As part of the US Geological Survey’s (USGS) National Water-Quality Assessment (NAWQA) project, sediment samples were collected from streams representing an urban gradient and selected agricultural lands in the southeastern United States (AL, GA, NC, SC, VA) in the summer of 2014. The study evaluated relations between sediment toxicity, sediment chemistry (metals, pesticides, organochlorines, and polycyclic aromatic hydrocarbons) and macroinvertebrate communities at 58 sites. Sediment toxicity was evaluated by conducting whole-sediment laboratory toxicity testing with the amphipod Hyalella azteca (28-d exposure), the midge Chironomus dilutus (10-d exposure), and the mussel Lampsilis siliquoidea (fatmucket; 28-d exposure) in accordance with ASTM and US EPA methods. Toxicity endpoints measured were survival and growth (weight and biomass). Mean control survival and growth at the end of the exposures met test acceptability criteria. Roughly one-half of the sediment samples were identified as toxic to at least one test species, based on a significant reduction of at least one endpoint relative to control sediment. Amphipod survival, weight and biomass declined significantly as the percentage of urban land within the basin increased. Concentrations of metals, PAHs, and a few organochlorines and current use pesticides infrequently exceeded individual sediment quality guidelines (i.e., Probable Effect Concentrations (PEC) and Likely Effect Benchmarks (LEB) for pesticides). A Reference Envelope scoring was calculated that tended to increase the sensitivity of the toxicity endpoints. Evaluation of concentrations relative to their benchmarks, both individually and as summed PEC or LEB quotients, was explored on a carbon-normalized and a dry-weight basis. Relations between sediment concentrations and benchmark quotients, sediment toxicity endpoints, and macroinvertebrate communities will be discussed.

Characterization of sediment chemistry, sediment toxicity and macroinvertebrate communities in wadeable streams of the southeastern United States

253rd National Meeting (2017)

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