Ecological Differences in the Distribution of two Tethya (Porifera, Demospongiae) Species Coexisting in a Mediterranean Coastal Lagoon

Abstract. In the Sicilian lagoon Stagnone di Marsala, Tethya aurantium and T. citrina show different ecological distributions, although some overlapping occurs. The first species reaches its highest density where linear currents are maximal, and in this habitat it is particularly frequent on Posidonia oceanica rhizomes. The second species is more abundant in still water locations and is equally common on Posidonia rhizomes and on calcareous concretions. Such distributions can be related to water movement, Posidonia shoot density, and associated factors such as sedimentation and food availability. These observations are consistent with an adaptive interpretation of the morphofunctional features distinguishing the two species.     

浙江沿岸海域虾类优势种空间生态位分析

生态位与种间竞争、资源利用密切联系，体现了物种在群落中利用资源的能力。为探明浙江沿岸海域虾类分布格局的形成和影响因素，通过相对重要性指数确定了虾类群落优势种，分别采用Levins公式和Pianka指数计测了虾类优势种生态位宽度和生态位重叠，并通过典范对应分析（CCA）研究生态位分化情况。结果表明:研究海域共出现13种虾类优势种，根据生态位宽度大小将研究海域内的虾类优势种分为3类，细巧仿对虾、细螯虾、鲜明鼓虾和中华管鞭虾属于第一类群，以上4种虾类的空间生态位宽度较宽；日本鼓虾、哈氏仿对虾、鹰爪虾、中国毛虾和葛氏长臂虾属于第二类群，这5种虾类空间生态位略低于第一类群，但其生态位仍相对较宽；戴氏赤虾、脊腹褐虾、东海红虾和大管鞭虾这4种虾类的空间生态位较窄，属第三类群；生态位重叠指数变化范围在0.00~0.78，将重叠指数按照大于0.6、0.3~0.6和小于0.3划分为重叠度较高、重叠度较低和重叠度低3个重叠度等级，结果表明，虾类优势种生态位重叠以较低和低2个等级为主；虾类分布受水深、底层溶解氧和底层盐度的影响较大，受水温影响较小。虾类群落优势种空间生态位与生活习性、种间竞争、摄食以及海洋环境因子等多种因素有关。     

舟山近岸海域主要甲壳类的生态位及其与种间联结性

本文基于2015年11月（秋季）和2016年5月（春季）在舟山近岸海域开展80个站位的渔业资源调查所获得的甲壳类资料，将调查海域划分为10个区域，并随机分层抽样选取20个站位进行分析。运用生态位测定、典范对应分析（CCA）、方差比率（VR）、卡方检验、联结系数、种对共同出现百分比、点相关系数等方法进行研究。结果表明:研究海域主要甲壳动物共19种，其中优势种3种，重要种6种。通过生态位宽度聚类分析可将主要甲壳类划分成3类，包括广生态位种、中生态位种和狭生态位种。生态位重叠值区间为[0，0.96]，表明物种对资源利用的相似性差异较大，部分甲壳动物存在资源利用性竞争。CCA排序显示，该海域甲壳类受环境因子中盐度、温度以及叶绿素a影响较大。VR值为4.40大于1，统计量W值为87.91超出置信区间（10.85，31.41），得出甲壳类动物群落总体呈显著正相关，卡方检验显示有61个种对的联结性显著（x2 ≥ 3.841），联结系数（AC）、共同出现百分比（PC）以及点相关系数（Ф）表明种间联结性较强，总体趋于正相关。     

辽东湾西海岸潮间带大型底栖动物群落生态位特征

基于2014年9月和2015年4月辽东湾西海岸潮间带10个断面3个潮区的调查数据,对12个优势种的生活型、生态位宽度和生态位重叠度进行了分析,结果表明:12个优势种分别隶属于3门4纲12科;面上生活类群和面下生活类群的比值GS/GSB表现为春季秋季;秀丽织纹螺、日本大眼蟹和丽核螺的生态位宽度较宽(2.171、2.170和2.169),猫爪牡蛎和短角双眼钩虾的生态位宽度较窄(0.637和0.173);生态位重叠较为显著的种类有四组,均是生态位宽度较宽的物种。以上结果也从一个侧面反映了底栖生物对季节和生境的适应情况,由于季节变化和生境不同,使物种生态位宽度值发生了变化,从而影响物种之间的生态位重叠值。     

浙江象山东部海域夏季大型底栖动物优势种群和生态位

为了解象山东部海域夏季大型底栖动物群落特征及种间相互作用情况,于2012年8月(夏季)对象山东部海域30个站位进行了大型底栖动物的调查研究。共采集,鉴定大型底栖动物36种(优势种20种),隶属于7门8纲24科,节肢动物15种(41.7%)最多,脊索动物7种(19.4%)次之。聚类分析和MDS排序结果表明,象山东部海域夏季大型底栖动物可以分为4个生态类群。选取Levins生态位宽度指数和Pianka重叠指数进行生态位分析,结果表明:象山东部海域夏季大型底栖动物优势种生态位宽度变化范围为5.22—21.66,生态位宽度值最高的为东方口虾蛄(21.66),最小的为小荚蛏(5.22);Pianka重叠指数大于0.60的优势种占19.5%,多样的生境以及生物本身的适应能力差异,使该海域大型底栖动物优势种的生态位重叠值偏小,减小了种间的竞争。该海域大型底栖动物优势种夏季生态位结构的形成主要与优势种的活动能力有关。     

Savonius型桨叶水动力特性研究

Savonius桨叶是一种典型的垂直轴阻力型桨叶,在风力发电中广泛应用。这种桨叶具有在多风向作用下单向转动的特性。利用该特性,将其应用于捕获水质点运动方向发生周期性或非周期性改变的波浪能的相关研究。采用Fluent数值仿真软件并基于UDF二次开发技术建立桨叶三维数值模型,分析叶片重叠率、相对入水深度和开口率等参数对桨叶动转矩和功率等水动力特性的影响,搭建实验平台,开展物理模型对照试验。研究结果表明:叶片重叠率有助于减小S型桨叶负转矩;当桨叶在水面上高度与波幅相等时,其功率系数达到最大;在叶片上增加弹片阀开口,可以增大桨叶动转矩系数,当开口面积达到一半时,动转矩系数比未开口桨叶提高28.3%。     

Influence of Ice Size Parameter Variation on Hydrodynamic Performance of Podded Propulsor

During ice-breaking navigation, a massive amount of crushed ice blocks with different sizes is accumulated under the hull of an ice-going ship. This ice slides into the flow field in the forward side of the podded propulsor, affecting the surrounding flow field and aggravating the non-uniformity of the propeller wake. A pulsating load is formed on the propeller, which affects the hydrodynamic performance of the podded propulsor. To study the changes in the propeller hydrodynamic performance during the ice podded propulsor interaction, the overlapping grid technique is used to simulate the unsteady hydrodynamic performance of the podded propulsor at different propeller rotation angles and different ice block sizes. Hence, the hydrodynamic blade behavior during propeller rotation under the interaction between the ice and podded propulsor is discussed. The unsteady propeller loads and surrounding flow fields obtained for ice blocks with different sizes interacting with the podded propulsor are analyzed in detail. The variation in the hydrodynamic performance during the circular motion of a propeller and the influence of ice size variation on the propeller thrust and torque are determined. The calculation results have certain reference significance for experiment-based research, theoretical calculations and numerical simulation concerning ice podded propulsor interaction.     

Relative importance of estuarine nurseries for species of the genus Diplodus (Sparidae) along the Portuguese coast

The relative importance of estuarine nursery areas for species of the genus Diplodus and their relations with several environmental variables was evaluated along the Portuguese coast. Nine estuarine systems were sampled with beam trawl surveys. Species of the genus Diplodus were only present in estuaries south of the Ria de Aveiro (40°38′). A latitudinal gradient of increasing species richness and abundance towards the south was found. Estuarine nurseries of Diplodus vulgaris, Diplodus sargus and Diplodus puntazzo were characterized by mud substrate, lower salinity and lower dissolved oxygen, with the exception of Ria Formosa. Diplodus bellottii was associated with estuaries with large areas and high volumes, the Tejo and the Sado. Diplodus bellottii nursery grounds were characterized by low depth. Diplodus annularis was associated with seagrass and saltmarsh habitats, certainly because it is the only species of the genus Diplodus which recruits exclusively to seagrass meadows. Diplodus annularis nursery grounds were also characterized by sand substrate, higher salinity and higher dissolved oxygen. Niche breath varied widely amongst species and location. Diplodus vulgaris generally presented the highest values of niche breath, except when D. bellottii was present. Niche overlap was not high, the highest value being that between D. vulgaris and D. sargus in the Mira estuary, with 76% spatial niche overlap. Considerations were made on these species progress towards the north in a climate warming context, taking into account the habitat associations described here.     

基于扫描统计的甲型H1N1流感聚集性分析

扫描统计已被广泛应用于地域性疾病的聚集性检测,且可检测这种聚集的差异显著性。文中使用扫描统计的方法,通过对2009~2012年全国各省的甲型H1N1流感数据进行时空扫描以及逐年的空间扫描,生成高发病率地区和低发病率地区聚类,并通过叠置分析反映各个地区归入聚类的频次。利用专题地图和统计表分析甲型流感在2009~2012年中的爆发情况和趋势,并对结果进行客观的分析。     

“天绘一号”卫星基于摄影任务的轨道维持策略

针对靶标场等摄影任务受轨道维持影响大的现状, 提出基于摄影任务的轨道维持策略。分析了卫星轨道特性和轨道维持对重要摄影任务的影响, 提出利用邻轨搭接特性对摄影区域完成两次摄影的方法。通过某靶标场摄影试验, 比较分析得到最优摄影方案, 验证了本文方法的可行性。同时完善卫星轨道维持策略, 作为卫星实施轨道维持的重要参考依据。