Reassessing the invasion of South African waters by the European shore-crab Carcinus maenas     

CA Mabin  JRU Wilson  JJ Le Roux 《African Journal of Marine Science》2017,39(3):259-267

The European shore-crab Carcinus maenas has been present in South Africa since 1983. Despite this species’ international reputation as a biological invader, its distribution in this region has only been considered by three outdated ‘snapshot surveys.’ The present study is the most comprehensive to date, providing an update on the species’ range and the first temporal assessment of its abundance and demographics. Along South Africa's Cape Peninsula and surrounding areas, C. maenas was absent from 12 intertidal sites surveyed, except for Sea Point, and no crabs were found during subtidal surveys along the open coastline. Subtidal harbour populations were recorded in the Cape Town harbours of Table Bay and Hout Bay (previously estimated as comprising approximately 164 200 and 6 500 individuals, respectively). Table Bay was surveyed monthly for one year, using baited traps, crab condos and postlarvae settlement collectors, to assess size distributions and reproductive seasonality of the crab. Reproductive females were recorded throughout most of the year. These results suggest that the harbour populations could be targeted by control programmes, but provide no strong evidence to support the initiation of management action during a particular season. The lack of detection of postlarval settlement, even among well-established populations, suggests this will not be a useful monitoring tool for detecting incursions.  相似文献   

秘鲁南部阿雷基帕段海岸岩基带找矿方向探讨     

沃特&#;卡约  丹德&#;索贝龙  刘君安  米瑞安&#;玛玛尼  里多&#;罗德里格斯  郭维民  丹尼尔&#;多特  阿兰&#;桑多 《地质通报》2017,36(12):2275-2286

通过详细的岩相学和锆石U-Pb年龄的研究,秘鲁海岸岩基带阿雷基帕段的填图工作得到了补充,该岩基带岩浆活动可分为7个阶段和4个旋回,各阶段都显示出不同的岩浆容量,其地貌主要表现为岩基和岩脉。旋回Ⅰ和旋回Ⅱ代表侏罗纪岩浆活动阶段（201~145Ma）,岩浆分异为辉长岩到花岗岩;旋回Ⅲ和旋回Ⅳ代表白垩纪岩浆,岩浆分异为英云闪长岩-二长花岗岩、闪长岩与花岗闪长岩及英云闪长岩-花岗闪长岩。对角闪石和黑云母矿物晶体的数量关系研究表明,旋回Ⅰ的侵入岩有大量辉石和角闪石结晶,并伴随金-铁成矿作用;旋回Ⅱ有大量的群集角闪石晶体和呈定向排列或群集的六边形黑云母,且伴随铜-金-铁成矿作用;旋回Ⅲ侵入岩内发育角闪石和黑云母,伴随着金-铜和铁成矿作用;旋回Ⅳ发育大量角闪石和六边形黑云母,岩石更偏长英质,并伴随铜-锌-金-银-铁和铜-金-钼成矿作用。  相似文献   

浑善达克沙地榆树种群结构、格局及动态研究   总被引：7，自引：6，他引：1  

赵丽  王晓江  刘果厚  牛海亮  潘臻 《中国沙漠》2009,29(3):508-513

以浑善达克沙地榆疏林为研究对象,研究了沙地榆疏林种群结构、分布格局与动态特征。结果显示：①丘间低地沙地榆种群呈衰退型种群。固定沙丘沙地榆种群呈增长型种群;②沙地榆种群总体分布格局呈聚集分布,都随着尺度的增大,聚集强度呈减小的趋势;③种群空间分布动态分析表明,丘间低地沙地榆种群,幼、中树随着立木级增大其聚集强度逐渐减弱,大树则在5 m×5 m尺度上呈现出随机分布;固定沙丘沙地榆种群,小、中树随着立木级的增大其聚集强度呈现逐渐增强的趋势,而大树则在10 m×10 m的尺度上呈现出随机分布。物种分布格局主要与物种本身的生物生态学特性和生境有关,育林作业面积应不低于25 m²。  相似文献   

气泡半径和含量对含气泡海水声波速度的影响     

李灿苹  刘学伟  杨丽  何静  卢良鑫 《现代地质》2010,24(3):528-533

通过对含气泡的海水水体声波速度的研究,分析了气泡半径和含量对海水声波速度（声速）的影响。气泡半径与海水深度的关系为,随着海水深度变浅,气泡半径逐渐增大。声速与气泡半径的关系为：气泡含量很小时,随着气泡半径的增大,声速先逐渐增大,然后保持平稳,最后缓慢减小,且声速变化幅度较小;气泡含量逐渐增大时,随着气泡半径的增大,声速都逐渐增大,且气泡含量不同,声速变化范围不同。声速与气泡含量的关系为：气泡含量较小时,气泡含量增加,声速逐渐减小;气泡含量较大且气泡半径小于临界半径时,气泡含量增加,声速逐渐减小,气泡半径大于临界半径时,气泡含量增加,声速先减小后逐渐增大,并且在气泡含量逐渐增大的不同阶段,声速的变化范围不同。  相似文献   

空化水射流破碎岩石的机理研究   总被引：9，自引：1，他引：8  

卢义玉  李晓红  向文英 《岩土力学》2005,26(8):1233-1237

在不同泵压和淹没压力条件下,针对不同类型的空化喷嘴,对空化水射流的空泡云特性和破碎岩石机理进行了一系列实验研究,探讨了空化水射流的空泡云与冲蚀能力之间的相互关系。优化空化喷嘴结构和工作条件以减小泵压,从而降低输入能量。空泡云的可视化研究显示缩放形喷嘴产生的空化云的长度和宽度比收敛形喷嘴的大。研究表明,空化水射流切割破碎岩石主要是由空泡的溃灭引起的,空泡云的长度等于靶距与切割深度之和;在切割破碎岩石时冲蚀效果只在开始几秒内发生,冲蚀深度并不随时间而增大。  相似文献   

European quaternary refugia: a factor in large carnivore extinction?     

Hannah J. O'Regan  Alan Turner  David M. Wilkinson 《第四纪科学杂志》2002,17(8):789-795

The extinction of large carnivores in Europe during the Quaternary is reviewed and the potential role of glacial refugia in these extinctions is investigated using the VORTEX model for population viability analysis. A model was built for a medium sized big cat similar to the extinct Panthera gombaszoegensis utilising life history data from the modern jaguar Panthera onca. This approach highlighted the potential importance of glacial refugia in the extinction process. Even model refugia the size of the Italian peninsula did not guarantee persistence of a population over a 1000 yr time span, illustrating the role of chance in survival in such a refugium. An area the size of the largest Mediterranean island was unable to support a big cat population for a period of 1000 yr. The models also demonstrated the importance of inbreeding as a mechanism for extinction in refugia. It is suggested that repeated genetic bottlenecks during successive glaciations would tend to remove lethal recessive alleles from the population, increasing the probability of survival in refugia in subsequent glaciations. The history of extinction of large carnivores in the European Quaternary is interpreted in the light of these results. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Distribution and characterization of Chilean populations of the brine shrimp Artemia (Crustacea, Branchiopoda, Anostraca)     

Oscar Zuñiga  Rodolfo Wilson  Francisco Amat  Francisco Hontoria 《International Journal of Salt Lake Research》1999,8(1):23-40

Hypersaline habitats in Chile, from marine solar salt pans to saline lagoons and pools in Andean salars, were prospected in search of Artemia populations. These saline ecosystems were characterized through physico-chemical parameters and ionic composition of their brines. Biometrics of cysts and nauplii, as well as morphometrics by using multivariate discriminant analysis for adult specimens evidenced that the Chilean populations of brine shrimp belong to A. franciscana. Cross-breeding results supported the former hypothesis of conspecific Chilean populations, and their differences with A. persimilis, also endemic to the New World, but restricted to Argentinean sites.  相似文献   

不同地理种群大黄鱼染色体核型的比较研究   总被引：7，自引：0，他引：7  

王德祥  苏永全  王世锋  王军 《海洋学报》2006,28(6):176-178

大黄鱼(Pseudosciaena crocea(Richardson)),隶属于鲈形目(Perciformes),石首鱼科(Scieani-dae),黄鱼属(Pseudosciaena),是我国重要的海水养殖种类.近年来,经过长期的人工繁育和人工养殖,大黄鱼的性状有了较大的变化.主要表现为个体小型化,性成熟提前,抗病力下降等.目前有关大黄鱼遗传背景的研究还十分缺乏,相关的研究仅见于国内学者对养殖、野生大黄鱼的染色体核型、同工酶酶谱、不同群体遗传多样性水平的研究[1~7],这些研究多是针对我国沿海3个大黄鱼地理种群之一的闽粤东族进行的.  相似文献   

近岸破碎波水体掺气及气泡输运过程研究     

邓斌  唐瑶  蒋昌波  王孟飞 《热带海洋学报》2018,37(6):33-40

为准确探讨破碎波作用下气体如何卷入以及气泡的形成与输运特性, 文章结合粒子图像测速技术(particle image velocimetry, PIV)、高速相机和气泡测量系统, 以及基于Navier-Stokes方程的三维数值模型对气泡形成及其运动过程进行研究。研究结果表明: 文章建立的数值模型能合理地捕捉到破碎波作用下气体的卷入及其输运过程; 波浪的破碎会形成较大的气腔, 其破裂过程又将产生大量的气体微团; 气泡会增加水体的紊动, 造成水体与空气交界面附近形成大量的漩涡以及水体的飞溅; 气泡的破裂会消耗大量的水体能量, 同时发现较大的紊动动能与气泡的生成有关, 且气泡数随平均紊动动能的增加呈线性增长关系。  相似文献   

Genetic variability analysis in five populations of the sea cucumber Stichopus (Apostichopus) japonicus from China,Russia, South Korea and Japan as revealed by microsatellite markers     

Yaqing Chang  Zhigang Feng  Jiaping Yu  Jun Ding 《Marine Ecology》2009,30(4):455-461

The genetic structure of populations of the sea cucumber Stichopus (Apostichopus) japonicus was investigated using 10 microsatellite markers. In all, 152 individuals from five natural populations were collected from Aomori, Japan (JA and JR), Yosu, South Korea (KY), Dalian, China (CD) and Vladivostock, Russia (RV). A total of 145 alleles were found at 10 loci. The number of alleles per locus ranged from 9 at PSC03 to 20 at SCZ06, with an average of 14.5. Average H_o and H_e ranged from 0.260 (JR) to 0.434 (JA) and from 0.654 (RV) to 0.778 (KY), respectively. No significant differences at A, H_o and H_e were found, indicating similar genetic diversity in the five populations. A single allele was found at the PSC05 locus in the RV population. Of the 50 loci, 42 significantly deviated from Hardy–Weinberg equilibrium, all showing heterozygote deficiency. The genetic distances were all relatively great, ranging from 0.497 (between JA and KY) to 1.029 (between KY and JR). This suggests the five populations are genetically distinct. Cluster analysis indicated that JA, KY and CD form one branch and RV and JR another in the UPGMA tree. A hypothesis is proposed for the evolution of the Japanese red sea cucumbers and the genetic relationship among the populations.  相似文献