A Study On Characteristics Of Environmental Variation In Netritic Zone Of Wetland The North Of Jiaozhou Bay

Seasonal and geographical variation of nutriens concentrations, as well as their correlation with salinity, were investigated at 21 station in neritic zone of the Dagu River wetland, located in the northwest part of the Jiaozhou Bay. Based on seasonal variation of nutrients contration, eutrophication level in the northeast part of Jiaozhou Bay was evaluated. Nutrients concentration, structure and long term change were compared between these two areas, in order to evaluate the function of wetland as wasterwater purification system.Annual salinity range in the neritic zone was between 27.60 and 31.99, with maximum in January and minimum in July. Salinity was similar in surface and bottom layers in all months but July, when it was significantly higher in bottom. Ammounia concentration varied from 0.22 to 8.78μmol/L in this study, with no signifiantly season trend. Geographically, it decreased from west to east stations in autumn and winter, but just the opposite in spring and summer. Nitrate concentration varied between 0.94 and 107.4μmol/L. It peaked in February and July, and concentrations in the other months were very similar. Nitrate concentration was observed decreased from the river mouth to offshore stations. Similar geographical trend was also observed in nitrite concentration, which varied between 0.23 and 8.54μmol/L. Generally, nitrite was comparatively high in spring and summer, but fluctuated among various months. Phosphate varied between 0.01 and 5.93μmol/L, with an annual average of 0.76μmol/L. It was highest in September and lowest in April. Phosphate decreased from east to west stations in all seasons but autumn. Silicate acid concentration varied 0.017～38.7μmol/L, with an evident annual cycle. It increased from February to Septermber, then decreased. Decrease from river mouth to offshore stations was observed only in spring and autumn. On nutrients concentration and structure, dissolved inorganic nitrogen cann't be limiting factor in this area. In this investigation, possibility of silicate acid as limiting factor was even higher than phosphate. However, on a rather long time scale, that of phosphate was increasing and that of silicate acid was decreasing.According to our results, nutrients concentration in neritic zone of the Dagu River wetland was similar to the overall average of the entire Jiaozhou Bay, but only half of that observed in the northeast area. Different pollution origins were suggest for these two areas, as the northwest area received mainly agricultual waste but the northeast received industrial and urban waste. Even though, our results indicated that wetland in the estuary can work as buffer for nutrients enrichment, since less eutrophication was observed comparing to the northeast area.