RELATIVE SENSITIVITY OF 5 BENTHIC INVERTEBRATE SPECIES TO REFERENCE TOXICANTS AND RESIN-ACID CONTAMINATED SEDIMENTS

Five sediment-dwelling native New Zealand freshwater invertebrate spec ies (amphipod, Chaetocorophium c.f. lucasi; clam, Sphaerium novaezelan diae; oligochaete, Lumbriculus variegatus; tanaid, Tanais standfordi; and the burrowing mayfly, Ichthybotus hudsoni) were assessed for their suitability for sediment toxicity testing by comparison of sensitivit y to reference toxicants [phenol and pentachlorophenol (PCP)] and cont aminated sediments. The 96-h EC50 values at 20 degrees C showed a grea ter range in test sensitivity for phenol (30-fold range) from the most sensitive test, amphipod (8.1 mg/L), to the least sensitive one, clam (243 mg/L), compared with PCP (14-fold range), with amphipod the most sensitive test species (0.13 mg/L) and tanaid the least sensitive (1. 8 mg/L). Clam reburial was a more sensitive end point than was lethali ty for phenol (by 20-fold) and PCP (by 2.4-fold). Four of the test spe cies, excluding the tanaid, showed good 10-d survival in reference mud s (greater than or equal to 87%) but lower survival in sand sediments (greater than or equal to 79%). Bleached kraft mill sediment containin g high resin-acid concentrations (total 1,900 mg/kg dry weight) showed significant reductions in amphipod survival (15%), clam reburial (30% ), and oligochaete survival (17%), and reproduction (49%). Amphipods, clams, and oligochaetes were the most promising species for sublethal test development.