Variability in temperature and geometry of the Norwegian Current over the past 600 yr; stable isotope and grain size evidence from the Norwegian margin

Core P1‐003MC was retrieved from 851 m water depth on the southern Norwegian continental margin, close to the boundary between the Norwegian Current (NC) and the underlying cold Norwegian Sea Deep Water. The core chronology was established by using ²¹⁰Pb measurements and ¹⁴C dates, suggesting a sampling resolution of between 2 and 9 yr. Sea‐surface temperature (SST) variations in the NC are reconstructed from stable oxygen isotope measurements in two planktonic Foraminifera species, Neogloboquadrina pachyderma (d.) and Globigerina bulloides. The high temporal resolution of the SST proxy records allows direct comparison with instrumental ocean temperature measurements from Ocean Weather Ship (OWS) Mike in the Norwegian Sea and an air temperature record from the coastal island Ona, western Norway. The comparison of the instrumental and the proxy SST data suggests that N. pachyderma (d.) calcify during summer, whereas G. bulloides calcify during spring. The δ¹⁸O records of both species suggest that the past 70 yr have been the warmest throughout the past 600 yr. The spring and summer proxy temperature data suggest differences in the duration of the cold period of the Little Ice Age. The spring temperature was 1–3°C colder throughout most of the period between ca. AD 1400 and 1700, and the summer temperature was 1–2°C colder throughout most of the period between ca. AD 1400 and 1920. Fluctuations in the depth of the lower boundary of the NC have been investigated by examining grain size data and benthic foraminiferal assemblages. The data show that the transition depth of the lower boundary of the NC was deeper between ca. AD 1400 and 1650 than after ca. AD 1750 until present. Copyright © 2003 John Wiley & Sons, Ltd.     

Submarine-spring controlled calcification and growth of large Rivularia bioherms, Late Pleistocene (MIS 5e), Gulf of Corinth, Greece

The cyanobacterium Rivularia haematites has calcified to form unusually large (up to 10 m high) bioherms in the Pleistocene Gulf of Corinth. Today R. haematites calcifies only in freshwater environments but these Gulf of Corinth bioherms have a brackish affinity, limited areal extent, and occur within marine deposits. Field relations and preliminary U-series dating suggest a marine isotope stage (MIS) 5e age for the bioherms. This age is compatible with published MIS 5e ages for corals in the marine sediments above the bioherms and is consistent with their current elevation based on average uplift rates. Bioherm growth during MIS 5e constrains their formation during a time of near sea-level highstand when the Gulf of Corinth was marine. Growth cavities in the bioherms are encrusted by brackish tolerant coralline algae. Field mapping of the MIS 5e highstand palaeoshoreline shows the bioherms grew in water <16 m deep. Mg contents of the bioherm calcites, and associated coralline algal skeletons, are both much lower than expected for marine MIS 5e carbonates. They are best explained if the calcites precipitated from brackish fluids with Mg/Ca ratios below 2, implying at least 60% input of freshwater with low Mg/Ca ratio. Sr isotopes confirm a strong input of groundwater that had partially equilibrated with Mesozoic limestones. The limited areal extent of the bioherms and their close association with karstified fault scarps suggest that they formed in shallow sea water where freshwater submarine springs delivered CaCO₃ saturated water that promoted rapid calcification of cyanobacteria. Rapid calcification and strong degassing of CO₂ from the spring water resulted in disequilibrium stable isotope compositions for the calcites.     

Compositional diversity of soluble mineralizing matrices in some recent coral skeletons compared to fine-scale growth structures of fibres: discussion of consequences for biomineralization and diagenesis

 In contrast to the purely crystalline model of the coral fibre, a transversal zonation is made visible within fibres by specific preparations (enzymatic or light acidic etchings). This growth zonation that corresponds to the successive positions of the secretory ectoderm during septal development shows that crystallization of coral fibre is controlled not only by an external organic coating of fibres, but also includes intra-fibrous organic components. This results in a micron-scaled internal structure of fibres, with a noticeable diversity depending on species. In parallel, soluble matrices also exhibit significant differences, although the global high content in acidic amino acids is always observed. Gathering these two sets of data allows the current ideas concerning structures and growth modalities of coral septa to be discussed. Basically, the respective role of centres of calcification and fibres during septal development appears clearly different from the current ideas, resulting in significant change in interpretation of coral structures, with concerns in both skeleton formation and understanding of diagenetic processes. Received: 2 November 1998 / Accepted: 10 May 1999     

黄龙嗜冷细菌胞外琥珀酸组分对碳酸钙矿化的影响

为探索黄龙钙华的生物成因,本研究以黄龙嗜冷细菌的胞外特征有机酸组分——琥珀酸为研究对象,通过模拟黄龙水体的低温沉积环境,利用X射线粉末衍射(XRD)和扫描电镜(SEM),考察了琥珀酸对钙化体系中的钙化动力学过程、碳酸钙晶型和形貌的影响。结果表明： ① 高浓度琥珀酸、低pH值,低温都会在一定程度上抑制碳酸钙沉积。② 高浓度琥珀酸可以诱导球霰石型碳酸钙的形成; ③ 高温促进了体系中碳酸钙微晶的聚合。综上可见,黄龙嗜冷细菌的胞外琥珀酸组分在一定程度上参与了碳酸钙的沉积过程,对晶体的晶型和形貌具有一定的调控作用。其结果可为黄龙钙华生物成因的探究提供理论基础。     

南沙珊瑚礁对大气CO2含量上升的响应

本文利用南沙海域的碳酸盐化学以及相关调查资料，分析了表层CaCO3饱和度的分布特征，通过碳酸盐的热力学计算模式，定量评估了未来大气CO2增加对表层CaCO3饱和度的潜在影响，利用CaCO3饱和度与珊瑚钙化速率的经验关系式，进一步预测了珊瑚礁对大气CO2上升可能产生的生物地球化学响应．初步结果显示，工业革命前至2100年，南沙海域的CaCO3饱和度将下降43％左右，从而将引起珊瑚礁的平均钙化速率减少33％．如果未来大气CO2浓度继续保持目前的上升趋势，南沙海域珊瑚礁可能会停止生长，甚至某些造礁生物面，临灭绝的危险．     

丛生盔形珊瑚共生体及骨骼的形态研究

"共生"和"钙化"一直是珊瑚生物生态学研究中两个最核心的问题,为加深对珊瑚共生和钙化生物过程的理解,以丛生盔形珊瑚(Galaxea fascicularis)作为研究模型,通过透射电镜和扫描电镜研究珊瑚共生体的细胞显微结构及骨骼的形态特征,并利用电感耦合等离子体质谱(Inductively Coupled Plasma...     

Bacteria-Induced Cementation Process in Loose Sand Medium

Several conventional methods for treatment of soil are available for engineers. The most widely used method includes solution/grout, but they alter the ground pH level and could be toxic. In order to avoid the potential environmental harms and make use of naturally occurring microorganisms, biological methods to improve the engineering properties of soils have been intensely studied. This article presents the results of a research project in which Sporosarcina pasteurii (formerly known as Bacillus pasteurii) was used to induce biological cementation in loose sand medium. The bacteria was injected into sand, which led to the development of cementation (calcium carbonate crystal) between sand grains. The calcification was observed using a scanning electron microscope (SEM).     

颗石藻Emiliania huxleyi对升温和温度波动响应的株间效应

在全球气候变化的背景下,极端天气频发,海洋生物也将受到环境异质性的影响,即环境条件基于平均水平的震荡变化。为研究温度波动变化对海洋碳循环中的重要种群颗石藻的影响,采用半连续培养的方式对海洋颗石藻优势种赫氏颗石藻(Emiliania huxleyi)的非钙化株系与钙化株系分别进行模拟培养实验,探究颗石藻在低(20℃)和高(25℃)平均温度下对升温及温度波动变化的响应。结果表明,升温与温度波动对两株E.huxleyi的生长均起到了抑制作用,而升温和温度波动变化对两株E.huxleyi的生长速率以及胞内碳水化合物含量、非钙化株系的颗粒有机碳含量及钙化株系的蛋白质和颗粒物无机碳含量、碳氮比及沉降速率产生了显著的交互效应,温度的波动变化在一定程度上增强了颗石藻应对升温的适应性。通过对两株系的生理响应结果进行对比分析,发现非钙化株系各生理参数对升温和温度波动变化更为敏感,表明颗石藻的钙化作用可能对其应对环境波动下的极端环境条件起缓冲保护作用。升温和温度波动变化显著削弱了颗石藻的沉降速率,可能会对颗石藻相关的海洋碳沉降与输出产生显著的削弱效应。因此,为了更准确地预测海洋颗石藻对气候变化的响应,未来相关研究需要考虑叠加在升温基础上的温度波动变化对颗石藻的生理生态学效应。     

锌在人体病理性矿化灶中分布的地球化学讨论

Zn是人体必需的微量元素之一,与疾病的发生发展关系密切。目前,Zn在人体病理性矿化灶中的分布尚不明确。本文利用同步辐射X射线荧光分析和成像技术,对乳腺癌、乳腺纤维腺瘤、乳腺增生症、乳腺炎症、卵巢浆液癌、主动脉钙化和冠状动脉钙化等病灶中的矿化物共28例中的元素含量和分布进行了测试分析,发现Zn与Ca在矿化灶中的分布总体一致,部分区域此消彼长,与Sr-Ca关系相似,提示Zn进入(碳)羟磷灰石晶格占据Ca的位置。 此外,乳腺癌与乳腺良性病变中矿化灶的Ca/Zn(摩尔浓度)值有显著差异(P<0.01),乳腺癌矿化灶中Zn元素含量较高。     

基于人工智能技术的非门控胸部CT平扫对冠状动脉钙化积分的准确性评价

目的：采用人工智能方法,探讨非门控胸部低剂量CT平扫对冠状动脉钙化积分（CACS）评价的准确性。方法：回顾性分析行冠状动脉CTA扫描的100例患者,所有患者均行心电门控钙化积分CT（ECGgated-CT）扫描和常规非门控胸部CT平扫检查,在Siemens后处理工作站采用Agatston钙化积分软件记录心电门控CT钙化积分,采用数坤科技胸部CT人工智能钙化积分软件记录非门控胸部CT平扫的钙化积分。两种扫描方法分别获得Agatston评分,其中包括冠状动脉总评分（TOTAL）,左主干（LM）评分,前降支（LAD）评分,回旋支（CX）评分,右冠状动脉（RCA）评分,采用配对t检验比较两组钙化积分的统计学差异,采用Pearson相关系数分析两组钙化积分的相关性,采用组内相关性系数（ICC）对两组钙化积分的危险度分层进行一致性检验,P<0.05为有统计学显著差异。结果：采用配对t检验比较发现两组方法测量TOTAL,LM、CX、RCA的Agatston积分无统计学显著差异（P<0.05）,LAD的钙化积分两组间有统计学显著差异（P<0.05）,Pearson分析发现两组间TOTAL,LM、CX、RCA、LAD的Agatston积分均有显著相关性。ICC分析发现两组所获的Agatston钙化积分在危险度分层方面具有较好的一致性,组内相关系数为0.938,P<0.001。结论：基于人工智能技术的非门控胸部CT平扫对冠状动脉钙化积分的评价具有较高的准确性,在危险度分层方面与传统门控检查一致性很好,可用于冠心病风险的筛查评估。