The general approach for the USGS sediment-toxicity study in the Niagara River AOC is outlined below as six sequential tasks; (1) planning/reconnaissance, (2) establishing subcontracts, (3) field surveys, (4) toxicity testing, (5) data analysis and interpretation, and (6) preparation of an interpretive sediment-toxicity report.
Task 1 – Project planning and reconnaissance will occur during winter/spring of year 1 and consist of finalizing a draft work plan, obtaining RAP committee and other stakeholder input, selecting target study sites, and reconnaissance visits. Prospective study sites will be visited to evaluate accessibility and bed sediments. The sampling plan and field logistics will be finalized following the reconnaissance visits.
Task 2 - Subcontracts for testing acute and chronic toxicity of sediments (using USEPA-approved methods for two invertebrate species - Chironomus dilutus and Hyallela azteca) will be established during spring of year 1. This will entail identifying subcontractors, inviting bids for toxicity tests, assessing bids, selecting the final contract laboratory, and assembling a purchase (or services) agreement.
Task 3 - The field surveys will be done during the summer of year 1, and will consist of collecting benthic-community and sediment samples once from as many as 55 sites in the Niagara River. The Niagara survey does not involve a direct BUI assessment; therefore, a probabilistic sampling design is planned to establish baseline toxicity and community information across the entire AOC prior to active remediation. This design will enable us to define the current conditions in depositional areas with statistically defensible metrics; i.e., with known levels of variability (Diaz-Ramos et al., 1996; Stevens and Olsen, 1999). Ten percent of sediment samples will be collected in duplicate to evaluate the reproducibility and precision of endpoints for the toxicity tests. At each site, a Petite Ponar sampler will be used to collect 5 replicate macroinvertebrate-community samples, and to collect a single composite sediment sample for toxicity testing. Bed-sediment size and organic content will be quantified by a NYSDEC subcontract laboratory using a split from the composite sediment-toxicity sample.
Task 4 - The sediment toxicity tests or bioassays will be conducted by a subcontract laboratory during summer/fall of year 1 to define the current levels of toxicity in sediments from study sites in the AOC. Acute (survival) and chronic (growth) toxicity tests will be conducted using C. dilutus and H. azteca and follow standard USEPA-approved methods (ASTM, 2010; USEPA, 1994, 2000).
Task 5 - Data analysis and interpretation will be conducted during the winter/spring of year 2. Graphical and statistical analyses, including multivariate ordination methods, will be used to summarize current (baseline) sediment toxicity levels and potential contaminant and toxicity strata across the Niagara River AOC. Results will also be used to quantify variability and to evaluate the suitability of the current benthos-BUI designation.
Task 6 - One USGS report or peer-reviewed journal manuscript (paper) will be prepared during the spring/summer/fall of year 2 in collaboration with NYSDEC and NOAA staff. This report will summarize baseline sediment-toxicity levels and identify potential toxicity strata across the Niagara AOC. The report/paper will undergo USGS technical and editorial reviews and revision prior to submission for publication internally or via a peer-reviewed journal.
USEPA, 1994. Methods for measuring the toxicity and bioaccumulation of sediment-associated contaminants with freshwater invertebrates. First Edition. US Environmental Protection Agency, Office of Research and Development, Duluth, MN.
USEPA, 2000. Methods for measuring the toxicity and bioaccumulation of sediment associated contaminants with freshwater invertebrates. Second Edition. US Environmental Protection Agency, Office of Research and Development, Duluth, MN.