Influence of plankton concentration on gametogenesis and spawning of the black lip pearl oyster Pinctada margaritifera in Ahe atoll lagoon (Tuamotu archipelago, French polynesia)

Pearl culture industry represents one of the dominant business sector of French Polynesia. However, it still entirely relies on unpredictable spat collection success. Our aim was to assess the influence of natural plankton concentration fluctuations on maturation and spawning of the black lip pearl oyster Pinctada margaritifera, during a 4months survey conducted in Ahe atoll lagoon. Plankton concentration was assessed by chlorophyll a extraction and by microscope counts while gonadic index, gonado-visceral dry weights and histology were used to measure pearl oysters reproduction activity. We found that (i) plankton concentration fluctuations were mainly related to wind regime, (ii) gametogenesis rate was mainly related to plankton concentration, (iii) spawning occurred when maximal gonad storage was reached, (iv) plankton concentration was the main spawning synchronizing factor. These results contribute explaining P. margaritifera spat collection variability in French Polynesian atoll lagoon.     

Natural attenuation of septic system nitrogen by anammox

On-site disposal of sewage in septic systems can lead to groundwater plumes with NO(3)(-)-N concentrations exceeding the common drinking water limit of 10 mg/L. Currently, denitrification is considered as the principal natural attenuation process. However, at a large seasonal-use septic system in Ontario (256 campsites), a suboxic zone exists where nitrogen removal of up to 80% occurs including removal of NH(4)(+)-N. This zone has both NO(3)(-)-N and NH(4)(+)-N at >5 mg/L each. In the distal NH(4)(+)-rich zone, NH(4)(+)-N concentrations (8.1 ± 8.0 mg/L) are lower than in the proximal zone (48 ± 36 mg/L) and NH(4)(+)-N is isotopically enriched (concentration-weighted mean δ(15)N of +15.7‰) compared to the proximal zone (+7.8‰). Furthermore, δ(15)N-NH(4)(+) isotopic enrichment increases with depth in the distal zone, which is opposite to what would result if nitrification along the water table zone was the mechanism causing NH(4)(+) depletion. Bacterial community composition was assessed with molecular (DNA-based) analysis and demonstrated that groundwater bacterial populations were predominantly composed of bacteria from two Candidatus genera of the Planctomycetales (Brocadia and Jettenia). Together, these data provide strong evidence that anaerobic ammonium oxidation (anammox) plays an important role in nitrogen attenuation at this site.     

利用气孔大小分布和玻璃地球化学研究约束墨西哥波波卡特佩特火山脱气过程

波波卡特佩特火山爆炸式喷发活动是对周围人口稠密地区的一个严重威胁,因此在短时间内认识喷发类型（从爆炸式到熔岩盾形成）指标的变化是非常重要的。本次研究,我们给出来自波波卡特佩特火山5次主要普林尼武喷发（大约23～1．2ka）、2001年部分熔岩盾坍塌时的小喷发和1997年4次喷发（5月11日、6月14日、15日和30日）产生的原生碎屑中气孔大小分布（VSD）和基质玻璃成分分析的结果。对基质玻璃主元素的分析（WDS—EPMA）可以估计出喷发的岩浆进入不平衡（晶体和岩浆之间）的深度,通过利用Blundy和Cashman（2001）的石英一钠长石一正长石三元系计算平衡压力来获得。利用CSD软件通过气孔大小分布分析定量解释原生碎屑（浮岩或火山渣）结构来建立岩浆上升时的物理变化和喷发条件之间的关系。原生碎屑内气泡化的程度和类型也与喷发的类型和持续时间有关,特别是可用来识别气孔结构的变化,这种变化代表了从爆炸式到熔岩盾喷发的转变（Manganand Sisson,2000;Adamsetal,2006）。本次研究给出了波波卡特佩特火山比早期认为的更为复杂的岩浆存储历史,这对该火山目前的研究是一个重要的贡献。     

几次强震有争议的非双力偶机制：二阶矩方法

地震震源机制（用等效于岩体破裂的力描述震源几何形状及其强度）通常被模拟为矩张量（MT）,将震源描述为一个点。然而,有时这种近似是不够的,因为地震辐射会由于震源的有限范围而持有方向性。转换为矩张量就可能产生有偏差的机制。Adamov和íleny（2010）进行的综合研究说明即使是纯双力偶（DC）震源其机制中也出现假非双力偶分量。他们的方法设计了减少假震源分量,通过二阶矩方法来评估假分量在记录中的影响并将它们从数据中去除。在本文中,我们将这个方法应用到具有大非剪切分量的5个中等到大的区域地震事件。它们大多位于预计主要是纯剪切滑动的大构造断层。我们研究了著名的北安纳托利亚断层上的一个地震、太平洋地区的3个地震以及玻利维亚的一个地震。在多数情况下,非双力偶分量实质上减少了,机制的几何形状基本上保持不变。这证实了这样的假设,由于忽视了矩张量检索的常规程序中震源的有限性,区域矩张量解中的部分非双力偶分量可能是假的。此外,由二阶矩（震源椭球和破裂速度矢量）提供的震源的几何学和运动学特征多数与先前研究中的断层几何、余震分布及破裂速度估计一致。     

南盘江地区二叠纪-三叠纪之交浅水台地古氧相研究

海洋缺氧被认为是导致二叠纪末生物大灭绝的重要原因之一,但是缺氧时限和缺氧程度在不同地区的差异仍未得到很好的解决.为深入探索二叠纪-三叠纪之交浅水相区海洋缺氧的演变过程和形成机理,对位于"大贵州滩"台地内部打讲剖面的二叠系-三叠系界线地层中的生物组成和关键地球化学指标进行了系统研究.大灭绝前的浅水碳酸盐岩台地表现出低硫(总硫,黄铁矿硫),低黄铁矿硫/有机碳比值(硫黄铁矿/C有机),低黄铁矿化系数(DOP)的特征,同时记录了碳同位素的负偏和硫化氢气体释放事件,表明该时期以氧化环境为主;大灭绝后的各种地球化学指标显示浅水台地开始向贫氧-缺氧环境转变,但缺氧程度不高,主要为贫氧-缺氧相.以此为基础,本文提出该时期南盘江盆地古氧相的基本演变模式,即大灭绝前频繁的火山活动释放大量CO2,SO2等气体,使得气温出现上升,导致陆地生态系统开始瓦解,陆地风化速率加快,陆源输入的增加引发碳同位素负偏;与此同时,陆源物质输入的增加还导致海洋贫氧层(OMZ)扩张.当OMZ间歇性入侵透光带时,导致H2S气体向浅水台地释放,从而引发黄铁矿埋藏脉冲式上升的现象.大灭绝后,气温急剧上升,陆地风化速率加剧,OMZ急剧扩张,"大贵州滩"浅水台地开始向贫氧-缺氧环境转变.由此可见,二叠纪末的生物大灭绝是由火山活动增强,升温事件和海洋缺氧等一系列环境因素引发的.结合最新的研究结果,笔者认为该时期的升温事件是引发生物大灭绝的主导因素,同时也是导致海洋缺氧加剧的主要原因.此外,本文新的地球化学数据进一步证实了该地区的微生物岩形成于贫氧-缺氧环境.     

2011年Mw9．0东北近海地震高滑动片区周围的前兆地震活动

根据1923年以来的日本气象厅地震目录,参考以被低滑动区隔开形成两个高滑动（≥20m）片区为特征的滑动分布,研究了2011年Mw9．0东北近海地震之前的地震活动。北高滑动片区的滑动峰值位于海沟附近,而南高滑动片区的滑动峰值位于主震震中东南约40kin处,距海沟约70km。据估计,主震时首先使南高滑动片区发生破裂,然后扩展到更大的邻近地区,包括北高滑动片区。主震之前两天开始的前震活动的震中分布在北高滑动片区的西缘,此处过去90年曾发生过其他比较强烈的活动,例如1981年地震。根据这两个高滑动片区周围的地震活动时空分布图我们推断,2011年东北近海地震是由前震活动触发的,因为前震活动中持续增加的应力可以抵消南高滑动片区的强度,此处之前已经由于2003年以来的一系列周边大地震而变得足够脆弱了。其他主要活动,比如1981年地震,并没有触发如此巨大的地震,主要是之前类似的应力条件还没有具备。南高滑动片区峰值周围形成的环状地震活动图像表明存在极强的片区,这些片区在过去很长的时间并没有由于周围发生大地震而破裂。     

测量风速的一种新方法

风速表在应用研究和工业应用中广泛使用。下面简单介绍一下各种风速表的一些特性。热线风速表和热膜风速表是根据风的冷却率来测定风速的,一般说来,其体积小,在气压相差较大情况下也适用。热线风速表在瞬时气流测量上是很好的。它的频率响应特性可达几百千赫。但是其检定曲线随着周围温度的改变,探头的污染和长期持续使用而变化。热线装置容易损坏,因此不太适用于风向多变的场合。热膜仪器比较结实,而且膜的电阻高,能提供较大的信噪比增益。热膜风速表主要用来测量液体湍流,也可测量气体中的湍流。膜     

余滑、颤动和迪纳利断层地震

使用2002年M7．9阿拉斯加迪纳利断层地震（DFE）周围的地震形变和无震形变的观测资料,检验了余滑应该伴有颤动的假设。余滑比自发慢滑动发生得更频繁,而且已在更广泛的构造环境中观测到了。因此,伴随余滑的颤动存在与否能提供有关颤动生成的新线索。我们还搜寻了前兆颤动,即假定加速滑动导致破裂的证据。我们的搜寻在迪纳利断层地震前5天及其后3个月内的几个时段均未得到颤动。这种否定结果和一系列其他观测结果,或许都可用破裂穿透到假定的闭锁区以下到达摩擦过渡区内来解释。尽管并非独一无二,但这种解释确证了先前巨大逆冲断层和转换断层地震破裂完全延展到过渡区的模型。     

ANN application for prediction of atmospheric nitrogen deposition to aquatic ecosystems

The occurrences of increased atmospheric nitrogen deposition (ADN) in Southeast Asia during smoke haze episodes have undesired consequences on receiving aquatic ecosystems. A successful prediction of episodic ADN will allow a quantitative understanding of its possible impacts. In this study, an artificial neural network (ANN) model is used to estimate atmospheric deposition of total nitrogen (TN) and organic nitrogen (ON) concentrations to coastal aquatic ecosystems. The selected model input variables were nitrogen species from atmospheric deposition, Total Suspended Particulates, Pollutant Standards Index and meteorological parameters. ANN models predictions were also compared with multiple linear regression model having the same inputs and output. ANN model performance was found relatively more accurate in its predictions and adequate even for high-concentration events with acceptable minimum error. The developed ANN model can be used as a forecasting tool to complement the current TN and ON analysis within the atmospheric deposition-monitoring program in the region.     

Improving benthic monitoring by combining trawl and grab surveys

Environmental monitoring is performed on seafloor communities since these organisms are relatively stationary and integrate the environmental conditions over many years. Standard practices involve sampling by grab. Epifaunal taxa, often missed by grab sampling, are likely to have different ecological functions. We investigate how current environmental assessments represent the benthic community as a whole by comparing taxonomic and functional components sampled by grabs and epibenthic trawls. Faunal communities sampled by trawl (filtrating or predator, epifauna) and grab (infaunal, detrivore) differs widely by sampling distinct functional components, and these may be expected to respond to different human-induced stressors. Neither component appears to be a good surrogate for the community as a whole. We suggest a benthic monitoring by combining both techniques. Sustainable ecosystem functioning is intimately tied to the health of both components of the benthic community, and is recognized as an important goal by signatories of the Convention on Biological Diversity.