源自生物絮团产絮凝剂的异养硝化-好氧反硝化菌xt1的鉴定及其脱氮特性

为了高效进行水体脱氮,本实验从形成于凡纳滨对虾(Litopenaeus vannamei)养殖水体的生物絮团中分离到一株具产絮能力的脱氮菌xt1,经16S r RNA基因测序与生理生化分析确定菌株xt1为短小芽孢杆菌(Bacillus pumilus)。在此基础上,本文研究了该菌的脱氮特性。结果表明:菌株xt1最佳碳源为葡萄糖,以其为底物对氨氮、硝态氮去除率分别达95.56%和57.40%。以蔗糖为碳源亦具较高脱氮率,对氨氮、硝态氮去除率分别达69.95%和49.50%;该菌能利用有机氮加速生长,添加0.25%、0.5%、1%和2%的蛋白胨能促进OD600,分别达到0.925、1.034、1.103和1.314,均高于未加蛋白胨下的生长,且氨氮去除率均超过90%,硝态氮去除率均超过88%;该菌能适应20—200mg/L无机氮浓度;该菌能以NH4+-N、NO2–-N或NO3–-N为唯一氮源进行异养硝化-好氧反硝化,反应84h去除率分别达到94.16%、47.60%和91.17%。其中,该菌的硝化形式是将氨氮转化为气态氮脱除,其硝态氮反硝化形式是先将硝态氮转化为亚硝氮,再以气态氮脱除。在进行异养硝化-好氧反硝化同时,菌株xt1体现絮凝特性,絮凝率最高分别达到82.28%、73.15%和75.60%;此外,添加该菌于养殖水体中能加速生物絮团形成,同时提高脱氮率。各项结果表明,菌株xt1可作为水产养殖水体脱氮的备选菌株。     

第六节 海水中无机氮

海水中无机氮主要包括NO3-N、NO2-N及NH4-N。它是浮游植物所必须的营养盐之一。浮游植物大量繁殖时，海水中的无机氮下降，其中NO3-N可被消耗殆尽，浮游植物又是浮游动物的饵料，其排泄物或残骸分解释放的有机氮经细菌作用转化成无机氮而使海水中无机氮得以再生无机氮在不同环境下经细菌或酶进行硝化或反硝化而互相转化。     

溶解无机氮在胶州湾沉积物一海水界面上的交换速率和通量研究

应用实验室培养法测定了溶解无机氮(DIN)在胶州湾16个站位沉积物-海水界面上的交换速率。结果表明, NH4 -N,NO2 -N和NO3 -N的交换速率一般分别在-0.5~1.6,0.005~0.67, + - --2.0~2.8 mmol/(m2·d)范围内。由于间隙水中DIN主要以NH4 -N形态存在,DIN在胶州湾沉 +积物-海水界面上的交换以NH4 -N的扩散为主,在大部分站位表现为由沉积物向水体的释放, +NO3 -N主要来自NH4 -N的硝化反应,而NO2 -N是NH4 -N和NO3 -N之间化学转化过程的中 - + - + -间产物。考虑胶州湾沉积物类型, 在胶州湾沉积物-海水界面上的交换通量为9.68×108 DINmmol/d,是河流输入DIN的50%左右,可提供维持胶州湾初级生产力所需DIN的52%。     

福建福宁湾无机氮含量的变化特征及其对浮游植物的影响

本文根据2002-2003年福宁湾海域的监测资料对NO2-N、NO3＋N、NH4-N三态DIN的变化特征和相互关系进行分析，并分析其对浮游植物生物量的影响．研究表明：NO3-N、DIN含量均呈冬季最高、夏季最低，NO2-N含量秋季最高，冬季最低；福宁湾海域赤潮高发期水体DIN中三氮所占比例与年平均相比变化最大的是NO3-N，其次是NH4-N，NO2-N最小；NO3-N、DIN与盐度均呈明显负相关；NO3-N与DIN呈明显正相关；NO3-N是福宁湾海域DIN的主要存在形式；三态氮中仅NO3-N为福宁湾海域浮游植物生长限制因子；浮游植物对DIN的吸收主要以NO3-N形式为主。     

两株海水氮降解菌的分离鉴定及其无机氮去除特性初步研究

为解决海水养殖环境中的无机氮污染问题,从河鲀(Takifugu rubripes)养殖池塘的水体和底泥中筛选出2株可有效去除氨态氮、亚硝态氮和硝态氮的菌株——盐单胞菌(Halomonas sp.DN3)和枯草芽孢杆菌(Bacillus subtilis HC),并初步探讨了2株菌在不同无机氮源中的氮去除特性。研究表明,2株细菌均具有较好的无机氮去除效果。在初始无机氮浓度为42 mg·L~(-1)的单一氮源基础降解液中,菌株DN3对氨态氮、亚硝态氮和硝态氮的去除率分别为84.1%、62.1%和98.8%;菌株HC对三者的去除率分别为81.2%、49.0%和90.3%。在氨态氮去除过程中,虽未检测到硝态氮和亚硝态氮的积累,但从系统的氮收支分析,总氮浓度均显著下降,推测可能存在硝化过程;在硝态氮和亚硝态氮去除过程中,菌株DN3还原硝态氮时具有亚硝态氮的积累,菌株HC氧化亚硝态氮时具有硝态氮的积累。而从总氮浓度均有下降推测,可能存在好氧反硝化过程。在初始无机氮浓度为42 mg·L~(-1)的混合氮源基础降解液中,2株菌均具有良好的同步去除无机氮能力。以氨态氮和亚硝态氮为氮源时,菌株DN3和HC的总无机氮去除率分别为75.4%和66.6%;以氨态氮和硝态氮为氮源时,菌株DN3和HC的总无机氮去除率为69.5%和75.6%,2株菌在2种混合氮源中的氨态氮去除率均在90.0%以上。综合分析,菌株DN3和HC对无机氮去除机制主要以菌体的同化作用为主,同时推测具有一定的硝化和反硝化作用。研究结果表明,菌株DN3和HC均可高效去除无机氮,其在海水养殖水环境调控中具有潜在的应用价值。     

水样中氮磷营养盐的短期保存技术研究

用8种保存方法对淡水和海水水样中四个氮磷营养盐（NH3-N、NO3—N、NO3-N、PO4—P）参数及总氮的稳定性进行了7d保存效果的比较研究。结果表明,淡水与海水氮磷营养盐的最佳保存方法与效果各不相同,但淡水和海水的总氮值在各种方法保存下均十分恒定。综合考虑有效性及可操作性后提出了5d内的短期保存技术：（1）海水水样用5‰氯仿4℃条件下保存,供NH3-N、NO2—N和N03-N三个营养盐的测定,用5‰甲醛4℃条件下保存供PO4-P测定;（2）淡水用5‰氯仿4℃条件下保存,供NH3-N测定,5‰甲醛4℃条件保存供NO2-N、NO3-N和PO4-P测定。     

海水人工湿地系统脱氮效果与基质酶活性的相关性

利用海水人工湿地系统处理海水养殖外排水,分析了人工湿地对不同形态氮的净化效果,探讨了人工湿地表层基质酶活性变化及其对系统脱氮效果的影响。选取互花米草作为人工湿地植物,煤渣、珊瑚石和细砂作为人工湿地基质,实验期间连续进水,系统运行稳定。研究结果表明:海水人工湿地系统对氨氮(NH4-N)、亚硝态氮(NO2-N)、硝态氮(NO3-N)、总氮(TN)和可溶性有机氮(DON)去除效果显著,去除率分别为(99.6±0.7)%、(99.9±0.0)%、(98.2±2.0)%、(92.6±1.5)%和(86.1±4.8)%。人工湿地表层基质下行池脱氢酶、硝酸还原酶和脲酶的酶活性均高于上行池,下行池对污染物的去除效果更好。脱氢酶活性与海水人工湿地系统氨氮的去除有关;硝酸还原酶活性影响着海水人工湿地硝态氮的去除;脲酶活性与人工湿地总氮和硝态氮的去除存在明显相关趋势。下行池硝酸还原酶和脲酶的酶活性间具有显著相关性(r=0.76, P0.05)。人工湿地微生物种类丰富,下行池微生物多样性高于上行池,植物根部微生物多样性最高,提高了系统脱氮的效率。上述研究结果将有助于阐明海水人工湿地系统中不同形态氮的迁移转化机理。     

一株麦氏交替单胞菌的异养硝化-好氧反硝化特性研究

本文研究了以硫酸铵、亚硝酸钠和硝酸钾为氮源时异养硝化-好氧反硝化菌Alteromonas macleodii 8D的脱氮特性。研究表明,当分别以硫酸铵、亚硝酸钠和硝酸钾为唯一氮源时,培养48h,菌株对氨氮(NH_4~+-N)、亚硝态氮(NO_2~--N)和硝态氮(NO_3~--N)的去除率分别为58.64%、67.41%和50.28%。NH_4~+-N去除过程中并未检测到明显的NO_2~--N和NO_3~--N的积累,然而在NO_2~--N和NO_3~--N去除过程中却明显检测到了NH_4~+-N的积累。NH_4~+-N和NO_2~--N共存时,NO_2~--N抑制了菌株对NH_4~+-N的去除,而NH_4~+-N则将NO_2~--N去除效率提高了22.95%。NH_4~+-N和NO_3~--N共存时,NO_3~--N将NH_4~+-N去除效率提高了12.46%,而NH_4~+-N对NO_3~--N去除无显著影响。NO_2~--N和NO_3~--N共存时,将NO_2~--N和NO_3~--N的去除效率提高了29.19%和15.48%。NH_4~+-N、NO_2~--N和NO_3~--N共存时,将3种无机氮的去除效率提高了38.57%、27.17%和42.56%。研究结果显示,3种无机氮共存时菌株Alteromonas macleodii 8D有最好的除氮表现,作为除氮的理想菌株,该菌株可用于实际养殖水体无机氮的去除。     

长江水体溶解态无机氮和磷现状及长期变化特点

于2006年2、5、8和11月对长江从攀枝花至河口和上游的两条支流雅砻江和嘉陵江的溶解态无机氮(NO-3-N、NO-2-N和NH+4-N)和磷酸盐(PO43--P)进行了取样调查,同时结合长江营养盐的历史数据,分析了长江水体中溶解态无机氮、磷的长期变化特点。结果表明,长江NO-3-N、NH+4-N、DIN(包括NO-3-N、NO-2-N和NH+4-N)和PO3-4-P浓度从上游到下游显示出增加趋势,但存在季节差异;NO2-N浓度总体较低,在长江中下游(武汉—南京)浓度较高。长江从上游到下游DIN通量的变化主要受径流量的影响,从上游到下游单位面积年产N量逐渐升高;PO3-4-P输送通量从上游往下游呈增加趋势,也主要受径流量控制,但从季节变化来讲,PO3-4-P的月输送通量受其浓度的控制更加明显。自20世纪60年代来,长江水体中NO3--N、NO2--N、DIN和PO3-4-P的浓度都处于缓慢上升趋势,但到80年代上升速度明显加快;不同阶段DIN和34PO-P的季节变化特点也不尽相同,反映了其来源的差异。目前,长江水体中溶解态无机氮、磷浓度与国内及国际河流相比处于中等水平。     

广西钦州内湾贝类养殖海区三氮的含量和百分组成

本文根据1998年10月和1999年5月的调查资料，报道了钦州内湾帆类养殖海区三态氮的含量和百分组成。结果表明：NO3－N是本水域无机氮的主要存在形式；三态氮之间的相互转化以春季进行得比较充分，95．70％均已转化为NO3－N，基本达到了热力学平衡状态，NO3－N与NH4－N和NO2－N之间均具有显著的正相关关系；秋季，只有79．87％的无机氮转化为NO3－N，没有达到热力学平衡状态，但NO3－N与NH4－N却具有高度显著的负相关关系，与NO2－N的相关性较差。     

海马齿对不同盐度水质的碳汇作用以及不同形态氮利用的研究

为探讨海马齿(Sesuvium portulacastrum)对水域环境修复作用,本文研究了水培海马齿对不同盐度水质的碳汇作用以及不同形态氮的利用情况。实验设计0、10、20、30、35盐度梯度,海马齿水培时间82 d,然后测定植株干重、营养元素含量以及积累速率,最后在抑菌与不抑菌条件下研究海马齿根际与铵态氮(NH₄⁺-N)、硝态氮(NO₃^--N)、无机磷(PO₄^3-)以及色氨酸(Trp)吸收转化关系。研究结果表明,盐度10条件下海马齿植株干重、有机元素含量以及积累速率最高,有机碳、有机氮与有机磷积累速率分别为(5.572±1.611)、(0.313±0.058)、(0.057±0.013)mg/(d·ind.),而高盐环境35盐度条件下对海马齿生长造成一定胁迫。盐度0～35范围,海马齿均未出现死亡现象。不同盐度抑菌培养条件下,色氨酸与无机氮共存时均能被能被海马齿利用,色氨酸利用量远高于硝态氮、铵态氮;不抑菌条件下铵态氮则表现出增加的结果。海马齿作用在盐度...     

基于转录组测序对两种氮素营养条件下多形微眼藻氮代谢途径的解析

探究微藻的氮代谢通路对了解其对不同氮源利用的分子机制具有重要意义。本研究利用Illumina高通量测序技术对两种氮素营养条件下(硝酸氮和尿素)多形微眼藻的转录组进行分析,通过基因功能注释及数字基因表达谱分析,研究了多形微眼藻细胞内氮代谢的调控机制。结果检测出15种参与氮代谢的酶,对应76个编码基因,构建了多形微眼藻的氮代谢通路图。其中10个酶编码基因在两种不同氮素营养条件下存在差异表达,最显著的是谷氨酸合成酶、谷氨酸脱氢酶和谷氨酰胺合成酶相关基因。有机氮源(尿素)实验组中,多形微眼藻细胞内的硝酸盐还原酶、亚硝酸盐还原酶等基因的差异表达明显高于无机氮源(硝酸钠)实验组,表明当环境中的氮源为尿素时,会对多形微眼藻细胞内硝酸盐的转化和利用有一定影响。本研究初步阐述了硝酸盐、尿素的吸收转运对多形微眼藻细胞内氮代谢的影响机制,可为硅藻在不同氮素营养条件下的吸收利用机制及氮代谢响应研究提供依据。     

Effect on marine sediment nitrogen fluxes caused by organic matter enrichment with varying organic carbon structure and nitrogen content

Enrichments with five types of organic carbon, differing in nitrogen content and type of organic carbon, were made to a marine sediment in order to study effects on nitrogen fluxes. The enrichments used were Ulva lactuca, Ascophyllum nodosum, Zostera marina, Ceratium spp., lignin, and mixtures of U. lactuca and A. nodosum. Fluxes of ammonium, nitrate, and phosphate were measured in short-term (48 h) microcosm experiments, using a carbon enrichment loading similar to that at the sampling site. Changes in microbial community growth and structure due to three types enrichments were also detected using molecular methods in a microcosm experiment run for 4 days to allow for detection at DNA-level.Ammonium fluxes changed from an efflux in the control to an influx for all enrichments apart from U. lactuca. The change was significantly related to the added material's C:N ratio when Ceratium spp. was excluded. All enrichments induced an influx of nitrate suggesting the formation of anoxic micro zones, but there was no relationship with C:N ratio. Instead, the magnitude of the nitrate influx is suggested to be related to the structure of the organic carbon, where enrichments containing a large pool of cellulose and lignin (Z. marina and lignin) gave rise to a lower influx, compared to algal material with more easily degraded organic matter like lipids and starch, which induced the highest influx of nitrate (Ceratium spp., U. lactuca, and A. nodosum). The occurrence of an ammonium influx together with increased nitrate influx and a lower efflux of phosphate in the enrichments suggests a growth of heterotrophic bacteria. This was also confirmed using molecular methods (PCR-DGGE) where the relative abundance of bacterial species in the enrichments increased.The sum of ammonium and nitrate fluxes showed that total nitrogen removal was enhanced in all enrichments compared to the nonenriched control sediment, but in different ways. Ceratium spp. induced the highest removal followed by A. nodosum, U. lactuca, Z. marina, and lastly, by lignin. The same pattern was observed also in a second experiment. These results indicate that easily degradable organic carbon, together with a lower C:N ratio of the added material, will remove nitrogen from the water phase, making the recycling of nitrogen to the overlying water mass smaller.     

Nitrogen Uptake in Permanently Well-mixed Temperate Coastal Waters

Uptake rates of ammonium, nitrate, urea and nitrite were measured for 1 year (1988) at a coastal station in the well-mixed waters of the western English Channel. Ammonium was the major form of nitrogen (N) utilized (48%) by phytoplankton, followed by nitrate (32%), urea (13%) and nitrite (7%). Seasonal changes of uptake of ammonium, nitrate and urea showed a broad, intense summer maximum. Nitrite uptake was low throughout the year except for a peak value in June. Uptake rates of ammonium and nitrate were independent of substrate concentrations, whereas those of urea and nitrite were not. The summer maxima of ammonium, nitrate and total N uptake, and the significant relationships of N-uptake index to ambient light, and of chlorophyll-a-specific N uptake to surface-incident light, indicate that light is the major factor controlling N uptake in these waters. This is due to the permanent vertical mixing which reduces the mean light available for N uptake to <15% of the incident light. Mixing also injects regenerated N continuously into the euphotic zone, thus alleviating nitrogen limitation and accounting for the larger proportion of regenerated N uptake in total N uptake.     

Chemical and microbiological studies of sea-surface films in the Southern Gulf of California and off the West Coast of Baja California

Sea-surface films and the corresponding 10-cm subsurface waters were sampled on three cruises to the eutrophic and oligotrophic waters in the Gulf of California and off the west coast of Baja California. The following constituents and properties were measured: NH₄⁺, NO₂⁻, NO₃⁻, PO₄³⁻, SiO₃²⁻, urea, ATP and Chl-a; dissolved and particulate organic carbon and nitrogen; lipid, protein and carbohydrate; total viable and nitrifying bacteria; simulated in situ bacterial heterotrophy; microplankton and simulated in situ primary productivity; surface potential and film pressures; ultraviolet absorption; and film-formation rates using surface potential and chemical methods.Mean enrichment factors (film concentration/10-cm concentration) for the three cruises were: 1.1–2.4 for the soluble inorganic nutrients, dissolved organic carbon, nitrogen, urea, carbohydrate, and lipid; 1.3–2.0 for ATP, Chl-a, microplankton and bacteria; and 1.1–3.7 for particulate carbon and nitrogen and both dissolved and particulate protein. Particulate and dissolved carbon and nitrogen were the only constituents never depleted in the films relative to the subsurface waters. Systematic, significant correlations between the various chemical and biological parameters measured were few, reflecting the complexity of processes which form and maintain surface films.Protein, carbohydrate and lipid carbon accounted for 15–114% (mean = 50%) of the total particulate organic carbon and 14–42% (mean = 28%) of the total dissolved organic carbon in both the films and 10-cm waters. Lipid was not the major identified constituent of films, averaging 18% of the particulate organic carbon and 2.5% of the dissolved organic carbon. There was more protein relative to carbohydrate in film samples compared to 10-cm water; there was also more protein relative to carbohydrate in particulate compared to dissolved mater. Microplankton plus bacterial carbon averaged 16% of the particulate organic carbon in films and 19% in 10-cm waters.     

Potential rates and environmental controls of denitrification and nitrous oxide production in a temperate urbanized estuary

Denitrification may play a major role in inorganic nitrogen removal from estuarine ecosystems, particularly in those subjected to increased nitrate and organic matter loads. The Douro estuary (NW Portugal) suffers from both problems: freshwater input of nitrate and organic load from untreated wastewater discharges. To assess how these factors might control sediment denitrification, a 12-month survey was designed. Denitrification potential and nitrous oxide (N₂O) production were measured at different locations using the slurry acetylene blockage technique. Denitrification rate ranged from 0.4 to 38 nmol N g⁻¹ h⁻¹, increasing towards the river mouth following an urban pollution gradient. N₂O production, a powerful greenhouse gas implicated on the destruction of the ozone layer, was significantly related with sediment organic matter and accounted for 0.5–47% of the N gases produced. Additional enrichment experiments were consistent with the results found in the environment, showing that sediments from the upper less urban stretch of the estuary, mostly sandy, respond positively to carbon and, inversely, in organic rich sediments from the lower estuary, the denitrification potential was limited by nitrate availability. The obtained results confirmed denitrification as an important process for the removal of nitrate in estuaries. The presence of wastewater discharges appears to stimulate nitrogen removal but also the production of N₂O, a powerful greenhouse gas, exacerbating the N₂O:N₂ ratio and thus should be controlled.     

湛江湾沉积物中反硝化和厌氧氨氧化细菌的丰度、多样性及分布特征

采用实时荧光定量PCR、高通量测序等方法对湛江湾沉积物中四个月份的反硝化细菌与厌氧氨氧化细菌的多样性和丰度进行了分析。结果表明:湛江湾沉积物中反硝化细菌和厌氧氨氧化细菌丰度在四个月份的变化和空间分布趋势为:nirS型反硝化细菌在二月份最高,四月份最低,且其平均丰度有从湛江湾湾内向湾口附近呈现先升高再降低的趋势;nirK型反硝化细菌丰度在九月份最高,十一月份最低;nosZ型反硝化细菌在四月份最高,其余月份变化不大;厌氧氨氧化细菌丰度在九月份最高,二月份最低。通过相关性分析结果表明,亚硝酸盐、铵盐等共同调控着湛江湾沉积物中反硝化和厌氧氨氧化细菌丰度变化。系统发育分析表明:湛江湾中存在着一些广泛分布的反硝化细菌,但也生活着一些新奇的nirK型和nosZ型反硝化细菌。对于厌氧氨氧化细菌而言,其主要属于浮霉菌门及Candidatus Scalindua属,具有较高的耐盐性,另外湛江湾海区的厌氧氨氧化细菌也生活着一类在其他地方没有的新分支。典范对应分析分析结果表明:硝酸盐显著影响湛江湾反硝化细菌和厌氧氨氧化细菌的群落结构。湛江湾沉积物中反硝化细菌和厌氧氨氧化细菌存在特殊的竞争与共存的关系,且由亚硝...     

Seasonal changes of concentrations of inorganic and organic nitrogen in coastal marine sediments

The seasonal fluctuations of the concentration of nitrogenous compounds in sediments was investigated for three regions of the Seto Inland Sea in Japan; the variation of nitrogenous compounds in sediments was also studied in a laboratory experiment.The amounts of ammonium, dissolved organic nitrogen, nitrite and nitrate, as percentages of the dissolved total nitrogen of the interstitial water, were in the ranges of 47–99%, 10–50%, 0·1–0·6% and 0·3–4·1%, respectively. Ammonium was the major component and organic nitrogen was the next most important. The concentrations of these nitrogenous compounds changed seasonally: dissolved total nitrogen was higher in the warm month of September than in May; ammonium increased in warm months and decreased in cold months, but nitrite and nitrate increased in cold months. It was possible to explain the seasonal fluctuation of nitrogenous compounds in terms of the rates of the metabolic pathways of nitrogen in the sediments.Ammonium was not necessarily correlated with dissolved organic nitrogen. From this, it was considered that ammonium did not occur from solubilization of particulate organic nitrogen followed by mineralization, but from direct mineralization of particulate organic nitrogen in sediments.For the sediments of Suho Nada, Hiuchi Nada and station B-47 in Beppu Bay, the ratio of dissolved ammonium to adsorbed ammonium in the sediments was in the range 10–25%, but the ratio was 60–70% of adsorbed ammonium in the considerably anaerobic sediments at station B-45 in Beppu Bay. The ratio of dissolved ammonium to adsorbed ammonium increased with the increase of the concentration of sulfide in sediments. It was recognized that the anaerobic conditions of the sediments led to the dissolution of adsorbed ammonium.