Redistribution of Wetland Soil Phosphorus Ten Years after the Conclusion of Nutrient Loading

There is considerable concern about ecological recovery in wetlands that have been enriched with P; however, there are few long-term studies tracking the distribution of the soil P after the termination of P loading. The Blue Cypress Marsh Conservation Area in Florida contains areas with elevated soil P levels from historical loading. The local spatial variation of soil P was determined in a 750- by 150-m area proximal to the historic surface water inflow point and a second area of the same size located in the center of the marsh with no record of historical P impacts. The average soil total P was estimated at 847 mg kg(-1) in the P-enriched area and 643 mg kg-1 in the marsh interior (unenriched). When compared with previously determined historical data, it was estimated that soil P has decreased in the P-enriched area by about 61%. Meanwhile, there was an increase of 82% in P within the unenriched area during this same time period. These results suggest that P has been mobilized from the impacted areas toward the unimpacted marsh along the water flow patterns in the wetland. These observations have implications for restoration of high-P wetland systems. Remobilization from P-impacted to unimpacted areas can expand the area of increased nutrients despite termination of P inputs into the marsh. If remobilization predominates over burial, then it is also unlikely that the overall nutrient status of the system will return to pre-impact levels within a reasonable management time frame (<25 yr).