Research Product

Sediment chemical and biological quality is summarized for 97 targeted sites in the Gulf of Mexico, most of which are affected by point and non-point contaminant sources. Chemical contamination and adverse biological effects occurred more frequently in estuarine areas receiving treated wastewaters and urban stormwater runoff. Contaminant concentrations in 51% and 84% of the sediments were less than TEL and PEL sediment quality guidelines proposed for Florida coastal areas, respectively. The guidelines were exceeded for 16 (>TEL) and 11 (>PEL) analytes. Total individual exceedances at each site were usually 3 or less (79% of sediments). Exceedances (>TEL less than or equal to PEL) were more common for copper, cadmium and DDE; and lead, zinc and DDD (>PEL). Concentrations of cadmium, copper, chromium, lead and zinc were above background levels more frequently in sediments collected from areas affected by urban stormwater runoff and treated wastewater discharges. Results for acute and chronic toxicity (benthic invertebrates), genotoxicity (microbial) and phytotoxicity (rooted vascular plants) showed varied biological responses and different measures of sensitivity. Acute toxicity to at least one of six test species was observed in 8% of the toxicity tests. Chronic toxicity to benthic invertebrates, microbial genotoxicity and phytotoxicity were observed in 33%, 54% and 57% of the corresponding toxicity tests, respectively. Benthic diversity was classified as poor for 61% of the sediments (Shannon-Wiener diversity index values <2.0). The biological and chemical results were concordant for 50% to 60% of the sediments. Increase utilization of chronic toxicity tests, the need for reference biocriteria and the identification of cause(s) of impairment are needed to increase the relevancy of sediment hazard assessments and to ensure successful management of this important habitat.