2010年秋季南海北部浮游植物群落结构研究   总被引：5，自引：0，他引：5  

马威  孙军  薛冰  戴民汉  胡建宇 《海洋学报》2016,38(4):43-53

2010年10月26日-11月24日在南海北部进行了浮游植物群落结构的调查,共鉴定浮游植物4门70属204种(包括未定种12种),浮游植物以硅藻为主,其物种数为146种,其细胞丰度占总浮游植物细胞丰度的93.17%;甲藻次之,其物种数为51种,占总浮游植物细胞丰度的0.63%;金藻门3属4种及蓝藻门2属3种;蓝藻门中以红海束毛藻(Trichodesmium erythraeum)为主。调查区浮游植物的细胞丰度介于0.06×103~107.50×103 cells/L之间,平均值为5.00×103 cells/L。海南岛东北部和粤东近岸表层浮游植物丰度较高。垂直分布上,表层和25 m层的浮游植物细胞丰度较高。浮游植物主要优势种类有菱形海线藻(Thalassionema nitzschioides)、舟形藻(Navicula spp.)、中肋骨条藻(Skeletonema costatum)、旋链角毛藻(Chaetoceros curvisetus)、斯氏几内亚藻(Guinardia stolterforthii)、具槽帕拉藻(Paralia sulcata)等。调查区表层和5 m层Shannon-Wiener多样性指数平均值分别为3.14和2.83,Pielou均匀度指数平均值分别为0.73和0.77;两种指数在表层和5 m层均表现出较高的一致性。环境分析表明除硅酸盐外,浮游植物细胞丰度与其他环境因子均呈极显著性的相关性,主要受到氮元素及磷酸盐的共同限制作用。  相似文献   

Structure and dynamics of demersal fish assemblages over three decades (1985–2012) of increasing fishing pressure in Guinea     

ML Camara  B Mérigot  F Leprieur  JA Tomasini  I Diallo  M Diallo 《African Journal of Marine Science》2016,38(2):189-206

In a context of growing fishing pressures and recommendations for an ecosystem approach to fisheries, there is a need to monitor changes in fish communities over time. In this study, we analysed data from scientific trawl surveys carried out on the continental shelf off Guinea between 1985 and 2012. We performed factorial analyses and calculated biodiversity indices to characterise the changes in the structure and composition of fish communities that occurred over the 28-year period in this area, particularly given intensive fishing activities. We show that, over the study period, fish communities on the Guinean shelf were structured primarily according to spatial factors, with temporal changes being less pronounced than expected. However, a temporal analysis of biodiversity indices and species dominance showed that the intensification of fishing had significant effects on the general ecological features of the fish assemblages under study. There was a decrease in fish density and in mean trophic level. In addition, there were changes in species dominance, whereby large, slow-growing species with high commercial value were gradually replaced by smaller, fast-growing species of lesser commercial interest. These results from field observations are in line with some conclusions from previous modelling studies in the same geographical area, and provide further support for the hypothesis of a progressive ‘ecosystem effect of fishing’ occurring in Guinean waters.  相似文献   

Novel evaluation metrics for sparse spatio-temporal point process hotspot predictions - a crime case study     

Monsuru Adepeju  Gabriel Rosser 《International journal of geographical information science》2016,30(11):2133-2154

Many physical and sociological processes are represented as discrete events in time and space. These spatio-temporal point processes are often sparse, meaning that they cannot be aggregated and treated with conventional regression models. Models based on the point process framework may be employed instead for prediction purposes. Evaluating the predictive performance of these models poses a unique challenge, as the same sparseness prevents the use of popular measures such as the root mean squared error. Statistical likelihood is a valid alternative, but this does not measure absolute performance and is therefore difficult for practitioners and researchers to interpret. Motivated by this limitation, we develop a practical toolkit of evaluation metrics for spatio-temporal point process predictions. The metrics are based around the concept of hotspots, which represent areas of high point density. In addition to measuring predictive accuracy, our evaluation toolkit considers broader aspects of predictive performance, including a characterisation of the spatial and temporal distributions of predicted hotspots and a comparison of the complementarity of different prediction methods. We demonstrate the application of our evaluation metrics using a case study of crime prediction, comparing four varied prediction methods using crime data from two different locations and multiple crime types. The results highlight a previously unseen interplay between predictive accuracy and spatio-temporal dispersion of predicted hotspots. The new evaluation framework may be applied to compare multiple prediction methods in a variety of scenarios, yielding valuable new insight into the predictive performance of point process-based prediction.  相似文献   

Socioeconomic characteristics and crash injury exposure: A case study in Florida using two-step floating catchment area method     

《Applied geography (Sevenoaks, England)》2017

The objective of this study is to investigate the exposure of different population groups to severe injury crash hotspots using an empirical-Gaussian two-step floating catchment area (EG-2SFCA) method based on roadway network distances and a socioeconomic-based weighting approach. This is performed by developing a special form of a crash-to-population ratio index that incorporates the severe crash hotspots relative to the locations of populations they might impact. While identifying these hotspots, four different age groups are considered: 17 and younger, 18 to 21, 22 to 64 and 65 and older. For each age group, severe crash hotspots are identified based on the roadway network and the number of severely injured crash occupants that belong to the specific age group. Using these age-specific crash hotspots and the EG-2SFCA method, communities that were exposed to elevated crash injury risk (crash injury exposure) have been identified. Furthermore, from a residential perspective, a socioeconomic analysis is conducted in order to develop a socioeconomics-based crash injury exposure measure. This measure assesses the exposure of different socioeconomic groups to the risk of being injured. Results demonstrated by applying this measure in the Tampa Bay region, FL show that different population groups are under varying risk of being injured depending on their residential location. The developed approach has the potential to be a social fairness measure able to be applied by agencies, which could enhance the well-being of communities that are subject to elevated injury risk.  相似文献   

Structural analysis of the segmentation of the Central Indian Ridge between 20°30′S and 25°30′S (Rodriguez Triple Junction)     

Anne Briais 《Marine Geophysical Researches》1995,17(5):431-467

The morphological characteristics of the segmentation of the Central Indian Ridge (CIR) from the Indian Ocean Triple Junction (25°30S) to the Egeria Transform Fault system (20°30S) are analyzed. The compilation of Sea Beam data from R/VSonne cruises SO43 and SO52, and R/VCharcot cruises Rodriguez 1 and 2 provides an almost continuous bathymetric coverage of a 450-km-long section of the ridge axis. The bathymetric data are combined with a GLORIA side-scan sonar swath to visualize the fabric of the ridge and complement the coverage in some areas. This section of the CIR has a full spreading rate of about 50 mm yr^–1, increasing slightly from north to south. The morphology of the CIR is generally similar to that of a slow-spreading center, despite an intermediate spreading rate at these latitudes. The axis is marked by an axial valley 5–35 km wide and 500–1800 m deep, sometimes exhibiting a 100–600 m-high neovolcanic ridge. It is offset by only one 40km offset transform fault (at 22°40S), and by nine second-order discontinuities, with offsets varying from 4 to 21 km, separating segments 28 to 85 km long. The bathymetry analysis and an empirical orthogonal function analysis performed on across-axis profiles reveal morphologic variations in the axis and the second-order discontinuities. The ridge axis deepens and the relief across the axial valley increases from north to south. The discontinuities observed south of 22°S all have morphologies similar to those of the slow-spreading Mid-Atlantic Ridge. North of 22°S, two discontinuities have map geometries that have not been observed previously on slow-spreading ridges. The axial valleys overlap, and their tips curve toward the adjacent segment. The overlap distance is 2 to 4 times greater than the offset. Based on these characteristics, these discontinuities resemble overlapping spreading centers (OSCs) described on the fast-spreading EPR. The evolution of one such discontinuity appears to decapitate a nearby segment, as observed for the evolution of some OSCs on the EPR. These morphological variations of the CIR axis may be explained by an increase in the crustal thickness in the north of the study area relative to the Triple Junction area. Variations in crustal thickness could be related to a broad bathymetric anomaly centered at 19°S, 65°E, which probably reflects the effect of the nearby Réunion hotspot, or an anomaly in the composition of the mantle beneath the ridge near 19°S. Other explanations for the morphological variations include the termination of the CIR at the Rodriguez Triple Junction or the kinematic evolution of the triple junction and its resultant lengthening of the CIR. These latter effects are more likely to account for the axial morphology near the Triple Junction than for the long-wavelength morphological variation.  相似文献   

2001年冬季渤海的浮游植物群落结构特征   总被引：17，自引：0，他引：17  

孙军  刘东艳  白洁  高会旺  韩笑天 《中国海洋大学学报(自然科学版)》2004,34(3):413-422

研究了2001年冬季覆盖渤海56个测站的浮游植物物种及其群落特征。共发现浮游植物3门37属72种(不包括未定名物种)。物种主要以温带近岸型硅藻为主，优势种主要尖刺伪菱形藻、浮动弯角藻、偏心圆筛藻、具槽帕拉藻(Parnlia sulcata)和环纹劳德藻。其中的尖刺伪菱形藻、偏心圆筛藻和具槽帕拉藻是冬季渤海浮游植物的关键种。分析认为：细胞丰度的平面分布由浮游硅藻的分布所决定。同1983年同期资料相比发现，优势种没有较大变化，但其优势程度顺序和细胞丰度发生了一定的改变，整个浮游植物群落的细胞丰度有大幅度增加。冬季渤海浮游植物群落的多样性程度是低的。  相似文献   

Indicators for ecosystem-based management on the Scotian Shelf: bridging the gap between theory and practice     

O'Boyle  R.; Sinclair  M.; Keizer  P.; Lee  K.; Ricard  D.; Yeats  P. 《ICES Journal of Marine Science》2005,62(3):598-605

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Effects of fisheries on marine ecosystems: a conservationist's perspective   总被引：4，自引：1，他引：4  

Agardy  Tundi 《ICES Journal of Marine Science》2000,57(3):761-765

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胶州湾及其邻近水域渔业生物多样性的调查研究   总被引：12，自引：7，他引：12  

曾晓起  朴成华  姜伟  刘群 《中国海洋大学学报(自然科学版)》2004,34(6):977-982

根据2003年10月-2004年5月逐月采集胶州湾及其邻近水域作业的定置网和底拖网具渔获物的分析与测定，记述了该海区出现的106种渔业生物，并进行了定置网和底拖网的渔获物组成的比较，分析了种类组成特点及生物多样性的季节变化情况。结果表明，本调查区域渔获物以小型低值鱼类、经济无脊椎动物和经济幼鱼为主，渔获个体偏小。据此提出了保护近海生物多样性与合理利用近海渔业资源的一些建议。本次调查还首次记录了我国黄海沿岸罕见的蛇鳗科鱼类一长吻沙蛇鳗Ophisurusmacrorhynchus，为青岛近海的渔业生物多样性的研究增添了新的资料。  相似文献   

我国的海洋生物多样性及其保护   总被引：20，自引：0，他引：20  

马程琳  邹记兴 《海洋湖沼通报》2003,(2):41-47

本文综述了我国海洋生态系统多样性、海洋物种多样性及其利用以及海洋生物遗传多样性的现状，指出过度捕捞、生境丧失、环境污染、生态入侵是威胁我国海洋生物多样性的主要原因。文本还阐述了我国在海洋生物多样性保护、海洋生态环境监测、海洋自然保护区建设及管理上所取得的成就，以及在海洋生物多样性可持续利用方面所取得的进展。  相似文献