2000 Progress Report: Evaluation of Endocrine-Distrupting Chemical Effects Across Multiple Levels of Biological Organization: Integration of Physiology Behavior and Population Dynamics In FishesEPA Grant Number: R827399
Title: Evaluation of Endocrine-Distrupting Chemical Effects Across Multiple Levels of Biological Organization: Integration of Physiology Behavior and Population Dynamics In Fishes
Investigators: Thomas, Peter , Rose, Kenneth A. , Fuiman, Lee A.
Institution: The University of Texas at Austin
EPA Project Officer: Klieforth, Barbara I
Project Period: October 1, 1997 through September 30, 1999 (Extended to February 29, 2004)
Project Period Covered by this Report: October 1, 1999 through September 30, 2000
Project Amount: $862,290
RFA: Endocrine Disruptors (1997) RFA Text | Recipients Lists
Research Category: Economics and Decision Sciences , Health , Safer Chemicals , Endocrine Disruptors
Objective:The overall aim of this project is to estimate the impacts of several representative endocrine disrupting chemicals (EDCs) on Atlantic croaker (Micropogonias undulatus) populations in marine environments using a suite of reproductive and larval responses inputs into an integrated population model.
Specific objectives are to: (1) determine the effects of the representative EDCs on bio markers of gonad production and gonadal growth; (2) investigate the impacts of the EDCs on bio marker of gamete maturation, fertilization success and larval survival; (3) assess the parental transfer of the EDCs to gametes and offspring; (4) determine the effects of parental exposure to the EDCs on ecological performance skills of larvae; (5) determine the influence of parental exposure to the EDCs on larva metabolism, growth and development; and (6) develop a suite of predictive computer models for scaling individual-level effects of EDCs to fish population responses.
Progress Summary:Croaker were fed 20µg or 100µg Aroclor 1245/100g bw/day in the diet for 2 months during the beginning of ovarian and testicular recrudescence. The highest concentration of PCB caused significant reductions in gonadal growth of females and males. Both doses of PCB caused a decrease in the production of fully mature oocytes in the females. Decreases in androgen production in males and estrogen production in females were also observed after PCB exposure.
Both PCB treatments also significantly impaired final gamete maturation. Oocyte maturation was drastically decreased from 80 percent in controls to 11 percent at the highest PCB dose, which was probably related to the decline in production of fully mature oocytes. Sperm motility showed a dose dependent decline after the PCB treatments from 77 percent motile sperm to 43 percent at the high dose. Impairment of several measures of reproductive success, including hatching success (controls 76 percent, high dose 43 percent) and larval survival (24 hour control 87 percent, low dose 43 percent, high dose 57 percent, 48 hour control 80 percent, low dose 15 percent, high dose 27 percent) were also observed.
It is concluded from these studies that PCBs can impair three critical stages of the reproductive cycle: gonadal growth, gamete maturation, and fertilization/early egg and larval survival. However, dose-related effects of the PCBs were not observed with all the reproductive biomarkers.
Exposure of croaker to the PCBs during gonadal recrudescence resulted in significantly greater accumulation in the gonads of the females than in the males (females: low dose 5.1 ppm, high dose 34.5 ppm; males: low dose 0.24 ppm, high dose 1.1 ppm). Thus the oocytes account for the majority of the parental transfer of PCBs to the offspring. PCB concentrations in spawned eggs ranged from 0.8 ppm to 1.6 ppm.
Survival skills investigated in larvae were activity, swimming speed, and responsiveness to a vibratory stimulus on days 5, 9, and 13 post-hatching. These measures are indicators of the ability of a larva to forage for food successfully and to avoid predators. No differences were found in the activity of control and low-dose treated larvae on days 5, 9, and 13 post-hatching, although the control larvae tended to be more active. Also, rate of travel (time-averaged swimming speed) on days 5 and 9 were not significantly different for the control and low-dose treated fish. However, rate of travel was significantly higher in the control fish on day 13 (P<0.012). The proportion of fish in the control and low-dose treatment spawns responding to the vibratory stimulus were not significantly different on days 5 and 9, however, the proportion responding on day 13 was significantly higher (P<0.018) in the control fish. Thus, parental exposure to low doses of Aroclor 1254 significantly impairs two of the survival skills (rate of travel and responsiveness to a vibratory stimulus) in 13 day-old Atlantic croaker larvae. A significant decrease in growth rate was also observed in the low dose PCB group.
A matrix model code that simulates the population dynamics of fish and other taxa was developed. The model is general, flexible and allows for any number of life stages, specification of probability distributions for stochastic variation in matrix elements, a choice of several functions for representing density-dependent effects on matrix elements, and capability for different time steps for different life stages. Incorporation of stochastic and density-dependent options is important for realistic simulation of population dynamics. Allowing for multiple time steps permits simultaneous solution of the model in situations when life stages vary greatly in their stage durations. The model is coded in C++ and runs under Windows platforms. Input and output is simple ASCII (text) files.
The model is being tested using previously developed matrix models of the Gulf of Mexico and Southern Atlantic croaker populations. Relatively simple (no stochasticity nor density-dependence) matrix models of these two populations of croaker were formulated. The simple formulation of these matrix models enabled analytical solution of population growth rates and stable age-distributions for both populations. Preliminary comparisons of these known analytical solutions with the predictions from the newly developed matrix model code indicate the code is working correctly. The new matrix model code will be checked against other known solutions, and matrix versions that include stochasticity and density-dependence will be configured. Newly available information from ongoing croaker stock assessments on growth, survival, fecundity, and recruitment dynamics is being obtained to further refine the matrix models.