Distribution of nutrients and eutrophication assessment in Tianjin Coastal Area
天津近岸海域氮磷营养盐分布及富营养化评价

The physical and chemical factors and the concentrations of ammonia, nitrite, nitrate, phosphorous, and COD of the Tianjin coastal seawater were investigated from October 2007 to August 2008. The spatial and temporal variations of nutrition, as well as the eutrophication level and type, were discussed. The concentrations of inorganic nitrogen, inorganic phosphorous, and COD reached the highest values on October 2007. Most of the nitrogen concentrations were higher than the forth-rate seawater standard of China. In addition, the nitrogen contents in summer and autumn were higher than those in winter and spring because of the contribution of surface runoff. The concentrations of phosphorus were relative low, and the N/P values indicated the phosphorus might become the limiting factors to phytoplankton growth. The results of eutrophication type assessment showed moderate phosphorus limited potential nutritional status of seawater in August 2008. The eutrophication indice of all the sampling months were higher than 1 except for the value of March 2008 in Caijiapu. The highest value of eutrophication indices, 64, occurred on October 2007.