东濮凹陷古近系成烃生物特征及其生烃潜力研究

通过光学显微镜和扫描电镜对东濮凹陷古近系沙河街组烃源岩的成烃生物进行了研究。结果显示,研究区沙河街组的成烃生物发育,种类繁多,主要包括沟鞭藻、绿藻、蓝藻、颗石藻等。发育于东濮凹陷北部咸水区的成烃生物优势组合是沟鞭藻、蓝藻、颗石藻,且三者均可形成藻纹层;南部淡水区的成烃生物优势组合是绿藻及高等植物,发育于块状泥岩之中。对分别取于咸水区和淡水区的两个样品进行了热模拟实验,实验结果显示,北部咸水区的蓝藻和颗石藻的生烃潜力高,生油门限低,在低熟阶段即可大量生油,生成低熟油的控制因素是蓝藻的勃发;沟鞭藻和绿藻类的生油门限较高,其中沟鞭藻由于能大量勃发,是重要的成烃生物;南部淡水区的绿藻类较沟鞭藻类生烃潜力更低,生油门限更高。     

不同光照条件下石灰岩表面蓝藻生物岩溶侵蚀能力与生理活性研究

野外和室内监测试验结果初步表明,不同光照环境下石生蓝藻的生理学特性有明显差异。阴生生境下生长的石生蓝藻,其生理活性,包括光合放氧速率,叶绿体光化学活性,尤其是影响生物岩溶过程的关键酶--碳酸酐酶(CA)的活性明显高于阳生环境下生长的同类,最终导致阴生生境下生长的蓝藻对石灰岩溶蚀的速率也明显快于阳生生境下的蓝藻。     

Acyclic Alkanes in the Soil over Heshang Cave in Qingjiang, Hubei Province

Biomarkers have been widely used to exploreglobal change such as paleocli mate and paleovegeta-tion based on the analyses of marine sedi ments( Volkman et al ., 1995 ) , lacustrine sedi ments(Sheng et al ., 1999) , snow and ice ( Xie et al .,1999) ,peat (Xie et al .,2004) ,and stalagmites (Xieet al ., 2005 , 2003a) . Research into biomarkers inChina has been conducted in many soils . Aseries ofbiomarkers were identified from the Jiuzhoutaipaleosol-loess profilein Lanzhou,andn-alkanes werepr…     

Wind erodibility of soils at Fort Irwin,California (Mojave Desert), USA,before and after trampling disturbance: implications for land management

Recently disturbed and ‘control’ (i.e. less recently disturbed) soils in the Mojave Desert were compared for their vulnerability to wind erosion, using a wind tunnel, before and after being experimentally trampled. Before trampling, control sites had greater cyanobacterial biomass, soil surface stability, threshold friction velocities (TFV; i.e. the wind speed required to move soil particles), and sediment yield than sites that had been more recently disturbed by military manoeuvres. After trampling, all sites showed a large drop in TFVs and a concomitant increase in sediment yield. Simple correlation analyses showed that the decline in TFVs and the rise in sediment yield were significantly related to cyanobacterial biomass (as indicated by soil chlorophyll a). However, chlorophyll a amounts were very low compared to chlorophyll a amounts found at cooler desert sites, where chlorophyll a is often the most important factor in determining TFV and sediment yield. Multiple regression analyses showed that other factors at Fort Irwin were more important than cyanobacterial biomass in determining the overall site susceptibility to wind erosion. These factors included soil texture (especially the fine, medium and coarse sand fractions), rock cover, and the inherent stability of the soil (as indicated by subsurface soil stability tests). Thus, our results indicate that there is a threshold of biomass below which cyanobacterial crusts are not the dominant factor in soil vulnerability to wind erosion. Most undisturbed soil surfaces in the Mojave Desert region produce very little sediment, but even moderate disturbance increases soil loss from these sites. Because current weathering rates and dust inputs are very low, soil formation rates are low as well. Therefore, soil loss in this region is likely to have long‐term effects. Published in 2006 by John Wiley & Sons, Ltd.     

两种蓝细菌中7对毒素-抗毒素系统的分析和鉴定

蓝细菌(cyanobacteria)是一类能进行放氧光合作用的原核生物。蓝细菌生长速度较快, 几乎存在于所有的陆地和水生环境中。毒素-抗毒素(toxin-antitoxin, TA)系统在原核生物中分布十分广泛, 在细菌的生命活动中扮演了重要的角色, 如维持水平基因转移元件的稳定性以及应对环境胁迫压力等。已有的基因组分析表明, 蓝细菌基因组中含有大量潜在的毒素-抗毒素系统, 但是目前对蓝细菌毒素-抗毒素系统的实验鉴定仍较少。本文分别以淡水和海水代表菌株集胞藻PCC6803(Synechocystis sp. PCC6803)和聚球藻WH7803(Synechococcus sp. WH7803)为研究对象, 对二者基因组上的毒素-抗毒素系统进行预测, 并选取预测结果中的7对潜在的毒素-抗毒素系统进行实验验证。结果表明, 集胞藻PCC6803的两对毒素-抗毒素系统BAD01932-1933 和 BAA18559-New ORF7中的毒素具有明显的细胞毒性。本文的研究结果有助于后续对蓝细菌毒素-抗毒素系统及其生态和生物学功能的研究。     

Oceanic circulation in the head of the Hikurangi trench,east coast,New Zealand

The geostrophic flow and direct current measurements in the inflow of the Southland Current into the Hikurangi Trench east of New Zealand confirm the geostrophic circulation pattern previously found. The northwards inflow of the Southland Current at the latitude of the Chatham Rise (44°S) is estimated at 1.7 × 10⁶ m³.s^‐1, which compares favourably with that of 1.2 × 10⁶ m³.s^‐1 calculated previously off Kaikoura.     

Food of barracouta (Teleosti: Gempylidae) in eastern Cook Strait

The stomach contents were examined from 244 barracoota, Thyrsites atun (Euphrasen), caught in eastern Cook Strait, New Zealand. In the year of sampling (1966–67) the euphausid Nyctiphanes australis Sars was most commonly taken as food during the cooler months, replaced by the teleost hoki, Macruronus novae‐zelandiae Hector, in summer. The proportions of full and empty stomachs suggested that the barracouta fed sparingly before spawning but heavily afterwards.     

First record of Australian bonito,Sarda Australis,from New Zealand

The range of the Australian bonito, Sarda australis (Macleay, 1880), previously known only from eastern Australia and Norfolk Island, is now extended to include New Zealand. Data on two specimens examined from northern New Zealand are presented.     

Spatio-temporal variation in density of microphytoplankton genera in two tropical coral reefs of Mauritius

Spatial and temporal (seasonal and interannual) variation in microphytoplankton was investigated at two tropical coral reef sites off Mauritius (Belle Mare [BM] and Flic-en-Flac [FEF]), from 2010 to 2012. Each site was divided into three zones: coast, lagoon and reef. Microphytoplankton, nutrient and chlorophyll a samples were collected, and physico-chemical parameters were measured in situ. A total of 56 microphytoplankton genera were identified (43 diatoms, 8 dinoflagellates and 5 cyanobacteria). Total microphytoplankton density exhibited spatial and temporal variation, being higher at BM and near the coast, and mostly high in summer. Nutrient concentrations were highest near the coast as a result of run-off events and anthropogenic inputs, especially during heavy rainfall, and this resulted in elevated total microphytoplankton density. There were no clear diversity patterns at the two sites or within the different zones. At both sites, Navicula, Cocconeis and Fragilaria were the dominant diatoms, and Gymnodinium, Alexandrium and Protoperidinium were the dominant dinoflagellates. There was a shift in dominance from Navicula in summer to Fragilaria in winter. This seasonal shift may reflect how these species respond differently to environmental change, which could have implications for primary production at spatial and temporal scales.