Long-Term Effects of Dredging Operations Program. Development of a Chronic Sublethal Bioassay for Evaluating Contaminated Sediment with the Marine Polychaete Worm Nereis (Neanthes) arenaceodentata
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS ENVIRONMENTAL LAB
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Development of a chronic sublethal sediment bioassay with the polychaete Nereis Neathes arenaceodentata is described. The sublethal test end point was estimated individual somatic growth rate milligrams dry weight per day. The test was initiated with 2- to 3-week-old post-emergent juvenile worms and continued for 28 days. 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 seawater to salinities less than or equal 15 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 0.7 mgL un-ionized ammonia or greater than or equal 5 mgL hydrogen sulfide. Survival of juvenile worms to concentrations of the reference toxicant, cadmium chloride, approximating the 96-hr LC50 5 mgL was used as a quality control measure. Results are expressed in control chart format analogous to methods used in analytical chemistry. Chronic, Neanthes, Sublethal, Growth, Sediment.