Grantee Research Project Results
2000 Progress 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
Current 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 Period Covered by this Report: October 1, 1999 through September 30, 2000
Project Amount: $727,255
RFA: Ecological Indicators (1998) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Ecological Indicators/Assessment/Restoration
Objective:
Molecular genetic traits of the mummichog, Fundulus heteroclitus, are being evaluated as bioindicators of population-level effects of pollution.Progress Summary:
The following seven hypotheses are being tested:
- Fundulus 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, indicative of a cost of tolerance.
- Performance of individuals and populations is related to genetic variation and lower variation is associated with poor measures of fitness.
Field survey results were analyzed and additional field sampling included in order to more generally assess Hypothesis 3. Current analysis resulted in rejection of Hypothesis 2 and acceptance of Hypotheses 1, 3, and 5. Hypothesis 4 was supported by tests for differences in embryonic development and juvenile growth for inter-estuarine (Elizabeth River versus York River), but not intra-estuarine (Elizabeth River sites), populations. Consequently, the study was expanded to include more Elizabeth River sites (Figure 1, open circles) and York River sites (Figure 1, arrow on map insert). It is clear at this point that genetic differentiation, but not genetic diversity, reflects a population effect at the Atlantic Wood (AW) site.
Figure 1. Original (filled circles), and new (open circles) Elizabeth River and York River (arrow in inset map) sites. The rectangular box in inset map shows the location of the Elizabeth River relative to the York River.
To test hypotheses 1-3 and 5, a survey was conducted of nine Elizabeth River sites (Figure 1, solid circles) including several highly polluted sites. Fish were sampled and assessments made of genetic (allozyme, DNA) and histopathological characteristics. Sediment PAH concentrations spanned four orders of magnitude with much lower variation in chlorinated hydrocarbons, tributyltin, and metals. A threshold PAH concentration-effect relationship was suggested by an abrupt increase in the prevalence of proliferative lesions in mummichog livers between 68,411 and 371,212 ng/g of dry sediment.
Allozyme and mitochondrial DNA (476 bp of d-loop) data indicate that overall genetic variability did not differ with PAH concentration; therefore, Hypothesis 2 was rejected. Allozyme frequency analyses indicated statistically significant differences in isocitrate dehydrogenase-2 (ICD-2) allele frequencies at the most contaminated site (AW) relative to all other sites. Wright's F-statistics, specificity FST, indicated that these distinct ICD-2 allele frequencies at AW were maintained despite high levels of migration. With the important exception of the highly-contaminated AW site, the survey indicated little genetic distinctness among sites.
There is evidence of high migration among localities, based on the FST statistic. Nevertheless, the mummichog at the AW locality exhibited distinct ICD-2 allele frequencies. Supporting Hypotheses 1 and 3, Mantel matrix correlation analysis indicated that the genetic differences among populations were correlated more with the level of PAH-contamination than with geographical distance. This was true for separate analyses of adult and juvenile fish. Embryo development and juvenile growth experiments designed to assess possible genetic adaptation of these populations indicated large differences in tolerance between fish from the York River versus Elizabeth River, but much smaller differences among populations from four Elizabeth River sites. Consequently, the spatial scale of the field survey was expanded to include populations from another branch of the Elizabeth River estuary (Eastern Branch) and from the adjacent York River estuary (Figure 1). Including these new sites allows assessment of chemical and genetic differences between estuaries, between branches of an estuary, and among populations within an estuary. Because York River mummichog populations have been used in many studies as a reference population for AW mummichogs, the expanded design allows comparison to other studies and provides valuable genetic insights into results from past studies. The underlying mechanism (genetic versus nongenetic) for the differences will be addressed with assays conducted with the lab-reared second generation of fish from Elizabeth and York River stocks.
Future Activities:
Observation of a large difference for Elizabeth and York River stock responses to PAH-contaminated sediments and much smaller differences in responses of Elizabeth River stocks required further scrutiny. Additional hypotheses to be tested with the expanded field survey are the following: (1) Is the same ICD-2 allele frequency shift at contaminated sites seen on another branch of the Elizabeth River? and (2) Does PAH-contamination effect genetic diversity in a second branch of the Elizabeth River?
Results from this EPA Science to Achieve Results (STAR) study and those of other researchers currently working on the AW mummichog population have made it crucial that the question of genetic adaptation versus nongenetic acclimation to the PAH contamination be more rigorously tested. Stocks from field sites will be reared with identical nutritional and environmental backgrounds. Embryo toxicity tests will be repeated for these second generation fish and the following hypotheses will be tested: (1) Are differences in effects genetically based? and (2) Are differences in stock sensitivities related to estuary of origin or PAH-exposure histories?
Preparation to test Hypothesis 7 are progressing on schedule. Mummichog stocks are established and candidate bacterial pathogens are being evaluated for pathogen challenge tests. To date, Vibrio anguillarum cultures have been obtained from Diane Nacci (EPA) and Charles Rice. Charles Rice also provided a Vibrio carchariae culture and John Hawke will soon send a Streptococci b strain originally isolated from Fundulus.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 13 publications | 4 publications in selected types | All 4 journal articles |
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Type | Citation | ||
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Mulvey M, Newman MC, Vogelbein W, Unger M. Aquatic toxicology genetic structure of fundulus heteroclitus from PAH-contaminated and neighboring sites along the Elizabeth River. Aquatic Toxicology 2002;61(3-4):195-209 |
R826593 (2000) |
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Supplemental Keywords:
water, watersheds, sediments, estuary, ecological effects, carcinogen, egentic, PAHs, indicators, Chesapeake Bay., 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.