Nutrient Distribution and Eutrophication Assessment for the Adjacent Waters of the Yellow River Estuary

Based on the nutrient data from two cruises of oceanographic survey including 33 stations carried out in the adjacent waters of the Yellow River estuary (38°02′00″～37°20′00″N、119°03′24″～119°31′00″E) in May and August of 2005,the distribution and composition of silicate (SiO3-Si)、reactive phosphate (PO4-P) and dissolved inorganic nitrogen (DIN) were studied,and the degree of eutrophication was evaluated. The results showed that the high nutrient concentration area was located to the south of the Yellow River estuary. SiO3-Si and PO4-P concentrations were higher in August than those in May,but DIN concentration was lower in August than that in May. Both SiO3-Si and DIN concentration in the surface seawater showed significant negative relateship with salinity (P0.01 ),while DIN in the surface seawater showed significant positive relateship with COD. The ratio of DIN to P was 136 and 54.3 in May and August,respectively,and PO4-P was the nutrient limiting phytoplankton growth. The average eutrophication index (EI) was larger than 1 and the eutrophication area occurred at sea area to the south of the Yellow River estuary,and COD and DIN maybe the primary factor leading to the eutrophication.