Relative sensitivity of five benthic invertebrate species to reference toxicants and resin‐acid contaminated sediments

Five sediment‐dwelling native New Zealand freshwater invertebrate species (amphipod, Chaetocorophium c.f. lucasi ; clam, Sphaerium novaezelandiae; oligochaete, Lumbriculus variegatus; tanaid, Tanais standfordi; and the burrowing mayfly, Ichthybotus hudsoni ) were assessed for their suitability for sediment toxicity testing by comparison of sensitivity to reference toxicants [phenol and pentachlorophenol (PCP)] and contaminated sediments. The 96‐h EC50 values at 20°C showed a greater 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 lethality for phenol (by 20‐fold) and PCP (by 2.4‐fold). Four of the test species, excluding the tanaid, showed good 10‐d survival in reference muds (≥87%) but lower survival in sand sediments (≥79%). Bleached kraft mill sediment containing 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.