Abstract:
Thedistnibution of nutrients in surface seawater in adjacent area of Weizhou Island was analyzed based ondata obtained from30 surveys from 2004 to 2013.Theresult showed that the concentrationsof DIN and PO4-Pinseawater decreased gradually in onder of winter,autumn,and summer.However,the concentration of SiO³-Sishowed no obvious seasomal vanation.Becauseof the terrestrial input,the inter-aunnual DIN waried greatly andshowed anupgrade tendency.NOz-N showed thesameannual fluctuationas DIN and contributed mostlyto DIN.The annual mean concentration of NH4-N and SiO¹-Si decreased slightlywhile theannual mean concentration of PO4-P increased fistly before it decreased.Further analysis of the nutrients limitation for phytoplankton gowthimplied that theadjacent waters of Weizhou Island was in oligotmophic status of PHimitation.In recent 10 years,Si/N ratio gradually decreased and N/P ratio decreased firstly and then increased,which may change the phyto-plankton community structure.