Toxicity of sediment-associated nitroaromatic and cyclonitramine compoundsto benthic invertebrates

The toxicity of nitroaromatic (2,4-diaminonitrotoluene [2,4-DANT] and 1,3,5 -trinitrobenzene [TNB]) and C-14-labeled cyclonitramine compounds (hexahydr o-1,3,5-trinitro-1,3,5-triazine [RDX] and octahydro-1,3,5,7-tetranitro-1,3, 5,7-tetrazocine [HMX]) to the marine polychaete Neanthes arenaceodentata an d the estuarine amphipod Leptocheirus plumulosus following 10-or 28-d expos ures to spiked sediments was investigated. Oganismal-level effects on survi val, growth, and reproduction and cellular-level effects on apoptosis (prog rammed cell death) were evaluated. Because cyclonitramines have low affinit y for sediment, overlying water was not exchanged in the RDX and HMX exposu res. Nitroaromatics sorbed strongly to sediment, resulting in near complete resistance to solvent extraction. Cyclonitramines sorbed weakly to sedimen t, as more C-14-activity was found in the overlying water than in the sedim ent at exposure termination. No significant decrease in survival or growth was observed with cyclonitramines at initial sediment concentrations as hig h as 1,000 mug/g. Survival was significantly affected by nitroaromatics at nominal sediment concentrations as low as 200 mug/g, with L. plumulosus bei ng more sensitive than N. arenaceodentata. Growth was significantly decreas ed at sublethal concentrations of 2,4-DANT for N. arenaceodentata. Reproduc tion, measured only with L. plumulosus, was significantly decreased only in the highest RDX treatment and also in the lower TNB treatment. However, no decrease was observed in higher concentrations of TNB. Body burden at expo sure termination was below detection limit (1 mug/kg) for all compounds. Si gnificant inhibition of apoptosis was not accompanied by significant decrea ses in growth or reproduction. Because of its critical function in many bio logical processes, alterations in this endpoint may result in adverse effec ts on the organism and could be used as an early indicator of toxicity.