Nitrogen, phosphorus nutrient distribution in spring and potentially eutrophic evaluation of seawater in culture zones of Tangdao Bay

On the basis of investigation data during 2 cruises from March to May 2010 ,variation characteristics of inorganic nutrient (NO₃^--N, NO₂^--N, NH₄⁺-N and PO₄^3--P) in net-cage culture areas of Tangdao Bay were analyzed. Finally the eutrophication degree in Tandgao Bay was assessed with the potential eutrophication assessment model. The results showed that the overall nitrogen nutrient content of Tangdao Bay in the spring farming areas, especially for NO₃^--N, is the majority. During winter the water accumulated PO₄^3--P, the water is of eutrophication nutrition level. Late in the season, with the rise of temperature, microorganism and plankton began to use small enrichment of PO₄^3--P. In the spring DIN content is significantly increased, eutrophication evaluation is of significant potential eutrophication level with restrictive phosphorus nutrition.