底栖硅藻生物膜附着基对扇贝幼虫附着和变态的影响

为了建立生态、高效的扇贝幼虫附着和变态诱导技术,采用底栖硅藻生物膜附着基对栉孔扇贝和海湾扇贝开展了附着和变态诱导的现场实验。实验围绕底栖硅藻在扇贝幼虫培育池内的数量变动、存活状态、在栉孔扇贝食谱组成中的贡献以及其对两种扇贝附着和变态的诱导效果开展。结果表明,底栖硅藻附着基能极显著提高海湾扇贝和栉孔扇贝幼虫的附苗量和变态率(P<0.01)。在海湾扇贝实验中,底栖硅藻处理组比对照组附苗量提高220.19%(P<0.01),变态率和壳长两组差异不显著(P>0.05)。在栉孔扇贝实验中,底栖硅藻处理组比对照组附苗量提高43.02%(P<0.01),变态率提高87.31%(P<0.01),底栖硅藻处理组壳长和对照组差异不显著(P>0.05)。对照组附着基比对照组早3d检查到变态的稚贝。底栖硅藻附着基在进入幼虫培育池的黑暗环境后光合作用受限,对于扇贝幼虫的日常管理导致底栖硅藻脱落,数量有一定的下降,但丰度最终能保持为56.0-183.9个/mm2。使用基于混合模型对栉孔扇贝稚贝食物来源进行分析结果显示金藻Isochrysis galbana对稚贝的食物贡献较高,底栖硅藻的贡献较低,其0.95水平的置信区间的贡献率为0%-44%,表明底栖硅藻也是扇贝物来源之一。本研究为底栖硅藻生物膜在贝类幼虫附着变态过程中作用的研究奠定了良好的基础,并为生态、高效的商业化苗种培育提供理论和技术支撑。     

氮磷硅对咖啡双眉藻和缢缩菱形藻繁殖速度和油脂积累的影响

采用光密度法和尼罗红染色法,探索了氮、磷、硅对从温州海区分离出的底栖硅藻咖啡双眉藻(Amphora coffeaeformis)和缢缩菱形藻(Nitzschia constricta)的繁殖速度和油脂积累的影响。结果显示,2种底栖藻在NO3-N质量浓度为1.746 mg/L时,细胞均不繁殖,且在实验第7天开始死亡,当NO3-N质量浓度再升高后,细胞繁殖速度开始加快,质量浓度达8.820 mg/L后,藻细胞的繁殖速度不再明显加快;2种藻类的繁殖速度均随H2PO4-P质量浓度升高而加快,但当质量浓度达到0.884 mg/L后,藻细胞的繁殖速度不再明显加快;2种底栖藻类均随Si O3-Si质量浓度增加而加快,但质量浓度对2种底栖硅藻细胞繁殖速度影响并不显著。3种元素对2种底栖硅藻繁殖速度的影响力:NPSi。实验期间,2种底栖硅藻的油脂含量均呈先降后升的变化规律,油脂的积累主要集中在实验后期,氮磷硅限制均能促进2种底栖硅藻细胞油脂的积累,对2种硅藻细胞油脂积累的影响程度,氮限制比磷和硅限制都要大。     

氧含量及附着面积对海洋底栖硅藻生长和胞外多聚物的影响

胞外多聚物(extracellular polymeric substance, EPS)是海洋底栖硅藻在水下表面附着时分泌的物质,环境因素对胞外多聚物的组成和分泌行为有直接影响,本文重点探讨了氧含量和附着面积对胞外多聚物的影响。采用热溶剂浸提法提取硅藻胞外多聚物,利用苯酚-硫酸法定量其中的多糖成分,利用考马斯亮蓝G-250法定量蛋白质成分,通过血球计数板法和紫外分光光度法计算细胞数量。结果表明,在氧含量高、可附着面积大的条件下,硅藻的生长繁殖速率快,且单个细胞的胞外多聚物分泌量大。氧含量对胞外多聚物主要成分中的水溶性多糖含量影响大,而对其余成分含量影响小。可附着面积对硅藻附着和生长的影响比氧含量影响小。     

象山港潮间带底栖硅藻的分布及其与环境关系探讨

于2005年5月和11月对浙江省象山港潮间带底栖硅藻进行采样调查,分析了底栖硅藻的种类组成、丰度、优势种、多样性及群落结构的季节变化和平面分布特征.并讨论了底栖硅藻与水温、营养盐、潮汐等环境因子之间的关系.共鉴定硅藻33属124种.硅藻数量分布随季节变化明显,春季细胞丰度高于秋季.主要优势种为柱状小环藻(Cyclotella stylorum),春、秋季平均占总细胞数的25.8%.种类的季节变化反应硅藻对水温的适应性,潮汐、盐度、pH值对底栖硅藻组成影响并不明显.秋季营养元素含量升高,多样性指数降低.     

三种海洋硅藻胞外多聚物形态、微细结构及组成的初步研究

利用光镜和扫描电镜对厦门近海三种常见附着硅藻——爪哇曲壳藻亚缢变种(Achnanthes javanica var．subconstricta)、咖啡形双眉藻(Amphora coffeaeformis)和多枝舟形藻(Nav-icula ramosissima)胞外多聚物(Extracellular polymeric substances,EPSs)的形态和微细结构进行了研究,并初步分析了其化学组成。结果表明,A．javanica var．subconstricta的胞外多聚物为透明的长柄,分为领、柄及垫状物三部分,电镜显示其徽细结构为由许多纤维组成的双层实心管;Amphora coffeaeformis分泌的EPS为由串连的小节组成的实心管状结构,许多管交织成厚的胶质块;Navicula ramosissima的EPSs则为透明的薄膜并形成胶质膜。三种硅藻胞外多聚物的水溶性和水不溶性的主要成分均为多糖类,达总量的70％以上,蛋白质含量次之．不含脂类物质,但不同藻类EPS的组成差异较大。此外,还探讨了EPSs的功能及其分泌机理。     

盐度和pH对底栖硅藻胞外多聚物的影响

研究了盐度和pH值对底栖硅藻新月筒柱藻(Cylindrotheca closterium(Ehr.)Reimannet Lewin)增殖、蛋白质含量和胞外多聚物(Extracellular Polymeric Substances,EPS)的影响.结果表明新月筒柱藻最适生长的盐度和pH值分别是15和8,属半咸水性生活.高盐度(>15)和低pH值(相似文献   

马尾藻多不饱和脂肪酸提取、分离及成分分析

采用超声波细胞破碎和索氏回流相结合的方法对马尾藻(Sargassum sp.)总脂质进行了提取,对提取过程中的超声波细胞破碎功率和时间、料液比、溶剂等关键因素进行了优化;对总脂质中的多不饱和脂肪酸进行了分离,并分析了马尾藻脂肪酸组成成分和含量。结果显示,总脂质的最佳提取条件为超声破碎功率80 W、破碎时间20 min、料液比(m/m)1:8、石油醚(60~90℃)为溶剂、85℃水浴回流8 h;总脂质最高提取率为1.77%,其中总脂肪酸平均含量为30.84%;总脂肪酸中共含有11种成分,多不饱和脂肪酸含量约占13.21%~14.60%;薄层色谱分离出2种多不饱和脂肪酸C18:2ω6和C20:4ω6。     

羊栖菜岩藻聚糖硫酸酯的提取纯化和化学组成研究

研究分析羊栖菜岩藻聚糖疏酸酯化学组成,为产品研制开发提供理论依据。采用稀酸提取和乙醇沉淀的方法得到羊栖菜岩藻聚糖硫酸酯粗品,粗品通过Q-Sepharose F.F.阴离子交换树脂进行分级纯化,得到硫酸基含量不同的3个组分(F-1,F-2和F-3),并对这3个组分的总糖、硫酸基、糖醛酸、氨基糖的含量及中性单糖组成和得率等进行了全面的分析。结果表明,羊栖菜岩藻聚糖硫酸酯主要由岩藻糖、半乳糖、甘露糖、葡萄糖及少量的鼠李糖、木糖和阿拉伯糖组成。3个组分中F-3的硫酸基含量最高(40.2%)但得率太低(0.8%);F-1的总糖(68.4%)和糖醛酸(17.9%)含量最高;3者氨基糖的含量均很低(≤1.0%);F-1,F-2和F-3相对分子质量分别约为210 000,160 000和140 000,F-2和F-3的纯度较高。     

海绵内生真菌胞外多糖理化性质及自由基清除活性研究

从1株海绵内生真菌(Alternaria sp.)链格孢菌的发酵液中提取胞外多糖,对其进行Q Sepharose FF离子交换色谱分离纯化,得到2个组分JJY-W和JJY-S。运用各种化学方法及波谱方法对JJY-W和JJY-S的理化性质及结构进行分析,并对多糖清除自由基活性进行了评价。结果表明,JJY-W和JJY-S的分子量分别为1.4KD和1.8KD;JJY-W以半乳糖、葡萄糖为主,含有少量甘露糖,摩尔比为:甘露糖∶葡萄糖∶半乳糖=1∶2.5∶11。JJY-S以甘露糖、葡萄糖为主,含有少量半乳糖,摩尔比为:甘露糖∶葡萄糖∶半乳糖=3∶2∶1。JJY-W总糖含量为46.3%,未检测出糖醛酸,蛋白含量为2%。JJY-S总糖含量为52%,糖醛酸含量为6.1%,蛋白含量为14%。活性分析表明,2种多糖均具有一定的体外抗氧化活性,并随着浓度的增加清除自由基能力均增强,JJY-W清除DPPH自由基的活性要强于JJY-S,而JJY-S清除OH.自由基的活性要强于JJY-W。     

我国典型潮间带底栖硅藻群落空间分布特征

底栖硅藻是河口、泥质海滩生态系统的重要生物类群,其数量与分布变化直接或间接地影响到多种海洋生物的饵料供给、海鸟的生存与迁徙。通过对我国从南到北14个典型潮间带表层沉积物中底栖硅藻的分析,共鉴定出硅藻153种,其物种多样性（Shannon-Weaver 指数范围:1.61~4.39）与生物量（范围:0.09×103 ~ 10×103个/g,干质量）在空间上存在显著差异;聚类分析与相似性分析检验（r=0.738,P=0.1%< 0.01）表明,14个调查区域的硅藻群落在空间上可分为4个大的组合,分别对应着渤、黄、东、南海4个区域,吻合了我国近海浮游植物的地理分布特征。与环境因素的相关性分析表明,底栖硅藻群落的物种多样性与生物量受沉积物类型与盐度的影响显著,泥质区域更有利于硅藻的保存,而生物多样性在泥砂质低盐区域相对较高。此外,底栖硅藻生物量与表层沉积物中TOC含量表现出显著正相关性;δ13C数值的空间变化范围为-25‰~-20‰,指示了有机质陆海混合的特征,其中,涧河河口、黄河口、大沽河口、苏北浅滩区域,δ13C数值明显偏正,表明底栖硅藻可能是这些区域沉积物中有机碳的重要贡献者。     

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.     

Assessing the Validity of Seismo-Acoustic Predictor Equations for Obtaining Seabed and Sub-Surface Sediment Physical Properties

The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths.     

A Review of Some Environmental Issues Affecting Marine Mining

This article reviews information recently available from existing marine and coastal mining for responses to environmental issues affecting marine mining at different depths. It is particularly but not exclusively concerned with those issues affecting seabed biodiversity impact and recovery. Much information has been gathered in the past 10 years from shallow mining operations for construction aggregate, diamonds, and gold, from coastal mines discharging tailings to shallow and deep water, and from experimental deep mining tests. The responses to issues identified are summarized in a series of eight tables intended to facilitate site-specific consideration. Since impacts can spread widely in the surface mixing layer SML, and can affect the biologically productive euphotic zone, the main issues considered arise from the depth of mining relative to the SML of the sea. Where mining is below the SML, the issue is whether it is environmentally better to bring the extraction products to the surface vessel for processing (and waste discharge), or to process the extraction products as much as possible on the seabed. Responses to the issues need to be sitespecific, and dependent on adequate preoperational environmental impact and recovery prediction. For deep tailings disposal from a surface vessel, there are four important environmental unknowns: (1) the possible growth of "marine snow" (bacterial flocs) utilizing the enormous quantities of fine tailings particles (hundreds or thousands of metric tons per day) as nuclei for growth, (2) the possibility that local keystone plankton and nekton species may migrate diurnally down to and beyond the depth of deep discharge and hence be subjected to tailings impact at depth, (3) the burrow-up capability of deep benthos and their ability to survive high rates of tailings deposition, and (4) the pattern and rate of dispersion of a tailings density current through the deep water column from discharge point to seabed. Actions to obtain relevant information in general and site-specifically are suggested.     

Increased Particle Fluxes at the INDEX Site Attributable to Simulated Benthic Disturbance

Particle fluxes were measured 7 m above the sea bottom during the predisturbance, disturbance, and postdisturbance periods by using time series sediment traps attached to seven deep-sea moorings deployed in the INDEX experiment site in the Central Indian Basin. The predisturbance particle fluxes varied between 22.3 to 55.1 mg m -2 day -1 . Increased and variable particle fluxes were recorded by the sediment traps during the disturbance period. The increase observed was 0.5 to 4 times more than the background predisturbance fluxes. The increases in particle fluxes (~4 times) recorded by the sediment trap located in the southwestern direction (DMS-1) were the greatest, which could be the result of preferential movement of resuspended particles generated during the deep-sea benthic disturbance along the general current direction prevailing in this area during the experimental period. Also, the traps located closer to the disturbance area recorded greater fluxes than did the traps far away, across the Deep Sea Sediment Resuspension System path. This variability in recorded particle fluxes by the traps around the disturbance area clearly indicates that physical characteristics such as grain size and density of the resuspended particles produced during the disturbance had an important effect on particle movement. The postdisturbance measurements during ~5 days showed a reduction in particle fluxes of ~50%, indicating rapid particle settlement.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification

An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm.     

Determination of In Situ Sediment Shear Strength from Advanced Piston Corer Pullout Forces

The advanced piston corer (APC) has been used by the Ocean Drilling Program since 1985 for recovering soft sediments from the ocean floor. The pullout force measured on extracting the core barrel from the sediment is shown to correlate with the average shear strength of the sediment core measured in the ship's laboratory. A simple rule of thumb is derived relating the shear strength of the sediment to the pullout force. Multiple APC holes at individual sites allow the consistency of the pullout measurements to be assessed. The effects of different operational procedures during APC coring are also explored. Although generally applicable, the correlation between pullout force and laboratory measurements of shear strength breaks down for some APC holes, possibly because of the disturbance of some sediment types during the APC coring process. A better understanding of the physical process of APC coring, and its effect on the properties of the sediment both inside and immediately outside the core barrel, would indicate what confidence can be put on the measurement of pullout force as a way of evaluating the in situ shear strength of deep sea sediments.     

Interannual Sea Level Variations and Annual Tides in the Northwestern Pacific

Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone.     

Flow Cytometric Analysis of Coastal Lagoon Bacterioplankton and Picophytoplankton: Fixation and Storage Effects

The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics.