Project 4 – Understanding Evolved Adaptations to Environmental Pollution

Killifish embryos. Whitehead et al., 2017

Overview

Project 4 continues the Duke Superfund Research Center’s long-running research at the Elizabeth River, VA. For years, polycyclic aromatic hydrocarbons (PAHs) were discharged into the river from several facilities that used creosote to treat wood. The Center has spent years studying how the native killifish (Fundulus heteroclitus) respond to living in in these contaminated waters.

Previous research showed that these killifish are able to survive through pollution-driven genetic adaptations, while fish from cleaner waters are unable to survive if exposed to these PAHs. However, this adaptation comes with a cost. Killifish are less fit and able to cope with environmental challenges such as increased water temperature or decreased oxygen levels.

Objective

Take killifish from sites along the Elizabeth River with differing levels of PAH pollution and study these fish and their offspring in the lab to understand some of the changes that occur for these fish to survive in PAH-polluted waters. Assess any health and behavioral impacts in live fish, and tweak environmental conditions (e.g., raise water temperature or make water less oxygen-rich) to determine if these changes come with fitness costs. Assess the condition of a fish’s organs (see image below) and mitochondrial health to help answer why we see changes in overall health and behavior. Zebrafish (Danio rerio) will also be used to help assess the underlying mechanisms leading to these changes.

Whole-body view of killifish organs after being exposed to polluted Elizabeth River sediment in the lab. Left: fish from the PAH-polluted Atlantic Wood site. Right: fish from an unpolluted control site. The control-site fish is not able to adapt to this pollution and has lots of blood in the pericardial cavity (areas A and B), while the Atlantic Wood fish has adapted to this pollution, and has no blood in the pericardial cavity. Brown et al., 2017.

Importance

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants that humans are exposed to on a daily basis when they prepare food (particularly when grilling or smoking), smoke cigarettes, live near high-traffic roads, and more. These contaminants are linked to a number of health issues, including cancer.

In addition to the human health risks, PAH pollution can alter ecosystems. By comparing sites with differing levels of contamination (some that have recently undergone cleanup), Project 4 researchers can help inform ecological and human health risk assessments of contaminated sites. Are local fish species that have evolved to tolerate PAHs more vulnerable to climate change impacts (e.g., hotter or less oxygen-rich waters) at these sites? Will un-adapted fish come back after a site is cleaned up? These are the types of questions that Project 4 researchers can help answer.

Project Aims

  1. Determine how PAH-exposed killifish in the Elizabeth river differ genetically from less exposed or unexposed populations
  2. Evaluate killifish responses to stressors like hypoxia (low oxygen in the water) and high water temperatures in order to assess any physiological effects from the evolved adaptations to PAH exposure
  3. Assess if and how PAH exposure affects mitochondrial health in killifish and zebrafish, and if this in turn impacts cardiovascular and neurodevelopmental health
  4. Assess killifish originating from a polluted site on the Elizabeth River that is being cleaned up to determine if and how genetic and physiological traits may change through time.

Want to learn more?