Benthic Impacts of Intertidal Oyster Culture, with Consideration of Taxonomic Sufficiency

An investigation of the impacts from elevated intertidal Pacific oyster culture in a New Zealand estuary showed enhanced sedimentation beneath culture racks compared with other sites. Seabed elevation beneath racks was generally lower than between them, suggesting that topographic patterns more likely result from a local effect of rack structures on hydrodynamic processes than from enhanced deposition. Compared with control sites, seabed sediments within the farm had a greater silt/clay and organic content, and a lower redox potential and shear strength. While a marked trend in macrofaunal species richness was not evident, species composition and dominance patterns were consistent with a disturbance gradient, with farm effects not evident 35 m from the perimeter of the racks. Of the environmental variables measured, sediment shear strength was most closely associated with the distribution and density of macrofauna, suggesting that human-induced disturbance from farming operations may have contributed to the biological patterns. To evaluate the taxonomic sufficiency needed to document impacts, aggregation to the family level based on Linnean classification was compared with an aggregation scheme based on `general groups' identifiable with limited taxonomic expertise. Compared with species-level analyses, spatial patterns of impact were equally discernible at both aggregation levels used, provided density rather than presence/absence data were used. Once baseline conditions are established and the efficacy of taxonomic aggregation demonstrated, a `general group' scheme provides an appropriate and increasingly relevant tool for routine monitoring.     

Water security: Old concepts,new package,what value?

“Water security” has come to infiltrate prominent discourse in the international water and development community, and achieving it is often viewed as a new water sector target. Despite the elevated status that the concept has increasingly acquired, understandings of the term are murky and quantification is rare. To promote a more tangible understanding of the concept, this paper develops an index for evaluating water security at a country level. The index is comprised of indicators in five components considered to be critical to the concept: (i) basic needs; (ii) agricultural production; (iii) the environment; (iv) risk management; and (v) independence. Achieving water security in these components can be considered necessary but insufficient criteria to measure the achievement of security in related areas such as health, livelihoods, and industry. After populating indicators with data from Asia‐Pacific countries, results are interpreted and the viability of methods is discussed. This effort comprises an important first step for quantifying and assessing water security across countries, which should spur more concrete understanding of the term and discussion of its added value.     

Assessment Tools for Urban Catchments: Developing Stressor Gradients1

Abstract: This is the first in a series of three articles designed to establish empirically defined biological indicators and thresholds for impairment for urbanized catchments, and to describe a process by which the biological condition of waterbodies in urbanized catchments can be applied. This article describes alternative gradients of urbanization for assessing and selecting a nationally applicable biological index (article 2 – Purcell et al., this issue ) and defining the potential of biological communities within a gradient of cumulative stressors (article 3 – Paul et al. this issue ). Gradients were designed to represent the most prominent mosaic of stressors found in urban settings. A primary urban gradient was assembled based on readily obtained information of urbanization to include three broad‐scale parameters: percent urban land use/land cover, population density, and road density. This gradient was used as the standard by which alternative urban gradients, which included fine‐scale instream chemical and hydrologic parameters, were assessed. Five alternative gradients were developed to provide numerous environmental management options based on availability of data from water program resources. The urban gradients were developed with the intent that they be applied throughout the country; therefore, data from three different regions of the United States (Mid‐Atlantic, Midwest, and Pacific Coast) were used to validate the urban gradient model. Our study showed that a relatively straightforward stressor gradient consisting of human population density, road density, and urban land use is useful in providing a framework for developing relevant biological indicators and evaluating the potential of biological communities as a basis for assessing attainment of designated aquatic life use.     

1951-2006年西北太平洋热带气旋活动时空特征

西北太平洋是全球热带气旋(TC)发生次数最多、强度最大的区域之一,其TC研究受到该区域学者的广泛关注。基于日本气象厅(JMA)东京台风中心西北太平洋TC最佳路径数据资料,分析了该区域1951-2006年的TC频数和强度时空分布特征。首先,统计和分析了56年间(1951-2006年)TC的年际和年内变化,并通过建立1°×1°网格计算了落在每个网格内的TC次数,分析了多年TC的空间分布格局;其次,根据国际气象组织按照风速划分TC等级的标准,统计和分析了56年间不同强度TC的年际和年内特征,通过风速强度指数计算,获取了1°×1°网格单元区域内遭受TC影响的强度等级。结果显示,区域频数和强度时空分布规律较好地反映了该区域的TC影响特征,进而为区域台风灾害预报以及台风灾害风险评估提供了支持。     

新型汽封在超临界600MW机组的应用

介绍了一种新型汽封在国产600 MW机组节能改造中的应用。改造方案为将汽轮机组原通流部分及轴端的梳齿型汽封改为新型接触式密封齿＋蜂窝汽封＋铁素体齿的组合汽封,改造后漏汽量大幅减少,高、中、低压缸效率和机组运行的经济性明显提高,对同类型汽轮机通流部分节能改造具有较好的借鉴意义。     

北太平洋地区沙尘沉降与海洋生物兴衰的关系

通过对2001年4月中亚强沙尘暴过程在中国、韩国、日本和北美大陆地面PM10观测结果进行统计分析,推算出了北太平洋PAPA地区的沙尘沉降通量,结合同期PAPA地区的海洋表层有机碳和叶绿素观测结果,探讨了北太平洋沙尘与海洋生物兴衰的关系.结果表明,本次强沙尘暴过程可以给PAPA地区带去大约3.1～5.8μg/m³的风成Fe元素,它激发了海洋生物泵,引起海洋浮游植物的快速繁盛.     

橡胶密封件加速老化试验影响因素分析及验证

通用的橡胶材料加速老化试验方法未考虑初始压缩率、密封形式、密封介质等工程应用的细节因素。通过一系列对比试验,初步掌握了上述各因素对橡胶密封件加速老化试验结论的影响程度,为工程实践中科学评估装备贮存寿命提供了依据。     

西南地区夏季极端降水的水汽来源分析

西南地区地形复杂,极端降水极易形成山洪并引发地质灾害,1998年夏季西南降水达709.3 mm,超出平均降水约23.9%。经使用水汽追踪模型WAM2layers和ERA-Interim再分析资料等大数据追踪西南降水水汽来源,发现西南夏季降水主要有四个源区,分别是西南季风区、西风带区、本地和东南季风区,1998年夏季分别贡献了330.1 mm、110.0 mm、104.8 mm和65.6 mm水汽,约占所追踪降水的52.2%、17.4%、16.6%和10.4%。西南季风区作为最大源区,贡献了超过一半的降水水汽。增加的降水其水汽主要来自西南季风区、西风带区和本地,比平均分别多贡献80.1 mm、29.3 mm和27.1 mm,合占所增加降水的99.9%;其中又以西南季风区贡献占主导。进一步发现,1998年夏季太平洋副高向西南延伸,并在北孟加拉湾和我国南海形成两个高压中心异常,导致西南季风向我国西南地区的水汽输送异常强劲,从而造成西南地区降水异常增多。     

Population dynamics of splitnose rockfish (Sebastes diploproa) in the Northeast Pacific Ocean

We developed an age-structured population model of splitnose rockfish, Sebastes diploproa, in the Northeast Pacific Ocean. Splitnose rockfish is a bycatch species that co-occurs with several commercially important species that are currently declared overfished. Bycatch species are typically not the focus of stock assessment efforts because of their limited economic importance, but they may suffer the same population declines as species with which they co-occur. To examine the dynamics of splitnose rockfish for the first time, we analyzed data from three groundfish fisheries and four research surveys conducted in the Northeast Pacific Ocean. To develop a model, we used Stock Synthesis, a statistical framework for the construction of a population dynamics models utilizing both fishery-dependent and fishery-independent data. In the model, we reconstructed the total catch of the species back to 1900, estimated the dynamics of the stock spawning output and recruitment and evaluated biomass depletion relative to the stock's unfished state, as well as sources of uncertainty in model outputs. The results indicate that the splitnose rockfish is currently not overfished even though it has experienced several periods of abrupt decline in its biomass. Revisiting age data from earlier years, monitoring fishery discard, and investigating the spatial dynamics of splitnose rockfish is important to further improve the understanding of this species’ population dynamics, and decrease uncertainty in model results.     

Multi-level governance for large marine commons: Politics and polycentricity in Palau's protected area network

This paper brings together institutional theories of polycentricity and critical human geography theory on scalar politics to advance understanding of the form and function of nested, polycentric regimes for the governance of large-scale common pool resources. We focus on institutional changes associated with a national marine protected area network in Palau through which national government and NGOs gain influence in local decision-making processes. Influence is gained through an attempt to scale up common-pool resource governance to an ecologically-relevant spatial scale in an effort to protect coral reef resilience and biodiversity across Palau. An institutional approach informed by scalar politics brings into focus potential tradeoffs between organizing governance reform around ecologically versus institutionally relevant scales. Our analysis suggests that prioritization of ecologically-relevant scales in institutional reform resulted in more nested but less polycentric institutional arrangements governing the network. We conclude that less distributed decision-making in the overall nested governance system could threaten the sustainability and resilience of coral reefs in the long-term by constraining institutional innovation and diversity. Results demonstrate the potential for interdisciplinary dialog to advance the research frontier on multi-level governance for large common pool resources.