Toxicity of nickel-spiked freshwater sediments to benthic invertebrates-Spiking methodology, species sensitivity, and nickel bioavailability

This report summarizes data from studies of the toxicity and bioavailability of nickel in nickel-spiked freshwater sediments. The goal of these studies was to generate toxicity and chemistry data to support development of broadly applicable sediment quality guidelines for nickel. The studies were conducted as three tasks, which are presented here as three chapters: Task 1, Development of methods for preparation and toxicity testing of nickelspiked freshwater sediments; Task 2, Sensitivity of benthic invertebrates to toxicity of nickel-spiked freshwater sediments; and Task 3, Effect of sediment characteristics on nickel bioavailability. Appendixes with additional methodological details and raw chemistry and toxicity data for the three tasks are available online at [http://pubs.usgs.gov/ sir/2011/5225/downloads/]. Task 1 compared three spiking methods: Direct (direct addition of aqueous nickel solution to sediment at target nickel concentrations); Indirect (direct spiking of high-nickel ‘super-spike’ sediments, followed by dilution with unspiked sediment to target nickel concentrations); and Indirect+Iron (indirect spiking of nickel plus equimolar concentrations of ferric chloride or ferrous sulfide—to oxidized or reduced sediments, respectively). All sediments were pH-adjusted after spiking and were equilibrated in anaerobic conditions. Studies in Task 1 also evaluated the effects of the duration of the equilibration period for spiked sediments and the rate of replacement of overlying water in sediment toxicity tests. Results were evaluated based on the stability of sediment characteristics (for example, acid-volatile sulfide or AVS); distribution of nickel among sediment, pore water and overlying water; and toxicity of spiked sediments to the amphipod, Hyalella azteca. The methods selected for subsequent studies were indirect spiking; minimum 10-week anaerobic equilibration followed by 1 week of equilibration with aerobic overlying water in toxicity test chambers; and a high rate of replacement of overlying water (eight volume-additions/day) during the pre-test and toxicity testing periods. Task 2 evaluated the relative sensitivity of invertebrate taxa to toxic effects of two nickel-spiked sediments: sediment from the Spring River, Missouri, which had low concentrations of the important metal-binding components, total organic carbon (TOC) and AVS; and sediment from West Bearskin Lake, Minnesota, which had high TOC and high AVS. Eight taxa were tested in flow-through sediment exposure systems with automated replacement of overlying water: two amphipods, Hyalella azteca and Gammarus pseudolimnaeus; two midges, Chironomus dilutus and Chironomus riparius; two oligochaetes, Lumbriculus variegatus and Tubifex tubifex; a mayfly, Hexagenia sp.; and a freshwater mussel, Lampsilis siliquoidea. These tests lasted at least 28 days and included multiple chronic toxicity endpoints (survival, growth, and biomass for all eight taxa; adult emergence and egg production for Chironomus spp.; and number of offspring for Hyalella azteca and Tubifex tubifex) to determine the most sensitive responses of each species. The nematode, Caenorhabditis elegans, was tested in small test chambers without 1 U.S. Geological Survey, Columbia Environmental Research Center, Columbia, Mo. 2 East Carolina University, Department of Biology, Greenville, N.C. 2 Toxicity of Nickel-Spiked Freshwater Sediments to Benthic Invertebrates water replacement, with endpoints of survival and production of larvae. Water-only nickel toxicity tests with all nine species also were conducted to aid in interpreting results of sediment tests. Results of sediment toxicity tests were used to estimate the chronic ten-percent and twenty-percent effect concentrations (EC10 and EC20, respectively) for sediment nickel, expressed as total-recoverable nickel concentrations (TR-Ni). Reliable toxicity values were generated for four species in the Spring River sediment and for seven species in West Bearskin sediments. Toxicity values from one flow-through test (Gammarus in Spring River sediment) were flagged because of low control survival, and several other tests did not produce statistically significant toxic effects. Static tests with nematodes also did not allow reliable comparisons with other taxa, because of low control survival in some sediments and high nickel concentrations in overlying water. The taxa most sensitive to toxicity of nickel-spiked sediments were Hyalella, Gammarus, and Hexagenia. Toxicity values for TR-Ni were consistently lower for Spring River sediment than for West Bearskin sediments, with lowest EC20s (for Hyalella biomass) of 202 micrograms per gram (μg/g) in Spring River sediment and 1,177μg/g in West Bearskin sediment. Lowest TR-Ni EC10s (for the same endpoint) were 131 μg/g and 855 μg/g, respectively. In Task 3, the three most sensitive taxa (plus Tubifex) were tested with six additional sediments that represented a gradient of physicochemical characteristics, including AVS, TOC, and particle size distribution. Nickel distribution coefficients (Kd = concentration in sediment/concentration in pore water) differed by more than a factor of 10 among the sediments tested, suggesting a similar wide range of nickel-binding capacity. The endpoints, Hyalella survival, Gammarus survival, and Hexagenia growth, were selected to evaluate differences in nickel bioavailability among the eight sediments tested in Tasks 2 and 3, based on their sensitivity and low variability. For all three taxa, toxicity values based on TR-Ni differed greatly among sediments. Toxicity values for TR-Ni had statistically positive correlations with AVS for Hyalella and Gammarus, but not for Hexagenia. Toxicity values based on sediment nickel concentrations normalized to AVS (or to AVS and TOC) did not have substantially less variation among sediments, but toxicity values based on pore-water nickel concentrations had lowest among-sediment variation, especially for the two amphipods. Toxicity of nickel-spiked sediments to the amphipods, Hyalella and Gammarus, was consistent with the hypothesis that AVS is a primary control on pore-water nickel concentrations and on toxicity of nickel in sediments. For these taxa, nickel-spiked sediments were not toxic if nickel concentrations were less than AVS concentrations on a molar basis. In contrast, toxic effects on the burrowing mayfly Hexagenia occurred in several sediments with nickel concentrations less than the theoretical AVS binding capacity. These divergent results could indicate that AVS does not strongly control nickel bioavailability to Hexagenia, perhaps because ingestion of sediment particles was an important route of nickel exposure for this species. Alternatively, it is possible that the sampling methods used in this study did not adequately measure localized concentrations of AVS or pore-water nickel (or both) in the burrows inhabited by Hexagenia. Chapter 1—Development of Methods for Preparation and Toxicity Testing of Nickel-Spiked Freshwater Sediment