Sources of Cd, Cu, Ni and Zn in Portuguese coastal waters

In order to identify the major sources of trace metals (TM) in the Portuguese coastal waters, 58 surface water samples were collected during September 1988. The area sampled extended from the Tagus Estuary (down to a salinity of 25) to cape Ste Marie on the southern coast of Portugal. Dissolved metal concentrations in the fully marine waters ranged from 30 to 250 pM for Cd, 0.7–15 nM for Cu, 0.9–20 nM for Zn and 1.8–4.5 nM for Ni. Within the Tagus Estuary (salinity 25), concentrations increased to 3400 pM for Cd, 26 nM for Cu, 14 nM for Ni and 230 nM for Zn.The large-scale distribution of these metals is dominated by two strong continental sources, both probably linked to the exploitation of pyrite ores. In the Tagus Estuary, TM enrichments can be mostly attributed to a pyrite roasting plant located on the shore in front of Lisbon. Concerning the south Portuguese shelf waters, several hypotheses are proposed to explain their elevated metal concentrations. We particularly discussed the likely influence of the Tinto/Odiel rivers located 100 km eastward, an influence well known in the shelf waters of the Gulf of Cadiz. These rivers are extremely metal-rich because of acid mine tailings originating from their catchment. Between these two regions, upwelling of relatively metal-poor water largely contributes to the dilution of the continental inputs. Indeed, water exchanges on the shelf linked to the upwelling involve water fluxes 500 times higher than the Tagus River flow, and renew the coastal waters that are thus cleaned from terrestrial contamination. Contrary to many other upwelling systems in non-contaminated areas, the Portuguese upwelling does not act as a source of trace-metal enrichment of the continental margin waters.     

Population dynamics of Cyathura carinata (Isopoda) in a eutrophic temperate estuary

From January 1993 to September 1995, Cyathura carinata was a target species of a monitoring programme carried in the Mondego Estuary (Portugal). Being one of the key species of the intertidal mud flats, this isopod was found to be most abundant in a eutrophic area, where seasonal macroalgal blooms usually occur. Its density decreased towards downstream areas, where some Zostera noltii beds exist. At the Mondego Estuary, the present work stated that C. carinata: (a) had a 2-year life span, even though, 80–90% of the individuals died when 1 year old, revealing a strong post-reproduction mortality; (b) produced a single cohort per year; (c) showed continuous growth (with lower rates during winter); (d) evidenced protogynous hermaphroditism and (e) presented a high growth production and a low turnover ratio. A latitudinal gradient reflected in the life features of C. carinata was described. Except for the life span and the frequency of reproduction, which are generally valid for all populations, C. carinata from the Mondego Estuary fitted the characteristics of other populations from the south of Europe.The effects of macroalgal blooms were assessed. Cyathura carinata seemed to temporarily benefit from the presence of macroalgae, due to higher energy resources and more efficient protection against predators. In a long term, algal blooms had negative consequences. It was particularly evident on the recruitment success, which had repercussions in population abundance, and on the secondary production. Therefore, repeated events of algal blooms embracing the distribution areas of C. carinata represent a threat to this species in eutrophic estuaries.     

海河口近岸海域2005-2010年间水环境变化分析

通过分析海河口及其邻近海域2005-2010年进行的多次环境现场调查资料,同时结合历史数据进行对比分析,结果表明:(1)河口水体中COD、BOD5、氨氮是突出污染因子,海河口水体污染程度整体呈现先降低再升高的趋势而大沽排污河河口区域水质状况相对更差整体仍然呈现进一步恶化态势;邻近海域水体中无机氮为最主要污染物,而其中硝酸盐是无机氮中最主要组成部分,不过亚硝酸盐所占比例正在逐年升高,说明区域水体氧化还原环境潜在变化正在发生;(2)丰水期陆源大量无机氮输入使得区域水体大部分时间超该区域功能区划要求的Ⅳ类海水水质标准;不过底质沉积物环境相对比较稳定,各监测项目全部符合一类海洋沉积物质量标准要求;(3)与1983年历史监测数据相比,海河口邻近海域活性磷酸盐、无机氮含量增速迅猛,丰水期时最高增幅活性磷酸盐和无机氮分别高达了2430%和5919%;整体看来同一时期水质和底质环境有缓和趋势,但潜在威胁仍然严重;最后,在认真分析对海河口及其邻近海域造成污染的各污染源基础上,进一步提出了有针对性的对策建议。     

基于GOCI影像的长江口及其邻近海域CDOM遥感反演及其日内变化研究

采用静止轨道海洋水色卫星（GOCI）数据对长江口及其邻近海域有色溶解有机物（CDOM）反演。以QAA-CDOM算法为基础,根据实测数据,利用BP神经网络模型来拟合QAA-CDOM算法中需要针对长江口水体进行优化的悬浮颗粒后向散射系数b_bp与吸收系数a_p的关系,从而准确估算CDOM的浓度。结果表明,反演结果准确度较高,平均相对误差为0.35。基于GOCI日内连续成像的优势,选取2014年3月15日8景GOCI影像,利用优化后的QAA-CDOM-BP算法,对长江口及其邻近海域CDOM的日内变化进行反演和分析,得到的变化规律如下:长江口及其邻近海域的CDOM日变化主要受潮流、长江径流等共同影响。长江口内CDOM浓度在涨潮期高于退潮期,由于受长江冲淡水的作用,CDOM从口外往外海区呈现逐渐递减趋势。     

Climate variability and planktonic communities: The effect of an extreme event (severe drought) in a southern European estuary

As a consequence of climate change, flood and drought events are increasing in frequency throughout the world. Nevertheless, knowledge of the effects on zooplankton estuarine communities is still scarce. The present study aimed to examine zooplankton ecology over two contrasting environmental conditions: regular years and extreme dry years, in a shallow temperate southern European estuary, the Mondego Estuary (Portugal). Monthly samples were carried out during three consecutive years: 2003 characterized as a regular temperate year concerning precipitation and river flow, and an extremely dry period during 2004–2005. The spatial and temporal structure of the biological data was evaluated by a three-mode principal component analysis (PCA), which allowed us to distinguish three distinct ecological areas based on their biological composition and their relationship with hydrologic parameters. The severe drought in 2004–2005 was responsible for spatial shifts in the estuary regarding zooplankton community and interannual variability, with an increase in abundance and diversity during the period of low freshwater flow. This freshwater flow regime influenced the composition of the zooplankton community at the most upstream section of Mondego estuary (zone 3), with a replacement of the freshwater community by one predominantly dominated by estuarine organisms. The occurrence of such estuarine community contributed to the increase in zooplankton abundance which is ascribed to the estuarine species Acartia tonsa. The comparison with previous data obtained for this estuarine ecosystem, demonstrated the occurrence of a different scenario at times of high freshwater flow, being defined the existence of two sub-estuarine systems, the north and south arm, presenting the south one the highest values of abundance.     

The influence of an extreme drought event in the fish community of a southern Europe temperate estuary

Between 2003 and 2006, a severe drought occurred throughout the Mondego River catchment's area, inducing lower freshwater flows into the estuary. As a consequence, both 2004 and 2005 were considered as extreme drought events. From June 2003 to June 2006, the fish assemblage of the Mondego Estuary was sampled monthly in five stations during the night, using a 2 m beam trawl. Fish abundance was standardized as the number of individuals per 1000 m² per season and the assemblage was analyzed based on ecological guilds: estuarine residents, marine juveniles, marine adventitious, freshwater, catadromous and marine species that use the estuary as a nursery area. A total of 42 species belonging to 23 families were identified, with estuarine residents and nursery species dominating the fish community. Variations in the fish community were assessed using non-metric MDS, being defined as three distinct periods: summer and autumn 2003, 2004/2005 and winter and summer 2006. The main drought-induced effects detected were the depletion of freshwater species and an increase in marine adventitious in 2004/2005, due to an extended intrusion of seawater inside the estuary and a significant reduction in abundance during the driest period of estuarine resident species. Nevertheless, from the management point of view, it could be stated that although some variations occurred due to environmental stress, the main core of the Mondego Estuary fish community remained relatively unchanged.     

A modelling study of residence time in a macro-tidal estuary

This paper outlines a numerical modelling study to predict the average residence time of a conservative tracer in a macro-tidal estuary, namely the Mersey Estuary, UK. An integrated hydrodynamic-dispersion model was used to predict the average residence time in the estuary for various tidal level and freshwater discharge conditions. The numerical model was verified against six sets of field measured hydrodynamic data, with the model-predicted water elevations and salinity levels generally agreeing well with the field measurements. The numerical model results show that in the Mersey Estuary both the tidal level and river discharge affect significantly the predicted average residence time. The value of the average residence time is also shown to be closely linked to the intensity of the residual tidal current. This is due to the fact that a large proportion of the Upper and Inner Estuary dries out during low tides, thus a significant amount of the tracer material is transported through the deep channels. An increase in the freshwater discharge causes a considerable increase in the intensity of the residual current along the main channels and thus a reduction in the average residence time. The predicted overall tracer residence time for the whole estuary is relatively short for a relatively large estuary, ranging from less than 1 day to 4 days for various tidal level and freshwater flow combinations. When the tidal range and freshwater discharge are both small, then the local tracer residence time in the upper part of the estuary can be significantly longer than the values predicted for the middle and lower reaches of the estuary.     

珠江口海域主导光学因子的遥感分类及其变化特征

基于2014年5月和8月珠江口海域的现场和实验测量数据,分析了光学因子和生态参数的动态变化特征,并找出该海域的主导光学因子;基于模拟的MODIS数据,构建了水体组分特征波长处吸收系数的遥感反演模型,并结合MODIS卫星遥感影像,依据IOCCG规则对主导光学因子进行遥感分类,揭示了珠江口海域2014年逐月水体主导光学因子的动态变化特征。结果表明,珠江口海域水体以a_d、a_g以及两种共同主导类型为主,并且a_g、a_d两种光学因子主导类型所占比例最大,其次是a_g主导类型,a_d主导类型所占比例最小。同时发现a_d（442）、a_dg（442）均与无机悬浮物浓度有较好的正相关关系,说明CDOM和悬浮泥沙具有相似的来源和动力变化过程。     

Effects of the Anthropogenic Activities on the Morphological Evolution of the Modaomen Estuary, Pearl River Delta, China

Owing to the intensive human activities, the Modaomen Estuary has been significantly modified since 1950s, which has resulted in considerable changes of hydrodynamics and morphodynamics in the area. In this paper, the effects of the anthropogenic activities on the hydrodynamics and morphological evolution in the estuary at different stages are systematically assessed based on the detailed bathymetric data and field survey. The results show that the human activities have caused the channelization of the enclosed sea area in the Modamen Estuary; fast seaward movement of the mouth bar with high siltation; expansion of the channel volume due to channel deepening. The paper also highlights the main hydrodynamic changes in the estuary, including the rise of the water level; the distinguishing changes of tidal range before and after the 1990s (decrease and increase respectively); as well as the increase of the divided flow ratio. It is found that reclamation is the main factor promoting the transition of nature of the estuary from runoff dominant to runoff and wave dominant, and sand mining activities are mainly to strengthen the tidal dynamic and to low the water level. The results provide useful guidance for better planning of the future developments in the estuary and further research in the area.     

A methodology for defining homogeneous water bodies in estuaries – Application to the transitional systems of the EU Water Framework Directive

A methodology is developed and tested for division of estuarine and coastal systems into water bodies for monitoring and management purposes. This division is often implicit in the choice of sampling stations and in pollution abatement measures applied to different locations – it is now an explicit requirement of European Union Directive 2000/60/EC (Water Framework Directive) and recommended by United States Agencies such as EPA and NOAA. The approach considers both natural characteristics and the human dimension, by means of a stepwise methodology, which considers, on the one hand, morphology and salinity distribution, and, on the other, appropriate indicators of pressure and state. In the present application, nitrogen and phosphorus loading was used as the pressure component and chlorophyll a and dissolved oxygen as indicators of state. The criteria for system division were defined based on (1) an adimensional shape factor and salinity classes for the natural component; and (2) a normalised pressure index and (ASSETS) eutrophication symptom classes for the human dimension. Water quality databases and GIS were used to develop spatial distributions for the various components, and the results were aggregated into a final water body division, using tidal excursion as a “common sense” test. The methodology was applied to three well-studied systems in Portugal, a tubular estuary (Mondego), a wide lagunal estuary (Sado) and a coastal barrier island system (Ria Formosa). Although a final definition of water bodies will usually be a policy decision, this type of approach for the division of coastal systems into management units scientifically informs the decision-making process.     

Management of a shallow temperate estuary to control eutrophication: The effect of hydrodynamics on the system’s nutrient loading

The Mondego estuary, a shallow warm-temperate intertidal system located on the west coast of Portugal, has for some decades been under severe ecological stress, mainly caused by eutrophication. Water circulation in this system was, until 1998, mainly dependent on tides and on the freshwater input of a small tributary artificially controlled by a sluice. After 1998, the sluice opening was effectively minimised to reduce the nutrient loading, and the system hydrodynamics improved due to engineering work in the upstream areas. The objective of the present study was to evaluate the effect of the mitigation measures implemented in 1998. Changes to the hydrodynamics of the system were assessed using precipitation and salinity data in relation to the concentrations of dissolved inorganic nutrients, as well as the linkage between dissolved N:P ratios and the biological parameters (phytoplankton chlorophyll a concentrations, green macroalgal biomass and seagrass biomass). Two distinctive periods were compared, over a ten year period: from January 1993 to January 1997 and from January 1999 until January 2003. The effective reduction in the dissolved N:P atomic ratio from 37.7 to 13.2 after 1998 is a result of lowered ammonia, but not the oxidised forms of nitrogen (nitrate plus nitrite), or increased concentrations of dissolved inorganic phosphorus. Results suggest that the phytoplankton is not nutrient limited, yet maximum and mean biomass of green macroalgae was reduced by one order of magnitude after the mitigation measures. This suggests that besides lowering the water residence time of the system, macroalgal growth became nitrogen limited. In parallel to these changes the seagrass-covered area and biomass of Zostera noltii showed signs of recovery.     

基于PCA法的沉积物质量评价模型构建及其应用

本研究针对我国沉积物质量评价存在的问题,基于近海沉积物监测常规指标和海洋沉积物质量标准,结合主成分分析法（PCA）构建了沉积物质量的评价指标体系和数学模型,划分出三类沉积物质量综合指数（F）的量化区间值,并在九龙江及毗邻海域进行了示范应用。模型结果显示九龙江口沉积物质量以二类为主,具有面源和点源的复合污染特征,关键区域为漳州近岸海域;单因子评价结果表明主要污染指标为Zn、Cu和Pb。评价结果较好地反应了沉积物环境质量现状,为九龙江口底质保护和治理提供了技术支撑。     

长江口南支潮流的一个数值模拟

为了能够精确地拟合天然水域不规则的水陆边界,并能保持有限差分数值计算在矩形网格中进行,本文利用Thompson的数值网格生成技术,在长江口南支七丫口至横沙河段设计了一个椭圆型边界拟合坐标系,并在这个坐标系下建立了平面二维潮流数学模型。通过数值求解此数学模型,实现了计算区域内现状潮流的一个数值模拟,模拟结果表明,模式的设计是成功的。     

Short-term Effects of Intertidal Macroalgal Blooms on the Macrohabitat Selection and Feeding Behaviour of Wading Birds in the Mondego Estuary (West Portugal)

The possible effects of intertidal macroalgal blooms on the feeding distribution and behaviour of the waders in the Mondego Estuary (West Portugal) are discussed in the present paper. The presence of algae over the sediments did not deter the waders absolutely from feeding in a place, but most species did show some tendency to avoid highly eutrophic areas. However, there were no clear signs that the species redistributed themselves within the Estuary as the amount of algae changed, nor did the alternative feeding habitats (the salt pans) seem to be used more when algae were particularly abundant on the mud flats. In one species, bird numbers, rather than the amount of algae present, explained the numbers of birds using the salt pans when the two factors were considered together in a multiple regression analysis. There were no striking differences between algae-free and algae-weeded areas in some aspects of the foraging of two representative species, the scolopacid DunlinCalidris alpinaand the charadriid Grey PloverPluvialis squatarola. The results suggest either: (1) that the presence of algae did not strongly influence the distribution of the feeding waders, at least in the conditions prevailing during the study; or (2) that most waders were able to adapt to feeding on weeded areas; perhaps through subtle and undetected alterations in their feeding behaviour.     

PEIOS系统远程用户信息集成若干问题的探讨

PEIOS系统是珠江口海域立体监测技术示范系统，其总体是研制一个以水质监测为核心，以珠江口水域为监测范围的河口区近海洋环境监测东范系统，该系统接收多种来源的远距离观测数据（卫星，岸基雷达，自动气象站，自动水质测试仪等），并具有数据实时更新的能力，它的远程用户模块可通过可电话拨号连接主数据库，进行相关的空间信息查询与分析，是相对独立的功能模块，同时，该模块还具有集成本地（用户端）数据的功能，作者提基于优秀地理信息系统平台的技术解决方案，并在AutodeskWorld2.0平台上成功开发了远程用户模块，实现了多源数据在远程用户端的GIS集成。     

长江口夏季低氧区形成及加剧的成因分析

通过对比长江口及其邻近海域历史调查资料和目前的现场监测数据(1958-09—1959-09,2003-09,2005-07及2009-08),分析了长江口夏季低氧区的历史变化,探讨了低氧形成及其加剧的原因。结果表明:20世纪90年代之后长江口季节性低氧区出现扩大化、严重化趋势;低氧区的形成主要受控于物理过程和自然作用,包括长江冲淡水、沿岸流、上升流、台湾暖流及黑潮等各大流系及其与温度等理化因素相互作用下形成的水体层化、锋面过程、气旋式冷涡;低氧现象加剧原因复杂,影响因子有气候变化导致的海水温度上升,长江径流量、输沙量变化,长江流域降雨变化等,而富营养化的加剧对低氧加剧并非起主导作用。     

徐六泾控制节点污染物运移轨迹模拟

对三维多功能动力-生态耦合模式(COHERENS)进行二次开发,运用"网格冻结法"实现了漫滩和露滩过程中的干湿交替,突破其为固定边界和限制水深的局限,使COHERENS模式成功应用于长江口浅滩过程的模拟。对潮位和水流流速的模拟结果进行了较好地验证。在斜压流场的基础上对示踪颗粒拉格朗日运移进行追踪,对污染物欧拉输运进行数值模拟。以徐六泾控制节点横断面设置颗粒示踪子和污染物排放点,对排放的悬浮颗粒物质和溶解性污染物的运动轨迹和特征进行了模拟和比较分析,给出了模拟期间的流场特征和污染物输移规律。     

Tidally driven pore water exchange within offshore intertidal sandbanks: Part II numerical simulations

Field measurements presented by [Gibbes, B., Robinson, C., Li, L., Lockington, D.A., Carey, H., 2008. Tidally driven pore water exchange within offshore intertidal sandbanks: Part I Field measurements. Estuarine, Coastal and Shelf Science 79, pp. 121–132.] revealed a tidally driven pore water flow system within an offshore intertidal sandbank in Moreton Bay, Australia. The field data suggested that this flow system might be capable of delivering nutrients, and in particular bio-available iron, across the sediment–water interface. Bio-available iron has been implicated as a key nutrient in the growth of the toxic marine cyanobacteria Lyngbya majuscula and therefore this pore water exchange process is of interest at sites where L. majuscula blooms have been observed. In this study two-dimensional numerical simulations were used in conjunction with hydraulic data from field measurements to further investigate the tidally induced pore water flow patterns. Simulation results generally showed good agreement with the field data and revealed a more complex residual pore water flow system in the sandbank than shown by the field data. The flow system, strongly influenced by the geometry of the sandbank, was characterized by two circulation cells which resulted in pore water discharge at the bank edge and also to a permanently ponded area within the sandbank interior. Simulated discharge volumes in these two zones were in the order of 0.813 m³ and 0.143 m³ per meter width (along shore) of sandbank per tidal cycle at the bank edge and sandbank interior respectively. Transit times of pore water circulating through these cells were found to range from ≈ 17 days to > 60 years with an average time of 780 days. The results suggest that the tidally driven flow systems might provide a mechanism for transport of bio-available iron across the sediment–water interface. This flow could constitute a previously unrecognized source of bio-available iron for L. majuscula blooms in the Bay.     

珠江河口一维河网、三维河口湾水动力连接计算

对珠江河口一维河网和三维河口湾斜压模型的水动力连接计算进行了研究。通过一维河网求解公式递推出口门连接处水位、流量关系式,然后依据三维模型计算得到口门连接处流量值,根据口门连接处的水位及流量连接条件计算出口门连接处的水位值,以此水位作为边界条件分别计算一维河网和三维河口湾斜压模型,实现了一维和三维斜压模型的水动力连接计算。对模型的连接计算进行验证对比,结果基本令人满意。     

Seasonal Investigations of Dissolved Organic Carbon Dynamics in the Tamar Estuary, U.K.

A high temperature catalytic oxidation (HTCO) technique was used to measure dissolved organic carbon (DOC) during seasonal surveys of the Tamar Estuary, U.K. At the time of the programme, the field of DOC analysis had been plagued by numerous analytical difficulties. However, using thorough calibration of the analytical systems and the systematic analysis of an internal reference material, a valuable estuarine DOC data set was produced. The range of DOC concentrations observed (478–110 μM C) is consistent with the published data for riverine and coastal sea waters respectively. The Tamar Estuary is a freshwater DOC-dominated system, with strong correlation between lateral DOC distribution and salinity. However, mixing behaviour was not strictly conservative. During tidal cycle studies at a fixed station, DOC concentrations appeared to be uncoupled from salinity, and were inversely related to turbidity. It is concluded that tidally-induced resuspension of bottom sediments provided the dominant control mechanism for DOC concentration. The Tamar Estuary shows contrasting behaviour to the larger, more heavily impacted, Severn Estuary. Hence it is likely that the behaviour of DOC in estuaries cannot be classified as typical per se, but is a function of the natural and anthropogenic characteristics of the catchment and hydrology.