The effects of final treated effluent and in-mill waste streams from a Canadian thermomechanical pulp and paper mill on mummichog (Fundulus heteroclitus) reproduction

The effect on fi sh reproduction of fi nal treated effl uent from a thermomechanical pulp mill in Saint John, New Brunswick, Canada, was studied using mummichog (Fundulus heteroclitus), an endemic fi sh species of the Atlantic coast of North America. A 1997 artifi cial stream study at the same mill showed a reduction in gonad sizes in mummichog after a 28-day exposure to 3% final treated effluent. In 2005, we reevaluated final treated effluent, and conducted a toxicity source evaluation to identity waste stream sources within the mill that may cause reproductive effects. Relative to reference, no significant differences in gonad size, plasma levels of gonadal sex steroids, egg production, or stage of egg development were observed in fi sh exposed to 1, 3, 10, 30, and 100% final treated effluent or in-mill waste streams. Unlike the previous study in 1997, these data indicate a low potential for an effect of final effluent on fish reproduction. Since the 1997 study there were no major process changes that could explain the differences in the results. However, there was high variability in gonad size, egg production, and endocrine endpoints measured in the more recent test, which resulted in low power to detect differences. This has prompted research to refine the current reproductive test by optimizing study design.