MULTIGENERATIONAL EXPOSURE OF THE ESTUARINE SHEEPSHEAD MINNOW (CYPRINODON VARIEGATUS) TO 17β-ESTRADIOL. II. POPULATION-LEVEL EFFECTS THROUGH TWO LIFE CYCLES

摘要

The evaluation of multigeneration, population-level impacts is particularly important in the risk assessment of endocrine-disrupting compounds, because adverse effects may not be evident during the first generation of exposure. Population models were developed for the sheepshead minnow (Cyprinodon variegatus) exposed to 17β-estradiol (E_2) for two complete generations (F1 and F2) to determine population-level effects of multigenerational exposure to a model estrogen. Stage-structured matrix models were used to determine interactions between treatment and the number of generations exposed. Reproduction was significantly reduced in both the 0.08 and 0.2 μg E_2/L treatments in both generations, and embryo and larval stages experienced reduced survival at 0.2 μg/L in the second generation only. However, increased female to male sex ratio in these treatments compensated for the loss in reproductive output, and significant population-level effects only occurred in the 0.2 μg E_2/L treatment of the F2 population. The F2 population in the 0.2 μg E_2/L treatment also had an altered, stable stage distribution relative to the control population of both generations and the F1 population in the 0.2 μg E_2/L treatment, resulting in additional population-level effects. These results demonstrate that continued exposure to E_2 had compounding effects on sheepshead minnow populations and that long-term exposures may be necessary to understand the risk that exposures to environmental estrogens pose to native populations. Although population-level effects did not occur in the F1 generation, a risk decision based on F1 organism-level effects would be protective of the population exposed for two generations.