Developing an Understanding of Multiple Stressor Influences on Fish Reproduction in Inland Waters: Interactive Effects of Hypoxia and Estrogen Agonists

EPA Grant Number: F13E31006
Title: Developing an Understanding of Multiple Stressor Influences on Fish Reproduction in Inland Waters: Interactive Effects of Hypoxia and Estrogen Agonists
Investigators: Saari, Gavin
Institution: Baylor University
EPA Project Officer: Lee, Sonja
Project Period: August 25, 2014 through August 25, 2016
Project Amount: $42,000
RFA: STAR Graduate Fellowships (2013) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Fellowship - Environmental Toxicology


Inland surface waters in arid to semi-arid regions are effluent-dominated or dependent and often nutrient enriched, with the prevalence of endocrine- disrupting chemicals causing stress on water quality. This research will employ reproductive assays to identify thresholds of low dissolved oxygen (hypoxia) on endocrine function. In addition, the research will define the interactive effects of environmentally relevant ethinylestradiol (EE2) exposure on fish endocrine function and reproduction across gradients of dissolved oxygen. These results will be used to understand potential impairments to fish populations.


The research will entail 21-day reproductive assays with fathead minnows (Pimephales promelas) to identify thresholds of hypoxia, EE2 and the interactive effects of EE2 exposure across gradients of dissolved oxygen on endocrine function and reproduction. The study design considers critical aspects of reproduction and early development. This approach will enable the collection of mechanism-specific stressor response data for basic diagnosis and potential extrapolation across species. Results regarding the responses of endpoints will give valuable information about endocrine function and reproduction processes occurring in fathead minnows. Ultimately, this information will be interpreted under the adverse outcome pathway framework relevant to ecological risk assessment.

Expected Results:

Continuous chronic exposure of hypoxia in aquatic systems impairs reproductive success and could potentially lead to long term effects on fish recruitment and population abundance. In addition to hypoxia stressing aquatic organisms in effluent-dominated inland waters, other stressors, such as EE2, also are prevalent and can cause reproductive impairment. The consequences of hypoxia and EE2 on fish reproduction have been well studied independently, but the interactions between the two are not well understood in terms of their potential impact on fish populations.

Potential to Further Environmental/Human Health Protection

Water quantity and the quality of wadeable streams and rivers in arid to semi-arid regions of the United States are decreasing because of water shortages as a result of drought and human consumption. Instream flows of surface waters in these regions are dominated by, and even dependent on, discharges from wastewater treatment plants, representing worstcase scenarios for instream exposures to multiple stressors. This research will determine the potential impairments of multiple environmentally relevant stressors, such as hypoxia and endocrine-disrupting chemicals, to fish reproduction. These results will elucidate the critical thresholds of interacting stressors relevant to maintaining aquatic populations. This type of study can be used in water resource management for sustainable approaches to environmental health.

Supplemental Keywords:

hypoxia, pharmaceuticals, wastewater treatment

Progress and Final Reports:

  • 2015
  • Final