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Survey of Sediment Quality in St. Lucie Estuary, and Vicinity

The St. Lucie River Estuary is the largest tributary to the southern Indian River Lagoon in southeast Florida. The Estuary has been significantly altered by human activities, particularly nonpoint source pollution from agriculture, urban, marinas, and hydromodification.

Prior to human modifications, rainfall on the watershed was captured in natural systems and moved gradually through groundwater and surface wetland flows. Currently, rainfall runoff flows rapidly into drainage canals without buffering or cleansing by the natural ecosystem.

In addition, the size of the St. Lucie's natural watershed has been artificially increased through the construction of the C-44 canal, which discharges runoff and nonpoint source pollutants into the St. Lucie from Lake Okeechobee.

This environmental toxicity survey of the St. Lucie River Estuary includes: chemical analyses of sediment, nepheloid , fish and oyster tissue, and surface water; toxicity testing; biomarker assays; and benthic community assessment.

Phase I will define the environmental conditions in the St. Lucie, Indian River Lagoon, and adjoining ocean waters using the sediment quality triad, and event-based surface water sampling to examine causes and consequences of the observed contamination. Phase I will also recommend steps for more effective stewardship of the estuary's environment and resources.

Phase II fills data gaps to further define the ecological system.

The objectives of the surveys were to determine:

  1. The incidence and degree of toxicity of sediments.
  2. The spatial patterns (or gradients) in chemical contamination and toxicity, if any.
  3. The spatial extent of chemical contamination and toxicity.
  4. The statistical relationships between measures of toxicity and concentrations of chemicals in the sediments.
  5. The presence and concentrations of emerging contaminants of concern.
  6. The incidence of chemical residues in fish and shell fish.
  7. The utility of selected biomarkers.

Surficial sediment, suspended sediment and nepheloid layer samples were analyzed to quantify the concentrations of a suite of more than 80 organic and inorganic chemical contaminants. Surface water samples were analyzed for current use pesticides and alkyl phenol ethoxylates (indicators of sewage). Laboratory toxicity tests were performed as indicators of potential ecotoxicological effects in sediments. Correlation analyses were conducted to determine the relationships between measures of toxicity and concentrations of potentially toxic substances in the samples.

To conduct this study, NCCOS/ CCMA entered into a Joint Project Agreement with the State of Florida and collaborated with the National Marine Fisheries Service.

 

TIME FRAME: 1994-ongoing.

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St. Lucie Estuary Assessment Study