BROOKSVILLE, MAINE — The former Callahan Mine site is providing research opportunities for scientists even as it undergoes cleanup per its designation by the Environmental Protection Agency as a Superfund site.
A team of scientists including MDI Biological Laboratory staff scientist Ben King is studying how organisms can adapt to changing environments, and the Callahan Mine is one example. The Atlantic killifish, a small common fish found on the Atlantic coastline, is the subject of the study because of its ability to modify its gills to live in fresh or salt water.
The researchers’ study, published last summer in the journal “Molecular Biology and Evolution,” used the arsenic-laden water at the mine site as a tool to understand the natural process by which killifish gills change when they move from freshwater to saltwater. The goal was to identify the genes and regulatory networks responsible for that adaptive ability.
“These fish are actually quite amazing,” King said. “They normally can transition from fresh to saltwater and back very well, their gills change dramatically in what we call their morphology. There are some very practical things in studying this transition in the gills, and there’s a lot of biology there, but if we use this process as an example of how animals can respond to different environments,” the results may be broadly applicable, he said.
To track changes in genetic activity during the study, the researchers added arsenic to the fish’s water. Previous studies of fish living in polluted environments demonstrated that arsenic interferes with the fish’s ability to adapt to changing levels of salinity. The team conducted some of those studies at the Callahan Mine site. Using arsenic provided a point of contrast with fish in untreated water.
“Arsenic actually inhibits that ability (for the killifish gills to adapt), so it became a powerful tool to study how these fish can change the way the gills are working,” King said.
Studying the responses of these fish and other organisms to human impacts such as industrial pollution, he said, is a separate line of research.
A large National Science Foundation-funded study to identify why the killifish are so robust is underway, he said, led by MDIBL visiting faculty member Joe Shaw, associate professor at the School of Public and Environment Affairs at Indiana University. “They’ll study a set of populations of fish in a mine versus a nearby site that’s essentially clean to compare their DNA. Callahan is one of the sites in the study, along with other polluted and clean environments along the Northeast coast. “New Bedford Harbor, for example, traditionally has high levels of PCBs,” King said. “They’re comparing those fish to fish from Block Island, which is cleaner, to understand how the fish are adapting.”
Many of the scientists involved in these studies are part of an emerging field called environmental genomics. MDIBL offers one of the only courses on the topic for junior scientists, post-doctoral students and graduate students.
“A lot of what we know about genetics and how organisms adapt is due to using model organisms like the mouse, but what we’re trying to do is study natural populations,” King said. “We have these new tools that allow us to study complete genomes very rapidly. That empowers us to ask the same questions about evolution, the genes required for animals to adapt to change, using any population.
“The same technologies we’re using to study all these organisms are used to study human diseases,” he said. “That’s something that’s going to touch all of our lives, whether we’re scientists or not.”