This project continues the Duke Superfund Research Center’s long-standing research in the Elizabeth River, Virginia. For years, polycyclic aromatic hydrocarbons (PAHs) were discharged into the river from several wood treatment facilities that employed creosote. Dr. Richard Di Giulio and his colleagues have spent years studying a fish species native to the area, the killifish (Fundulus heteroclitus) and its response to living in contaminated environments. Their research has found that killifish at contaminated sites exhibit pollution-driven adaptation to high levels of PAHs at these sites. This evolution has also come with a cost to the killifishes’ fitness: they can survive, but they are less fit and able to cope with environmental challenges such as increased temperature or decreased oxygen levels. You can read more about our history of engagement at the site in the Prezi below:
The Atlantic Wood site has recently been remediated with a concrete wall around the PAH hotspot that has limited access for sampling. Another contaminated site on the Elizabeth River, the former Republic Creosoting, will now serve as the unremediated site, in addition to seven other sites of low, moderate, or high PAH contamination, including Money Point, a creosote contaminated site undergoing remediation by wetlands restoration. We will continue to study how killifish in the Elizabeth River area develop resistance to PAHs and how the fitness costs impact those populations. Our primary research questions for our current research are presented below, followed by descriptions of our research aims:
- How do killifish become resistant to PAHs at the molecular level?
- How do the killifish’s adaptations make them susceptible to other stressors?
- How are mitochondrial function and energetics impacted by PAHs and are those impacts inherited?
- How have killifish adapted to areas with different PAH remediation approaches and at different stages?
Aim 1: Mechanisms of Resistance through “Omics”
Our past research focused on the mechanisms and consequences of PAH toxicity. In our current grant period, we will explore the underlying mechanisms of resistance to PAH toxicity through a comprehensive “omics” approach. This means that we will follow molecular pathways of exposure through the genome, epigenome, transcriptome (all of the mRNA expressed from an organism), proteome (all proteins expressed by a cell), and the metabolome (all metabolites expressed by an organism) to understand how the resistant phenotypes of fish gain their traits.
Aim 2: Physiology and multiple stressors
We will evaluate the fitness costs of the killifish adaptation to PAH exposures, focusing on behavioral and bioenergetic costs of adaptation. Killifish are well-suited to their dynamic environment, but adaptation to PAH exposure may compromise their ability to adequately respond to environmental changes. Specifically, this includes their responses to increased water temperatures (thermal stress) and their response to low oxygen conditions (hypoxia).
Aim 3: Bioenergetics: Mitochondrial toxicity
Mitochondria are known targets of PAH toxicity, and early life exposure to PAHs can damage the mitochondria, with impacts that persist across generations. We are evaluating PAH damage and dysfunction to mitochondrial DNA using both killifish and zebrafish (Danio rerio). The focus of this work will be on trans-generational impacts from both maternal and developmental exposure, including genome-wide epigenetic changes across generations as well as assessments of energetics and neurobehavioral toxicity through behavioral studies.
Aim 4: Responses to remediation
There are three former creosote wood treatment plants on the Elizabeth River: Atlantic Wood, Republic Creosoting, and Money Point. Atlantic Wood has undergone remediation, with a concrete wall in place to isolate the areas with the highest PAH levels. Republic Creosoting has not been remediated, though there are plans to do so in the future. Money Point was remediated using soil removal and creation of a constructed wetland. We will collect sediment and killifish samples at each of the locations to evaluate the impact of each of the remediation approaches on sediment PAH concentrations and the presence of the resistant killifish phenotype.
These studies will elucidate relationships among PAH exposures and selected aspects of molecular biology in these populations, as well as their responses to remediation. Laboratory studies will employ offspring of wild-caught killifish to explore fitness costs associated with adaptation to PAH contaminated environments. Studies with both killifish and zebrafish will elucidate impacts of PAH exposures on mitochondrial structure and function and associated impacts on aerobic performance and behavior.
Who are we?
- Di Giulio RT, Clark BW. The Elizabeth River Story: A case study in evolutionary toxicology. J Toxicol Environ Health. 2015;Part B 18(April 2017):2159-2258. doi:10.1080/15320383.2015.1074841.