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The Jianghan Plain and the Dongting lake area, located in the middle reaches of the Yangtze River are famous for their abundant freshwater lakes. The lakes have undergone changes in size and number over thousands of years due to natural causes and human activities. The 20th century particularly, witnessed dramatic changes in the freshwater resources of this region. This paper traces and analyzes lake evolution in the middle reaches of the Yangtze River over the past century. Lakes greater than 0.1 km2 in size are mapped using Geographic Information System. Data is acquired and integrated from drainage network maps, relief maps, historical maps and remotely sensed images for different time periods. The results indicate that while there has been little change in the number of lakes over the past century, the lake area has experienced a dramatic decrease of 58.06%. The paper also examines the natural processes and human activities that may have contributed to the decrease in lake area. The results show that the decrease in total lake area appears to coincide with periods of rapid land reclamation in the middle reaches of the Yangtze River. Moreover, uncontrolled land reclamation activities can create an increase in sediment deposition in lakes thereby further reducing the lake size. Reduction of the lake area directly affects flood-control and has a negative ecological impact on the environment and on human life and property. [Copyright &y& Elsevier]

Abstract: The Yangtze Estuary is one of the largest estuaries in the world, with three-order bifurcations and four outlets into the sea. In recent years salt intrusion has been given more attention due to the increase in its level and frequency. In this paper, for the first time, an analytical model is applied to the Yangtze Estuary to analyze the salt intrusion. This model has been tested in 18 estuaries in the world. Originally it was derived for single channel estuaries, which makes the application to the Yangtze Estuary challenging. The results show that this model can describe the salt intrusion from the sea in the Yangtze Estuary very well, with a good fit between computed salinity and measurements. The good results for the Combined South Branch and Combined South Channel indicate that the multi-channel estuary system functions as an entity. Additionally, this model can be used to estimate the river discharge distribution over the separate channels. Further work is needed based on more detailed salinity measurements and accurate bathymetry, particularly for the North Branch of the estuary system. [Copyright &y& Elsevier]

Abstract: Matrix bound phosphine (MBP) is commonly considered an important phosphorus form in the natural environment. This paper presents an investigation of the spatial distribution of MBP and its relationship with the environmental factors in the Changjiang Estuary and its adjacent shelf areas (29.5–32°N, 122–124°E). A total of 32 surface sediment samples were collected from April 24 to 30, 2008. MBP was detected in all samples from the Changjiang Estuary and its adjacent shelf surface sediments (0.1–29.7 ng kg−1). The concentration of MBP decreased from the Changjiang Estuary to the East China Sea shelf. Environmental factors such as organic matter, type of sediments, and redox conditions were found to affect the concentration and distribution of MBP in the marine sediments. Although the MBP levels were low in the marine sediments, the marine biogeochemical cycles of MBP in sediments were established and the information presented here will contribute to the understanding of the biogeochemical cycle of phosphorus. [ABSTRACT FROM AUTHOR]

Abstract: Waterline technique based on satellite remote sensing is potentially one of the most effective tools for studying changes in tidal flat environment and coastlines. However, multi-temporal waterlines obtained from satellite images are often difficult to compare directly because fluctuant tidal conditions may produce different elevation of waterlines. To overcome the difficulty, this study developed a comparable waterline solution to estimate active lateral evolutions using TM satellite images at different tide conditions. Owing to the dynamic properties, the Yangtze River mouth was selected as the case example to test the suitability of the approach, and totally four time slices were partitioned during 1987–2004 for investigating coastline changes. The first step of this technique is to digitize waterlines with various elevations labeling in a time slice. In the second step, the waterlines were merged to generate DEMs and contour maps using the linear gridding interpolation method. In the last step, any interested contour line may be extracted from DEMs and used for comparison of tideland changes. To evaluate the errors in digitizing and interpolation process, quantitative checks were examined after the DEMs were constructed. In order to monitoring the rate of coastline spread, a proposed approach for estimating mean coastline spread distance between two time spans is developed in this paper. To conclude, this work demonstrates the importance of TM/ETM images to provide high-frequency historical topography and morphodynamics information for coastal monitoring and evaluation. [Copyright &y& Elsevier]

Abstract: The Changjiang (Yangtze River) is known to contribute significantly to the eutrophication that has caused drastic changes to the ecosystem of the East China Sea. However, evidence for historical changes in nutrient concentrations and composition and the consequent effects on the ecosystem in the coastal water is sparse. In this paper we present some long-term data for nutrient concentrations and Si:N:P ratios in the freshwater and the river plume and the long-term response of the ecosystem structure in the river plume. These data reveal increases in the dissolved inorganic nitrogen and phosphate concentrations in the Changjiang freshwater by a factor of five from the1960s to the end of the 1990s and a reduction in dissolved silicate by two thirds over the same period. Concomitantly, an increase in DIN concentration and a reduction in silicate concentration both by a factor of two were observed in the surface water of the Changjiang plume. As an ecological consequence to such nutrient changes, the chlorophyll a concentration increased by a factor of four since the 1980s and harmful algal blooms increased rapidly since 1985 in the Changjiang estuary and adjacent sea areas. The macrozoobenthic biomass decreased sharply from the mid 1980s to the present, suggesting that the Changjiang estuary has been in a high eutrophication state since that time. We predict that, due to the continuously increasing nutrient pressure, the symptoms of eutrophication associated with nutrients will worsen in the Changjiang plume in the near future. [Copyright &y& Elsevier]

This paper discusses the distributions of micronutrients in the Yellow Sea (YS) and the East China Sea (ECS), based on the data obtained during field observations. It is pointed out that there are abundant nutrients in the area of the east and northeast of the Changjiang River estuary throughout the year. It is believed that the nutrients come from the extension of the Changjiang River diluted water and the transportation of the Subei coastal water. The maximum extension range of the nutrients of the Changjiang River diluted water was observed during the catastrophic flooding period of the Changjiang River in the summer of 1998. Based on the Redfield ratio (Si:N:P = 16:16:1) at which three essential nutrients are utilized by marine phytoplankton, the Si/N/P ratios are calculated and studied for the upper water of the YS and the ECS. The results indicate that the Si/N ratios are very high, which suggests that silicate is not the limiting factor for the growth of phytoplankton in the YS and the ECS. Under the influence of terrestrial runoff, especially the Changjiang River runoff which is rich in combined nitrogen and has very high N/P ratios, high N/P ratios occur in the Changjiang estuary and its adjacent areas such as the south and southwest of the YS, the inshore area of the ECS and the area east of the Changjiang estuary in spring and summer. As a result, in contrast to general open marine systems, the systems in these areas resemble estuarine ones rather than typical marine ones. The primary production in a considerable portion of the YS and the ECS may be limited by phosphate rather than nitrogen. [Copyright &y& Elsevier]