Stable isotopes in juvenile marine fishes and their invertebrate prey from the Thames Estuary,UK, and adjacent coastal regions     

Chris D.B. Leakey  Martin J. Attrill  Simon Jennings  Mark F. Fitzsimons 《Estuarine, Coastal and Shelf Science》2008

Estuaries are regarded as valuable nursery habitats for many commercially important marine fishes, potentially providing a thermal resource, refuge from predators and a source of abundant prey. Stable isotope analysis may be used to assess relative resource use from isotopically distinct sources. This study comprised two major components: (1) development of a spatial map and discriminant function model of stable isotope variation in selected invertebrate groups inhabiting the Thames Estuary and adjacent coastal regions; and (2) analysis of stable isotope signatures of juvenile bass (Dicentrarchus labrax), sole (Solea solea) and whiting (Merlangius merlangus) for assessment of resource use and feeding strategies. The data were also used to consider anthropogenic enrichment of the estuary and potential energetic benefits of feeding in estuarine nursery habitat.  相似文献   

长江口及邻近海域浮游端足类分布特征   总被引：1，自引：0，他引：1       下载免费PDF全文

蔡萌  徐兆礼  朱德弟 《海洋学报》2008,30(5):81-87

根据2002—2003年长江口28°00'~32°00'N,122°00'~123°30'E海域4个季节的海洋调查数据,运用定量、定性方法探讨了长江口及邻近海域浮游端足类总丰度的平面分布、季节变化及与渔场的关系,分析了优势种的数量变动和对浮游端足类总丰度的贡献,并与东海外海种类的生态特征做了比较。结果表明,长江口及邻近海域浮游端足类丰度季节变化主要受温度的影响,而平面分布变化则与盐度相关。平均丰度在夏季最高(2.75个/m3),在冬季最低(0.10个/m3)。本次调查共发现浮游端足类49种,江湖独眼钩虾(Monoculodes limnophilus)和裂颏蛮(Lestrigonus schizogeneios)是最主要的优势种,江湖独眼钩虾在四季中对端足类总丰度都有很大贡献,在春秋冬三季为第一优势种,说明江湖独眼钩虾对相对较低的温度具有一定的适应能力,裂颏蛮则只在春夏秋季有较大贡献,其中夏季裂颏蛮贡献率为0.87,高于江湖独眼钩虾,这与裂颏蛮具有较高温度的环境适应能力有关。浮游端足类种类数与总丰度都与表层温度的线性相关显著,同表层盐度的相关不显著。作为长江口鱼类的重要饵料之一,浮游端足类的数量分布对长江口和舟山海域渔场的形成有重要的意义。  相似文献   

Temporal and spatial distribution of dissolved copper, lead, zinc and cadmium in the Changjiang Estuary and its adjacent waters     

WANG Changyou  WANG Xiulin  WANG Baodong  ZHANG Chuansong  SHI Xiaoyong  ZHU Chenjian 《海洋学报(英文版)》2008,27(4):73-82

Heavy metal concentrations were measured in the Changjiang Estuary and its adjacent waters. Results from a systematic survey in April 2002 to March 2003 indicate that the ranges of the concentrations of dissolved copper, lead, zinc and cadmium in the study waters are 1.01 - 6.86, 0. 10 - 0.39,3.17 - 9.12 and 0.011 - 0. 049 μg/dm^3 , respectively. Similar to zinc, the behavior of dissolved copper was essentially conservative, but high scatter has been observed for high salinity samples, which can be attributed to the decomposition or mineralization of organic matter by bacteria. Dissolved lead may have active behavior with an addition at high salinity. Overall concentrations of dissolved cadmium increase with salinity. The mean values of these dissolved metals calculated for the surface waters were higher than those for the middle and bottom ones. External inputs of dissolved heavy metals to the surface waters were the likely explanation for these higher values. The maximum seasonal average values of dissolved copper and zinc were found in summer, reflecting higher amounts of riverine input in this season. In contrast, the maximum seasonal average values of dissolved lead and copper were found in winter and the lowest ones in summer, respectively, which might be asso- ciated with a combination of low concentration with heterogeneous scavenging. Concentrations of these dissolved metals found for the Changjiang Estuary fall in the range observed for the other estuaries but are noticeably higher than those from uncontaminated rivers, except for cadmium. Compared with observations for the Changjiang Estuary in the last two decades, it is clear that the Changjiang estuarine waters has been contaminated with copper, lead, zinc and cadmium during China＇ s industrialization, but concentrations of them have decreased in the last few years.  相似文献   

Field investigation of ridge–runnel dynamics on an intertidal mudflat     

Jon J. Williams  Paul A. Carling  Carl L. Amos  Charlie Thompson 《Estuarine, Coastal and Shelf Science》2008

Flow-parallel linear ridge–runnel (R–R) bedforms composed of mainly cohesive sediments have been investigated at an intertidal site located at Hills Flats in the Severn Estuary, UK. It is argued that the sequences of sand–mud laminae in the ridge sediments indicate strongly that R–R are depositional bedforms. Faint R–R topography scoured in the underlying soft bedrock and parallel rows of coarser particle now found at the base of ridges are evidence of secondary vortices that may have provided a catalyst for mud ridge growth. Bed shear stress remains below the erosion threshold for all but the most recent and weak surficial mud deposits which are removed by evorsion [mechanical erosion by turbulent flows that may also carry sand and/or gravel] during Spring tidal flow ca. 60 cm/s. Differences in flow characteristics between ridges and runnel are minor. Corrasion [to erode or be eroded by abrasion] by sparse coarse sediment largely prevents net deposition in the runnels. Over time a slight imbalance between mud deposition and erosion rates allows slow growth of the ridges suggesting that these mudflats may be especially sensitive to slight changes in the local hydrodynamic regime and/or sediment supply.  相似文献   

利用小型底栖动物对沉积物重金属污染的评估     

华尔  张志南  范士亮  刘海滨 《中国海洋大学学报(自然科学版)》2009,39(3)

采用Hakanson的生态风险指数法和自由生活海洋线虫与底栖桡足类数量之比(N/C比值)的变动对长江口及其邻近海域沉积环境重金属污染状况进行评估.结果表明,研究海域沉积物受到重金属元素Cr,Cu,Zn和As不同程度的污染,近岸站位受测各污染物均呈现中度污染,离岸站位为轻度污染,其中Zn累积最严重.单个污染物潜在生态危害参数表明,受测污染物对海洋生态系统的潜在生态危害非常轻微,其中As和Cu是最主要的生态风险贡献因子.小型底栖动物群落丰度及分布验证了此结果,对As和Cu累积具有明显的生态响应.N/C比值法对研究海域沉积物重金属的污染评估结果与Hakanson的生态风险指数评估结果基本一致,特别是对Cu和As元素的污染评估.结合生物群落分析,利用小型底栖动物两大类群数量之比(N/C)是一个简易可行的沉积环境监测方法.  相似文献   

Nutrient budgets averaged over tidal cycles off the Changjiang (Yangtze River) Estuary   总被引：1，自引：0，他引：1  

Lei Gao  Dao-Ji Li  Ping-Xing Ding 《Estuarine, Coastal and Shelf Science》2008

During the spring tide period in November 2005, continuous observations were conducted over 25 h (approximately two M₂ tidal cycles) at 12 stations within the Changjiang (Yangtze River) Estuary; and among them nine stations formed a closed rectangle. The observation items included current, salinity, suspended particulate matter (SPM), and nutrients. By establishing a simplified model, physical and chemical hydrography data were used to calculate the net and tidal-averaged budgets of seawater, salt, SPM, and nutrients in this rectangle. The results showed that the inflows and outflows of conservative seawater and salt, as well as SPM, matched well with deficits less than 10%; whereas the outputs of the five nutrient species were only 52%–86% of the respective inputs, suggesting the study area acted as a nutrient sink. Processes that might contribute to the nutrient budgets in the study area were discussed, including phytoplankton uptakes, exchanges at sediment-water interface, atmospheric depositions, nitrogen fixation, and denitrification.  相似文献   

Analyzing the habitat suitability for migratory birds at the Chongming Dongtan Nature Reserve in Shanghai,China   总被引：1，自引：0，他引：1  

Bo Tian  Yunxuan Zhou  Liquan Zhang  Lin Yuan 《Estuarine, Coastal and Shelf Science》2008

The Dongtan Nature Reserve, one of the largest nature reserves in East Asia, is located in the mouth of the Yangtze Estuary and is an important habitat for migratory birds. The Dongtan wetlands were listed in the Chinese Protected Wetlands in 1992, and were designated as internationally important under the Ramsar Wetlands Convention in 2001 and as a national nature reserve in 2005. By their very nature and location, the estuarine and coastal habitats are dynamic and their biodiversity conservation and management relies on up-to-date spatial information. By establishing qualitative and quantitative relationships between bird populations and key habitat factors such as elevation, land cover type, tidal creek density and macrophytobenthos biomass, we developed an object-oriented image approach, in conjunction with Geographical Information Systems and the data from current field surveys, to analyze and assess the habitat suitability for the main types of birds, namely Anatidae, Charadriidae, Ardeidae and Laridae, at the reserve. The results from this study showed that about 40% of the total area of the Dongtan Reserve contained suitable habitats for these four bird families. The Scirpus mariqueter zone, mudflat zone, and tidal creeks were the most important habitats for these birds. This study indicated the potential of this approach for objective and effective evaluation of the species habitat suitability in a dynamic estuarine and coastal area. The implications of the results as a tool for biodiversity conservation, wetland conservation, and ecosystem management are discussed.  相似文献   

Approach of moving boundary and its application in 3D tidal current simulation of Changjiang (Yangtze) River Estuary based on ECOMSED model   总被引：1，自引：0，他引：1  

KUANG Cuiping  SUN Bo  LIU Shuguang  GU Jie  YU Weiwei 《海洋学报(英文版)》2009,28(4):78-85

Considering three-dimensional model ECOMSED can not simulate wetting-drying of shoal with its fixed boundary, an approach to represent moving boundary in the model is introduced here. This approach smoothly joints the internal and external mode by making use of wetting and drying technique and is verified by a numerical test which presents a good agreement with the previous test results obtained by other researchers. A three dimensional numerical model is established to simulate the hydrodynamics in spring tide in the Changjiang (Yangtze) River estuary by this modified ECOMSED model which is also validated through the observed field data, the simulation presents a good periodic tidal change. It also successfully simulates the tidal current of computational areas and reproduces the tidal flat intermittent appearance.  相似文献   

Particulate suspended matter concentrations in the Bahía Blanca Estuary,Argentina: Implication for the development of phytoplankton blooms     

Valeria A. Guinder  Cecilia A. Popovich  Gerardo M.E. Perillo 《Estuarine, Coastal and Shelf Science》2009

The inner zone of the Bahía Blanca Estuary is shallow, nutrient-rich and turbid. Tidal energy and water turbulence strongly affect the water column resulting in a well-mixed structure and high concentrations of suspended sediment. The phytoplankton community is mostly dominated by diatoms and the annual pattern has been characterized by a recurrent winter-early spring bloom. Here, we investigated to what extent the temporal variations of suspended particulate matter (SPM) regulate the phytoplankton blooms in the head of the estuary by light-limitation. Sampling was done on a fortnightly basis (weekly during the blooming season) at a fixed station in the inner zone of the estuary from January 2007 to February 2008. SPM concentrations and light extinction coefficients (k) in the water column were significantly correlated and showed relatively lower values during the phytoplankton maximal biomass levels. During winter, SPM and k reached values of 23.6 mg l⁻¹ and 0.17 m⁻¹ which were significantly lower than the annual means of 77.6 mg l⁻¹ and 2.94 m⁻¹, respectively. The particulate organic matter (POM) concentration was significantly correlated with the calculated phytoplankton biomass although the contribution of the latter to the total POM was rather low. Both, POM and biomass, had maximal values during winter (21.8 mg l⁻¹ and 393.5 μg C l⁻¹) and mid summer (24.3 mg l⁻¹ and 407.0 μg C l⁻¹), with cell densities up to 8 × 10⁶ cells l⁻¹ and chlorophyll a up to 24.6 μg l⁻¹. Our results suggest that the decrease of SPM concentrations in the water column with a concomitant increase in the penetration of solar radiation seems to be one of the main causes for the development of the phytoplankton winter bloom in the Bahía Blanca Estuary.  相似文献   

GIS支持下近百年来闽江口海底地形地貌演变     

徐晓晖  陈坚  赖志坤 《台湾海峡》2009,28(4):577-585

利用ArcGIS建立了闽江口1913、1950、1975、1986、1999、2005年海底数字地形模型，在坐标系统和潮位基准面转换的基础上分析研究了闽江口的岸线、浅滩面积、海底冲淤和河口断面地形近百年来的变化特征．研究结果表明：①闽江口河道从1913年到2005年期间，梅花水道西段变窄，乌猪水道向东迁移，琅岐岛东岸淤积；梅花镇东侧的闽江口南岸岸线向前推进，但近年来推进速率明显减小．②梅花水道浅滩不断发育，闽江北支由单一的川石水道变成川石水道和壶江水道并存，并且闽江北支成为闽江入海泥沙的主通道．③1913—1950年间闽江口海底淤积较快，1913～1999年淤积速率逐渐减小，1986～1999年间出现净冲刷．④河口三角洲前缘在河口南部以侵蚀后退为主，河口区北部以进积为主．  相似文献