Sharks caught in the KwaZulu-Natal bather protection programme,South Africa. 14. The smooth hammerhead shark Sphyrna zygaena (Linnaeus)     

ML Dicken  H Winker  MJ Smale  G Cliff 《African Journal of Marine Science》2018,40(2):157-174

The current study provides long-term catch-rate, biological and feeding data for smooth hammerhead sharks, Sphyrna zygaena, caught in South Africa’s KwaZulu-Natal bather protection programme. In total, 2 512 S. zygaena were caught in net installations between 1978 and 2014, and 72 S. zygaena were caught on drumlines between 2007 and 2014. There was no significant log-linear year trend in the net catch rate over time (slope = 0.0054, t = 1.808, p = 0.07). However, there was a significant temporal increase in mean size of the captured sharks (slope = 0.0012, t = 3.502, p < 0.001). A quasi-Poisson generalised additive mixed model showed that increasing latitude, winter months, colder sea temperatures and the deployment of drumlines all had a significant positive effect on the catch rate of sharks in nets. The size frequency of the catch was unimodal, with significantly more females caught in the nets and more males on the drumlines. The majority (93.1%) of all sharks caught were immature and measured between 80 and 120 cm precaudal length. Teleosts and cephalopods dominated the sharks’ diet in terms of all dietary indices. The prey species consumed indicate that immature S. zygaena are feeding primarily within the pelagic zone of shallow coastal habitats.  相似文献   

海洋沉积物黏土矿物相对含量不同计算方法对比研究     

舒雨婷  刘志杰  余佳  孔敏  田先德  刘升发 《海洋通报》2019,(5):585-590

海洋沉积物黏土矿物相对含量计算存在多种计算方法,并不统一,限制了异源黏土矿物的整合和使用。文章选取了两种较为常见的计算方法,即Biscaye和国标中规定的计算方法,分别对东印度洋109个表层样品黏土矿物的相对百分含量进行计算,分析对比了两种方法计算结果之间的差异。结果显示,两种计算方法结果存在显著正相关,都能显示黏土矿物分布的变化趋势,4种黏土矿物相关系数由高到底分别为:蒙皂石0.986、伊利石0.974、绿泥石0.924、高岭石0.923。相对于Biscaye计算方法,国标计算方法会增加伊利石和高岭石的相对百分含量而降低蒙皂石和绿泥石的相对百分含量。两种计算方法黏土矿物的含量相关性较好,可以建立起相互数学转换关系式。但在不同的海区,由于矿物成因、结晶程度以及混层矿物的出现可能会使衍射峰形态发生改变,从而相关性系数和转换关系也会相应发生改变。  相似文献   

Burial and degradation of organic carbon in Louisiana shelf/slope sediments     

Troy P. Sampere  Thomas S. Bianchi  Mead A. Allison  Brent A. McKee 《Estuarine, Coastal and Shelf Science》2011

The primary focus of this paper is to better understand carbon burial on the Louisiana continental margin using spatial scales that covered various shelf depositional areas far-field and near-field (sediment and organic carbon inputs relative to river mouth proximity) and covering a variety of sedimentation rates. Box-cores samples were collected in July 2003; cores were collected along two depositional transects extending westward and southward from the Southwest Pass (SW Pass). A key difference between the two transects sampled in this study was the greater occurrence of mobile muds derived from spillover from shallower regions along the westward 50 m isobaths. The dominant mechanism for mixing in the surface active zone (SAZ) on the inner Louisiana shelf was due to physical, not biological, forces. Burial efficiencies for organic carbon (57.2–91.5%) and total nitrogen (44.2–86.9%) ranged widely across all shelf stations. Lower burial efficiencies for bulk organic carbon, total nitrogen, and pigment biomarkers were associated with mobile muds west of Southwest Pass. Chlorophyll a concentrations were significantly higher than pheopigments at depth at the Mississippi River and Southwest Pass stations, making up 40.4 and 77.4% of total pigment concentrations in the (SAZ) and 46.2 and 63.2% in the accumulation zone (AZ), respectively. These results are in agreement with earlier plant pigment studies which showed that a large fraction of the phytodetritus delivered to the inner shelf was derived from coastal and river diatoms. The amount of lignin preserved with depth decreased with increasing residence time in the SAZ and diagenetic zone (DZ) along the canyon transect but not along the western transect. Trends for lignin concentration followed previously identified surface sediment trends indicating overall lower burial of refractory terrestrial material at depth with greater distance offshore.  相似文献   

Phytoplankton pigment patterns and community composition in the northern South China Sea during winter   总被引：1，自引：0，他引：1  

�Ժ��  ������  ��ѧ��  ����  �ַ��  �Ǿ� 《中国海洋湖沼学报》2011,29(2):233-245

Phytoplankton pigment patterns and community composition were investigated in the northern South China Sea using high-performance liquid chromatography and the CHEMTAX software from February 11 to 23, 2009. We recognized four different vertical distribution patterns of pigments: chlorophyll a (Chl a)-like type, divinyl chlorophyll a (DV Chl a) type, even distribution type, and surface type. The average value of ratios of accessory photo-protective pigments (APP) to accessory photo-synthetic pigments was 0.89±0.63 in the upper 50 m and 0.16±0.06 below 50 m depth. With increasing depth, APP decreased and photo-synthetically active radiation was attenuated. There was an obvious succession in the phytoplankton community from inshore to the open sea. Diatoms were dominant in the inshore region, while pelagophytes, Prochlorococcus, cyanobacteria and prymnesiophytes were dominant in the open sea. The vertical distribution of phytoplankton also differed greatly from inshore to the open sea. In the coastal and shelf region, diatoms were important components in the whole water column. Cyanobacteria also had a high abundance at the Subsurface Chlorophyll a Maxima (SCM) in the shelf region. In the slope and open sea, Prochlorococcus and cyanobacteria were important groups above the SCM, while pelagophytes dominated below the SCM.  相似文献   

粗粒土三轴试验数值模拟与试样颗粒初始架构初探   总被引：4，自引：1，他引：3  

王光进  杨春和  张超  马洪岭  冒海军  侯克鹏 《岩土力学》2011,32(2):585-592

试样颗粒初始架构是粗粒土室内三轴试验中一个难以人为控制的因素。基于元胞自动机方法,结合粗粒土的室内三轴试验开发了能制备不同颗粒初始架构粗粒土试样的HHC-CA模型,该模型制备的粗粒土试样表征了粗粒土各粒组分布的不均匀性和随机性,再借助FLAC3D进行粗粒土三轴数值模拟试验,并探讨了试样剪切带内的砾石含量和试样砾石含量对内摩擦角的影响。数值模拟结果表明,同一粒径级配下,粗粒土的内摩擦角值与剪切带内的砾石含量呈增函数关系;试样砾石含量的增加可能会出现内摩擦角减小的现象,但同一粒径级配下的内摩擦角均值随试样砾石含量的增加而明显增大。  相似文献   

发光细菌法在环渤海污水样品遗传毒性检测中的应用     

崔志松  栾晓  高伟  李倩  杨官品  郑立 《海洋与湖沼》2015,46(1):228-232

建立了以经过遗传改造的发光细菌Acinetobacter sp.Rec A为受试物种的环境污染物遗传毒性快速检测方法,该方法最快可在3h内得到毒性评价结果。采用该方法评价了环渤海排污口12份污水样品的遗传毒性。环渤海12个排污口的污水样品均表现出了不同水平的遗传毒性,并呈现出一定的分布特征。其中,高毒水质集中出现在山东半岛污水样品中,中毒水质集中出现在辽东半岛地区,而低毒水质主要集中于京津冀地区。综上,在环渤海的污水样品遗传毒性检测中,这种新型发光细菌法具有快速、灵敏、简便等优点,可为以后近海环境的水质生物毒性检测提供参考依据,具有应用于近海环境水质快速监测与评价的潜力。  相似文献   

浮游植物化学分类法—CHEMTAX运算在南中国海应用的改进和优化   总被引：3，自引：1，他引：2  

王磊  黄邦钦  柳欣  肖武鹏 《海洋学报(英文版)》2015,34(2):124-131

In order to determine the phytoplankton community composition, the modification and optimizing of the CHEMical TAXonomy (CHEMTAX) running was carried out through samples grouping, successive run and ev...  相似文献   

番红砗磲外套膜色素提取条件优化及成分分析     

付正祎  刘二田  顾志峰  石耀华  王爱民  吴川良  刘春胜 《海洋科学》2019,43(6):71-77

以番红砗磲(Tridacna crocea)为实验对象,通过单因素对比实验对其外套膜色素的提取条件进行了优化,并利用薄层层析色谱法对色素组成进行了初步分析。结果表明:丙酮和乙醇为适宜的番红砗磲外套膜色素提取剂;使用丙酮为提取剂时,浸提时间为4 h,提取温度为25℃,料液比为1︰40。使用乙醇为提取剂时,浸提时间为4 h,提取温度为30℃,料液比为1︰200;利用薄层色谱法分离外套膜颜色为蓝色和红棕色的番红砗磲外套膜色素后发现,蓝色番红砗磲外套膜色素由9种色素组分构成,红棕色个体番红砗磲外套膜色素由10种色素组分构成。  相似文献   

Fragility and risk assessment of freestanding building contents     

Michalis Fragiadakis  Spyridon Diamantopoulos 《地震工程与结构动力学》2020,49(10):1028-1048

Multistorey buildings often have a valuable inventory consisting of objects that their possible damage during an earthquake will cause unacceptable losses. The paper presents a novel, fully performance-based seismic reliability and risk assessment framework for freestanding structural components and contents that can be modelled as rocking rigid blocks. The seismic response of building contents depends on several parameters such as the geometry of the object, the dynamic characteristics of the building and the storey that the object is located. The demand at the storey level is first obtained, and then the response of the contents is calculated using the storey acceleration response history. The demand of the structure is obtained with the aid of a modified version of the Incremental Dynamic Analysis method and subsequently the fragility curves of the rocking building contents are derived for every storey of interest. Different options for fragility assessment are discussed, and the underlying details of the problem are investigated. A simplified approach, where the fragility of the freestanding components and the structure are derived separately, is also presented. The method combines existing fragility curves and thus is suitable for quickly assessing the reliability of a building's inventory, offering sufficient risk estimates.  相似文献   

用多层感知器模型由吸收光谱反演浮游植物色素   总被引：1，自引：0，他引：1       下载免费PDF全文

周雯  曹文熙  王桂芬  梁少君  赵俊  孙兆华 《热带海洋学报》2010,29(2):46-51

浮游植物吸收光谱已逐渐成为高光谱水色遥感的可获取参量。文章采用了多层感知器模型, 由珠江口担杆群岛附近水体的浮游植物吸收光谱进行了色素浓度的反演, 感知器的输入量是浮游植物吸收光谱, 输出量分别对应叶绿素a、叶绿素b、叶绿素c、光保护类胡萝卜素和非光保护类胡萝卜素五大类主要色素的浓度。分析结果表明, 叶绿素a和叶绿素c估算结果的平均相对偏差比较低, 在测试数据集中两者的偏差分别为19.06%和15.90%; 光保护类胡萝卜素和非光保护类胡萝卜素的估算浓度的相对偏差比较高, 对于测试数据而言, 分别为37.62%和36.96%; 叶绿素b浓度在测试数据集中的估算相对偏差约为27.47%。五大类色素在测试数据集和训练数据集的估算偏差比较接近, 已训练好的多层感知器可用于担杆岛水体中色素信息的反演。同时, 此色素反演方法也为遥感监测水体浮游植物种群动态提供了重要的手段。  相似文献