Cooperative Fish and Wildlife Research Units Program: Colorado
Education, Research and Technical Assistance for Managing Our Natural Resources

Colorado Project

Preliminary evaluation of Santa Ana Sucker responses to Waste Water Treatment Plant Effluent in the Santa Ana River.

August 2017 - June 2019


Participating Agencies


The Santa Ana sucker (Catostomus santaanae) is a federally threatened fish to the larger streams of southern California’s Los Angeles Basin: the Los Angeles, San Gabriel, and Santa Ana River watersheds in Los Angeles, Orange, Riverside, and San Bernardino counties. The Santa Ana Sucker was listed as an endangered species in 2000 and the primary threat to its continued presence is hydrological modifications that degrade and reduce available habitat (USFWS 2014). Water quality is also considered a high priority concern (priority 2). The Santa Ana River is heavily influenced by wastewater treatment plant (WWTP) effluent and WWTP effluent comprises the majority of the flow in the river throughout most of the year (Allen 2002, 2003). It is crucial to begin to understand how Santa Ana Suckers are responding to both acute and chronic exposure to WWTP effluents and the potential population consequences of exposure. Many WWTPs discharge to the environment a mixture of endocrine disrupting contaminants (EDCs), particularly estrogens and estrogen mimics (Kolpin et al. 2002). Long-term exposure to low-dosages of estrogenic EDCs can have adverse effects on survival, reproduction, and population viability (Mills and Chichester 2005, Schwindt et al. 2015), and removal of estrogenic contaminants can improve population recovery (Barber et al. 2012, Blanchfield et al. 2015). The Santa Ana sucker may be particularly vulnerable to the effects of WWTP-derived EDCs. Many estrogenic EDCs bioconcentrate in stream biofilms (Writer et al. 2011), resulting in elevated exposure of benthic grazing organisms like the Santa Ana sucker (Greenfield et al. 1970). Surface waters of the Santa Ana River have been demonstrated to be estrogenic in vivo in the mosquitofish, and in vitro in yeast-based estrogen screen assay (Jenkins et al. 2009). However, biomarkers of endocrine disruption have not yet been evaluated in Santa Ana suckers inhabiting these WWTP effluent impacted habitats. The preliminary work outlined in this proposal will evaluate histological and molecular biomarker responses to estrogenic EDCs. The presence or absence of biomarker responses will inform managers on the potential for EDC-induced reproductive impairment as a contributor to population recovery, and inform future management and research options.