CCLEAN commissioned the University of California Davis Marine Pollution Studies Laboratory at Granite Canyon to perform bioassays using fathead minnows (Pimephales promelas) to test for endocrine disruption activity in each participant’s wastewater effluent at estimated effluent dilutions provided by each respective outfall diffuser. Observation endpoints included fecundity and fertilization success, behavior and appearance, nuptial turbcle scores, weight, gonadosomatic index, dorsal fat pad index, embryo hatch success, and plasma vitellogenin. The results suggested that there was likely no impact on fathead minnow reproduction in any of the treatment plant effluents at the concentrations tested. While some parameters measured in the test are possible indicators of endocrine disruption due to effluent exposure, only the Santa Cruz treatment had significantly lower fecundity, the primary endpoint indicating reproductive impairment. Based on the fact that the pre-exposure egg production in the Santa Cruz aquaria did not significantly differ from the effluent exposure egg production, it was concluded that reduced egg production in the Santa Cruz effluent was not caused by endocrine disruption.
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