The Jiaojiang Estuary is shallow,macro-tidal dominated and extremely turbid,with a larger variation of the freshwater discharge.The estuarine stratification and classification are analysed by using a set of field data observed in wet season.
In spring tide,the depth-mean peak tidal currents can reach 2 m/s.During flood tide the water column is vertitally homogeneous,but the horizontal salinity gradient is large and there is a fresh water front.A 1 m thick fluid mud layer capped by lutocline is formed when the tidal current is less than 0.3 m/s.As the low-salinity trapped in the fluid mud layer,underlying saltier water enhances vertical mixing when the fluid mud layer is eroded and the water column is only slightly stratified during ebb tide.

The horizontal and vertical distribution patterns of five planktonic copepods,Calanus sinicus, Acartia pacifica, Tortanus derjugini, Acartiella sinensis and Pseudodiaptomus poplesia, predominant in the Jiulong Estuary, were investigated from May 2003 to April 2004. The results showed that the distribution of these copepods was related to the tidal period but that each species had its own specific pattern. C. sinicus showed no tidal vertical migration behavior and was thought to be a non-resident species in this estuary. Among Acartia pacifica,T. derjugini,Acartiella sinensis, more individuals occurred in the surface than in the bottom waters during flood tide, and the pattern was reversed during ebb tide. The epibenthic copepod P. poplesia usually remained in the bottom waters in the upstream part of the estuary, but it displayed strong tidally-oriented vertical migration in the middle reaches of the estuary.Taking into account the hydrographic characteristics of the Jiulong Estuary,it was hypothesized that the planktonic copepods in this estuary had more or less adopted the mechanism of vertically migrating to the surface waters during flood tide in order to make use of the inflowing tide, and then sinking to the bottom during ebb tide to avoid being carried out of the estuary by net outflow.

The ZRE is a very complicated estuary with multi-river inlets.The total sum of river discharge in the upstream(away from the tidal influence region) of the Zhujiang River can be easily measured.However,when the total river discharges into the estuary from eight inlets,it is a very difficult task to obtain a continuous river discharge flux data from each branch of the Zhujiang River.However,the different ratios of river discharges between the river branches can significantly affect the estuarine circulation feature and baroclinic process.Moreover,the accuracy of numerical forecast for the estuarine circulation is very much dependent on the accuracy of the time history of the river discharge flux for each branch.Therefore,it is important to estimate river discharge from each branch in order to improve the accuracy of the model forecast for the circulation of the ZRE.The development of a new estimation method of the river discharges is focused on based on the system identification theory,numer modeling and the time history from the CODAR observed sea surface current.The new approach has been applied to estimating the time history(hourly) of river discharge from each branch in the upstream of the ZRE.

A comprehensive study on the phytoplankton standing stocks, species composition and dominant species in the eutrophic Changjiang (Yangtze River) Estuary (CE) was conducted to reveal the response of phytoplankton assemblage to Changjiang Diluted Water (CDW) and upwelling in the spring. Phytoplankton presented peak standing stocks (13.03 μg/L of chlorophyll a, 984.5×10³ cells/L of phytoplankton abundance) along the surface isohaline of 25. Sixty-six species in 41 genera of Bacillariophyta and 33 species in 19 genera of Pyrrophyta were identified, as well as 5 species in Chlorophyta and Chrysophyta. Karenia mikimotoi was the most dominant species, followed by Prorocentrum dentatum, Paralia sulcata, Pseudo-nitzschia delicatissima and Skeletonema costatum. A bloom of K. mikimotoi was observed in the stratified stations, where the water was characterized by low nitrate, low phosphate, low turbidity, and specific ranges of temperature (18-22 °C) and salinity (27-32). K. mikimotoi and P. dentatum accumulated densely in the upper layers along the isohaline of 25. S. costatum was distributed in the west of the isohaline of 20. Benthonic P. sulcata presented high abundance near the bottom, while spread upward at upwelling stations. CDW resulted in overt gradients of salinity, turbidity and nutritional condition, determining the spatial distribution of phytoplankton species. The restricted upwelling resulted in the upward transport of P. sulcata and exclusion of S. costatum, K. mikimotoi and P. dentatum. The results suggested that CDW and upwelling were of importance in regulating the structure and distribution of phytoplankton assemblage in the CE and the East China Sea.

The hacterioplankton production and bacterioplankton abundance were surveyed in dilution zone of the Changjiang Estuary and a mesocosm experimental device for enriched phosphate experiment and oil contaminated experiment was placed in the waters nearby Luhua Island during October 1997 and May 1998.The results showed that the average bacterioplankton production in spring was higher than that in autumn, the production at the surface water was higher than that at the bottom in the surveyed area; the higher values appeared in the middle of the area.The results from mesocosm experiment with adding phosphate and oil contaminated showed that the bacterioplankton production increased rising trend day by day during the experiment period.

The retrieval of dissolved organic carbon (DOC) distribution by remote sensing is mainly based on the empirical relationship of DOC concentration and colored dissolved organic matter (CDOM) concentration in many literatures. To investigate the nature of this relationship, the distributions and mixing behaviors of DOC and CDOM are reviewed in the world's major estuaries and bays. It is found that, generally, the CDOM concentration is well correlated with the salinity in most estuaries, while DOC usually shows a nonconservative behavior which leads to a weak correlation between the DOC concentration and the CDOM concentration. To establish a good satellite reversion of the DOC concentration, the East China Sea(ECS) was taken as an example, and the mixing behavior of DOC and CDOM as well as the influence of biogeochemical processes were analyzed except for the physical mixing process with the data from late autumn (November, 2010) and winter (December, 2009) cruises. In the two ECS cruises, the CDOM concentration was found to be tightly correlated with the salinity, influenced little by the photochemical or biological processes. The data from the winter cruise show that DOC followed a conservative mixing along the salinity gradient, while in the late autumn cruise it was significantly affected by the biological activities, resulting in a poor correlation between the DOC and the CDOM. Accordingly, an improved DOC algorithm (CSDM) was proposed:when the biological influence was significant (Chl a greater than 0.8 μg/dm³), DOC was retrieved by the conservative and biological model, and if the conservative mixing was dominant (Chl a less than 0.8 μg/dm³), the direct DOC concentration and CDOM concentration relationship was used. Based on the proposed algorithm, a reasonable DOC distribution for the ECS from satellite was obtained in this study, and the proposed method can be applied to the other large river-dominant marginal sea.

In order to characterize the features of radium isotopes in estuaries of Tianjin, a continuous survey and sampling of typical estuaries were conducted from 2013 to 2017 in this study. The activities of natural radioactive radium isotopes (²²³Ra, ²²⁴Ra, and ²²⁸Ra) in groundwater and surface water were measured by the radium-delayed coincidence counting (RaDeCC) system. The non-conservative behavior of the radium isotopes was investigated under hydrogeochemical conditions and urbanization. The results indicated that in terms of horizontal distribution, the activities of radium in groundwater (Hangu, Tanggu, and Dagang) showed an upward trend from north to south and demonstrated a higher figure than surface water (Haihe River and Duliujian River). Concerning the vertical distribution, the activitives of radium at a 15 m burial depth was higher than that at a 30 m burial depth in all measurements. The activities of radium isotopes in the study area increased with the increase of total dissolved solids, and their desorption behavior on Fe-Mn oxides was constrained by the redox intensity. Different hydrogeological conditions resulted in variations in the vertical profile of radium activities. The activity of radium was regulated by seasonal variation and precipitation in groundwater and surface water. In addition, the rapid urbanization has caused a significant impact on the features of radium isotopes in typical estuaries of Tianjin. Meanwhile, radium isotopes can be applied to reflect the impact of urbanization on surface water-groundwater systems. Clarifying and cleverly utilizing the relationship between behavior of radium isotopes and urbanization will promote the development of the Tianjin Binhai New Area in a healthy way.

A simple one-dimensional mathematic model is presented to discuss the balance and behavior of elements in estuary system.The results are as follows:(1) Besides chemical and biological factors, the removal of non-conservative elements is closely concerned with physical processes.(2) When the behavior and balance of non-conservative elements are studied, the mean residence time of these elements is a useful parameter, which can be obtained by combining the information from field-observation with mathematical model.(3) Based on different situations in estuary, the sensitivity and accuracy of the analytical method used must be considered in the study of the removal of such elements.

This paper lists 50 fish species in the Huanghe Estuary, which belong to 9 orders, 22 families and 37 genera.The paper describes the seasonal distributions of these fish species and the succession of the importan fish species during the past 50 a.The anthors discuss the main factors that have resulted in the changes in fish species diversity and the fishery resources.These include the overexploitation of the fishery and the sharp reduction in the fresh water discharges from the Huanghe River.

As a summary of the finding from the investigation of fishes in Beitang Estuary,Tianjin,the paper deals with the young fishes' biomass, composition and change, and studies the spawning habit, spawning time, fecundity, age structure and type of the spawning stocks in the estuary.