高的去除,甲烷被氧化形成的中间产物可能为醇类或醛类物质,为反硝化菌提供所需碳源。【结论】AME-D极限脱氮由多种微生物协同实现,其功能微生物为甲烷氧化菌、亚硝化菌、硝化菌和反硝化菌,应用研究显示该系统在城镇污水处理系统中具有较大的应用潜力。     

乌梁素海富营养化湖泊湖滨湿地过渡带细菌群落结构的高通量分析

摘要:【目的】揭示乌梁素海富营养化湖泊湖滨湿地沉积物与土壤过渡带细菌群落的组成、丰度以及多样性变化,结合土壤理化因子探讨其对细菌群落结构的影响。【方法】采用湿地土壤总DNA提取方法提取沉积物和土壤总DNA,对细菌群落的16S rRNA 基因的V1-V3区进行高通量测序,分析各样品中细菌群落结构的组成、丰度以及多样性指标;土壤理化性质采用标准方法测定,分析其对细菌群落结构的驱动作用。【结果】富营养化湖泊湖滨湿地水陆过渡带的芦苇沼泽沉积物、碱蓬群落盐碱化土壤和白刺群落荒漠化土壤中,细菌群落组成和各类群细菌的相对丰度差异较大,门水平上的细菌类群主要有Proteobacteria、Bacteroidetes、Chloroflexi、Actinobacteria、Planctomycetes和Gemmatimonadetes,细菌群落多样性指数随陆向分布依次在增高,门水平上Proteobacteria和属水平上Sulfurimonas对湖泊退化演化敏感;环境因子最佳子集为总磷、水溶盐总量和铵态氮的组合对整个细菌群落结构的影响最为明显,相关系数最高(R=0.8857),Mantel检验结果表明这种相关关系为显著相关(P=0.037)。【结论】乌梁素海富营养化湖泊湖滨湿地过渡带细菌群落结构差异较大,Sulfurimonas属在乌梁素海富营养化湖泊沉积物的生物地球化学循环中扮演着重要的角色,应在以后的研究中得到更多的关注。     

Activity and species composition of aerobic methanotrophic communities in tundra soils

The low-temperature, methane-oxidizing activities and species composition of methanotrophic communities in various tundra bog soils were investigated by radioisotopic and immunofluorescent methods. Methanotrophic bacteria carried out the methane oxidation process through all horizons of seasonally thawed layers down to permafrost. The highest activity of the process has been observed in the water surface layer of overmoistured soils and in water-logged moss covers. Up to 40% of¹⁴CH₄ added was converted into¹⁴CO₂, bacterial biomass, and organic exometabolites. By immunofluoresecent analysis it was demonstrated that the representatives of I+X (Methylomonas, Methylobacter, andMethylococcus) and II (Methylosinus, Methylocystis) methanotrophic groups occurred simultaneously in all samples at 61.6% and 38.4%, respectively. The number of methane-oxidizing bacteria in the ecosystems studied was 0.1–22.9×10⁶ cells per gram of soil. Methanotrophic organisms ranged from 1% to 23% of the total bacterial number.     

Activity, distribution, and abundance of methane-oxidizing bacteria in the near surface soils of onshore oil and gas fields

Methane-oxidizing bacteria (MOB) have long been used as an important biological indicator for oil and gas prospecting, but the ecological characteristics of MOB in hydrocarbon microseep systems are still poorly understood. In this study, the activity, distribution, and abundance of aerobic methanotrophic communities in the surface soils underlying an oil and gas field were investigated using biogeochemical and molecular ecological techniques. Measurements of potential methane oxidation rates and pmoA gene copy numbers showed that soils inside an oil and gas field are hot spots of methane oxidation and MOB abundance. Correspondingly, terminal restriction fragment length polymorphism analyses in combination with cloning and sequencing of pmoA genes also revealed considerable differences in the methanotrophic community composition between oil and gas fields and the surrounding soils. Principal component analysis ordination furthermore indicated a coincidence between elevated CH₄ oxidation activity and the methanotrophic community structure with type I methanotrophic Methylococcus and Methylobacter, in particular, as indicator species of oil and gas fields. Collectively, our results show that trace methane migrated from oil and gas reservoirs can considerably influence not only the quantity but also the structure of the methanotrophic community.     

Emission and oxidation of methane in Equisetum fluviatile stands growing on organic sediment and sand bottoms

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     

Diversity and activity of methanotrophs in landfill cover soils with and without landfill gas recovery systems

Aerobic CH₄ oxidation plays an important role in mitigating CH₄ release from landfills to the atmosphere. Therefore, in this study, oxidation activity and community of methanotrophs were investigated in a subtropical landfill. Among the three sites investigated, the highest CH₄ concentration was detected in the landfill cover soil of the site (A) without a landfill gas (LFG) recovery system, although the refuse in the site had been deposited for a longer time (∼14–15 years) compared to the other two sites (∼6–11 years) where a LFG recovery system was applied. In April and September, the higher CH₄ flux was detected in site A with 72.4 and 51.7 g m⁻² d⁻¹, respectively, compared to the other sites. The abundance of methanotrophs assessed by quantification of pmoA varied with location and season. A linear relationship was observed between the abundance of methanotrophs and CH₄ concentrations in the landfill cover soils (R = 0.827, P < 0.001). The key factors influencing the methanotrophic diversity in the landfill cover soils were pH, the water content and the CH₄ concentration in the soil, of which pH was the most important factor. Type I methanotrophs, including Methylococcus, Methylosarcina, Methylomicrobium and Methylobacter, and type II methanotrophs (Methylocystis) were all detected in the landfill cover soils, with Methylocystis and Methylosarcina being the dominant genera. Methylocystis was abundant in the slightly acidic landfill cover soil, especially in September, and represented more than 89% of the total terminal-restriction fragment abundance. These findings indicated that the LFG recovery system, as well as physical and chemical parameters, affected the diversity and activity of methanotrophs in landfill cover soils.     

Diversity of methanotrophs in urea-fertilized tropical rice agroecosystem

Laboratory experiments were conducted to study the population size, diversity and methane oxidation potential of methanotrophs in tropical rice agroecosystem under the influence of N-fertilizer. Results indicate that the diversity of methane oxidizing bacteria (MOB) is altered in fertilizer treated soils compared to untreated control. Nevertheless, Type I MOB still dominated in the fertilized soils whereas the diversity of Type II methanotrophs decreases. Control soils have higher MOB population and CH₄ oxidation capacity than fertilized soils. Rhizospheric soil is more populated than non-rhizospheric soil in both unfertilized and fertilized conditions. Variation in K_m and V_max of methane oxidation in soils appears to be due to variation in methanotrophic community. Experimental results indicate that methanotrophic community differs both quantitatively and qualitatively in unfertilized and fertilized soils.     

Methanotrophic Activity,Abundance, and Diversity in Forested Swamp Pools: Spatiotemporal Dynamics and Influences on Methane Fluxes

Methane oxidation (methanotrophy) in the water column and sediments of forested swamp pools likely control seasonal and annual emission of CH₄ from these systems, but the methanotrophic microbial communities, their activities, locations, and overall impact, is poorly understood. Several techniques including ¹⁴CH₄ oxidation assays, culture-based most probable number (MPN) estimates of methane-oxidizing bacteria (MOB) and protozoan abundance, MOB strain isolation and characterization, and PCR techniques were used to investigate methanotrophy at a forested swamp near Ithaca, New York. The greatest methanotrophic activity and largest numbers of MOB occurred predominantly at the low oxygen sediment/water interface in the water column. Seasonally, methanotrophic activity was very dynamic, ranging from 0.1 to 61.9 μ moles CH₄ d^?1 g^?1 dry sediment, and correlated most strongly with dissolved inorganic carbon (r = 0.896). Incorporation of methanotrophic variables (abundance and activity) into existing CH₄ flux regression models improved model fit, particularly during mid summer when CH₄ fluxes were most dynamic. Annually integrated methane flux and methanotrophic activity measurements indicate that differences in methanotrophic activity at the sediment/water interface likely accounted for differences in the annual CH₄ emission from the field site. Direct isolations of MOB resulted in the repeated isolation of organisms most closely related to Methylomonas methanica S1. A single acidophilic, type II MOB related to Methylocella palustris K was also isolated. Using a PCR-based MPN method and 16S rRNA genome copy number from isolates and control strains, type I and type II MOB were enumerated and revealed type I dominance of the sediment-associated MOB community.     

The role of <Emphasis Type="Italic">Campsurus notatus</Emphasis> (Ephemeroptera: Polymitarcytidae) bioturbation and sediment quality on potential gas fluxes in a tropical lake

About 30% of the total area of Lake Batata (Amazon) was impacted by the disposal of bauxite tailings originated from the process of washing bauxite. This effluent, composed by fine particles of clay and water, settled on top of the natural sediment, originating a new substratum with a different physical and chemical composition. This phenomenon created a new distinct habitat (impacted sediment) influencing the benthic community. The aim of this study was to evaluate the impact of bioturbation by Campsurus notatus (Ephemeroptera: Polymitarcytidae) on potential gas fluxes in the sediment of natural and impacted areas of the lake. The natural sediment had a significantly higher methane concentration when compared to the impacted one. In incubated sediment cores, the presence of C. notatus nymphs resulted in a significant increase in oxygen consumption and methane and carbon dioxide release to the water column. The effect of the presence of nymphs on methane was ambiguous. The C. notatus nymphs strongly decreased methane concentration in natural sediment samples, probably because of the enhancement of the oxic sediment area. However, this effect was not observed in impacted samples. Finally, the new substratum of Lake Batata decreased methane concentration in sediment and water column. C. notatus nymphs demonstrated to have a significant role on gas flux (methane and CO₂) from sediment to water column as well as on oxygen consumption in Lake Batata, consequently influencing the carbon cycle in this lake. Handling editor: S. M. Thomaz