| The nutrient in the Ocean is widely studied for its importance to support a high primary productivity, and the absence of any element may limit the growth of the phytoplankton. At present, most studies are focused on the nutrient concentrations of the Yellow Sea and East China Sea, and little is known about the nutrient dynamics of the studied area. The nutrient concentration and distribution in the East China Sea and Yellow Sea are discussed in this paper as well as the nutrient exchange rates between the sediment and the overlying water. Together with the result of the wet and dry atmospheric deposition, the contribution of each nutrient input process is evaluated. Chongming Wetland is also studied for its nutrients removal efficiency. At the same time, the Jiaozhou Bay is explored to update its nutrients data and to get further information about the nutrient fluxes between the Jiaozhou Bay and the Yellow Sea.Based on the results of several representative transects, it is known that Transect PN is influenced by several processes, such as Changjiang runoff, the Taiwan Warm Current and the Kuroshio. The nitrogenous nutrients and silicate mainly come from the river input while phosphate has two main resources, that is, river input and Kuroshio input. The nutrients distribution is highly stratified, with the surface concentration lower than the bottom. Phosphate is a limited factor in the coastal area while in the outer sea area both phosphate and DIN will limit the growth of the phytoplankton. Yellow Cold Water Occupied the bottom of the east of transect A and YE, while in the surface, the influence of the coastal current is more obvious. Transect B is controlled by the Changjiang runoff and Zhejiang Coastal Current. P and DIN in turns act as the limiting factor of the YT section. The nutrients distribution along AS reflects the existence of the Kuroshio. From station to station, the influence of the tide whilp. at E1 E3 E5 it can he clearlv observed that the nutrient concentrationsrise when the tide is low and decline when the tide is high.Sediment-water nutrient fluxes are related to the sediment type, the redox conditions, the temperature etc. The NO3", NO2", DIN, TDN, PO43", DOP, TOP show a net exchange flux from water to sediment, while SiCh2", NHj* are released from sediment to seawater, which will balance the nutrients structure of East China Sea. The exchange flux does show seasonal variation for phosphorous nutrients.With regards to Chongming Wetland, the nutrient removal efficiency is 80.1% for N(V, 56.3% for PO43", 48.8% for SiO32", 78.3% for DIN, 61.3% for TDN and 17.8% for TDP, and for NO2", NH,+, the removal efficiency is less than 4%, while DON, DOP increase 11.8%, 2.0% respectively after flowing through the wetland. The removal efficiency showed seasonal variation, which is highest in winter. After comparing the nutrient concentrations in the groundwater with the overlying water, it is evident that the sediment of the wetland is the source of SiOs2" and the sink of NOs".In October, 2002 and May, 2003, two cruises are conducted in Jiaozhou Bay, both including grid and anchor station. It is obvious that the nutrient concentrations and distribution in Jiaozhou Bay are significantly influenced by the terrestrial input. Compared with spring, the concentration of phosphate and silicate in autumn is high while the concentration of nitrogen compounds is low. The possibility of silicate limit is much higher in spring than in autumn. During a complete tide cycling, the nutrients of Jiaozhou Bay will be inputted from the north of the Bay mouth, and will be outputted from the south.A simple model is established to estimate the nutrient budgets of East China Sea. The result shows that the contribution of the Kuroshio overruns the river runoff, especially for P. Nutrient budgets demonstrate that in the East China Sea, net sink of nitrate and phosphate are estimated to be 201.9><109 mol-yr"1, 14.2*109 mol-yr"1 respectively, 70% of which will then be further transported into the sediment, net source of s... |
PDF Full Text Request