DEVELOPMENT OF A CHRONIC SUBLETHAL BIOASSAY FOR EVALUATING CONTAMINATED SEDIMENT WITH THE MARINE POLYCHAETE WORM NEREIS-(NEANTHES)-ARENACEODENTATA

Development of a chronic sublethal sediment bioassay with the polychaete Nereis (Neanthes) arenaceodentata is described. The sublethal test end point was estimated individual somatic growth rate (milligrams dry weight per day). The test was initiated with two- to three-week-old post-emergent juvenile worms and continued for 28 d. The potential bias due to selected nontreatment factors on polychaete survival and growth was evaluated. For example, grain size had no significant effect, whereas the number of worms placed in each exposure vessel was critical. Direct transfer from 30 parts per thousand seawater to salinites less-than-or-equal-to 15 parts per thousand had a highly significant and adverse effect on survival and growth. Both survival and growth of juvenile worms may be adversely affected if test conditions involve exposures to greater than or equal to 0.7 mg/L un-ionized ammonia or greater than or equal to 5 mg/L hydrogen sulfide. Survival of juvenile worms to concentrations of the reference toxicant, cadmium chloride, approximating the 96-h LC50 (5 mg/L) was used as a quality control measure. Results are expressed in control chart format analogous to methods used in analytical chemistry.