4. Discussion
The higher dissolved nutrient concentrations in the water column and porewater reported in the vicinity of nutrient sources compared with more distant areas confirm the presence of such gradients in our study area and the fact that there are influxes of nutrients into Xincun Bay. We also collected water samples of nutrient runoff at site 2H (effluent from shrimp pond) and site 3H (effluent of sewage), which flow into the bay, and found that the DIN levels in runoff at site 2H varied between 23 and 105 lM, whereas the phosphate levels were approximately 3 lM, and that the DIN levels in runoff at site 3H varied between 15 and 45 lM, whereas the phosphate levels were around 16 lM.