Differential release of nitrogen and phosphorus from anoxic sediments

Release of dissolved NH4+, NOx, filterable reactive P, Fe(II), and S2- from reservoir sediments under anoxic conditions were measured using mesocosms. The sediments were a net sink for NOx, but were a net source of both ammonia and Fe( II). Unexpectedly, the sediments did not release reactive P to any great extent over the 28 d of the experiment. This resulted in an increase in the ratio of dissolved inorganic nitrogen to filterable reactive phosphorus in the overlying water over time. Maintaining a high concentration of dissolved inorganic nitrogen to filterable reactive phosphorus ratios in the overlying water column is a potential method for minimizing the occurrence of cyanobacterial blooms. Therefore, understanding the underlying mechanisms responsible for the retention of P has implications for the ongoing management of the reservoir.