Grantee Research Project Results

1999 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: R826593
Title: 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, 1998 through September 30, 1999
Project Amount: $727,255
RFA: Ecological Indicators (1998) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Ecological Indicators/Assessment/Restoration

Objective:

The objective of this research is to evaluate molecular genetic traits of the mummichog, Fundulus heteroclitus, as bioindicators of population-level effects of pollution.

Progress Summary:

All milestones were met with 1 month delay in constructing the mesocosms. Molecular genetic traits of the mummichog are being evaluated as bioindicators of population-level effects of pollution by testing the following seven hypotheses:

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 are being analyzed; preliminary analyses suggest that Hypotheses 1-3 and 5 will be rejected. Hypothesis 4 is supported by preliminary tests. Four lines have been established for testing the remaining hypotheses.

Figure 1. Gradient of PAH concentrations (Sum of Aromatic Fraction, ng/g) in sediments from the nine sites. Site NM (not shown) is 11.1 km upriver of Site CF. For scale, the distance between Sites AW and CF is 1.54 km.

To test Hypotheses 1-3 and 5, a survey was conducted of Elizabeth River sites including several highly polluted sites (Figure 1). Mummichog from nine sites, including a distant site (NM), were sampled and assessments of genetic (allozyme, DNA) and histopathological characteristics were made. Sediment samples showed polycyclic aromatic hydrocarbon (PAH) concentrations spanning four orders of magnitude for these sites and considerably lower variation in chlorinated hydrocarbons, tributyltin, and metals. A threshold PAH concentration-effect relationship was suggested by the abrupt increase in the prevalence of proliferative liver lesions between 68,411 and 371,212 ng/g of sediment (Figure 2).

Figure 2. Relationships among d-loop haplotypes and distribution among Elizabeth River Populations.

Allozyme and mitochondrial DNA (476 bp of d-loop and 500 bp segment of NADH dehydrogenase subunit 4 or ND4) analyses suggest that overall genetic variability does not differ with PAH concentration. We tentatively reject Hypothesis 2 that populations at polluted sites exhibit lower than expected genetic variability. Indeed, 6 of the 12 rare mtDNA haplotypes were observed in mummichog from the most contaminated site, AW, and not at other sites (Figure 3).

Figure 3. Prevalence (%) of altered hepatocellular foci and heptic neoplasms at the nine sites.

Preliminary allozyme frequency analyses did not indicate correlation with level of contamination. Although further matrix analysis is essential to formally test Hypotheses 1 and 3, the survey results provide little evidence that populations residing in contaminated sites are genetically distinct from populations of neighboring, clean sites or that genetic structure over a landscape reflects the mosaic of polluted and clean habitats.

Embryo and juvenile assays to assess the genetic adaptation of these nine populations are underway. During the first year of this study, the results will be used in combination with the genetic survey data to test the hypothesis that populations at polluted sites are locally adapted and persistent, and are not replenished by recurrent migration from nearby clean sites. The survey data suggest little genetic distinctness at the most contaminated sites; preliminary data analyses provide minimal evidence of genetic isolation due to pollution and, instead, suggest a homogeneity of sites expected with continual migration.

Precise and accurate tests of contaminated sediment effects to embyros and juveniles have been developed during the summer of 1999. Final tests are being conducted now using mummichogs taken from sites AW, JC, CM, and RS and held in the laboratory for a month. The Atlantic Wood (AW) and Refueling Station (RS) sites have been historically contaminated with PAHs. Jones Creek (JC) and Channel Marker 2 (CM) sites represent nearby, less contaminated sites (see Figure 1). Preliminary embryo toxicity tests indicate enhanced tolerance for mummichogs from the heavily contaminated sites. The underlying mechanism (genetic versus nongenetic) for this difference will be addressed with assays conducted with the laboratory-reared generation of fish from these four lines. The four lines have been successfully established in our wet laboratories. Also, outdoor mesocosms have been built to hold these lines and to test Hypothesis 4 (populations residing in contaminated sites display tolerance to local contaminants that are inhibitory to populations from clean sites).

Future Activities:

The remaining hypotheses will be tested as described in the proposal. Results will be integrated with those from a Virginia Commonwealth Department of Environmental Quality study.

Journal Articles:

No journal articles submitted with this report: View all 13 publications for this project

Supplemental Keywords:

effects, indicators, aquatic, genetics, Environmental Monitoring and Assessment Program, EMAP, Chesapeake Bay., RFA, Health, Ecosystem Protection/Environmental Exposure & Risk, Geographic Area, Ecological Indicators, Risk Assessments, Ecosystem Protection, Chesapeake Bay, Ecosystem/Assessment/Indicators, exploratory research environmental biology, Ecological Effects - Environmental Exposure & Risk, EMAP, fundulus heteroclitus, bioindicator, human exposure, risk assessment, ecosystem indicators, genetic variability, monitoring, contaminant impact, estuarine ecosystems, aquatic ecosystems, genetic diversity

Progress and Final Reports:

Original Abstract

The 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.