Efficacy of a multi-metric fish index as an analysis tool for the transitional fish component of the Water Framework Directive

The WFD has introduced an international commitment to assess the ecological status of transitional waters (TWs), within which fish communities are a key biological monitoring component. The Transitional Fish Classification Index (TFCI) outlined in this paper uses 10 ecological measures to analyse fish populations caught from various ecological niches using a variety of gear types within the Thames estuary. These reach and method-specific communities are then compared to a reference population created from a 'healthy' population from TWs of a similar type. The results indicate a progressive downstream increase the quality of fish communities, consistent with previous work; variation between methods can be accounted for by gear selectivity. Overall, the TFCI is an effective communication tool for converting ecological information into an easily understood format for managers, policy makers and the general public.     

Environmental transformation of the Bilbao estuary,N. Spain: microfaunal and geochemical proxies in the recent sedimentary record

The distribution and abundance of benthic foraminifera and a range of elements have been analysed in six long cores (up to 10 m long) from the Bilbao estuary, N. Spain, to document environmental transformation of this estuarine ecosystem and to determine sediment contamination levels. Three different environmental zones could be distinguished in the recent sedimentary record based on its microfaunal and geochemical contents. Initially, a pre-industrial zone containing very abundant and diverse foraminiferal assemblages together with baseline metal levels. Secondly, an older industrial zone exhibiting co-existence of abundant and diverse foraminiferal assemblages with high concentrations of metals. Finally, a younger industrial zone with extreme concentrations of metals and barren of indigenous foraminifera. This environmental transformation has been caused by the discharge of untreated domestic and industrial effluents during the last 150 years. The occurrence of foraminifera in the two industrial zones and along the estuary is not related to defined levels of metals, and this seems to confirm oxygen limitation as the key factor to explain complete estuarine defaunation during deposition of the younger industrial zone (period 1950-2000). Effectiveness of current regeneration schemes could be assessed using microfaunal and geochemical proxies as environmental quality indicators.     

An evaluation of hemolymph cholinesterase activities in the tropical scallop,Euvola (Pecten) ziczac,for the rapid assessment of pesticide exposure

The use of sequential measurements of hemolymph cholinesterase activities as a non-invasive biomarker of seasonal organophosphate/carbamate exposure was investigated for the tropical scallop, Euvola (Pecten) ziczac. Overall activities of both acetylcholinesterase and butyrylcholinesterase were relatively high compared to studies with bivalve tissues. Acute in vivo experiments showed inhibition of hemolymph acetylcholinesterase activity at concentrations of the organophosphate insecticide chlorpyrifos of 0.1, 1 and 10 ng l(-1). Monthly sampling of hemolymph from scallops at two sites in Bermuda over a 15 month period showed seasonal acetylcholinesterase and butyrylcholinesterase inhibition. Direct and indirect evidence suggests that this inhibition did not relate to biochemical or physiological changes associated with gonad maturation and spawning, but rather reflected diffuse contamination of the marine environment by cholinesterase inhibitors or increased bioavailability of such inhibitors at these times. Repetitive sampling of scallop hemolymph for cholinesterase activities represents a rapid, sensitive and non-invasive method for assessing seasonal, sublethal pesticide exposure in these commercially important bivalves and suggests a wider use in marine pollution monitoring.     

Effects of antifouling paint components (TBTO,copper and triazine) on the early development of embryos in cod (Gadus morhua L.)

To assess the risk of antifoulant use to the commercially important cod (Gadus morhua L.), fertilised cod eggs were exposed to triazine, copper and TBTO singly or combined in laboratory tests with running seawater. At the highest tested concentrations (11.5 microg Cu l(-1); 5 microg TBTO l(-1)) larval mortality was increased. The highest concentration of triazine (40 microg l(-1)) did not cause any significant mortality. Fertilised eggs that had been exposed to all the three chemicals singly for five days showed a higher buoyancy than the controls. No synergistic or antagonistic effects were indicated. Embryos/larvae exposed to 0.004-0.8 microg TBTO l(-1) did not show any changed respiration compared to the controls after hatching. It is concluded that existing known field concentrations of the three antifoulants are hardly expected to cause detectable effects on fish embryonic/larval development.     

由兰德斯和赫克托矿地震的地震波触发的地震

加州1992年兰德斯7.3级地震和1999年赫克托矿7．1级地震的接近和相似允许人们对触发地震的假设进行检验，而这在以前是不可能的。赫克托矿地震证实了对兰德斯地震所提出的推断：瞬时、振荡的“动态”形变以地震波的形式辐射，能触发地震活动速率的增加(Hill，et al，1993；Anderson，et al，1994；Gomberg and Bodin，1994；Spudich，et al，1995；Gomberg，1996；Gomberg and Davis，1996)。在本文中，我们对地震活动速率的空间和时间变化(Matthews and Reasenberg，1988)进行了量化。在兰德斯地震的北部地震活动速率增加，而对赫克托矿地震这种增加主要发生在震中以南。我们认为破裂方向性分别使兰德斯和赫克托矿断层的北方和南方动态形变提高，这可以由地震波速度场的不对称性得到证明。对于触发作用，动态和静态应力变化都很重要，距离较远处动态应力变化起主要作用。峰值波速证明了动态触发闽值的存在，并约束了动态触发闽值的范围。在大多数地区，这个阈值依赖当地的条件，从零点几到几MPa变化，超过静态闽值一个量级以上。在某些地点触发过程直到动态形变平息了之后才开始。这些观测现象的物理机制可能与导致液化和循环疲劳的机理相似。     

岩石破裂实验研究中强震发生前主破裂形成时能量释放过程的分析

分析用方程Q（t)=Q(t1) A1-A2(tf-t)^m[1 ccos(2πlog(tf-t)/p-φ)]来模拟强震前地震能量释放过程的一些条件，式中的Q（t)是在时间t以前所累积的“贝尼奥夫”总应变，tf是主震的时间，A1，A2，c,m,p,ψ都是模型的参数，Q（t1)是已知量（t1≤tf时）。表明在一定假定条件下幂指数m=α（2-d) 1。这里d是主震周围地震潜在震源群震中的尺寸，参数α决定着幂律。根据这个规律，地震时释放的地震能量和总能量的比值随地震的震级而变化。模型可用于分析实验研究岩石破裂释放声能的动力学，也适用于对堪察加一些强震前地震活动性的回溯性分析。     

基于变分自动编码器的探地雷达噪声压制及双曲线识别

受仪器设备和环境的影响,使用探地雷达(GPR)进行数据采集的过程中会引入各种不同的噪声,从而干扰目标体反射信号,对数据处理及解释造成困难.由此,本文提出了一种能够同时实现GPR剖面数据噪声压制及双曲线异常识别的变分自动编码器(VAE)神经网络结构.首先,详细阐述了模型结构、数据集建立及网络参数选择;然后,通过合成数据实验验证该算法的有效性及模型的泛化能力,相比于深度卷积自动编码器(CDAE),本文算法在噪声压制能力和双曲线识别能力上均表现更优;最后,通过对隧道衬砌和管线的实测数据进行处理,验证了本文算法的实用性.     

晚第四纪中亚高山湖泊的演化

中亚晚第四纪商山湖泊的演化受到复杂的气候波动釤响,主要由水汽的变化、湖盆冰川作用和径流与 流址的变化而引起的。冷干条件伴随右融水补给的减少和湖退;暖湿条件引起了冰川的后退,增加了融水补给,引起湖进。分布于不同海抜高度的天山和帕米尔竑原地区的湖泊,普遍处于较干旱的环境中,通过对湖盆地貌学、冰川和湖泊沉积物的分布和成份的研究、以及对湖泊沉积物的孢粉分析和埋藏植物碎屑的^l4C年代测定,可以里违晚贝新世以来益山湖泊的演化阶段和中亚高山区的古地理环堍。22000-17000a B.P.,天山查特尔库尔湖和帕米尔喀拉湖为外流淡水湖,面积超过目前的2-3倍。湖泊沉积物中孢粉以干草原植被为主,反映气候较暖湿。16000-11000a B.P.,冻川活动达到极盛,气候寒冷、干燥,湖泊干涸、消失。孢粉频率低,以旱生植物花粉为主。10000-8000a B.P.,温度、湿度提中湿植物和蒿属相对藜科增加,开始湖进。查特尔库尔湖水位较今高12m,面积超过现今3倍;8000—4000a B.P.,天山和东帕米尔的湖盆气侯相对暖湿。4000—3500a B.P.,气候变干,旱生植物花粉增加。3000a B.P.以来以气候干旱化为特征,植被以高山干草原和草原-荒漠为主。1500a B.P.以来气候更趋干早,干旱植物花粉增加,湖水位下降,一直持续至今。据历史和考古资料,公元14-16世纪天山气候暖干化,发生湖退;17—18世纪天山和帕米尔湿度增加,出现湖进。目前该地区湖水位普遍处于下降时期,仅若干冰融水补给湖泊有湖进的迹象。