Date of Award


Level of Access Assigned by Author

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)


Biological Sciences


Rebecca Van Beneden

Second Committee Member

Bruce Sidell

Third Committee Member

Adria Elskus


Adverse effects on fish populations of discharges from pulp and paper mills with conventional chlorine bleaching and no secondary effluent treatment have been well documented in many countries over the last two decades. Following installation of secondary treatment, changes to elemental chlorine-free bleaching and other process changes, adverse effects on fish were eliminated or reduced at some mills. Because no two mills are exactly alike, it is difficult to predict adverse impacts of any given mill on fish populations. In 1994, a study of the Androscoggin River, Maine showed induction of mixed function oxidase, reductions in gonad size and plasma estradiol, and an increase in plasma testosterone in female white sucker (Catostomus commersoni) downstream of discharges from three large pulp and paper mills and host community municipal sewage treatment plants, suggestive of metabolic disruption (including a subset, endocrine disruption). After all three mills switched to elemental chlorine-free bleaching in the late 1990's, studies from 2001 to 2003 found that reproductive impacts on white sucker populations measured in 1994 had been eliminated. In addition, in 2002 to 2003, population estimates of white sucker using mark-recapture techniques found that densities and biomass were well within the range for those of a reference population and literature values reported for unimpacted populations. Detailed studies immediately above and below each mill/sewage treatment plant showed no evidence of metabolic disruption. There was, however, a clear pattern of eutrophication, which increased cumulatively downstream below each mill and sewage treatment plant. Separate studies of freshwater mussels (Elliptio complanata) from the Kennebec River, Maine in 2003 documented induction of vitellin, a female reproductive protein, in males below a large pulp and paper mill, suggestive of endocrine disruption. Studies of caged mussels and fish from the Kennebec and Penobscot rivers from 2004 to 2006 found no induction of vitellin in mussels below bleached kraft mills on either river. Vitellogenin in female white sucker was lower than expected at the reference station on the Penobscot River below two other pulp and paper mills and sewage treatment plants, compared to the reference station on the Kennebec River. Combined with lower gonad size, this suggests endocrine disruption at this station. The current data suggest that the fish populations at all other stations in both rivers are responding primarily to eutrophication rather than metabolic disruption.