Evaluation of Physicochemical Environment and Water Quality in the Laizhou Bay in Spring of 2013

Abstract:

In recent years, the marine environment and ecosystem in the Laizhou Bay have obviously deteriorated, which caused serious damage to the ecological environment and biological community. In order to understand the environmental qualities of the Laizhou Bay and the adjacent sea areas, we analyzed the distribution of salinity, pH, dissolved oxygen (DO), chemical oxygen demand (COD), disolved inorganic nitrogen (DIN) and PO4-P based on field data obtained from the Laizhou Bay in June 2013. The nutrition level and organic pollution in this area were also evaluated with potential eutrophication assessment standards and grading of organic pollution respectively. The results showed that DO and COD concentrations at all surveyed stations met the first class seawater quality standard. DIN pollution was serious mainly caused by the terrestrial input. At approximate 31% of investigated stations the DIN concentration exceeded the limit of the fourth class seawater quality standard. The level of PO4-P was lower and satisfied the first class seawater quality standard at all investigated stations. Our results suggested that the N/P ratio was higher than the Redfield value 16, and that phosphate was the limiting factor in the growth of phytoplankton. The nutritional pattern in the Laizhou Bay had evolved from nitrogen limiting to phosphorus limiting. The higher N/P ratio may alter the phytoplankton population, which will consequently affect the whole ecosystem. The nutrition status in the Laizhou Bay was phosphorus limiting potential eutrophication, and the organic pollution remained at the second level in spring 2013. These indicated organic pollution in this sea area; however, the pollution was alleviated compared to the summer 2007.