Microbial genotoxicity as an environmental indicator for near-coastal sediment pore waters

The genotoxic potential of sediment pore water collected from coastal areas in the Gulf of Mexico has not been reported frequently in the literature. This report summarizes a study of the microbial mutagenicity of 31 pore water samples obtained from sediment affected by non-point source runoff and compares the results with those for more traditional chemical and biological indicators of sediment quality. Genotoxicity was determined pre- and post-enzyme activation using a proprietary short-term microbial assay for pore water centrifuged from sediment collected adjacent to a Florida coastal golf complex and from an urbanized bayou-estuary. Sediment and the associated pore water also were analyzed for acute toxicity to Hyallela azteca, Palaemonetes pugio, or Americamysis bahia and for benthic macroinvertebrate diversity (sediment only). Genotoxicity (direct and enzyme-activated) was detected in 4 of 17 (golf complex) and in 10 of 14 (urbanized bayou) pore water samples. The lowest toxic pore water concentrations were between 1.8% and 44.4% (direct) and between 2.6% and 25% (enzyme-activated). The results of the genotoxic assay paralleled those based on exceedance of proposed sediment quality guidelines, pore water acute toxicity and Shannon-Wiener diversity index values for 81%, 58%, and 65% of the comparisons, respectively.