Using algal biomass to evaluate numeric nutrient criteria in an estuary: A case study of Daliaohe Estuary in China

This paper presents an initial inquiry into model-based numeric nitrogen and phosphorus criteria for estuaries based on stressor-response models between nutrients and algal biomass (Chl-a concentration) and further studies the effect of salinity (S) on nutrient criteria. Field data collection and associated indoor modeling were conducted in Daliaohe Estuary. Dissolved inorganic nitrogen (DIN), total nitrogen (TN), phosphate (PO43−) and total phosphorus (TP) eco-criteria of Daliaohe Estuary in China were calculated at salinities of 15, 25 and 31. The results suggested that the variation in S had significant influence on the DIN and TN eco-criteria and no obvious effect on the PO43− and TP eco-criteria. The values of DIN and TN eco-criteria increased with either higher or lower salinity concentrations, and were strongly linked to the effects of salinity on algal nutrient absorption and utilization, growth, metabolism, and osmotic pressure.