The Loyalty—New Hebrides Arc collision: Effects on the Loyalty Ridge and basin system,Southwest Pacific (first results of the ZoNéCo programme)

The ZoNéCo 1 and 2 cruises of Ifremer's Research Vessel L'Atalante, collected new swath bathymetry and geophysical data over the southern and northern segments of the basins and ridges forming the Loyalty system. Between the two surveyed areas, previous studies found evidence for the resistance of the Loyalty Ridge to subduction beneath the New Hebrides trench near 22°S–169°E. On the subducted plate, except for seismicity related to the downbending of the Australian plate, recorded shallow seismicity is sparse within the Loyalty system (Ridge and Basin) where reliable focal mechanism solutions are almost absent.Swath bathymetry, seismic reflection and magnetic data acquired during the ZoNéCo 1 and 2 cruises revealed a transverse asymmetric morphology in the Loyalty system, and an along-strike horst and graben structure on the discontinuous Loyalty Ridge. South of 23°50S and at 20°S, the two WSW-ENE-trending fault systems, respectively, sinistral and dextral, that crosscut the southern and northern segments of the Loyalty system, are interpreted as due to the early effects of collision with the New Hebrides Arc. A NNW-SSE trend, evident along the whole Loyalty system and on the island of New Caledonia, is interpreted as an inherited structural trend that may have been reactivated through flexure of the Australian lithospheric plate at the subduction zone.Overall then, the morphology, structure and evolution of the southern and northern segments of the Loyalty system probably result from the combined effects of the Australian plate lithospheric bulge, the active Loyalty-New Hebrides collision and the overthrust of the New Caledonian ophiolite.     

Two new species of Lecithochirium LUKE, 1901(Trematodes: Hemiuridae)

1.Lecithochiriumfukenensissp.nov.(Fig.1)(Basedon6wholemounts)ThisspiceswascollectedinthestomachofTrichiurushaumelafromXiamenandNan'ao.Bodydividedintosomaandecsoma.Soma1,31~3.48×0.426~1.05(2.69×0.737),ecsoma0.22~0.80(0.448)longwhenprotruded,usuallycomple…     

一种提高粘土矿物去除赤潮生物能力的新方法

在研究粘土颗粒与赤潮生物絮凝作用的基础上，建立了粘土表面改性对其絮凝作用影响的理论模型，认为改变粘土颗粒的表面性质提高其去除赤潮生物能力的主要途径，提出在粘土中引入ＰＡＣＳ（聚羟基氯化铝）的改性方法。结果表明，对于微型原甲藻（Ｐｒｏｒｏ－ｃｅｎｔｒｕｍ ｍｉｎｉｍｕｎ）体系，粘土中引入微量ＰＡＣＳ后，其去除率达９０％以上的高岭土用量由原来的２ｇ／Ｌ降至０．１ｇ／Ｌ，去除效率提高近２０倍。考察了ＰＡ     

Correspondence between the distribution of hydrodynamic time parameters and the distribution of biological and chemical variables in a semi-enclosed coral reef lagoon

Hydrodynamic modeling can be used to spatially characterize water renewal rates in coastal ecosystems. Using a hydrodynamic model implemented over the semi-enclosed Southwest coral lagoon of New Caledonia, a recent study computed the flushing lag as the minimum time required for a particle coming from outside the lagoon (open ocean) to reach a specific station [Jouon, A., Douillet, P., Ouillon, S., Fraunié, P., 2006. Calculations of hydrodynamic time parameters in a semi-opened coastal zone using a 3D hydrodynamic model. Continental Shelf Research 26, 1395–1415]. Local e-flushing time was calculated as the time requested to reach a local grid mesh concentration of 1/e from the precedent step. Here we present an attempt to connect physical forcing to biogeochemical functioning of this coastal ecosystem. An array of stations, located in the lagoonal channel as well as in several bays under anthropogenic influence, was sampled during three cruises. We then tested the statistical relationships between the distribution of flushing indices and those of biological and chemical variables. Among the variables tested, silicate, chlorophyll a and bacterial biomass production present the highest correlations with flushing indices. Correlations are higher with local e-flushing times than with flushing lags or the sum of these two indices. In the bays, these variables often deviate from the relationships determined in the main lagoon channel. In the three bays receiving significant riverine inputs, silicate is well above the regression line, whereas data from the bay receiving almost insignificant freshwater inputs generally fit the lagoon channel regressions. Moreover, in the three bays receiving important urban and industrial effluents, chlorophyll a and bacterial production of biomass generally display values exceeding the lagoon channel regression trends whereas in the bay under moderate anthropogenic influence values follow the regressions obtained in the lagoon channel. The South West lagoon of New Caledonia can hence be viewed as a coastal mesotrophic ecosystem that is flushed by oligotrophic oceanic waters which subsequently replace the lagoonal waters with water considerably impoverished in resources for microbial growth. This flushing was high enough during the periods of study to influence the distribution of phytoplankton biomass, bacterial production of biomass and silicate concentrations in the lagoon channel as well as in some of the bay areas.     

Ecology of beach wrack in northern New England with special reference to Orchestia platensis

The northern New England beach wrack community with special reference to the cosmopolitan amphipod crustacean, Orchestia platensis, was examined at estuarine and open coastal habitats. Beach wrack was dominated by the plant genera Ascophyllum, Zostera, Spartina and Chondrus, and was most abundant during spring and late summer. Animal community numbers, biomass and frequency in fresh to moderately decomposed wrack were dominated by O. platensis throughout the year at all habitats; oligochaetes and Collembola were also important. The abundance of O. platensis showed high spatial and temporal variability, with low abundance generally associated with decreased amounts of wrack during colder months. An exception was the winter presence of the species at one estuarine habitat, in patchy aggregations within gravel-cobble refuges. The abundance of O. platensis averaged 1280 (0.04 m²)⁻¹, with a maximum of 7040 (0.04 m²)⁻¹. The life cycle of O. platensis is bivoltine, with summer-hatched young reaching maturity within 1 month. Laboratory studies indicate females with up to 4 broods (30 days)⁻¹, averaging 18 eggs brood⁻¹.Orchestia platensis is omnivorous, eating fresh plant tissue, live oligochaetes, Limulus eggs and diatom ‘fuzz’. The rate of laboratory consumption of algae and Zostera was 0.05 mg plant mg⁻¹ wet body weight day⁻¹. Presumptive predators of O. platensis are juvenile green crab, Carcinus maenus, and the earwig. Anisolabis maritima. The mobility, aggregation and aggressiveness of O. platensis assist the species in establishing and maintaining populations in the rigorous wrack habitat. The general competitive superiority of O. platensis over its congener, O. gammarella, and the co-occurrence of these species on both eastern and western Atlantic shores is discussed.     

基于神经网络方法的芦苇叶面积指数遥感反演

提出了一种从TM图像上获取芦苇冠层叶面积指数的方法:首先对芦苇的生长背景进行分类;然后,对不同的背景光谱利用冠层反射率(FCR)模型计算得到查找表;最后,利用实测数据和查找表中的数据作为参数进行BP神经网络模型训练,从而得到芦苇冠层LAI。结果表明,人工神经网络方法有很强的非线性拟合能力,能够消除背景对反演结果的影响,有效提高LAI反演的精度。     

三峡库区高切坡致灾因素及防护对策——以重庆市万州区为例

三峡库区百万移民的搬迁建设导致大量高切坡的形成。未及时治理或治理不当的高切坡,不同程度地发生破坏,影响了人们的正常生活,甚至引发了地质灾害。因此,科学认识及治理高切坡十分必要。重庆市万州区高切坡主要有风化及差异风化、崩塌和土体滑塌等破坏形式。影响破坏的因素主要为工程地质条件、气候及时间效应。针对高切坡不同的破坏形式,以安全、经济及环境和谐的人文理念作为设计指导思想,充分论证了高切坡的防护方案,即：削坡、排水以及格构防护较适合万州区高切坡的防护。这些措施,既能很好地解决高切坡的防护问题,又能兼顾环保、降低造价。研究结果可以作为三峡地区高切坡类地质灾害防护设计的参考。也可为其它流域类似问题借鉴。     

三峡水库区兴山后坝滑坡成因分析

文章通过对三峡水库区兴山后坝滑坡的地质、结构及变形特征研究以及稳定性分析,阐明了该滑坡成因和影响因素。研究发现,滑坡活动主要受地形地貌、地层岩性、人类工程活动以及降雨等因素的影响。运用剩余推力法对比分析天然及暴雨条件下不同层位的滑坡稳定性系数,得出在暴雨作用下滑坡表层滑带稳定性系数最小,不同滑带的稳定性受降雨的影响也各不相同,呈表层〉浅层〉深层的规律;这主要受滑带土的粘土矿物组分的影响。     

钢筋混凝土桩网复合地基沉降计算方法优选

钢筋混凝土桩网复合地基是一种新的地基处理技术。本文对适用于钢筋混凝土桩网复合地基沉降计算的方法进行探讨。