AgBioResearch

EAST LANSING, Mich. — A research team spearheaded by Michigan State University scientists has recently published findings in two journals detailing the impacts low levels of water contamination have on the behavior, simulated growth and survival of fish.

The studies were published in Environmental Science & Technology and Environmental Toxicology and Chemistry.

Cheryl Murphy, a professor in the MSU Department of Fisheries and Wildlife (FW) and director of the MSU Center for PFAS Research, helped lead the team, which included Janice Albers, a former doctoral student in FW and current fish biologist at the U.S. Geological Survey; Lori Ivan, a senior research associate in FW; Michael Jones, a professor emeritus in FW; and Juan Steibel, an adjunct professor in FW.

Also on the team were scientists from the U.S. Environmental Protection Agency, University of Wisconsin-Milwaukee, Mississippi State University and the U.S. Army Engineer Research and Development Center.

In Environmental Science & Technology, Murphy and her team examined the difference in gene expression, behavior patterns and expected population trends between two populations of an Atlantic killifish, one that had evolved tolerance to industrial pollution and one that had not. In these experiments, offspring of these two populations were exposed to low levels of contaminants, including methylmercury (MeHg) and polychlorinated biphenyl (PCB126), and control conditions.

Of the Atlantic killifish studied, findings showed gene expression changes in both the unevolved population and — contrary to what some might think — the population that had evolved tolerance to these contaminants.

“What’s really interesting is that people are assuming that the fish evolved to the contaminants are going to be fine, but we’re showing that there are still some genes being expressed when the fish are exposed, ultimately affecting their behavior,” Murphy said. “There’s enough adaptation for the population to survive, but they’re just not thriving. They’re only able to persist.”

Novel research led by Albers that was published earlier in Environmental Science & Technology allowed scientists in this study to identify the specific fine-scale behavior patterns being altered by contaminants. Murphy said identifying these behavior patterns granted her team the ability to link them to specific gene expression changes — an innovative approach that has hardly been explored in this field until now.

“When scientists reported behavioral measurements before, they usually used gross measurements such as average swimming speed,” Albers said. “What this new method does is it generates fine-scale behavior differences, and because we now have these keen differences, we can link them to actual gene expression which hasn’t been possible before. This lets us figure out what types of genes are linked to behaviors and what the potential population outcomes could be for species.”

Ivan said one of the challenges when doing ecological risk assessments is to be able to translate individual effects into impacts for entire populations.

“Usually if you’re studying a whole population, that means the damage has already been done,” Ivan said. “What we try to do in ecotoxicology is find ways to collect behavioral information at sub-organismal levels of biological organizations that are easier to measure and scale them up to represent whole populations.”

Understanding behavior can be complicated because scientists often study a select few species that can survive in the laboratory and extrapolate observed behaviors to natural populations. Nevertheless, Murphy said behavior remains a powerful tool to know when something is wrong with an organism in its environment, and when a typical behavior is impaired, it signals additional factors — such as contaminants — are at play.

In Environmental Toxicology and Chemistry, research similarly focused on how yellow perch and zebrafish — in addition to Atlantic killifish — responded to MeHg and PCB126. The team also tested the hypotheses that zebrafish serve as a good surrogate species to represent the behavioral patterns and population outcomes of other fish species, and that the inclusion of model uncertainty in these simulations is important to accurately gauge outcomes.

Based on how each species behaved when exposed to different contaminants, a mix of growth and survival outcomes were generated using computer simulations for the Atlantic killifish, yellow perch and zebrafish. These results didn’t support the hypothesis that zebrafish are representative of the other two fish species.

Murphy and her team additionally concluded that including model uncertainty, a degree of ambiguity around the parameters and range in behavior responses, adds value to ecological risk assessments because it provides a more conservative estimate of impact. This conservative estimate, the team argues, depicts a more realistic characterization of how toxicants alter growth and population outcomes.

“If we take these species and all the uncertainty associated with developing models and incorporate them together properly, we should get a more protective estimate of risk since we don’t have other information to go on,” Murphy said.

The assessments and models used in these studies can be applied to any contaminant, according to Murphy. She said population managers can also utilize the data to evaluate the risk of extinction for certain species.

“We found some trends and genes that suggested things that were really interesting, but there’s a lot more to be explored,” Murphy said. “Our data set could be used to further hypotheses, but, overall, I think we’ve just opened up some methods and ways of linking ideas together, and we hope that inspires the scientific community to build on these efforts and develop stronger linkages between genes, behavior and population impacts.”

Michigan State University AgBioResearch scientists discover dynamic solutions for food systems and the environment. More than 300 MSU faculty conduct leading-edge research on a variety of topics, from health and climate to agriculture and natural resources. Originally formed in 1888 as the Michigan Agricultural Experiment Station, MSU AgBioResearch oversees numerous on-campus research facilities, as well as 15 outlying centers throughout Michigan. To learn more, visit agbioresearch.msu.edu.