Anaerobic ammonium oxidation by anammox bacteria in the Black Sea

The availability of fixed inorganic nitrogen (nitrate, nitrite and ammonium) limits primary productivity in many oceanic regions. The conversion of nitrate to N2 by heterotrophic bacteria (denitrification) is believed to be the only important sink for fixed inorganic nitrogen in the ocean. Here we provide evidence for bacteria that anaerobically oxidize ammonium with nitrite to N2 in the world's largest anoxic basin, the Black Sea. Phylogenetic analysis of 16S ribosomal RNA gene sequences shows that these bacteria are related to members of the order Planctomycetales performing the anammox (anaerobic ammonium oxidation) process in ammonium-removing bioreactors. Nutrient profiles, fluorescently labelled RNA probes, 15N tracer experiments and the distribution of specific 'ladderane' membrane lipids indicate that ammonium diffusing upwards from the anoxic deep water is consumed by anammox bacteria below the oxic zone. This is the first time that anammox bacteria have been identified and directly linked to the removal of fixed inorganic nitrogen in the environment. The widespread occurrence of ammonium consumption in suboxic marine settings indicates that anammox might be important in the oceanic nitrogen cycle.     

A microbial consortium couples anaerobic methane oxidation to denitrification

Modern agriculture has accelerated biological methane and nitrogen cycling on a global scale. Freshwater sediments often receive increased downward fluxes of nitrate from agricultural runoff and upward fluxes of methane generated by anaerobic decomposition. In theory, prokaryotes should be capable of using nitrate to oxidize methane anaerobically, but such organisms have neither been observed in nature nor isolated in the laboratory. Microbial oxidation of methane is thus believed to proceed only with oxygen or sulphate. Here we show that the direct, anaerobic oxidation of methane coupled to denitrification of nitrate is possible. A microbial consortium, enriched from anoxic sediments, oxidized methane to carbon dioxide coupled to denitrification in the complete absence of oxygen. This consortium consisted of two microorganisms, a bacterium representing a phylum without any cultured species and an archaeon distantly related to marine methanotrophic Archaea. The detection of relatives of these prokaryotes in different freshwater ecosystems worldwide indicates that the reaction presented here may make a substantial contribution to biological methane and nitrogen cycles.     

N2 production by the anammox reaction in the anoxic water column of Golfo Dulce,Costa Rica

In oxygen-depleted zones of the open ocean, and in anoxic basins and fjords, denitrification (the bacterial reduction of nitrate to give N2) is recognized as the only significant process converting fixed nitrogen to gaseous N2. Primary production in the oceans is often limited by the availability of fixed nitrogen such as ammonium or nitrate, and nitrogen-removal processes consequently affect both ecosystem function and global biogeochemical cycles. It was recently discovered that the anaerobic oxidation of ammonium with nitrite--the 'anammox' reaction, performed by bacteria--was responsible for a significant fraction of N2 production in some marine sediments. Here we show that this reaction is also important in the anoxic waters of Golfo Dulce, a 200-m-deep coastal bay in Costa Rica, where it accounts for 19-35% of the total N2 formation in the water column. The water-column chemistry in Golfo Dulce is very similar to that in oxygen-depleted zones of the oceans--in which one-half to one-third of the global nitrogen removal is believed to occur. We therefore expect the anammox reaction to be a globally significant sink for oceanic nitrogen.     

Ocean nutrient ratios governed by plankton biogeography

The major nutrients nitrate and phosphate have one of the strongest correlations in the sea, with a slope similar to the average nitrogen (N) to phosphorus (P) content of plankton biomass (N/P = 16:1). The processes through which this global relationship emerges despite the wide range of N/P ratios at the organism level are not known. Here we use an ocean circulation model and observed nutrient distributions to show that the N/P ratio of biological nutrient removal varies across latitude in Southern Ocean surface waters, from 12:1 in the polar ocean to 20:1 in the sub-Antarctic zone. These variations are governed by regional differences in the species composition of the plankton community. The covariation of dissolved nitrate and phosphate is maintained by ocean circulation, which mixes the shallow subsurface nutrients between distinct biogeographic provinces. Climate-driven shifts in these marine biomes may alter the mean N/P ratio and the associated carbon export by Southern Ocean ecosystems.     

Effects of Nitrate Concentration in Main Anoxic Zone on Denitrifying Dephosphatation

The effects of nitrate concentration in the main anoxic zone on denitrifying dephosphatation capability were conducted based on modified University of Cape Town (MUCT) process. Meanwhile the relation between optimal nitrate concentration (Nopt) and influent C/N ratio was evaluated, in which the influent chemical oxygen demand (COD) concentration was stabilized at (290±10)mg/L, the influent total phosphorus (TP) concentration was stabilized at (7.0±0.5)mg/L. The results indicated that: (1) the nitrate concen...     

Warm tropical ocean surface and global anoxia during the mid-Cretaceous period

The middle of the Cretaceous period (about 120 to 80 Myr ago) was a time of unusually warm polar temperatures, repeated reef-drowning in the tropics and a series of oceanic anoxic events (OAEs) that promoted both the widespread deposition of organic-carbon-rich marine sediments and high biological turnover. The cause of the warm temperatures is unproven but widely attributed to high levels of atmospheric greenhouse gases such as carbon dioxide. In contrast, there is no consensus on the climatic causes and effects of the OAEs, with both high biological productivity and ocean 'stagnation' being invoked as the cause of ocean anoxia. Here we show, using stable isotope records from multiple species of well-preserved foraminifera, that the thermal structure of surface waters in the western tropical Atlantic Ocean underwent pronounced variability about 100 Myr ago, with maximum sea surface temperatures 3-5 degrees C warmer than today. This variability culminated in a collapse of upper-ocean stratification during OAE-1d (the 'Breistroffer' event), a globally significant period of organic-carbon burial that we show to have fundamental, stratigraphically valuable, geochemical similarities to the main OAEs of the Mesozoic era. Our records are consistent with greenhouse forcing being responsible for the warm temperatures, but are inconsistent both with explanations for OAEs based on ocean stagnation, and with the traditional view (reviewed in ref. 12) that past warm periods were more stable than today's climate.     

Sensitivity of coccolithophores to carbonate chemistry and ocean acidification

About one-third of the carbon dioxide (CO(2)) released into the atmosphere as a result of human activity has been absorbed by the oceans, where it partitions into the constituent ions of carbonic acid. This leads to ocean acidification, one of the major threats to marine ecosystems and particularly to calcifying organisms such as corals, foraminifera and coccolithophores. Coccolithophores are abundant phytoplankton that are responsible for a large part of modern oceanic carbonate production. Culture experiments investigating the physiological response of coccolithophore calcification to increased CO(2) have yielded contradictory results between and even within species. Here we quantified the calcite mass of dominant coccolithophores in the present ocean and over the past forty thousand years, and found a marked pattern of decreasing calcification with increasing partial pressure of CO(2) and concomitant decreasing concentrations of CO(3)(2-). Our analyses revealed that differentially calcified species and morphotypes are distributed in the ocean according to carbonate chemistry. A substantial impact on the marine carbon cycle might be expected upon extrapolation of this correlation to predicted ocean acidification in the future. However, our discovery of a heavily calcified Emiliania huxleyi morphotype in modern waters with low pH highlights the complexity of assemblage-level responses to environmental forcing factors.     

Discovery of Late Cretaceous foraminifera in the Songliao Basin: Evidence from SK-1 and implications for identifying seawater incursions

The Songliao Basin is the largest oil-bearing basin in China.In the absence of sufficient evidence,the possibility of seawater incursion(s) into the Songliao Basin remains controversial.Recently,we discovered relatively abundant foraminifera fossils from units 1 and 2 of the Nenjiang Formation of borehole SK-1.Benthic foraminifera (Gavlinella sp.,Anomalinoides sp.,Pullenia sp.,Haplophragmoides sp.,Karrorulina hokkaidoana,Clavulinoides sp.),as well as planktonic foraminifera (Archaeoglobigerina blowi,Archaeoglobigerina cretacea and Hedbergella flandrini),were identified.These fossils were widely distributed in the marine Cretaceous.According to the global distribution of the above-mentioned planktonic foraminifera,the age of these fossil bearing strata appears to be Late Coniacian to Santonian.More importantly,these foraminifera provide direct evidence for marine water incursions into the Songliao Basin during deposition of the Lower Nenjiang Formation.     

交替式A~2/O系统碳源量对去除氮磷途径的影响

采用市政污水研究进水碳源含量不同时交替式A2/O工艺去除氮磷的途径以及效果.调控进水COD浓度分别在150、200、300、400 mg.L-1左右,氮磷浓度不变,跟踪厌氧池与缺氧池内NO3--N与总磷(TP)的变化规律.实验结果显示,几种进水水质下,系统都具有优良的除磷脱氮性能;进水COD在300、400 mg.L-1时,缺氧池内NO3--N浓度始终低于1 mg.L-1,而TP浓度由于推流作用逐渐上升,系统主要通过反硝化异养菌利用外碳源进行反硝化作用去除NO3--N;进水COD在150、200 mg.L-1时,缺氧池内TP浓度一直较低,有反硝化聚磷现象,表明交替式A2/O系统内存在专性好氧聚磷菌与反硝化聚磷菌.     

稻田捕食性节肢动物种库对其群落重建的作用

在稻田生态系统中，非稻田生境和休耕期间稻田生境中的节肢动物群落系统可以称为节肢动物群落的种库，根据生境类型的不同，可以将种库分为许多不同的亚种库，如田埂亚种库、沟渠亚种库、菜地亚种库等等．从捕食性天敌的角度研究了稻田节肢动物种库对其群落重建的作用．结果表明在稻田天敌群落重建期间（水稻移栽后１个月之内），稻田的优势种天敌如食虫沟瘤蛛、水狼蛛等均来自种库，它们由种库向稻田群落迁居的过程是一个循序渐进的动态过程．其中，田埂作为一个主要的亚种库为它们迁移入田起到了重要的“桥梁”作用．     

珠江三角洲PRD16孔微体生物记录与晚更新世以来的古环境重建

对珠江三角洲PRD16孔的微体动物群进行了分析,共发现底栖有孔虫12属24种,介形类9属13种,它们可分别划分为3种生态类型。根据有孔虫和介形类微体动物群的分布特征、并结合岩性和沉积粒度特征,推断PRD16孔研究区晚更新世以来沉积环境演化经历了5个阶段:①34 600 cal a BP以前为河流相环境,形成了研究区最早的第四纪河床相砂砾沉积;②34 600～23 900 cal a BP推测为河口湾环境;③23 900～7 960 cal aBP受末次盛冰期影响,研究区暴露地表遭受风化剥蚀,形成花斑黏土;④7 960～2 810 cal a BP为全新世大海侵时期,研究区为河口海湾环境,发育以广盐性有孔虫和中盐-多盐性介形类为主的微体动物群,其间发生了2次小规模海平面波动,受地块区域沉降作用影响,研究区在3 873 cal a BP左右水深达到最大,主要有孔虫和介形类属种的丰度达到全新世最高值;⑤2 810 cal a BP以来海平面持续下降,研究区由潮坪环境变为河口砂坝,随后河流作用增强,又逐渐变为河流冲积-潮上带环境。     

Phosphonate utilization by the globally important marine diazotroph Trichodesmium

The factors that control the growth and nitrogen fixation rates of marine diazotrophs such as Trichodesmium have been intensively studied because of the role that these processes have in the global cycling of carbon and nitrogen, and in the sequestration of carbon to the deep sea. Because the phosphate concentrations of many ocean gyres are low, the bioavailability of the larger, chemically heterogeneous pool of dissolved organic phosphorus could markedly influence Trichodesmium physiology. Here we describe the induction, by phosphorus stress, of genes from the Trichodesmium erythraeum IMS101 genome that are predicted to encode proteins associated with the high-affinity transport and hydrolysis of phosphonate compounds by a carbon-phosphorus lyase pathway. We show the importance of these genes through expression analyses with T. erythraeum from the Sargasso Sea. Phosphonates are known to be present in oligotrophic marine systems, but have not previously been considered to be bioavailable to marine diazotrophs. The apparent absence of genes encoding a carbon-phosphorus lyase pathway in the other marine cyanobacterial genomes suggests that, relative to other phytoplankton, Trichodesmium is uniquely adapted for scavenging phosphorus from organic sources. This adaptation may help to explain the prevalence of Trichodesmium in low phosphate, oligotrophic systems.     

入侵植物南美蟛蜞菊对NH+4-N和NO-3-N的响应

为了阐明外来入侵植物是否对不同形态氮源具有偏向选择性,研究了外来入侵植物南美蟛蜞菊（Wedelia trilobata）对2种不同形态氮源（NH+4/NO-3）的响应. 结果表明:（1）南美蟛蜞菊在全铵营养条件下的生物量显著高于全硝营养条件;（2）南美蟛蜞菊在全铵营养和全硝营养条件下总生物量和叶绿素含量（SPAD）均显著高于本地种蟛蜞菊（Wedelia chinensis）;（3）在全铵营养条件下,南美蟛蜞菊根部游离氨基酸含量显著高于蟛蜞菊;与蟛蜞菊相比,在全硝营养条件下南美蟛蜞菊根部和叶部的硝酸还原酶活性显著升高,硝态氮累积显著减少. 结果表明南美蟛蜞菊为喜铵植物,具有较强的铵态氮同化能力和硝态氮还原能力,对全铵或全硝的极端环境有较强的调节能力,这可能是南美蟛蜞菊入侵成功的重要机制之一,也说明NH+4-N占优势的土壤生境更易遭受南美蟛蜞菊入侵,可能是南美蟛蜞菊在定居和扩散进程中的一个重要变化.     

Biodiversity improves water quality through niche partitioning

Excessive nutrient loading of water bodies is a leading cause of water pollution worldwide, and controlling nutrient levels in watersheds is a primary objective of most environmental policy. Over the past two decades, much research has shown that ecosystems with more species are more efficient at removing nutrients from soil and water than are ecosystems with fewer species. This has led some to suggest that conservation of biodiversity might be a useful tool for managing nutrient uptake and storage, but this suggestion has been controversial, in part because the specific biological mechanisms by which species diversity influences nutrient uptake have not been identified. Here I use a model system of stream biofilms to show that niche partitioning among species of algae can increase the uptake and storage of nitrate, a nutrient pollutant of global concern. I manipulated the number of species of algae growing in the biofilms of 150 stream mesocosms that had been set up to mimic the variety of flow habitats and disturbance regimes that are typical of natural streams. Nitrogen uptake rates, as measured by using (15)N-labelled nitrate, increased linearly with species richness and were driven by niche differences among species. As different forms of algae came to dominate each unique habitat in a stream, the more diverse communities achieved a higher biomass and greater (15)N uptake. When these niche opportunities were experimentally removed by making all of the habitats in a stream uniform, diversity did not influence nitrogen uptake, and biofilms collapsed to a single dominant species. These results provide direct evidence that communities with more species take greater advantage of the niche opportunities in an environment, and this allows diverse systems to capture a greater proportion of biologically available resources such as nitrogen. One implication is that biodiversity may help to buffer natural ecosystems against the ecological impacts of nutrient pollution.     

Methane formation from long-chain alkanes by anaerobic microorganisms.

Biological formation of methane is the terminal process of biomass degradation in aquatic habitats where oxygen, nitrate, ferric iron and sulphate have been depleted as electron acceptors. The pathway leading from dead biomass to methane through the metabolism of anaerobic bacteria and archaea is well understood for easily degradable biomolecules such as carbohydrates, proteins and lipids. However, little is known about the organic compounds that lead to methane in old anoxic sediments where easily degradable biomolecules are no longer available. One class of naturally formed long-lived compounds in such sediments is the saturated hydrocarbons (alkanes). Alkanes are usually considered to be inert in the absence of oxygen, nitrate or sulphate, and the analysis of alkane patterns is often used for biogeochemical characterization of sediments. However, alkanes might be consumed in anoxic sediments below the zone of sulphate reduction, but the underlying process has not been elucidated. Here we used enrichment cultures to show that the biological conversion of long-chain alkanes to the simplest hydrocarbon, methane, is possible under strictly anoxic conditions.     

Evidence for anoxygenic photosynthesis from the distribution of bacteriochlorophylls in the Black Sea

The contribution of anoxygenic photosynthesis to carbon cycling in the Black Sea, the world's largest body of anoxic marine water, has been vigorously investigated and debated for over four decades. Penetration of light into the sulphide-containing deep water may result in a zone of anaerobic primary production by photosynthetic bacteria. We report here the results of analyses of photosynthetic pigments in samples of suspended particulate matter collected from two stations in the western basin of the Black Sea. Our data demonstrate high concentrations of a bacterio-chlorophyll at the chemocline, and thus the potential for anoxygenic photosynthesis as a component of primary production in the carbon cycle of the Black Sea. More than 95% of the pigments in the bacteriochlorophyll-maximum are accounted for by a series of aromatic carotenoids and bacteriochlorophylls-e, including a previously unreported geranyl ester of 4-i-butyl bacteriochlorophyll-e. The distribution of pigments is characteristic of the obligate phototrophs Chlorobium phaeobacteroides and C. phaeovibriodes. Total depth-integrated bacteriochlorophyll at one station exceeded total chlorophyll-a in the overlying oxygenated portion of the euphotic zone. We suggest that anoxygenic photosynthesis is a relatively recent phenomenon in the Black Sea initiated by shallowing of the chemocline over the past decade and development of an anoxic layer devoid of O2 and H2S.     

生物转盘去除废水中硝酸氮和含碳有机物的试验研究

本文介绍了以豆制品废水为碳源、硝酸钾为氮源的缺氧生物转盘同时去除废水中的合碳有机物(BOD)和硝酸氮(NO_3-N)的试验研究,探讨了驯化和挂膜条件,取得了在确定BOD_5/NO_3-N比值条件下,去除NO_3-N和BOD_5的最小水力停留时间和最大盘面积负荷工艺参数。     

垃圾渗滤液处理厂活性污泥微生物种群结构和功能分析

对垃圾渗滤液处理厂活性污泥的16S rRNA基因和宏基因组进行高通量测序并分析, 探究垃圾渗滤液处理厂活性污泥微生物的种群结构、氮循环和有机污染物降解相关功能微生物和功能基因。结果表明, Calditrichaeota门微生物丰度最高(58.77%), 其次是 Proteobacteria (16.80%)和Bacteroides (6.19%); Calorithrix属是活性污泥的优势菌属(58.77%); 活性污泥中存在硝化、反硝化、同化硝酸盐还原、异化硝酸盐还原和氮固定 5 条氮循环途径, 反硝化相关基因丰度最高(78.84%), 主要分布于Calditrichaeota, Proteobacteria和Choroflexi中; 硝化作用由氨氧化菌Nitrosomonas完成。活性污泥中含有丰富的难降解有机污染物降解基因, Proteobacteria, Bacteroides, Planctomycetes, Calditrichaeota和Choroflexi是典型的有机污染物降解功能微生物。     

基于DEA模型的产业结构调整与氨氮排放效率关系的实证研究——以鄱阳湖生态经济区为例

经济和环境的协调发展已经成为区域发展不可忽视的重要问题,鄱阳湖生态经济区作为国家区域发展战略地区之一,其生态与经济的协调发展就显得至关重要.运用DEA方法对鄱阳湖生态经济区36个县(市、区)2009—2013年间氨氮排放效率及其变化率进行分析.结果显示:各县(市、区)之间氨氮排放效率差异明显,东湖区、西湖区、青云谱区和渝水区等8个县(市、区)氨氮排放效率较高,其他县(市、区)氨氮排放效率中等或低下.Malmquist生产率指数计算显示除了南昌县、余江县、高安市和万年县4个县(市、区)氨氮排放综合效率降低外其余都有所上升或不变.依据主导产业和氨氮排放效率将鄱阳湖生态经济区36个县(市、区)划分为高效率第二产业主导区、中效率第二产业主导区、低效率第二产业主导区等8类区域,并提出产业结构调整的相关建议.     

厦门钟宅泥滩海洋线虫群落的种类组成及其多样性

１９９９年２月和１９９９年５月在厦门钟宅泥滩３个取样站取样,获得自由生活海洋线虫４８种,隶属于３目１９科４１属。这些海洋线虫在厦门潮间带均是首次记录。主要优势种有变异毛咽线虫（Ｄｏｒｙｌａｉｍｏｐｓｉｓ ｕａｒｉａｂｉｌｉｓ）、Ｖｉｓｃｏｓｉａ ｓｐ．、吞咽线虫（Ｄａｐｔｏｎｅｍａ ｓｐｌ．）、囊咽线虫（Ｓｐｈａｅｒｏｌａｉｍｕｓｂａｌｔｉｃｕｓ）和Ｔｈａｌａｓｓｏｍｏｎｈｙｓｔｅｒａ ｓｐ．等五