Abstract:The distribution of dissolved nutrients in Sanggou Bay was investigated in April,July and November 2006 and January 2007.The concentration and distribution of dissolved inorganic nitrogen (DIN),phosphate (PO43-) and silicate in Sanggou Bay showed obvious seasonal variation.DIN reached the lowest level in spring and the highest level in autumn; PO43- concentration was at the lowest level in summer and the highest level in autumn; while Si concentration reached the lowest point in autumn and the highest point in summer.Limiting nutrients for the growth of phytoplankton were assessed by the method of theoretical half saturation constant (Ks) and stoichiometric ratios among DIN,PO43-and SiO2-3.The results showed that in spring,the percentage of stations with concentration of DIN and PO43-below Ks was 44% and 39%,respectively,suggesting for potential N and P limitation.In summer,the percentage of stations with PO43-concentrations below Ks was 68%,and potential P limitation was at 79% probability,N and Si limitation were at 5% and 0% probability,respectively.In autumn and winter,Si was the major limiting nutrient,and the potential Si limitation was at 94% and 78% probability,respectively.The effect of mariculture activities,land based input,and water exchange with Yellow Sea on the space time distribution of nutrients were discussed.Based on the long term data,more attention should be paid to DIN enrichment in Sanggou Bay.
