Fish scientists proved years ago that the tiniest traces of copper in water can affect a salmon’s sense of smell. Now, research shows that increasing levels of acidity in the oceans does the same thing.

Fish use their sense of smell to find food, avoid predators, find spawning areas, even to recognize one another. Losing it could threaten their very survival.

“In the environment that has some serious implications. If there are predators around and the fish are not able to response to these danger signals in the water, I guess they would be the next snack for these larger predators in the water.”

Jason Sandahl at Oregon State University was one of the first to show how contaminants can disrupt the chemical balance of sea creatures – and that copper levels at just two parts per billion impaired small coho salmon’s sense of smell.

Now, research at the University of Washington and NOAA’s Northwest Fisheries Science Center is the first to show that high CO2 levels do the same thing with salmon. Studies elsewhere showed that it can reduce the sense of smell in other fish by half.

 “We did this study because over the past almost 10 years   there’s been a lot of research coming out of Australia on tropical reef fish and a couple other places in the world looking at the effects if elevated CO2 in fish behavior.”  

Chase Williams and his UW research team exposed young coho salmon in tanks for two weeks with different acidity levels from today and predicted at 50 and 100 years out.

The cohos were exposed to the smell of ground up fish scales to indicate a predator attack, which usually prompts them to hide or swim away. The small fish exposed to the higher acidity levels did not appear to detect the smell.

The study also digs in deeper than earlier work by looking at where in the sensory-neural system the ability to smell erodes, and how it changes fish behavior.

 “We found that the salmon are still likely still smelling the odors. So there are no changes in the way their nose is detecting the odors. But we did pick up changes in the way that their brain was potentially processing those odor signals. So that’s what is likely driving the behavioral changes.”

The researchers hope their findings on such an iconic fish as salmon will alert people to the consequences of high carbon emissions.

Thanks to the assist from KBBI’s Aaron Bolton.