Distribution characteristics of C, N and P in Liusha Bay surface sediment and their pollution assessment

We collected the sediment and water samples from breeding areas, farming areas and non-farming areas outsideLiusha Bay quarterly during May, 2012 to January, 2013, and determined the total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) content in the sediment, as well asdissolved oxygen (DO) and temperature (T) in the bottom water, hydrodynamically analyzing the distribution characteristics of C, N, P and their pollution. The results indicate that the physical terrain of Liusha Bay determined the slow flow of water inside the bay and the slow water exchange between inner and outer parts of bay. The DO of bottom water significantly rose from spring to winter and reached the maximum. The DO inbottom water in inner bay was lower than that in outer bay. The TOC and TP contents in surface sediment had no significant seasonal changes, but the TN contents in spring and summer wereobviously higher than those in autumn and winter. The TOC and TN contents in the sediment of the breeding areas were significantly higher than that in the non-breeding area, being the highest in the inner bay. The TP content showed no significant time and spatial difference. The annual average pollution indices for TOC, TN and TP were 1.29, 2.98 and 0.92, respectively, which indicated that the bay had suffered medium organic carbon pollution and low nitrogen pollution, andcurrent aquaculture status had significantly acceleratedeutrophic sedimentation in Liusha Bay.