Summary

Description

Surface water and sediment contamination of the Loxahatchee National Wildlife Refuge Refuge is a resource management concern given the proximity of both agriculture and urban development to the Refuge. This study was undertaken to determine baseline data for contaminants present in, and entering into, the Strazulla Marsh Marsh section of the Refuge. The Marsh is an area bordering the perimeter canal that surrounds the Refuge interior, and receives water from rainfall and canal seepage. Water and sediment samples were collected from the same seven locations during a three year study 20012004. Surface water grab samples were collected quarterly for the determination of pesticide and metal concentrations and monthly for the determination of phosphorous and chloride concentrations. Composite sediment samples were collected annually for the determination of pesticide, metal, and polychlorinated biphenyl PCB concentrations. Metal and pesticide concentrations were compared to the state of Floridas Surface Water Quality Criteria SWQC and Sediment Quality Assessment Guideline SQAG values for potential contaminant risks to the Refuges ecosystem resources. While several metals beryllium, cadmium, copper, iron, mercury, lead, selenium were detected at least once in surface waters at a concentration that exceeded their respective SWQC, they were detected so infrequently that adverse impacts are unlikely. Metal concentrations in sediments did not exceed SQAG values. The legacy pesticides DDE and DDD were detected in several sediment samples at concentrations exceeding SQAG values. Total phosphorous TP concentrations in individual water samples ranged from 6 to 215 gL with an overall mean of 23 gL. Orthophosphate OP concentrations in individual water samples ranged from 2 to 58 gL with an overall mean of 11 gL. Total chloride Cl concentrations ranged from below detection to 32 mgL with a mean of 8 mgL over the entire Marsh. Differences between mean wet and dry season TP concentrations at each sampling location were not statistically significant. At one location, OP concentrations during the dry season were significantly lower than concentrations in the wet season. Significant differences in TP and OP were evident between sampling locations. Phosphorus TP and OP and Cl concentrations are relatively low compared to impacted surface waters in South Florida indicating that the Marsh is not severely influenced by waters from adjacent agricultural and urban sources. However, TP and OP concentrations did generally exceed State water quality criteria indicating the Marsh is not a totally rainwater driven system and may be influenced by factors such as levee seepage, groundwater discharge, or surface water backflow into the Marsh.