The characteristics of nutrients variation in the Daya Bay

Investigation data in-situ and simulation data in laboratory are used,combining with Chinese Ecological Research Network(CERN) investigation data of 8 cruises from 1997 to 1998 in the Daya Bay,to assess eutrophication status by nutrient quality index(NQI) method in the Daya Bay.Most of water areas of the Daya Bay are oligotrophication,except the cultural water area is mesotrophication.The growth of phytoplankton is governed now by phosphorus instead of by nitrogen in the past.The nutrients content and their chemical forms in the interstitial water,the overlying water and the bottom water are analyzed.The diffusive fluxes of nutrient across sediment-sea water interface have been calculated,and the,average fluxes of ammonium,nitrite,nitrate,phosphate and silicate are 302.0,-0.06,-1.82,2.53,47.96 μamol/(m²·d),respectively.The desorption-absorption of nutrients in surface sediments is simulated and the absorption isotherm of phosphate on sediments is studied under the natural sea water system.The relationship of nutrients and red tides in the Daya Bay are discussed.