Distribution and Migrations of two Cerithid Snails on a Sand Flat in Bermuda     

Wolfgang  Wieser  Manfred  Grabner Franz  Koch 《Marine Ecology》1981,2(1):63-75

Abstract. Two species of cerithid prosobranchs live on a sand flat in Bermuda. At low tide during day light Batillaria minima is found on the surface whereas Cerithium lutosum remains buried in the sediment. This correlates with much higher lethal and coma temperatures, as well as much greater resistance to desiccation, of the former species. However, at other diurnal or tidal stages the two species co-occur in the same layer of sand. Despite greater resistance to physical factors the population of B. minima seems to be declining since in 1980 juveniles of this species were rare on Tuckers Town Flat whereas the population of C. lutosum was thriving.  相似文献   

Adaptive Ecology, Growth Strategies and the Global Bloom Expansion of Dinoflagellates   总被引：2，自引：0，他引：2  

Theodore J. Smayda 《Journal of Oceanography》2002,58(2):281-294

Dinoflagellates exhibit unique differences from diatoms in their adaptive ecologies that may be favoring their increasingly successful exploitation of coastal waters and global bloom expansion. Dinoflagellates behave as annual species, bloom soloists, are ecophysiologically diverse and habitat specialists, whereas diatoms behave as perennial species, guild members and are habitat cosmopolites. Diatoms have a relatively uniform bloom strategy based on species-rich pools and exhibit limited habitat specialization. Dinoflagellates have multiple life-form strategies consistent with their diverse habitat specializations, but rely on impoverished bloom species pools. Niche structure and dinoflagellate competition for niche space are considered. The “open niche period” formulated originally for Narragansett Bay is extrapolated as a general bloom paradigm. It is suggested that successful niche occupancy leading to blooms involves adaptive strategies at three heirarchic taxonomic elements: phylogenetic, generic and species-specific, and in that sequence. Transoceanic expatriation of emigrant species leading to indigenous status and blooms requires completion of a three-stage colonization process. Anthropogenic seedings are not, in themselves, bloom stimulation events; they are only the first phase of a multiple-step process. The organismal and niche features required for a hidden flora member to become a bloom species are considered, and the interplay between niche structure, habitat carrying capacity, colonization requirements and stochasticity as factors in the changing global bloom behavior of dinoflagellates discussed. The question is posed whether traditional perspectives of phytoplankton behavior apply completely to dinoflagellates. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Niche characterization of dominant estuarine benthic species     

R. Warren Flint  Richard D. Kalke 《Estuarine, Coastal and Shelf Science》1986,22(6)

Benthic macroinfaunal species in a south Texas estuarine environment were studied over a 2·5 year period to characterize their distributions and ecology. The 13 dominant taxa chosen for investigation exhibited distinct habitat usage differences as judged both by the use of discriminant analysis and the differentiation of behavioral characteristics. Species coexistence in the estuarine bethic community of Corpus Christi Bay was examined with respect to resource partitioning for such parameters as food and space. Utilization of these resources by the dominant taxa differed in both temporal and spatial dimensions, with the spatial dimension consisting of horizontal and vertical attributes. Benthic species were separated according to (1) occurrences in certain sediment types with varying organic content, (2) presence in estuarine regions characterized by different phytoplankton productivity rates, (3) different periods of annual occurrence, and (4) occurrence in different sediment microhabitats characterized by varying sediment depth and relation to depth of oxygenated sediments. Superimposed upon differences in habitat usage of these species were behavioral traits, such as feeding differences, which further discriminated how benthic species obtained resources. Based upon species occurrence in a certain characteristic environment, we speculated on the structural division of the benthic habitat by various taxa often classified as common members of the same species' assemblages in the past. Although other investigators have demonstrated interactions among co-occurring benthic infaunal species, the information presented here illustrated how these species could minimize interactions in order to maintain their populations.  相似文献   

杭州湾跨海大桥南航道通航孔通航净空尺度     

徐骏  金允龙 《海洋学研究》2002,20(4):42-49

在杭州湾交通通道预可行性研究阶段的《通航标准论证报告》及杭州湾交通通道有关专题研究成果的基础上,依据浙江省交通厅文件的精神,结合杭州湾的水文、河势、港口、航道等基本状况、条件以及通航船舶现状与未来对通航发展的要求等,确定了杭州湾跨海大桥南航道的通航净空尺度和桥位航道中心线及通航孔的位置。在杭州湾南航道中心线设了3个通航孔,其中1个为主通航孔,2个为副通航孔。主通航孔可通行总长为97m,宽为14m的3000t级杂货船,净空高度不于31m,净空宽度不小于125m,单向通航;副通航孔可通行总长小于33m,宽为7.2m的小型船舶,净空高度不小于20m,净空宽度不小于50m,单向通航。最高通航水位为5.19m。  相似文献   

Tethya (Porifera,Demosponglae) Species Coexisting in a Maldivian Coral Reef Lagoon: Taxonomical,Genetic and Ecological Data     

Michele Sar  Giuseppe Corriero  Giorgio Bavestrello 《Marine Ecology》1993,14(4):341-355

Abstract. Tethya microstella, T. orphei, T. robusta, and T. seychellensis live in sympatry in a Maldivian coral reef lagoon (Gangehi Island, Ari Atoll). A morphological, morphometric, and electrophoretical study of these species show that their Maldivian populations are well separated morphologically and genetically. The genetic distances and the other data are more consistent with an immigration than with a local speciation hypothesis. Their coexistence may be explained by a differentiation in ecological requirements. The four species inhabit the shallow water biotope of the lagoon among the rubble of dead corals. Our data show that T. orphei and T. seychellensis occupy the upper rubble layer, T. microstella and T. robusta the lower one. This distinction agrees with the different morpho-functional features of the two pairs of species.  相似文献   

Urban niche dynamics of Kaifeng city     

Ding Shengyan  Li Zhiheng 《地理学报》2007,17(2):221-233

Niche theory is one of the most important ecological theories. It is widely applied to analyzing such phenomena as competition among, and evolution of, urban ecosystem func-tional modules. This paper describes a study concerning different functional modules of Kaifeng city urban ecosystem. Niche theory and techniques were used to analyze the changes of these functional modules in the period 1994–2003. The results showed that, in the period 1994–2003: (1) Niche value of the atmospheric environment and urban virescence modules increased, while niche value of the water environment and sound environment modules decreased; (2) niche value of the tertiary industry module increased, niche value of the secondary industry module decreased, while niche value of the primary industry module showed little change; and (3) niche value of the infrastructure, resource distribution, and production & social security modules increased, while niche value of the population module decreased. This study may contribute to macroscopic planning of urban functional modules, economic development, and environmental protection.  相似文献   

土地生态经济适宜性评价模型研究   总被引：4，自引：0，他引：4  

俞艳  何建华  袁艳斌 《武汉大学学报(信息科学版)》2008,33(3):273-276

从土地生态经济系统的角度,将土地适宜性评价看作是物种的最适生态位与评价单元所提供的现实生态位之间的匹配,从区域、评价单元以及单元之间关系3个层次构建评价指标体系,并引入模糊贴近度分析方法构建土地生态经济适宜性评价模型.以武汉市黄陂区为实例验证了模型的合理性.  相似文献   

土地经济生态位变化下的城乡空间景观格局表征——以广东省惠州市为例     

吴箐  李宇 《地理科学》2014,34(6):705-710

土地利用变化对生物多样性和生态过程有着深刻的影响,与城乡景观格局变化密切相关。尝试将土地利用变化驱动力——土地经济生态位的理论和方法引入到景观生态学当中,为城乡空间景观格局空间表征提供新的方法。通过选取表征景观格局指标的破碎化指数、分形维数,利用Envi4.8、Arcmap10.0,Fragstasts4.1等软件,以广东省惠州市为例,在分析土地经济生态位与景观类型、景观指数之间的关系基础上,对土地经济生态位变化下的城乡空间景观格局进行表征。结果表明：不同景观土地面积数量的增减与该类型土地经济生态位升降具有一致性的规律,土地经济生态位上升,相应的景观土地面积增大,反之则减小;土地经济生态位越小,表征景观格局的景观破碎化指数、分维数指数越大,破碎化指数与分维数指数的增减与土地经济生态位升降表现出一致性的规律,土地经济生态位上升,相应的破碎化指数、分维数指数则增大,反之则减小;城乡空间景观格局变化的发生主要出现在土地经济生态位高的区域。土地经济生态位的变化是城乡景观格局变化的重要影响因子,能够很好解释城乡空间景观格局特征。  相似文献   

小生境遗传算法在地震CT中的应用研究   总被引：3，自引：1，他引：2  

班书昊  杨慧珠 《地球物理学进展》2004,19(1):143-147

针对含单相饱和流体的孔隙介质,综合费马原理、等效孔隙介质理论、Radon变换等,提出了基于地震CT技术求解速度、孔隙度和岩石密度的小生境多参数反演算法．以此为基础,经过改进,形成了物性参数的隔离小生境反演算法．理论分析与实例计算结果表明,该方法简化了波在层状介质中的传播方程,具有一定的实用价值,可以有效解决井间测井地层问题,获得较高精度的地层物性参数;而且模型简单,有精度高、多峰优化等特点,可用于地下层状介质中油气的寻找,满足油气预测与勘探开发的要求．  相似文献   

古尔班通古特沙漠南缘不同立地条件植物多样性和优势种群生态位特征研究     

班卫强  严成  尹林克  杨美琳  王忠臣 《中国沙漠》2012,32(6):1632-1638

以古尔班通古特沙漠南缘不同立地条件植物群落为研究对象,分析了该区不同立地条件植物群落的种类组成、优势种群及优势种群的生态位特征。结果表明:①不同立地条件的植物群落均为灌木-草本模式,优势种群为梭梭、白梭梭、白皮沙拐枣、羽毛针禾、骆驼刺、琵琶柴、狭果鹤虱、沙蓬、倒披针叶虫实;②由于不同立地条件环境因子差异,造成其植物群落的α多样性指数存在差异;③Whittacker指数与Cody指数显示不同立地条件植物群落β多样性随环境变化可分为两个梯度,第一梯度为垄顶、迎风坡与背风坡上部,第二梯度为平坦荒地、丘间平地与背风坡中、下部;④生态位宽度大的物种间生态位重叠大。在古尔班通古特沙漠南缘进行受损群落植被恢复与重建时,可在适宜的立地条件种植梭梭与羽毛针禾。  相似文献