Threats to our environment can take many forms. They may look like drought, wildfires, or killer algae. They may also look like carp. Since the 1970s, Asian carp have been steadily spreading through American waterways and are currently speeding toward the Great Lakes. But scientists are hoping to stop them before they get there. The newest proposal? Carbonate the water. A new study found that Asian carp will swim away from water infused with carbon dioxide. The findings were published in the Transactions of the American Fisheries Society.

Image credit: Kenpei via Wikimedia Commons // CC BY-SA 3.0

Asian carp and other invasive species may not look scary, but that doesn’t stop them from destroying ecosystems. These resilient organisms are bullies, pushing their way into habitats, seizing all the resources for themselves, multiplying fast, and starving out the locals. (On top of that, huge individual Asian carp have been known to leap from the water and hit boaters right in the face, causing injuries and fish stories nobody will believe.)

Many different carp-control approaches have already been put forward. Local officials and researchers have proposed—and, in some cases, tried—electrifying the water, adding poison, building aquatic fences, and even genetically engineering the fish. But to date, the carp have survived and eluded every attempt to thwart them.

The idea of carbonating the water is not a new one; previous laboratory studies suggested that carbon dioxide could be an effective carp deterrent. But nobody had tested the hypothesis in open water until now. Scientists from the University of Illinois and the U.S. Geological Survey (USGS) stocked a secure research pond with invasive bighead carp (Hypophthalmichthys nobilis) and silver carp (H. molitrix), as well as four native species. They then added plumes of recycled carbon dioxide to the pond water, a little bit at a time, and watched to see how the fish would behave.

Sure enough, both carp species avoided CO2-treated areas of the pond, even crowding into smaller areas just to stay out of the carbonated water. They also changed their swimming patterns and slowed their movements.

The problem is that the carbonated water also drove out three out of the four local fish species. They huddled in the non-carbonated parts of the pond right along with the carp invaders.

So no, let’s not rush to carbonate the Great Lakes just yet.

“Further tests are needed before CO2 can be used in Asian carp management,” USGS scientist and co-author Jon Amberg said in a press statement. “Understanding the effects of long-term, elevated CO2 exposure on fish and other organisms can help assess its risks to native species.”