三峡水库蓄水前后干流总磷浓度比较   总被引：1，自引：0，他引：1  

娄保锋  印士勇  穆宏强  张翔 《湖泊科学》2011,23(6):863-867

为认识三峡工程蓄水对水库总磷浓度的影响,于蓄水前(1998 - 2002年)和蓄水后(2004 - 2009年)每月对三峡水库干流5个断面总磷浓度进行监测并对数据进行分析.结果表明,同蓄水前相比,蓄水后水库近坝水体总磷浓度显著降低,至2009年,巴东官渡口断面和坝上太平溪断面总磷浓度比蓄水前分别下降了42.8％和54....  相似文献   

三峡库区的入侵鱼类及库区蓄水对外来鱼类入侵的影响初探   总被引：2，自引：0，他引：2  

巴家文  陈大庆 《湖泊科学》2012,24(2):185-189

三峡水库已于2010年10月完成175 m的蓄水目标,蓄水后三峡库区形成一个生态位严重空缺的人造湖泊生态系统.近年来,库区及长江上游外来入侵鱼类呈增长态势,已发现外来入侵鱼类23种,且部分已处于种群数量暴发阶段.水库蓄水初期营养盐输入增加和初级生产力的提高通常也利于广适性鱼类和外来种的生存,对外来鱼类的入侵和种群数量的扩散暴发产生一定的促进作用.外来鱼类在生态位竞争上与土著鱼类相比处于明显优势地位,可能将严重危害三峡库区的渔业资源及其水域生态系统的安全.因此,对于三峡库区的鱼类入侵及其所带来的相关效应等问题,应引起密切关注和重视,尽早建立三峡库区入侵鱼类的预警和防治体系,严格评估人为引种活动,深入研究外来鱼类得以成功入侵的原因与机理.  相似文献   

三峡库区的蓄水效应及对仙女山断裂活动的影响   总被引：2，自引：2，他引：0  

邢灿飞  张燕  施顺英  杜瑞林 《大地测量与地球动力学》2006,26(3):69-72

为研究三峡水库蓄水所引起的库区地壳形变和断层活动,运用小波变换分析和处理了大坝附近两个定点形变台(周坪台和宜昌台)的倾斜观测数据,发现蓄水后库区仙女山断裂带的活动发生了一些变化,库区周围的倾斜场发生微动态变化,库区下游区域的倾斜场没有发生明显的变化。  相似文献   

The market for sustainable seafood drives transformative change in fishery social-ecological systems     

《Global Environmental Change》2019

Seafood certification and eco-labeling programs, which leverage market forces to incentivize fisheries improvements, have changed the face of the global seafood market through an expanding supply of and demand for certified seafood. To contribute towards conservation goals, these programs employ a strategy termed the ‘theory of change, which predicts that as market demand for certified products grows, additional fisheries will improve practices and management in order to gain certification; however, there is limited evidence that this actually occurs, particularly in fisheries that require significant improvements to meet certification requirements. Here, we examine the capacity of one of the largest seafood certification programs in the world, the Marine Stewardship Council (MSC), to foster transformative change in The Bahamas Caribbean spiny lobster fishery. Drawing on fishery documentation and interviews with fishery stakeholders, we assess the role of the sustainable seafood market throughout the fishery’s transformation from “unsustainable’ to an MSC-certified fishery. We found that the MSC played three key roles in transforming the fishery from an undesirable state towards long-term sustainability by creating a stimulus for change, serving as guide prior to and throughout the fishery’s transition, and helping to stabilize the fishery in its new trajectory. This study provides the first empirical evidence for the conservation strategy employed by seafood certification programs for improving fisheries that require transformative change in order to meet sustainability goals.  相似文献   

三峡库区蓄水对秭归归州水井观测的影响     

袁曲  黄仲  蒋玲霞  张卫华 《大地测量与地球动力学》2011,31(Z1):64-67

以秭归归州流体井观测资料为对象,结合当地水文地质概况,利用典型震例,研究井台流体正常动态变化规律、震前异常与蓄水效应特征,探讨三峡库区蓄水对秭归归州水井观测环境的影响,及秭归归州水井水温异常变化的原因。  相似文献   

高桥断裂的地震活动性分析   总被引：1，自引：1，他引：0  

董建辉 《大地测量与地球动力学》2004,24(2):83-87

应用地震学方法对高桥断裂的地震活动性进行了综合分析，得出以下结论：①长江三峡水库蓄水后高桥断裂的地震活动以中等频度、低强度的形式释放能量；②蓄水后的地震成因可能有3种，即水诱发型、天然构造型和岩溶型；③高桥断裂展布区可能是诱发构造型水库地震的潜在危险区，其东北段存在发生Ms3.0～4.0地震的可能性。  相似文献   

三峡水库二期蓄水以来巴东地区波速比特征分析     

陈俊华  王墩  李垠  薛军蓉 《大地测量与地球动力学》2007,27(Z1):28-31

研究了三峡水库二期蓄水后湖北省巴东地区微震波速比值的变化特征。研究表明,震前波速比降低，震后波速比回升,波速比值变化反映出地震前后震源区介质受到由水引起的微裂隙的破坏和溶蚀作用。  相似文献   

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张卫华  姚运生  李胜乐  梅建昌  李家明 《大地测量与地球动力学》2007,27(5):94-98

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Settlement patterns,size and growth of puerulus and juvenile rock lobster Jasus lalandii at an oyster farm in Saldanha Bay,South Africa     

《African Journal of Marine Science》2013,35(3):501-510

Trends in the abundance, size and growth of newly settled pueruli and early juveniles of the rock lobster Jasus lalandii were determined from samples obtained from mesh bags used for oyster mariculture in Saldanha Bay, South Africa. Totals of 3 842 lobster pueruli and 10 158 juveniles were captured between August 2005 and June 2006, and distinct puerulus settlement events were identified in November and January. Juveniles also peaked during these months as well as in March. The size of newly settled pueruli increased significantly between October and March. The carapace length (CL) of pueruli and juveniles overlapped between 8.5 mm (smallest juvenile) and 10.4 mm (largest puerulus), and 50% of pueruli moulted into juveniles by 9.5–9.6 mm CL. There was a size progression in juveniles, with larger individuals in February and March reflecting an accumulation of juveniles from the earlier settlement events. The estimated growth increment from puerulus to first juvenile instar was 0.5–1.5 mm (4.9–16.1%), increasing to 1.4–2.5 mm (14.4–23.3%) for the second instar. Recruitment of J. lalandii pueruli occurred during periods when strong southerly winds prevailed, which results in a general offshore movement of surface waters along the West Coast and upwelling of cold nutrient-rich bottom waters. However, specific settlement events appeared to coincide with a change in wind direction, reduction in upwelling strength and increase in surface water temperatures, implying that larvae may take advantage of landward movements of surface waters during downwelling, or reversal of upwelling, to return them to shallow coastal waters.  相似文献   

Variations in grain‐size and sorting on two kaikoura beaches     

Roger F. McLean 《新西兰海洋与淡水研究杂志》2013,47(2):141-164

Two exposed, high‐energy beaches on the Kaikoura coast of New Zealand are composed of sand and gravel derived from a greywacke terrain. Both beaches can be classified as mixed beaches although the sediment varies from dominantly gravel at the ends of the beach to dominantly sand at the centre, through transition zones in which sand and gravel are mixed. Sixty‐four surface samples were analysed for grain size; two sediment parameters, mean grain size (M_z) and sorting (σ_I), were calculated.

A striking feature of the cumulative frequency curves is that both unimodai and bimodal distributions include median sizes over the whole range of sampled material, even though bimodal samples display two strong modes in the sand and gravel grades. The general deficiency lof sediment dn the very coarse sand and granule classes (0 to — 2 _F ) noted by numerous authors in many parts of the world is apparent in the poorly‐sorted bimodal samples. However, the best‐sorted samples also occur in these two classes.

Mean grain size of samples ranges from medium sand (1.820) to medium pebbles (—4.7 _F ), and sorting ranges from very well sorted (0.250) to very poorly sorted (2.69 _F ). Mean erain size on the northern beach is significantly greater than on the southern beach, but values of sorting are comparable. The greater mean size on one beach compared with the other is thought to be a function of the grade of material supplied by local rivers; the similarity in sorting presumably reflects the similarity of the processes acting on the two beaches.

Mixed sand‐shingle beaches are relatively rare on a world scale but common in New Zealand. Sediment distributions along the Kaikoura beaches do not reveal a regular decrease in size away from the rivers which supply material to shore at present. Instead, the beaches are differentiated into a number of sediment zones composed of either sand, or mixed sand‐gravel, or gravel. On each beach a gravel zone is located furthest from the river outlets. Sorting generally improves toward the Kaikoura Peninsula. Explanations for these trends are not given. Variations in size and sorting across the two beaches do not show a well developed zonation because of the high level of wave energy which continually mixes the material across the beach.  相似文献