Pollutants in water making fish work harder just to stay alive, study suggests

A new study has found pharmaceuticals and other contaminants are forcing Hamilton's fish to work harder to survive.

A team of researchers from McMaster University have found that when exposed to elevated levels of pollutants in water, fish are burning more energy that would otherwise go towards vital functions, ultimately making them more vulnerable.

"The evidence is mounting that these sorts of chemicals are having impacts on the natural environment," said Graham Scott, a biologist at McMaster University and senior author of the paper that was published in the journal Environmental Science and Technology on Jan. 16.

Field research for the study was conducted over a three-week period in 2016, when researchers put wild sunfish in cages at different points downstream from the Dundas Wastewater Treatment Plant, before bringing them back to the lab to be observed.

"Specifically we were interested in working in the Dundas Wastewater Treatment Plant because it's so close to Cootes Paradise marsh, which is of course an important natural environment," said Scott.

Once in the lab, they compared the metabolism of the fish exposed to the wastewater to the fish held in unpolluted water.

Researchers measured how much oxygen the fish were consuming to get an indication of what their metabolism was.

Our wastewater treatment plants are definitely having impacts on the fish that live close by and many wastewater treatment plants release their effluent into water.- Graham Scott, biologist, McMaster University

Scott says the fish exposed to contaminants required more oxygen, meaning they require more nutrients just to stay alive.

According to Scott, the fish had to work at least 30 per cent harder to survive. 

"It means they won't have as much energy available to support the other important things that a fish needs to do like move around and interact with other fish whether it be for defending territories or for finding mates," said Scott.

"It might not have as much available to get away from predators, to do all the things that a fish needs to do to be a healthy, happy fish in the wild."

Scott says we need to think about how wastewater treatment plants are going to work in the future, because a natural environment like Cootes Paradise is important to both many different animals and people.

"The most important impact is that it suggests that our wastewater treatment plants are definitely having impacts on the fish that live close by and many wastewater treatment plants release their effluent into water that are natural environments," said Scott.