The toxicity of the explosives 2,4,6-trinitrotoluene (TNT); hexahydro-1,3,5-trinitro-1,3,5-triazine (royal demolition explosive [RDX]); and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (high-melting explosive [HMX]), was evaluated in spiked sediment with two freshwater invertebrates. The midge Chironomus tentans and the amphipod Hyalella azteca demonstrated significant toxic effects after exposure to TNT and its degradation products, 1,3,5-trinitrobenzene (TNB) and 2,4-diamino-6-nitrotoluene (2,4-DANT). Significant reductions in survival of C. tentans exposed to TNT, TNB, and 2,4-DANT were observed at nominal sediment concentrations as low as 200 mg/kg. Hyalella azteca was more sensitive to TNT, TNB, and 2,4-DANT than the midge, where significant reductions in survival were observed at nominal concentrations of 50, 100, and 200 mg/kg, respectively. Survival of the midge and the amphipod was unaffected after exposure to RDX or HMX at the highest concentrations of 1,000 and 400 mg/kg, respectively. Growth of the midge, measured as total weight, was significantly reduced by 2,4-DANT. However, significantly increased growth was observed after exposure to sublethal concentrations of RDX and HMX. Although significant reductions in amphipod survival were observed at high concentrations of TNB, growth was significantly increased at sublethal concentrations. The results of the current investigation suggest that organisms exposed to explosives at contaminated sites may be affected at concentrations less than 25 mg/kg through hormetic growth enhancement and at higher concentrations through increased mortality.

Abstract-Based on the need for a test to evaluate chronic sublethal toxicity in estuarine sediments, a 28-d sediment bioassay with the estuarine amphipod Leptocheirus plumulosus (Shoemaker) was developed. The test was initiated with animals less than 2 weeks old (i.e., 425-600 m sieved size class). Test endpoints included survival, growth (g dry weight/d), and reproduction (number of neonates/surviving female). Factors with the potential to influence test animal performance (i.e., nontreatment factors) such as artificial sea salts, salinity, food ration, size at test initiation, intraspecific density, sediment grain size, and diet were evaluated. For example, intraspecific densities between 10 and 60 animals/beaker (i.e., 0.18-1.4 animals/cm 2 ) did not affect survival, growth, or reproduction. Similarly, L. plumulosus were tolerant of a wide range of sediment grain sizes with only extremely fine grained (e.g., Ͼ75% clay) or coarse grained (e.g., Ͼ75% sand) material significantly affecting survival, growth, and reproduction. Test performance criteria included control survival (Ͼ80%) and reproduction (production of offspring in all control replicates), and response to a reference toxicant test with cadmium chloride in a control chart format.

Abstract-High levels of ammonia in sediment toxicity tests can potentially confound test results. At issue is whether the observed toxicity is due to elevated ammonia or the presence of more persistent anthropogenic contaminants. To evaluate the risk of ammonia toxicity, information on (1) the exposure-response relationship and (2) the probability of exposure are needed. Preliminary exposureresponse data were obtained for two different sieved size classes of the estuarine amphipod Leptocheirus plumulosus representing juveniles (425-600 m) and subadults (not reproductively active) (600-1,000 m) in 4-d water-only exposures with ammonia (NH 4 Cl). Resulting LC50 values were 44 (juvenile) and 89 mg NH 3 -N/L (subadult). Results from 4-d tests were used to establish exposure concentrations for two spiked-sediment studies: (1) a 10-d static exposure starting with subadults measuring survival and growth and (2) a 28-d exposure with daily renewal of overlying water starting with juveniles and measuring survival, growth, and reproduction. Risk of ammonia toxicity to L. plumulosus during sediment toxicity tests was characterized via a Monte Carlo simulation using the exposure-response curves from laboratory spiked-sediment studies and published porewater ammonia values for 322 marine sediments. Results indicate a significant potential for ammonia induced interference in the 10-d test (e.g., 2-18% probability of significant mortality due to ammonia alone). Risk in 28-d tests appears to be minimal due to rapid dissipation of ammonia via renewal of overlying water.

Abstract-A 3 ϫ 2 factorial experiment was conducted to evaluate the influence of food ration on observed toxicity in Neanthes arenaceodentata. Worms were fed one of three food rations: 0.25ϫ, 1.0ϫ, and 6.0ϫ. The 1.0ϫ ration was composed of 4 mg TetraMarin/worm/week and 2 mg alfalfa/worm/week. Worms in each food ration were exposed to one of two sediments: a clean control sediment collected from Sequim Bay, Washington, USA (SC) or a contaminated sediment collected from Black Rock Harbor near Bridgeport, Connecticut, USA (BRH) that was diluted with SC such that the final concentration of contaminated sediment was 12%. Survival and growth were monitored every 2 weeks for 8 weeks. Sediment treatment and food ration had strong effects on survival and growth patterns in N. arenaceodentata. Most of the mortality within any given treatment combination occurred during the first 2 weeks of the experiment. This decline in survival was greatest for worms exposed to BRH. Survival was significantly lower for worms in BRH compared to SC at the 0.25ϫ and 1.0ϫ ration levels. Survival was not reduced for worms in BRH compared to SC at the 6.0ϫ ration level. Worm size during the course of the experiment was positively related to ration level. Significantly reduced size in BRH worms was observed at each monitoring period within the 0.25ϫ and 1.0ϫ rations, but only at weeks 6 and 8 for the 6.0ϫ ration level. The percent difference in size between worms exposed to BRH and SC, when those worms were fed the 0.25ϫ or 1.0ϫ rations, ranged between 55 and 66%. The percent difference in size observed between BRH and SC worms fed the 6.0ϫ ration was much smaller (9-17%). The results of this study demonstrate that food ration has a strong influence on observed toxicity in N. arenaceodentata. The importance of food ration effects on toxicity must be considered while designing chronic sublethal bioassays. To ensure the relevance of bioassay results, the food ration used during a chronic bioassay should produce a pattern of growth in control animals that is similar to patterns of growth observed in nature.

The toxicity of the explosives 2,4,6-trinitrotoluene (TNT); hexahydro-1,3,5-trinitro-1,3,5-triazine (royal demolition explosive [RDX]); and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (high-melting explosive [HMX]), was evaluated in spiked sediment with two freshwater invertebrates. The midge Chironomus tentans and the amphipod Hyalella azteca demonstrated significant toxic effects after exposure to TNT and its degradation products, 1,3,5-trinitrobenzene (TNB) and 2,4-diamino-6-nitrotoluene (2,4-DANT). Significant reductions in survival of C. tentans exposed to TNT, TNB, and 2,4-DANT were observed at nominal sediment concentrations as low as 200 mg/kg. Hyalella azteca was more sensitive to TNT, TNB, and 2,4-DANT than the midge, where significant reductions in survival were observed at nominal concentrations of 50, 100, and 200 mg/kg, respectively. Survival of the midge and the amphipod was unaffected after exposure to RDX or HMX at the highest concentrations of 1,000 and 400 mg/kg, respectively. Growth of the midge, measured as total weight, was significantly reduced by 2,4-DANT. However, significantly increased growth was observed after exposure to sublethal concentrations of RDX and HMX. Although significant reductions in amphipod survival were observed at high concentrations of TNB, growth was significantly increased at sublethal concentrations. The results of the current investigation suggest that organisms exposed to explosives at contaminated sites may be affected at concentrations less than 25 mg/kg through hormetic growth enhancement and at higher concentrations through increased mortality.