清淤疏浚工程对七里海潟湖湿地水体交换的影响

七里海潟湖湿地受到人类活动的影响,湖盆淤积、湖面萎缩、水质恶化,其生态修复工程（一期）通过对湖盆进行清淤疏浚来改善潟湖生态环境.基于三重嵌套非结构网格建立七里海潟湖湿地水动力和物质输运数学模型,采用实测资料对模型的潮位、流速和流向进行验证,运用欧拉法计算潟湖整体滞留时间及其空间分布,分析工程对七里海潟湖水动力和水体交换的影响,结果表明：（1）工程对潮位的影响较小,工程后潮汐通道口门处涨落潮流量增大,涨落潮流速也随之增加;（2）工程后,潟湖纳潮量较工程前提升87%,滞留时间较工程前降低38%,水体交换能力自潮汐通道向潟湖内部逐渐减弱,工程对潟湖水体交换能力的改善主要集中在河道及潟湖中心水域;（3）工程前水体滞留时间的分布主要受到潟湖地貌影响,工程后水深增大,流场受地貌的影响变小,水体交换能力的分布主要受到潟湖流场影响.清淤疏浚工程有助于潟湖改善水体的交换能力和生态环境.     

Beyond the cage: Ecosystem modelling for impact evaluation in aquaculture

An ecosystem modelling approach was used in two areas of the Eastern Mediterranean in order to examine the effects of aquaculture on the ecology of the water column. Aquaculture expansion to meet demands of a growing population is followed by concerns about keeping impacts within socially acceptable limits. Primarily the study aimed at investigating the fate of nutrients from finfish culture and evaluating changes in chemical and biological characteristics of the water body. The model used, Aquaculture Integrated Model (AIM), is based on a complex generic biogeochemical model coupled to a 3D hydrodynamic model. Selected areas included a finfish farm in the Northern Aegean, Greece and an aquaculture development area in Vassiliko, Cyprus. Ecosystem effects were evaluated on the basis of scale and importance. Scenarios under different production levels and hydrodynamic conditions were explored at the sites. Model results showed that farm discharges are rapidly dispersed from their point source in addition to a tendency for effluents to accumulate at distances not normally associated directly with farming activity. The wide range of parameters available in the model helped identify parameters more likely to be affected by the farming activities. There was a satisfactory correlation between observed and predicted model outputs. This study demonstrates the importance of approaching aquaculture impacts at an ecosystem level and the utility of a modelling tool to this end.     

Application of a Random Forest algorithm to predict spatial distribution of the potential yield of Ruditapes philippinarum in the Venice lagoon, Italy

We present a modelling framework that combines machine learning techniques and Geographic Information Systems to support the management of an important aquaculture species, Manila clam (Ruditapes philippinarum). We use the Venice lagoon (Italy), the first site in Europe for the production of R. philippinarum, to illustrate the potential of this modelling approach. To investigate the relationship between the yield of R. philippinarum and a set of environmental factors, we used a Random Forest (RF) algorithm. The RF model was tuned with a large data set (n = 1698) and validated by an independent data set (n = 841). Overall, the model provided good predictions of site-specific yields and the analysis of marginal effect of predictors showed substantial agreement among the modelled responses and available ecological knowledge for R. philippinarum. The most influent environmental factors for yield estimation were percentage of sand in the sediment, salinity, and water depth. Our results agree with findings from other North Adriatic lagoons. The application of the fitted RF model to continuous maps of all the environmental variables allowed estimates of the potential yield for the whole basin. Such a spatial representation enabled site-specific estimates of yield in different farming areas within the lagoon. We present a possible management application of our model by estimating the potential yield under the current farming distribution and comparing it to a proposed re-organization of the farming areas. Our analysis suggests a reduction of total yield is likely to result from the proposed re-organization.     

Understanding land cover change in a Special Protection Area in Central Spain through the enhanced land cover transition matrix and a related new approach

This work analyses land cover changes occurring between 1990 and 2000 within a Natural Protected Area, southwest of Madrid (Spain). We develop a new methodology that considers the net change in different land cover categories in each municipality of the study area. Our methodology, which uses Factorial Correspondence Analysis, allows identification of the most important changes at the municipality level and groups the municipalities where land use dynamics are similar. This method is a powerful tool for synthesis and can potentially be applied to non-spatial geographical data sources (e.g. agrarian census statistics). Our results show that the land cover around SW Madrid is highly dynamic. The shrub vegetation, arable land, heterogeneous agricultural and human-created area categories show the highest total change. The dynamics of the changes detected are dominated by decreases in the area of different types of crops and increases in forest areas. These changes may have indirect effects on the conservation of natural resources and wildlife if not managed appropriately.     

Distribution of Alkalinity, Ph, Salinity and Carbon Dioxide Components in the Coastal Waters of Alexandria

The ara studied is located between El-Dikheila Harbour in Elmex Bay and Mandara, at longitude 29° 47' and 30° East and latitude 31° 17' North. the aim of the work is to look at carbon dioxide components in this areA and the effect of waste water discharged on their concentrations. Surface and bottom water samples were collected from 12 stations during January, April, August and November, 1995. Total alkalinity, salinity, temperature and pH were measured. Carbonate alkalinity, total alkalinity, partial pressure and dissolved carbon dioxide, carbonate and bicarbonate ions were calculated, since the studied area includes two differetn sources of pollution. It wAs found conventient to refer El-Mex Bay as region “A” which contains stations from I to VI and the area located between Kayet Bey outfall and Mandara which contains stations from VII to XII as region “B”. When specific alkalinity is used As A tracer for El-Umum drain water it is observed that the drain water could reach Sidi Bishr area especially in August and November, while in January and April drain water did not reach this area.     

Dissolved trace-metal concentrations along the Mediterranean Sea, to the north of the Nile Delta Region, Egypt

This work focuses on four marine sites of the Mediterranean Sea, north of the Nile Delta, Egypt. Surface-water samples were collected seasonally during 2003. The aim of this study is to assess the levels of some dissolved trace metals (Fe, Mn, Zn, Cu, and Pb) in two environmental conditions. The metal concentrations in the coastal zone were in the following ranges: 11.92-30.45 μg l^-1 for Fe, 5.79-17.36 μg l^-1 for Mn, 0.87-7.80 μg l^-1 for Zn, 0.40-1.87 μg l^-1 for Cu, and 1.53-10.31 μg l^-1 for Pb. In the sites with continental water input (mixing zone), the metals were scattered in the following ranges: Fe (19.72-60.33 μg l^-1), Mn (12.63-35.60 μg l^-1), Zn (2.67-22.00), Cu (0.83-8.10 μg l^-1), and Pb (1.72-29.7 μg l^-1). The results for the metal concentrations showed a remarkable decrease in the levels of the different metals going from the estuaries and outlets into the coastal sea water. Generally, the levels of the metals in the two zones are higher than the background levels of the unpolluted area. A comparison of the trace-metal levels in the coastal zone of the Mediterranean Sea north of Nile Delta with the minimal risk concentration (reported by water-quality criteria, WQC) showed a significantly lower content at the coastal area of the Mediterranean sea of Egypt. The study also indicated that the impact of anthropogenic inputs was limited in the distribution of the metals, except that the Pb content was slightly higher in the area of the mixing zone than that reported for WQC. The relationships between the different trace-metal concentrations and the other parameters (salinity, chlorophyll a and suspended particulate matter) were discussed, and the simple regressions between them were evaluated.     

阿斯旺建坝后尼罗河三角洲泻湖重金属污染特征及其环境意义

本研究以尼罗河三角洲泻湖(Manzala、Burullus、Edku)为典型区域,利用6根浅孔并选取Al、Cd、Cr、Fe、Mn、Pb、Cu、Zn等主要重金属元素,探讨了自然和人类活动(建坝)共同作用下河口泻湖湿地环境重金属时空分布及污染来源。研究结果表明,1964年阿斯旺建坝和海岸保护工程实施后,泻湖地区逐渐演变为稳定而封闭的沉积环境。钻孔上层(10~15 cm)沉积物重金属富集现象反映了建坝后三角洲泻湖环境污染加重。重金属空间分布表现为平原东西部Manzala和Edku湖污染较重,而中部的Burullus湖污染较轻。相关性分析和富集系数(EF)变化进一步揭示Manzala湖特征污染元素为Pb、Cu、Zn和Cd,污染源主要来自开罗石油化工等产业废水;Burullus湖特征污染元素为Mn和Pb,应该与湖区附近农业废水的大量排放有关;Edku湖特征污染元素则为Mn、Pb和Zn,其重金属可能来自邻近的Abu-Qir湾带来的亚历山大工业废水。     

Managing abandoned farmland to control the impact of re-vegetation on the environment. The state of the art in Europe

Background and aimsIn the last decades, large areas undergo a revegetation process as a result of land abandonment, producing significant environmental and landscape impacts. In this paper, revegetation impacts are identified. We present the solutions proposed by scientists to control the negative impacts of revegetation, from a literature review from studies carried out in Europe.ResultsSome scientists suggest letting the revegetation process continued to contribute to the naturalisation of the landscape, reduce soil erosion, increase carbon sequestration and encourage recreational use of the territory. Other scientists, however, suggest the need to control the revegetation processes and retrieve abandoned land with productive purposes (extensive livestock and leisure), environmental objectives (reduction of fires and increasing biodiversity) and preserve cultural landscapes.ConclusionThe scrubland clearing and extensive livestock is an appropriate strategy to manage abandoned lands, combining environmental, landscape and socio-economic benefits.     

Disposal of Coal Fly Ash at A Deep Water Site in the Eastern Mediterranean Off Israel - Six Years of Monitoring

Coal fly ash (CFA) is dumped at a deep sea disposal site (1,500m water depth) in the eastern Mediterranean, ca. 70km off the Israeli shore. Since 1989, about one million tons of CFA were dumped at the 200km² allocated area. Six years of monitoring at the dump-site shows that the CFA is heterogeneously distributed; there are areas where CFA covers about 1.3cm depth of the sea floor while at others no CFA is found. CFA is present as a fine powder, small aggregates and even as large blocks both in the dump-site as well as at its peripheries. Cadmium, copper and zinc concentrations in the CFA decreased as a result of the prolonged contact with sea water at in situ conditions while inconclusive changes in mercury, iron and manganese were detected. No changes were observed for lead, iron and aluminium concentrations. A controlled long term field experiment, now in progress at the site, is expected to clarify further chemical changes occurring in the CFA.     

Settlement seasonality and temporal changes in hard substrate macrozoobenthic communities of Lesina Lagoon (Apulia, Southern Adriatic Sea)

The macrofauna settling on experimental substrates was studied at two sites of the Lesina Lagoon to test its possible role in monitoring ecological variations in a brackish-water ecosystem. The community settlement was seasonally investigated on 3-month-old wooden poles; the development was monitored from 2001 to 2005. Comparisons with benthic assemblages settled on 10-yr-old poles were also performed. The main hydrological parameters were periodically measured during the study. A total of 38 species were collected. The assemblage reached the highest development in the central lagoon, showing relevant carbonate structures which supported a rich vagile fauna. Close to the sea-water inlet species richness and abundance values were lower, with the disappearance of some brackish-water species. A remarkable salinity drop during 2004 produced some faunistic changes in the assemblages, which however maintained different structures between the study sites, thus confirming macrozoobenthos as an efficient bioindicator of different environmental conditions for transition biotopes and a useful investigation tool in monitoring programmes.