Ecological Evaluation Technical Guidance - State of New Jersey

Appendix D - Sediment Toxicity TestingFreshwater Test SpeciesTwo benthic invertebrate species are usually tested simultaneously for freshwater(salinity of 3.5 ppt or less) sediment toxicity studies in New Jersey. They are theamphipod (Hyalella azteca) and the midge (Chironomus dilutus). Other potentiallyappropriate species mentioned in the USEPA and ASTM guidance include the amphipod(Diporeia spp.), the midge (Chironomus riparius) the mayfly (Hexagenia spp.) and theoligochaete worms Lumbriculus variegatus and Tubifex tubifex.H. azteca and C. dilutus are usually tested simultaneously to incorporate their varyingsensitivities and their different exposure pathways. H. azteca is epibenthic (lives andfeeds on top of the sediment, hidden by leaves and organic detritus), while C. dilutusburrows directly into the sediment. This distinction is important in situ, but in laboratorystudies, no leaves or cover objects are added to the test chambers, so both species burrowdirectly into the sediment. Testing is performed in accordance with USEPA (2000a) andASTM (2005a) guidance.Saltwater Test SpeciesThe most commonly used benthic invertebrates for estuarine and marine sedimenttoxicity testing in New Jersey are the amphipods, Leptocheirus plumulosus andAmpelisca abdita, and the polychaete worms Neanthes arenaceodentata and Neanthesvirens. Other amphipod species included in the ASTM methods are Eohaustoriusestuarius and Rhepoxynius abronius, Pacific species that are not applicable for use inNew Jersey.Marine sediment toxicity testing is usually performed with a single amphipod species. L.plumulosus is more appropriate for lower salinity (5 to 20 ppt), estuarine sedimentsamples, and A. abdita is more appropriate for higher salinity (20 to 35 ppt), marinesediment samples.Because of their relatively large size and available tissue mass, the polychaete worms N.arenaceodentata and N. virens are used for bioaccumulation studies in which the wormsare exposed to a test sediment for a specified time (e.g., 28 days) and then the tissue issubmitted for analysis of contaminants of concern.Toxicity Test TypesThere are three basic types of sediment toxicity tests:(1) static, nonrenewal tests, in which the overlying water is not changed throughoutthe test. These have the advantages of being simple, with minimal physicaldisturbance of the sediment or test organisms, and the disadvantage that theammonia and oxygen demand from the sediment may confound the results;(2) static-renewal tests in which the overlying water is exchanged periodically (e.g.,every 12 hours). These have the advantage of being able to address the ammoniaand dissolved oxygen issues but are more labor intensive and cause more physicaldisturbance to the sediment and test organisms; and(3) flow-through tests in which there is a continual or semi-continual flow of freshoverlying water through the test chambers for the duration of the test. These haveEcological Evaluation Technical Guidance Document 110Version 1.2 8/29/12