University of Texas Marine Science Institute, Port Aransas, TX

Keywords: ecological indicators; reproduction; modeling; endocrinology; molecular biomarkers; endocrine disruption; fish reproductive function

Biomarkers of reproductive function in Atlantic croaker and sheepshead minnow will be evaluated as early warning indicators of fish population hazards due to degradation of estuarine environments. Biomarker responses in fish collected from degraded and reference sites in Gulf of Mexico estuaries will be analyzed in computer models currently being developed for croaker, which predict the population consequences of reproductive effects measured in individuals. Another component of CEER-GOM will compare the croaker results to other individual and community level responses at these estuarine sites to determine their correspondence and potential utility as ecological indicators. We will examine the overall hypothesis that molecular, physiological, endocrinological and morphological reproductive biomarkers in individuals can be modeled to predict the effects of environmental stressors on fish population dynamics in Gulf of Mexico estuaries by testing the following subhypotheses (1) Gonadal sex differentiation, the production, maturation and fertilization of gametes, and development of yolk-sac larva are sensitive stages of the croaker reproductive cycle to disruption by environmental stressors associated with degraded environments; (2) The effects of environmental stressors on these sensitive reproductive stages can be predicted by measurement of a suite of molecular, physiological, endocrinological and morphometric reproductive biomarkers; (3) Reproductive biomarker responses can be used to model population consequences of exposure to environmental stressors. Specific objectives are to:

1. Determine the effects of hypoxia on biomarkers of puberty (croaker only), gamete production and maturation, fertilization success, and survival of yolk-sac larva (both species).
2. Develop molecular biomarkers of gonadal sex differentiation and other sensitive reproductive stages in adult croaker.
3. Compare reproductive biomarker responses in croaker and sheepshead minnow collected from degraded and reference sites in Gulf of Mexico estuaries.
4. Refine and test predictive models for scaling individual-level effects of environmental stressors to fish population responses.
5. Integrate the results with other components of the CEER-GOM program

Dr. Brian Scott Nunez nunez@utmsi.utexas.edu