Screening Level Probabilistic Aquatic Ecological Risk Assessment
of Canal C-111 and Adjacent Coastal Areas
G. M. Rand and J.F. Carriger, Southeast Environmental Research Center,
Florida International University
The first phase of an ecological risk assessment is underway to evaluate the potential risks of organic pesticides found in the water and sediment in the lower Canal 111 (C-111) Basin and adjacent tidal zones in South Florida. The goal is to develop a perspective on chemical stressors present in an area undergoing large-scale hydrologic restoration, as recommended by interagency evaluations of contaminant issues in Everglades restoration. It is the first phase in development of a retrospective ecological risk assessment, and it focuses on an area where a critical Everglades restoration project is underway (C-111 Project).
The results of the study are expected to identify areas with data gaps and information needs, that if met, will provide risk information detailed enough to support water quality management planning and increase the probability of success of Everglades restoration. Results are intended to be used by the appropriate state and federal jurisdictions for interpretation, evaluation, and application of appropriate remedial actions for protection of fishery and wildlife resources.
This risk assessment was conducted under the U.S. EPA ecological risk framework and focuses only on potential effects of water exposure concentrations to the herbicides atrazine and metolachlor and to the insecticides chlorpyrifos, endosulfan, and malathion. It did not take into account the potential additional effects of exposure of organisms to other contaminants present, such as heavy metals, or other types of exposure, such as through sediment or bioaccumulation from consuming food items that have also been exposed.
Results from initial evaluations of risk of acute effects in fresh- and estuarine –waters from pesticide exposure show:
Highest risk was associated with endosulfan effects on estuarine arthropods, followed by endosulfan on freshwater arthropods.
Highest risk of acute effects from joint toxicity of the compounds considered was to estuarine invertebrates.
Highest risk of acute effects in fresh water are associated at sites near water control structure S-178 and canal C-111e, a branch of canal C-111. The highest risk of acute effects for saltwater organisms is in Joe Bay, which receives water discharges from canal C-111.
Results from initial evaluations of risk of chronic effects from pesticide exposure show:
Highest risk is associated with endosulfan at S-178 in freshwater.
Probability-based statistical models of joint pesticide interactions (probabilistic risk assessment) showed risk increased from single to multiple exposures.
Information needs to reduce uncertainty include:
Ecotoxicity testing with indigenous, native indicator species exposed to metals and/or organics in water and sediment
Improved chemical monitoring in water, sediment, and organism body burdens
Rand, Gary, Florida International University, 3000 N.E. 151st Street, N. Miami, FL 33181, Phone: 305-919-5869, Fax: 305-919-5887,