This modeling work emphasizes the fact that sulfate from canal discharge is impacting even the interior portions of the Refuge, supporting work by other researchers. Statistical analysis indicated that our model is capable of capturing the spatial and temporal variations in surface water sulfate concentrations across the Refuge. The model has been calibrated and validated using long-term monitoring data (1995-2006). Meanwhile, sulfate removal resulting from microbial sulfate reduction in the underlying sediments of the marsh was estimated from the apparent settling coefficients incorporated in the model. In this research, we developed a sulfate mass balance model to examine the response of surface water sulfate in the Refuge to changes in sulfate loading and hydrological processes. Marshall Loxahatchee National Wildlife Refuge (Refuge), a remnant of the historic Everglades, in pumped stormwater discharges with a mean concentration of approximately 50 mg L-1, and marsh interior concentrations at times fall below a detection limit of 0.1 mg L-1. However, it has received less attention compared to phosphorus enrichment. Sulfate contamination has been identified as a serious environmental issue in the Everglades ecosystem. Our analyses will contribute to the understanding of hydrologic conditions that lead to pollutant intrusion into floodplain wetlands. Marsh areas with sediment elevations < 4.9 m were most sensitive to canal water movement. Stage differences between the canal and marsh influenced the movement of water into and out of the marsh, with high inflow rates in the canal increasing intrusion into the marsh. Canal water was always evident in the marsh, and the maximum measured intrusion was 3.9 km from November 2004 through January 2006. Canal water intruded into the marsh to different extents, with the greatest intrusion observed on the west side of the refuge. Using conductivity sondes, we examined canal water movement in and out of the marsh along four transects based on 350 and 500 μS cm−1 conductivity isopleths.
Because this habitat is among the last remaining rainfall-driven areas of the Florida Everglades, understanding the dynamics of canal water intrusion is important for marsh protection and restoration. Marshall Loxahatchee National Wildlife Refuge and subsequent intrusion into a natural soft-water marsh is causing ecosystem alterations. The discharge of nutrient and ion-enriched agricultural and urban runoff into perimeter canals surrounding the Arthur R.
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