Characterization of Mediterranean Magnetotactic Bacteria     

Lefèvre Christopher 《中国海洋大学学报(英文版)》2007,6(4):355-359

Magnetotactic bacteria are a diverse group of motile prokaryotes that are ubiquitous in aquatic habitats and cosmopolitan in distribution. In this study, we collected magnetotactic bacteria from the Mediterranean Sea. A remarkable diversity of morphotypes was observed, including multicellular types that seemed to differ from those previously found in North and South America. Another interesting organism was one with magnetosomes arranged in a six-stranded bundle which occupied one third of the cell width. The magnetosome bundle was evident even under optic microscopy. These cells were connected together and swam as a linear entire unit. Magnetosomes did not always align up to form a straight linear chain. A chain composed of rectangle magnetosomes bent at a posi- tion with an oval crystal. High resolution transmission electron microscopy analysis of the crystal at the pivotal position suggested uncompleted formation of the crystal. This is the first report of Mediterranean magnetotactic bacteria, which should be useful for studies of biogeochemical cycling and geohistory of the Mediterranean Sea.  相似文献   

Biogeochemical characteristics of nitrogen and phosphorus in Jiaozhou Bay sediments   总被引：3，自引：0，他引：3  

李学刚  宋金明  袁华茂  戴纪翠  李宁 《中国海洋湖沼学报》2007,25(2):157-165

Sediment samples were cored from 3 locations representing the inner bay, the outer bay and the bay mouth of Jiaozhou Bay in September 2003 to study the source and biogeochemical characteristics of nitrogen and phosphorus in the bay. The content and vertical distributions of total nitrogen （TN）, total phosphorus （TP）, organic nitrogen （ON）, organic phosphorus （OP）, inorganic nitrogen （IN）, inorganic phosphorus （IP）, the ratio of organic carbon and total nitrogen （OC/TN）, and the ratio of total nitrogen and total phosphorus （TN/TP） in the sediments were analyzed. The results show that both TN and TP in surface sediments decrease from the inner bay to the outer bay. In general, ON occupies 50%-70% of TN and IP accounts for more than 60% of TP. In ratio of OC：TN, the nitrogen accumulated in the sediments from the inner bay and the bay mouth came mainly from terrestrial sources, and the portion of autogenetic nitrogen was 28.9% and 13.1%, respectively. However, in the outer bay, nitrogen was mainly autogenetic, accounting for 62.1% of TN, whereas phosphorus was mainly land-derived. The sedimentation fluxes of nitrogen and phosphorus varied spatially. The overall diagenesis rate of nitrogen was higher than that of phosphorus. Specifically, the diagenesis rate of OP was higher than that of IP. However, the diagenesis rate of ON was not always higher than that of IN. In species, the diagenesis rate of IN is sometimes much higher than that of the OC. In various environments, the diagenesis rate is, to some degree, affected by OC, pH, Eh, and Es.  相似文献   

BIOGEOCHEMICAL PROCESSES OF PHOSPHORUS AND SILICON IN SOUTHERN BOHAI SEA SURFACE SEDIMENTS   总被引：3，自引：0，他引：3  

宋金明  罗延馨  吕晓霞  李鹏程 《中国海洋湖沼学报》2002,20(4):378-383

Based on the author’s previously obtained results on P and Si forms in southern Bohai Sea surface sediments,this study maindy foucusing on the controlling factors,existence forms,and biogeo-chemical processes of P and Si showed that the transferable forms of phosphorus in sediments were mainly controlled by the mineralization of organic matters and the reduction of high-valence iron;whereas the transferable forms of silicon were possibly controlled by the dissolution and precipitation as well as bio-chemical processes of living organisms.  相似文献   

Do social meanings matter? How and how much social meanings influence everyday transport practices?          下载免费PDF全文

Helen Fitt 《New Zealand geographer》2017,73(3):181-191

We live among a throng of social meanings. In a transport context, cars are described as symbols of status, bicycles as the toys of Middle Aged Men in Lycra, and buses as ‘loser cruisers’. This study asks ‘Do these social meanings matter?’ Do they influence people's transport practices, and if so, how and how much? The participants in this research reported that social meanings had widespread influences, particularly on their transport mode choices, vehicle choices, and travel performances. This research has implications for the ways that social meanings are incorporated into transport policy and future transport research.  相似文献   

极地冰川底部微生物多样性及对气候变化响应的研究概况及其前景          下载免费PDF全文

马红梅闫文凯  程永前张宇肖湘  史贵涛孙波 李院生 《极地研究》2017,29(1):1-10

极地冰盖/冰川底部微生物的生命形态特征及其适应机制研究是当前最前沿的方向之一。越来越多的研究表明: 极地冰盖/冰川底部存在液态水和有机质, 可以为微生物生存提供生境。此外, 微生物参与冰盖/冰川底部地球化学风化过程, 对受气候变化驱使的环境变化尤为敏感。围绕着极地冰川底部微生物多样性及其对气候变化响应的研究主题, 重点介绍极地冰川底部微生物的生命形态特征、可能来源、所参与的地球化学反应机制以及与C、N循环的相互作用。旨在为未来关于冰川底部的研究提供参考。  相似文献   

Response and Feedback of Marine Carbon Sink to Climate Change   总被引：1，自引：0，他引：1  

Jiao Nianzhi  Li Chao  Wang Xiaoxue 《地球科学进展》2016,31(7):668-681

The response and feedback of ocean carbon sequestration to climate changes is a international hot topic and requires large spatial/temporal scale, collaborative and multi-disciplinary research. In the first conference of GRC Ocean biogeochemistry, scientists focus on three biologically-driven ocean carbon pumps (Biological Pump, BP; Microbial Carbon Pump, MCP; Carbonate Counter Pump, CCP) and their environmental and climate consequences. As a sister meeting in China, we organized the session to show the efforts and progress of ocean carbon sequestration of Chinese scientists. The microbial ecological processes of phytoplankton, bacteria, archaea and viruses and interactions between them were highlighted in the session. Use coral reefs in the South China Sea as an example, the presenters and the participants come to an agreement that interdisciplinary collaborations are needed to ensure a comprehensive understanding of the interactions between microbes and their geochemical environment and the consequences of microbial processing of carbon on outgassing of CO₂ and carbon sequestration. The session also have presentations focusing on paleo-environmental reconstruction for carbon sinks as well as their paleo-ecological effects in ancient oceans with time spanning from the 1.8~0.8 Ga Proterozoic to the 2.5 Ma Quaternary. These talks provide specific geological cases for the oceanic carbon sink research and convey the emerging geological view of paleooceanic carbon sinks to the research community of modern ocean carbon sinks. As a summary, the discussion in this session of biological pump, microbial carbon pump and carbonate counter pump shows the latest research progress and future development trend in this field.  相似文献   

未来百年全球气候变化分析     

刘焰 《中国地质调查》2021,8(3):1-11

未来百年全球气候变化的影响是当前学术界激烈争议的议题,深入探讨全球气候变化的驱动机理才能正确认识全球气候变化。持续生长的青藏高原吸收了巨量的CO₂,导致大气中CO₂浓度大幅下降,使地球从温室气候进入到以冰期、间冰期交替出现为特征的冰室气候,青藏高原成为新生碳储库。在间冰期,青藏高原和蒙古高原将淡水输送到中低纬度内陆区(以下简称内陆区),导致内陆区的硅酸岩化学风化强烈,植被和湖相沉积发育,吸收了巨量大气CO₂,是碳汇; 在冰期,青藏高原、蒙古高原将内陆区表层淡水与尘埃最终输送到高纬度地区,导致内陆区荒漠化,对大气CO₂的吸收量远小于其自身的排放量,内陆区成为碳源,使大气CO₂浓度上升。这是中新世以来大气CO₂浓度维持低浓度、准动态平衡的机理。地表平均温度的变化驱动了淡水在高、低纬度地区之间循环。人类巨量碳排放使全球大气CO₂浓度暂时快速上扬,全球变暖,淡水回到内陆区,导致内陆区变绿,硅酸岩化学风化作用增强,吸收大气CO₂的能力大幅提高,内陆区又变成碳汇,抑制大气CO₂浓度的进一步上升; 初步测算,最早2050年、最迟2090年,当大气CO₂浓度达到(510±40)×10^-6时,其快速上升的趋势将得到抑制; 未来百年尺度的全球气候变化受地球和太阳内部的构造活动所驱动,是周期性变化的、是可预测。  相似文献   

海洋亚硝酸盐氧化细菌的多样性分布及其生态功能研究进展   总被引：1，自引：0，他引：1  

洪义国  焦黎静  吴佳鹏  龙爱民  王伟 《热带海洋学报》2021,40(2):139-146

微生物介导的硝化过程是全球氮循环的一个重要环节, 其中催化亚硝酸盐氧化过程的功能菌亚硝酸盐氧化菌(NOB)受到越来越广泛的关注。目前已鉴定的NOB涵盖4个菌门, 分属7个菌属。其中, 亚硝化螺旋菌属(Nitrospira)由于多样性高、分布广泛成为近年来的研究热点。文章综述了NOB多样性组成、系统进化关系、生态分布特征以及亚硝酸盐氧化和自养固碳的过程机制, 阐述了其在海洋碳氮生物地球化学循环中的功能, 并展望了本领域的研究热点。  相似文献   

雷达资料同化对暴雨预报影响的数值模拟研究   总被引：6，自引：3，他引：3  

杨艳蓉  曾明剑 《气象科学》2012,32(2):145-152

以CAPS研发的最新版ARPS模式为基础,利用其数据同化系统ADAS对南京多普勒雷达资料进行同化,模拟2009年6月5日江苏地区的一次暴雨过程,进行了不同的微物理方案设计以及何时同化雷达资料的敏感性实验研究。研究发现:(1)格距较小且不使用积云对流参数化的情况下,选择warm rain或Schultz微物理过程的模拟结果差别不大,且与实况较为相符,但选择ice微物理方案时,会造成1 h内的降水量突增百倍;(2)在参数一致的情况下,模拟研究时段前3、2、1 h分别同化,可以得到部分主要降水区域;但同化预报的时间越短,降水模拟的中尺度信息越明显,对降水量的控制也越好;(3)依据以上结论,在暴雨发生最初的1 h内进行每6 min一次的时间循环同化,然后积分2 h,可以得到较为精细的云内气象要素场分布,预报的结果与实况最接近。  相似文献   

枯落物处理对森林土壤碳氮转化过程影响研究综述   总被引：1，自引：0，他引：1  

陈玉平  吴佳斌  张曼  杨智杰  陈光水 《亚热带资源与环境学报》2012,7(2)

在全球变化背景下,植物枯落物输入的改变对森林生态系统土壤有机质的形成和稳定具有重要作用．通过论述近年来国内外在森林枯落物添加和去除处理（DIRT）对土壤有机质影响的最新研究进展,包括枯落物添加和去除对土壤碳氮贮量、土壤呼吸及其激发效应、土壤氮循环、土壤可溶性有机质以及土壤微生物、酶活性和小动物的影响,提出未来的可能研究方向,以期为国内该领域的研究提供参考．  相似文献