Spatio-temporal variation in the structure of a deep water Posidonia oceanica meadow assessed using non-destructive techniques

The Malta‐Comino Channel (Maltese islands, central Mediterranean), supports extensive meadows of the seagrass Posidonia oceanica that in some places extend to a depth of around 43 m, which is rare for this seagrass. To assess spatial and temporal variation in the state of the deeper parts of the P. oceanica meadow with time, data on the structural characteristics of the seagrass meadow at its lower bathymetric limit were collected during the summers of 2001, 2003 and 2004 from four stations (two stations within each of two sites) located at a similar depth, over a spatial extent of 500 m. Shoot density was estimated in situ, while data on plant architecture (number of leaves, mean leaf length, and epiphyte load) were successfully obtained using an underwater photographic technique that was specifically designed to avoid destructive sampling of the seagrass. Results indicated that P. oceanica shoot density was lower than that recorded from the same meadow during a study undertaken in 1995; the observed decrease was attributed to the activities of an offshore aquaculture farm that operated during the period 1995–2000 in the vicinity of the meadow. ANOVA indicated significant spatial and temporal variations in meadow structural attributes at both sites during the 3‐year study; for example, shoot density values increased overall with time at site A; a indication of potential recovery of the meadow following cessation of the aquaculture operations. Lower shoot density values recorded from site B (compared with site A) were attributed to higher epiphyte loads on the seagrass, relative to those at site A. The findings, which include new data on the structural characteristics of P. oceanica occurring at depths >40 m, are discussed with reference to the use of the non‐destructive photographic technique to monitor the state of health of deep water seagrass meadows.     

Response of the Baltic Sea to climate change—theory and observations

The dynamics controlling the response of the Baltic Sea to changed atmospheric and hydrologic forcing are reviewed and demonstrated using simple models. The response time for salt is 30 times longer than for heat in the Baltic Sea. In the course of a year, the Baltic Sea renews most of its heat but only about 3% of its salt. On the seasonal scale, surface temperature and ice-coverage are controlled by the atmospheric conditions over the Baltic Sea as demonstrated by e.g. the strong inter-annual variations in winter temperature and ice-coverage due to variations in dominating wind directions causing alternating mild and cold winters. The response of surface temperature and ice-coverage in the Baltic Sea to modest climate change may therefore be predicted using existing statistics. Due to the long response time in combination with complicated dynamics, the response of the salinity of the Baltic Sea cannot be predicted using existing statistics but has to be computed from mechanistic models. Salinity changes primarily through changes in the two major forcing factors: the supply of freshwater and the low-frequency sea level fluctuations in the Kattegat. The sensitivity of Baltic Sea salinity to changed freshwater supply is investigated using a simple mechanistic steady-state model that includes baroclinic geostrophic outflow from the Kattegat, the major dynamical factor controlling the freshwater content in the Kattegat and thereby the salinity of water flowing into the Baltic Sea. The computed sensitivity of Baltic Sea surface salinity to changes of freshwater supply is similar to earlier published estimates from time-dependent dynamical models with higher resolution. According to the model, the Baltic Sea would become fresh at a mean freshwater supply of about 60 000 m³ s⁻¹, i.e. a 300% increase of the contemporary supply. If the freshwater supply in the different basins increased in proportion to the present-day supply, the Bothnian Bay would become fresh already at a freshwater supply of about 37 000 m³ s⁻¹ and the Bothnian Sea at a supply of about 45 000 m³ s⁻¹. The assumption of baroclinic geostrophic outflow from the Kattegat, crucial for the salinity response of the Baltic Sea to changed freshwater supply, is validated using daily salinity profiles for the period 1931–1977 from lightship Läsö Nord.     

沿海深水岸段排污口近区污染物混合过程的模拟方法

本文提出一种将二维动态水质模型与三维稳态水质模型有机结合的新方法，用来处理沿海深水岸段排污口近区污染物混合问题，使之能较好地再现其客观混合过程。将这种方法应用于深圳大鹏湾某大型石化项目的环境影响预测中．结果令人满意。     

人工神经网络在风暴潮增水预报中的应用

本文根据1967～1982年问影响湛江站增水的热带气旋资料，选取了其中对湛江站增水影响比较显著的因子，运用人工神经网络中的BP算法，建立了湛江站风暴潮增水预报的人工神经网络模型，并使用贝叶斯优化算法提高了BP网络模型的预报能力，结果表明所建BP网络模型的训练拟合效果和预报效果都比较好。表明该网络模型可以用于湛江站风暴潮增水的预报。同时本文也为其它的港口、码头等近岸海洋工程风暴潮增水的预报提供了一个有效可行的方案。     

基于BP神经网络的天然气水合物相平衡计算及预测

针对天然气水合物相平衡问题,文中提出用基于带动量因子的BP神经网络进行计算和预测。首先用遗传算法优化确定BP神经网络的结构和参数,得到最优化结构的神经网络;其次结合Levenberg-Marquart优化算法,建立天然气水合物相平衡计算及预测的神经网络模型;最后以实验测定的(CH4 CO2 H2S)三元酸性天然气水合物体系的平衡数据为训练和预测样本进行了计算。计算表明,预测结果与实验数据有良好的一致性,而且由于BP神经网络作为所谓的“纯粹”的算法不需要热力学模型,这对于相平衡计算是非常方便的,所以是研究天然气水合物相平衡计算及预测的一种新的有效方法。     

Understanding water pollution management: Evidence and insights from incorporating cultural theory in social network analysis

Social network analysis gives a rigid assessment of network structure while cultural theory helps explain management outcomes in more detail. The combination of these methods provides significant and alternative insights about the complexity of water pollution management. Applied in the case study of the Calumpang Watershed in the Philippines, two types of relations were evaluated, namely, resource sharing and cooperative activities. Factors affecting cooperation and the creation of bridges were assessed in social network analysis, while cultural theory was used to reveal the underlying views of key actors on the nature of the river and its management. Evidence showed that cooperation was significantly influenced by resource sharing regardless of institutional affiliation, while bridges were created by becoming the pools of information and resources in the network. Using cultural theory, this study found out that local government officials dominantly have a mixture of hierarchist and egalitarian views characterizing belief in both rule-bound and group-motivated actions to solve the water pollution problem. However, their egalitarian views on management did not manifest in the current network. The study concludes that collaborative partnerships for water pollution management can be facilitated by promoting resource flow, utilizing influential bridges in the network, and understanding the unconventional values of government actors. Combining social network analysis and cultural theory is recommended to generate a more critical assessment of the institutional complexity of pollution and other water issues in watersheds.     

Complex resource supply chains display higher resilience to simulated climate shocks

Global resource supply chains deliver products such as fish, rice and minerals from producers to consumers around the world, linking disparate regions and economies. These supply chains are increasingly exposed to the impacts of a changing climate, yet receive little attention relative to the study of the production phase. Too often, business learns from experience if and how their supply chains can withstand and recover from climate shocks with little insight on proactively developing climate resilient supply chains. We use a network-based simulation approach to estimate the resilience of supply chains, particularly to disruption experienced during climate-related extreme events. We consider supply chain examples from three Australian resource industries – fisheries, agriculture and mining – that have experienced climate shocks in recent years. We derive four supply chain indices – evenness, resilience, continuity of supply and climate resilience – to estimate the performance of simple and complex supply chains in each industry. As with ecological systems, we show that complex supply chains with a large number of nodes and links are more resilient to disruption. Critically, all chains, regardless of their complexity, will have diminished resilience as climate disruptions become more frequent. This highlights the importance of considering the broader economic benefits of diversified chains, leading to risk reduction and improved design post-disruption. It also reinforces the importance of a systems approach to risk management in supply chains, particularly in considering adaptation options for addressing direct and indirect impacts on the chain as well as the global challenge of reducing greenhouse gas emissions.     

地震活动中地壳深部流体的作用研究进展

综述了地震深部流体研究的进展并提出了在地震领域应该深入研究的方面。已有大量资料表明岩石圈是一含流体的系统，也是地震发育的主要场所。深部流体赋存相态，运移方式及其与岩石的反应，对震源介质和构造活动有重要影响。     

Unusual comets (?) as observed from the Hubble Space Telescope

In separate projects, the Hubble Space Telescope has been used to assess the nature of 3 unusual objects: Chiron, Pholus and P/Shoemaker-Levy 9. This paper will compare these objects and discuss how the unique capabilities of the HST may be used to address the issue of cometary activity in each. Chiron, which has exhibited obvious cometary characteristics for several years, might have a bound dust coma that is unresolvable from the ground. In an attempt to directly observe this bound coma, we have obtained a series of images of Chiron with the HST Planetary Camera. Inner coma structure out to 0.2 has been detected. From these observations we infer a low bulk nucleus density for Chiron. Both HST and ground-based images of 5145 Pholus have been obtained to search for evidence of activity. The ground-based data give the most sensitive limits; however, it is shown that the WFPC-2 on HST can give limits 2–3 orders of magnitude more sensitive than conventional ground-based limits. Finally, as part of a collaborative effort, we have been obtaining HST observations of SL9 in order to determine the fragment sizes and to assess their nature (i.e., cometary vs. asteroid). Both ground-based observations from the UH 2.2m telescope on Mauna Kea and HST observations show that the near-nucleus dust is redder than the sun. While FOS spectra did not detect OH emission, the WFPC-2 HST data show that the inner coma remained very circular from July 1993 up until 2 weeks prior to impact, implying continued production of dust.     

深部物质运动的气体地球化学特征

根据氦同位素地球化学资料讨论了中国东部和云南腾冲地区上地幔的脱气。尽管地球脱气作用主要发生在地球形成时的十亿年间，但是后期的脱气作用仍是影响大气圈演化的主要因素。在两种力学性质不同的构造带──中国东部大陆裂谷和位于欧亚板块与印度板块缝合带的腾冲火山区，采集了天然气样，并分析了气体组分和氦同位素组成，较高的３Ｈｅ／４Ｈｅ值和地质、地球物理资料表明天然气和温泉气中的氦相当一部分是来自上地幔。来自上地幔的氦和其他气体自第三纪以来不断在气藏中聚集或向大气中逃逸。伴有源于上地幔的岩浆活动的地幔脱气是深部物质运动的具体表现形式，它对新生代气候演变可能有直接影响。