湖南台地泥盆纪末绝灭事件后的微生物沉积

湖南中南部浅水碳酸岩台地,泥盆系顶部假整合面之上,石炭纪海进最早期,相当四射珊瑚Cystophrentis-Uralinia间隔带和单房室有孔虫带的层位,普遍发育厚度不等(7~30m)的微生物沉积.宏观上为条带状或斑块、瘤状构造,大部分由核形石组成,局部发育凝块构造内碎屑.它们均属微生物成因,代表汉根卑尔格绝灭事件后(...     

中国东部农耕区土壤微生物碳的分布及影响因素

对中国东部不同纬度带的6个地区的土壤微生物碳进行了研究。结果表明土壤微生物碳的分布受地理位置的影响较为明显:由北向南,东北地区的土壤微生物碳要高于其他地区。作为土壤有机质变化的灵敏度指标———微生物熵(微生物碳/总有机碳),在同一耕作方式下,其在不同地区的变化受土壤利用方式的影响较为明显:在连作系统下,菜地>粮地;而在轮作系统下,粮食-蔬菜轮作>蔬菜-蔬菜轮作。利用相关性分析寻求影响微生物碳分布的环境因素,结果表明,微生物碳(Micro-C)与土壤有机碳(TOC)、全氮(TN)、土壤含水率呈极显著正相关,而有机碳和全氮的分布主要受地理位置的影响。对不同土壤类型的微生物碳和微生物熵进行相关性分析,结果显示pH、年均温、含水率、TOC和TN是主要影响因素,关键影响因素因土壤类型不同而各异。     

Chemosynthetic trophic support for the benthic community at an intertidal cold seep site at Mocha Island off central Chile

We analyzed C and N stable isotope ratios of benthic fauna and their potential food sources at an intertidal methane seep site and a control site without emanation at Mocha Island (central Chile). The objective was to trace the origin of the main food sources used by the local heterotrophic fauna, based on the hypothesis that chemosynthetic production could be partially fueling the local food web at the seep site. Food sources sampled at both sites included macroalgae, particulate organic matter and bacteria-like filaments found growing over the red algae Gelidium lingulatum within the areas of active methane release.     

Microbial mats implicated in the generation of intrastratal shrinkage (‘synaeresis’) cracks

Intrastratal shrinkage (often termed ‘synaeresis’) cracks are commonly employed as diagnostic environmental indicators for ancient salinity‐stressed, transitional fluvial‐marine or marginal‐marine depositional environments. Despite their abundance and use in facies interpretations, the mechanism of synaeresis crack formation remains controversial, and widely accepted explanations for their formation have hitherto been lacking. Sedimentological, ichnological, petrographic and geochemical study of shallow marine mudstone beds from the Ordovician Beach Formation of Bell Island, Newfoundland, has revealed that crack development (cf. synaeresis cracks) on the upper surface of mudstone beds is correlated with specific organic, geochemical and sedimentological parameters. Contorted, sinuous, sand‐filled cracks are common at contacts between unbioturbated mudstone and overlying sandstone beds. Cracks are absent in highly bioturbated mudstone, and are considered to pre‐date firmground assemblages of trace fossils that include Planolites and Trichophycus. The tops of cracked mudstone beds contain up to 2·1 wt% total organic carbon, relative to underlying mudstone beds that contain around 0·5 wt% total organic carbon. High‐resolution carbon isotope analyses reveal low δ¹³C_org values (?27·6‰) on bed tops compared with sandy intervals lacking cracks (?24·4 to ?24·9‰). Cracked mudstone facies show evidence for microbial matgrounds, including microbially induced sedimentary structures on bedding planes and carbonaceous laminae and tubular carbonaceous microfossils in thin section. Non‐cracked mudstone lacks evidence for development of microbial mats. Microbial mat development is proposed as an important prerequisite for intrastratal shrinkage crack formation. Both microbial mats and intrastratal shrinkage cracks have broad palaeoenvironmental distributions in the Precambrian and early Phanerozoic. In later Phanerozoic strata, matgrounds are restricted to depositional environments that are inhospitable to burrowing and surface‐grazing macrofauna. Unless evidence of synaeresis (i.e. contraction of clay mineral lattices in response to salinity change) can be independently demonstrated, the general term ‘intrastratal shrinkage crack’ is proposed to describe sinuous and tapering cracks in mudstone beds.     

城市纳污河流沉积物微生物群落结构特征

以南京市运粮河沉积物为研究对象,通过磷脂脂肪酸(PLFA)技术分析了不同水期城市纳污河流沉积物微生物群落结构特征。结果表明:在不同的水期运粮河沉积物微生物量出现了显著差异,温度是导致微生物量在丰、平、枯三期出现显著差异的主要因素(P<0.05);在相同水期,营养物质含量高的地方对应着高的微生物量;16:0 iso、17:0 anteiso、15:0 iso这几种PLFA所指示的革兰氏阳性菌(G+)是影响运粮河沉积物微生物群落构成的主要菌落,导致沉积物微生物群落结构出现显著差异的环境因素是水期;单不饱和/支链脂肪酸比值可以作为反映水环境系统整体营养水平的指标,在C/N比值升高时微生物会将单不饱和脂肪酸转变成环丙基或者饱和脂肪酸以适应新的环境;PLFA含量比[c(i15:0)+c(i17:0)]/[c(a15:0)+c(a17:0)]可以作为指示水环境碳素含量的标志。     

Microbial populations in contaminant plumes

Received, May 1999/Revised, October 1999/Accepted, October 1999     

海洋微生物多样性研究进展

海洋微生物多样性是生物多样性的重要组成部分。由于基础研究薄弱,目前对海洋微生物多样性的了解远远落后于陆地微生物,尤其是其研究方法亟待完善和提高。近年来,随着分子生物学技术的迅速发展和计算机的广泛应用,海洋微生物多样性的研究取得了一系列的研究成果。概述了海洋微生物多样性的概念和研究方法及其资源开发利用的研究进展。