Grantee Research Project Results
Final Report: Are Genetic Diversity and Genetic Differentiation Bioindicators of Contaminant Impact on Natural Populations? Fundulus heteroclitus as a Model Estuarine Species
EPA Grant Number: R826593Title: Are Genetic Diversity and Genetic Differentiation Bioindicators of Contaminant Impact on Natural Populations? Fundulus heteroclitus as a Model Estuarine Species
Investigators: Newman, Michael C. , Mulvey, Margaret , Unger, Michael A. , Vogelbein, Wolfgang K.
Institution: Virginia Institute of Marine Science , College of William and Mary-VA
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 1998 through September 30, 2001 (Extended to September 30, 2003)
Project Amount: $727,255
RFA: Ecological Indicators (1998) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Ecological Indicators/Assessment/Restoration
Objective:
The overall objective of this research project was to evaluate molecular genetic traits of the mummichog, Fundulus heteroclitus, as indicators of population-level effects of pollution.
The specific objectives of this research project were to test if:
- Populations residing in contaminated habitats are genetically distinct from populations in neighboring, clean sites;
- Populations at polluted sites exhibit lower than expected genetic variability;
- Genetic structure over a landscape reflects the mosaic of polluted and clean habitat;
- Populations at contaminated sites display tolerance to local contaminants.
- Populations at polluted sites are locally adapted and persistent, and are not replenished by Recurrent migration from nearby clean sites;
- Tolerant populations exhibit suboptimal performance for fitness-related traits when reared in clean habitat, indicating a cost of tolerance; and
- Performance of individuals and populations is related to genetic variation, and lower variation is associated with poor measures of fitness.
Summary/Accomplishments (Outputs/Outcomes):
Descriptions of results of molecular genetic traits of the mummichog were evaluated as potential indicators of population-level effects of pollution. Analyses of the field data resulted in acceptance of Hypotheses 1, 3, and 5, but not 2. Hypothesis 1 was supported by the distinct genetic qualities of fish from the Atlantic Wood (AW) Superfund site (see Figures 1 and 2). No support emerged for Hypothesis 2 using either allozyme or mtDNA data. Hypothesis 3 was accepted after significant correlations were found between population genetic distances and differences in organic carbon-normalized sediment polycyclic aromatic hydrocarbons (PAHs) concentrations of sites. Mantel analyses showed significant correlations between PAH concentration and genetic qualities of fish as measured with allozyme and mtDNA data. Hypothesis 4 was strongly supported by statistical testing of differences in embryonic development for populations from different estuaries (Elizabeth River versus York River), and for populations from the same estuary (Elizabeth River sites). Embryos produced from AW adults and reared in clean mesocosms retained their high tolerance. Embryos produced by fish from the clean York River (CI) were much more sensitive than AW embryos, regardless of where they were reared. Embryos from other Elizabeth River populations were intermediate in their sensitivity. Hypothesis 5 was supported by the distinct genetic qualities and tolerance of AW fish despite high effective migration rates (10 to 18 migrants per generation) among sites. Experiments associated with Hypothesis 7 were repeated several times to enhance statistical power but no evidence of suboptimal performance was noted for fish from contaminated sites. Hypothesis 7 was rejected based on results of these experiments. Expansion of the field survey, and difficulties with maintaining enough healthy mummichogs, did not allow Hypothesis 6 to be addressed as originally stated. However, results from bacterial challenge tests (Hypothesis 7) provided no evidence of reduced fitness in the adapted AW population.
Figure 1. The Original (Panel B, nine South Branch sites) and Additional (four York River sites and four Eastern Branch Elizabeth River sites) Sites From Which Mummichog Genetic Data Were Assessed.
Figure 2.PAH Sediment Concentrations at the 17 Elizabeth and York River Sites. York River sites are identified with a (Y). Other organic contaminants and metals also were measured at these sites.
Scientific Relevance. Genetic differentiation in mummichog populations was an effective and robust indicator of population-level effects of contamination. Analysis of the mDNA and allozyme data indicated that the mummichog from the AW site were genetically distinct from those of other sites. More importantly, genetic differences among site populations within a landscape were determined more by the differences in contamination than geographical distance. The genetic distinctiveness among populations was maintained despite high estimated migration rates of 10 to 18 individuals per generation. These conclusions from the field survey about genetic differentiation were reinforced by laboratory tests showing high tolerance of AW embryos and intermediate tolerance of Elizabeth River embryos relative to embryos from the York River, an estuary with relatively low concentrations of contaminants.
In contrast to genetic differentiation, genetic diversity was not an effective indicator of population-level effects of contaminants. This conclusion is significant because the scientific opinion has emerged that contaminants decrease genetic diversity by a variety of mechanisms. Because genetic diversity has been correlated to individual fitness and is essential for microevolution, such an influence of contaminants would be adverse. However, there was no evidence here of anthropogenic chemicals decreasing genetic diversity metrics based on allozymes or mDNA data.
Regulatory Relevance. The results provide a useful set of indicators for determining if populations occupying a coastal landscape with differing levels of contamination have been affected. Both sets of tools (allozymes and mDNA) produced the same conclusions, suggesting that the general approach is robust. Because Fundulus heteroclitus is widespread and abundant on the Atlantic Coast, the approach will be useful at many diverse locations.
Relative to the study region, results indicate that a population-level effect occurs for a fish species residing immediately adjacent to the AW Superfund site. Further, the genetic differentiation and enhanced tolerance measures used here could be used to monitor recovery associated with future remediation activities.
Binary logistic regression indicated statistically significant correlations between precancerous lesions and carbon-normalized sediment PAH concentrations. The associated model could be applied to determining the sediment PAH concentrations, at which lesion incidence is indistinguishable from background lesion incidence. That concentration could be set as a clean up goal for the sediments adjacent to the AW Superfund site (see Figure 3).
Figure 3. Three of the Four Sites With High Organic Carbon-Normalized PAH Concentrations had the Highest Level of Altered Foci in Mummichog Livers.
Figure 3 suggests that, with one exception, sites with sediment PAH concentrations above approximately 500 g PAH/kg of sediment carbon are associated with elevated incidence of altered foci. The one exception to the trend between altered foci and carbon-normalized PAH concentration was CM, a site with very low sediment organic carbon content (the number in brackets alongside the site abbreviation is the percent organic carbon in the sediment). The PAH concentrations were not unusually high at CM (see Figure 2) relative to the other Elizabeth River sites but, because of the very low organic carbon content, it appears to be in the range of the worst sites (i.e., AW, RS, and CS). The embryo toxicity testing provided evidence of slightly enhanced tolerance of CM mummichog to high PAH concentrations.
Journal Articles on this Report : 3 Displayed | Download in RIS Format
| Other project views: | All 13 publications | 4 publications in selected types | All 4 journal articles |
|---|
| Type | Citation | ||
|---|---|---|---|
|
|
Mulvey M, Newman MC, Vogelbein W, Unger MA. Genetic structure of Fundulus heteroclitus from PAH-contaminated and neighboring sites in the Elizabeth and York Rivers. Aquatic Toxicology 2002;61(3-4):195-209. |
R826593 (2002) R826593 (Final) |
Exit Exit |
|
|
Mulvey M, Newman MC, Vogelbein WK, Unger MA, Ownby DR. Genetic structure and mtDNA diversity of Fundulus heteroclitus populations from polycyclic aromatic hydrocarbon-contaminated sites. Environmental Toxicology and Chemistry 2003;22(3):671-677. |
R826593 (2002) R826593 (Final) |
|
|
|
Ownby DR, Newman MC, Mulvey M, Vogelbein WK, Unger MA, Arzayus LF. Fish (Fundulus heteroclitus) populations with different exposure histories differ in tolerance of creosote-contaminated sediments. Environmental Toxicology and Chemistry 2002;21(9):1897-1902. |
R826593 (2002) R826593 (Final) |
|
Supplemental Keywords:
water, watershed, sediment, estuary, ecological effects, carcinogen, genetic, polycyclic aromatic hydrocarbon, PAH, indicators, Chesapeake Bay, Virginia, VA., RFA, Health, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Ecosystem/Assessment/Indicators, Ecosystem Protection, exploratory research environmental biology, Risk Assessments, Ecological Effects - Environmental Exposure & Risk, Ecological Indicators, Chesapeake Bay, risk assessment, EMAP, monitoring, bioindicator, molecular genetics, fundulus heteroclitus, genetic variability, human exposure, ecosystem indicators, estuarine ecosystems, aquatic ecosystems, contaminant impactProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.