Phosphorus release during decomposition of the submerged macrophyte Potamogeton crispus

The decomposition rate of Potamogeton crispus and its rates of phosphorus (P) release and sedimentation were quantified during natural senescence in a microcosm experiment. The decay of P. crispus was characterized by an exponential model with a mean mass loss coefficient (k) of 0.05 day−1. During the first 10 days, the rapid decomposition phase, k was 0.068 day−1. The rates of P release and total P sedimentation, as well as the dissolved total P, soluble reactive phosphorus, dissolved organic phosphorus, and particulate phosphorus, were quantified throughout the 30-day study period. The nitrogen (N) and P contents of P. crispus increased whereas the carbon (C) content and the C:N, C:P, and N:P ratios decreased near the end of the decomposition phase. In addition, the pH, dissolved oxygen, and redox potential decreased during the rapid release of P. The results indicated that the rate of mass loss was slower from dried plants than from senescent plants. The rapid decomposition rate, which was associated with a high rate of P release, suggests that much of the accumulated P will eventually be returned to the aquatic ecosystem. These data illuminate the mechanisms of decomposition and suggest a strategy of reducing eutrophication by harvesting P. crispus prior to its senescence.