生物固氮速率测定中15N₂同位素示踪剂的引入     

陈盛保  张润  陈能汪  赖丽旻  陈敏  郑敏芳  邱雨生 《海洋学报》2018,40(10):42-50

生物固氮作用是一个重要的海洋新氮来源,在海洋生物地球化学循环中扮演着不可替代的角色。基于稳定同位素（15N₂）示踪吸收法,是目前直接测定海洋生物固氮速率最有效的手段。其中,高效、洁净地将15N₂引入海水培养体系,并准确定量培养体系底物的同位素示踪水平,是同位素示踪吸收法准确获取固氮速率的关键。本研究针对15N₂同位素示踪剂引入这一关键环节进行了探讨,确认改进气泡法是将15N₂引入海水培养体系的首选操作。在对培养体系造成的较小扰动的情况下,可将培养体系氮气底物的15N原子丰度提升至10%以上,相对于另一种导入同位素示踪剂的手段——预溶解海水法,改进气泡法将培养瓶中氮气底物的15N原子丰度提升了近200%。此外,改进气泡法还具有最小化痕量金属沾污、操作简便等优点。将改进气泡法结合与稳定同位素比值质谱测定结合,是准确测定水体生物固氮速率的推荐方法。  相似文献   

海带磷酸烯醇式丙酮酸-羟激酶的研究     

陈敏资  侯和胜  姚南瑜  徐志明  李建之 《海洋与湖沼》1994,25(6):596-600

于1986－1990年，在大连凌水养殖四场采集海带，对磷酸烯醇式丙酮酸羧激酶在海带不同部位、不同发育时期及不同外界条件下活性的变化予以研究。结果表明，该酶是海带体内唯一重要的催化CO2暗固定的酶；此酶活性由海带基部、中部至顶端逐渐减弱；酶活性在用正常水温预处理藻体时最高；正常盐度时酶的活性高于非正常盐度的酶活性；增加NH4+浓度可提高酶的活性。  相似文献   

聚乳酸(PLA)网格沙障耐老化性能及防沙效果     

屈建军  洪贤良  李芳  冯筱  孟一江  丁伊央  杨明全 《中国沙漠》2021,41(2):51-58

通过甘南玛曲高海拔沙化草地实地铺设和实验室加速老化试验,探索在高原极端环境下透风率20％-49％聚乳酸(PLA)网格沙障的使用寿命和防沙效果.结果表明,PLA网格沙障不仅耐辐射、耐老化,且防沙效果好,可成为严酷气候环境下替代草方格的一种新型沙障.  相似文献   

Summer phytoplankton blooms in the oligotrophic North Pacific Subtropical Gyre: Historical perspective and recent observations     

John E. Dore  Ricardo M. Letelier  Roger Lukas 《Progress in Oceanography》2008,76(1):2-38

The export of organic matter from the oceanic euphotic zone is a critical process in the global biogeochemical cycling of bioelements (C, N, P, Si). Much of this export occurs in the form of sinking particles, which rain down into the unlit waters of the deep sea. Classical models of oceanic production and export balance this gravitational loss of particulate bioelements with an upward flux of dissolved nutrients, and they describe reasonably well those areas of the ocean where deep winter mixing occurs. The surface waters of the North Pacific Subtropical Gyre (NPSG), however, are strongly stratified and chronically nutrient-depleted, especially in summer. Nevertheless, there is ample evidence that blooms of phytoplankton and subsequent pulses of particle export occur during the height of summer stratification in these waters, especially to the northeast of the Hawaiian Islands. These blooms impact regional bioelemental cycling and act as a food source to the deep-sea benthos. We review here numerous published observations of these events in the NPSG, and present new data collected at Station ALOHA (22.75°N, 158°W) during the first 176 cruises of the Hawaii Ocean Time-series program (1988-2005), along with results from transect cruises conducted in the region in 1996 and 2005. We suggest that the summer phytoplankton bloom can be considered a frequent, perhaps annual feature in the northeastern NPSG, and that its perceived stochastic nature is a manifestation of chronic undersampling in time and space. The bloom is typically dominated by only a few genera of large diatoms and the cyanobacterium Trichodesmium. It appears to be consistently supported by dinitrogen fixation, but the fate of the organic matter produced during the summer depends critically on the species composition of the responsible diazotrophs. We estimate that the summer bloom is responsible for up to 38% of N₂ fixation and up to 18% of N-based new production annually at Station ALOHA. We hypothesize that the spatial distribution, timing and magnitude of the bloom may be determined largely by the physical and biological processes controlling new phosphorus delivery into the euphotic zone during the summer and the preceding winter.  相似文献   

湿地生态系统氮素输入过程的研究进展   总被引：6，自引：0，他引：6  

孙志高  刘景双  王金达  李新华  杨继松 《地理与地理信息科学》2006,22(1):97-102

湿地生态系统的氮素输入过程主要包括大气氮沉降、生物固氮、人为氮和径流氮输入等途径,它们通过影响湿地系统自身的营养状况而决定氮素生物地球化学过程的运行。综述国内外湿地氮素各种输入途径的研究进展,分析当前研究中存在的问题,指出淡水沼泽湿地是目前研究的薄弱点。展望湿地氮素输入过程的研究前景,建议积极开展淡水沼泽湿地、湿地系统氮素交换的环境效应1、5N技术与氮素模型的结合以及各氮素输入途径的模型表征研究。  相似文献   

Improvement of Growth,Yield, and Pigmentation of Mung Bean Plants Using Ochrobactrum intermedium CP‐2 as Bioinoculant     

《洁净——土壤、空气、水》2017,45(6)

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基于RS/GIS的城市植被生态价值分析与评价     

王维磊  郭连杰  尚冉冉  吕秀美 《地理空间信息》2019,17(7):78-81,I0002

根据济南市历下区TM遥感影像获取了历下区植被归一化指数(NDVI),利用单窗算法提取了地表温度;通过对比NDVI分布与温度分布分析了植被对城市热岛效应的缓解作用。采用改进的CASA模型提取了植被第一性净生产力(NPP),进而获得了植被的固碳释氧能力,分析了城市植被的固碳释氧价值。采用影子替代法对植被生态价值进行定量化,从而可对济南市历下区植被分布进行科学规划,以提高城市整体的人居适宜性。结果显示,城市植被生态价值非常可观,热岛缓解价值最大可达249021元/hm^2,植被固碳和释氧价值最大分别为15818.2元/hm^2和18645.2元/hm^2。  相似文献   

Cyanobacterial blooms in Lake Atitlan, Guatemala     

Eliška Rejmánková  Ji?í Komárek  Margaret Dix  Jaroslava Komárková  Nancy Girón 《Limnologica》2011,41(4):296-302

Lake Atitlan, one of the most important lakes not only in Central America but in the whole world, is facing serious problems with increasing water pollution. Over the last several decades, the uncontrolled nutrient input into the lake has lead to high P levels and low N:P ratios, initiating cyanobacterial blooms. The first bloom occurred in December of 2008, followed by more extensive bloom in October 2009. The blooms are formed by cyanobacteria from the rare planktic Lyngbya hieronymusii/birgei/robusta complex. Based on the species morphology, the Atitlan population corresponds to L. robusta and this is the first case of reported bloom of this species worldwide. Remote sensing images documented that at the maximum bloom development, 40% of the 137 km² of the lake area were covered by dense patches of Lyngbya, with the chlorophyll a concentration reaching over 100 μg L⁻¹. The only toxins detected in the 2009 bloom were trace levels of cylindrospermopsin and saxitoxin with 12 and 58 ng g⁻¹, respectively. The nitrogen fixation followed a pattern expected in non-heterocytous cyanobacteria, i.e., the nitrogenase activity was minimal during the day, while during the night the activity reached 2.2 nmol C₂H₄ μg Ch a⁻¹ h⁻¹. Delta ¹⁵N of −0.86‰ was well in the range given for nitrogen fixing organisms. The cell C, N and P content was 36.7%, 5.9% and 0.9%, respectively, resulting in the molar ratio of 105:14.4:1. A well designed and executed lake monitoring program, strict control of nutrient input into the lake, and public education are the necessary prerequisites for potential prevention of even more severe blooms than the one from 2009.  相似文献   

The Study of Biological Soil Crusts: Hotspots and Prospects     

Chongfeng Bu  Yongsheng Xie  Xingchang Zhang 《洁净——土壤、空气、水》2013,41(9):899-906

Biological soil crusts (BSCs), which cover 35% of the continents and exceed 70% of the living cover in parts of region, play important ecological roles in the evolution of soil–water–plant systems in arid and semiarid areas. Since the 1980s, studies of BSCs have become hot topics in physical geography. By reviewing the last 30 years of study reports, the present paper proposes the following future research focus: (1) Understanding the function of BSCs in carbon and nitrogen fixation in the micro‐scale (block), monitoring its distribution patterns in the macro‐scale (region) by remote sensing technology and geographic information systems, and evaluate the role of carbon and nitrogen fixation in the whole ecological system. The response of BSCs to global climate change should also be evaluated. (2) Studying techniques for the artificial fast cultivation or restoration of BSCs, and implementing engineering propagation and application of artificial BSCs, and determining the appropriate parameters for environmental criteria, including light, temperature, soil water moisture, and fertilizer, among others. Artificial cultivation and rapid propagation techniques could present significant perspectives for engineering applications.  相似文献   

Optimization of medium and cultivation conditions for enhanced exopolysaccharide yield by marine Cyanothece sp. 113     

苏传东  池振明  卢伟东 《中国海洋湖沼学报》2007,25(4):411-417

Cyanothece sp. 113 is a unicellular, aerobic, diazotrophic and photosynthetic marine cyanobacterium. The optimal medium for exopolysaccharide yield by the strain was 70.0 g/L of NaCl, and 0.9 g/L of MgSO4 based on the modified F/2 medium for cultivation of marine algae. The optimal cultivation condition for exopolysaccharide yield by this cyanobacterial strain was 29°C, aeration, and continuous illumination at 86.0 μE/M2/S. Under the optimal conditions, over 18.4 g/L of exopolysaccharide was produced within 12 days. This was so far the highest exopolysaccharide yield produced with strains of Cyanothece sp. obtained.  相似文献