Abstract:In order to study the distribution characteristic of temperature, salinity, pH, dissolved oxygen, DIN and PO3-4-P and evaluate the nutrient level and organic pollution situation in Laizhou Bay and its adjacent waters, samples were collected and analyzed in August 2007. the results showed that the concentration of inorganic nitrogen was relatively high in both surface and bottom of west and southwest waters of Laizhou Bay, which showed an decreasing trend from the west and southwest to the northeast. The PO3-4-P in surface waters was well distributed, a small high value area was found in the middle waters of Laizhou Bay, the concentration decreased from the center toward the periphery gradually. Concentrations of PO3-4-P in bottom waters were different from those in surface waters correspondingly, but the scope of high value area was greater and isoline was more intensive. According to the correlation analysis between nutrient and salinity, there was significant negative correlation between DIN and salinity, indicating that the riverine input was the main sowrce of DIN. Since there was not significant correlation betweenPO3-4-P and salinity, riverine input was not the main source of PO3-4-P； the concentration of PO3-4-P was maintained mainly by the decomposition and mineralization of organic materials. In addition, mass reproduction of phytoplankton was another important influencing factor for PO3-4-P. According to water environment evaluation result, the value of N/P ratio was higher than the Redfield ratio of 16,and phosphate was the limiting factor for the growth of phytoplankton. Based on the evaluation mode of eutrophication and organic pollution index, The nutrient level of Laizhon By was medium phosphorus limiting potential eutrophication, and the organic pollution degree remained at the third level in summer 2007, which indicated that the water area had been polluted by organic materials slightly.
