A long-term record of epilimnetic phosphorus patterns in recovering Onondaga Lake, New York

Steven W. Effler, Susan M. O'Donnell
2010 Fundamental and Applied Limnology  
A retrospective analysis for a 23 year record of spectrophotometically determined forms of phosphorus (P) is presented for the epilimnion of Onondaga Lake, New York, a period over which it was transformed from severely culturally eutrophic to mesotrophic through reductions in point source inputs. Patterns of fi ve forms of P were evaluated, total P (TP e ), total dissolved P (TDP e ), soluble reactive P (SRP e ), particulate P (PP e = TP e -TDP e ) and dissolved organic P (DOP e = TDP e -SRP e
more » ... based on weekly observations from multiple epilimnetic depths for the April (spring turnover) -October (fall turnover) interval of each year. A 10-fold reduction in the effl uent concentration of the dominant source (TP Metro ), made in several steps, caused dramatic decreases in summer average epilimnetic P concentrations, 6.8-fold for TP e , 4.8-fold for PP e , 14.9-fold for TDP e , 8.4-fold for DOP e , and 70-fold for SRP e , as well as improvements in common metrics of trophic state. Long-term patterns of summer average concentrations of each of these forms tracked the progression of TP Metro at an annual time step. Both short-and long-term patterns of in-lake concentrations, particularly for SRP e , support the position that the lake remained often nutrient-saturated through much of the record, but shifted to distinctly P limited in response to the most recent (2005) reduction in TP Metro . The diagnostic value of monitoring the dynamics of these forms of P at multiple time steps to track lake metabolism and features of the P cycle is demonstrated, including uptake of dissolved forms, effects of Daphnia metabolism, dynamics of phytoplankton uptake, and long-term responses to reductions in external loading. Evidence is presented that a noteworthy fraction of the PP e pool is associated with non-phytoplankton particulates.
doi:10.1127/1863-9135/2010/0177-0001 fatcat:5wnbn6gjlbbz5bvgbnyhbxt23y