The toxicities of chemicals found in bleached kraft pulp mill effluent were assessed using a sea urchin sperm toxicity test. Sperm of the purple sea urchin, Strongylocentrotus purpuratus, were preincubated with 12 individual compounds, including resin acids, unsaturated fatty acids, their chlorinated derivatives and chlorinated guaiacols. Sperm were then coincubated with eggs and inhibition of fertilization and the effects on sperm motility were assessed. Resin acids, which are highly toxic to juvenile salmonids in freshwater, were less toxic in seawater (EC50s ranging from 2 to more than 20 mg/L). Unsaturated linoleic and linolenic fatty acids inhibited fertilization at lower concentrations (EC50s of 0.28 to 1.07 mg/L) than resin acids, although they are less toxic than resin acids to freshwater fishes. Oleic acid was not significantly toxic up to 75 mg/L. Chlorinated derivatives showed increasing toxicity with increasing chlorination, and chlorinated resin acids were more toxic than their unchlorinated parent compound. Dichlorostearic acid was the most toxic compound tested, with an EC50 of 0.057 mg/L. All compounds except fatty acids inhibited sperm motility.
These results indicate that some of the major constituents of pulp mill effluent exhibit very different levels of toxicity in seawater using a sea urchin sperm cell toxicity test as compared to freshwater bioassays using juvenile salmonids. In addition, mechanisms of action on the sperm appear to differ among the compounds. Accurate quantification of the compounds in effluent as well as the potential effect of the effluent on other marine organisms remains to be determined.