The U.S. Bureau of Reclamation is now carrying out tests in hope of finding out if bacteria can aid them in their struggle against invasive mussel species that are threatening to spread across the West’s waterways.

During the summer of 2008, a preliminary test was executed at Davis Dam on the Colorado River at Laughlin in Nevada. In this dam, Quagga mussels (Dreissena rostriformis bugensis) were exposed to dead bacteria of the Pseudomonas fluorescens species, a non-infectious bacterium that is commonly found in water, soil and food.

Quagga Mussels

During the first test the mussels where exposed to bacteria in jars, but the next test will take place in 10-20 gallon aquariums to in order to more accurately mimic real dam conditions. Water will flow through the aquariums, but will not be released back into the river – it will instead be disposed of through an evaporation pond. A third experiment is also planned, where bacteria will be released in a domestic water intake line which is currently encrusted with a 2-3 inches thick layer of mussels (approximately 5-7.5 cm).

“We are always looking for new, more effective techniques for managing mussels, and this one looks very safe and very promising,” says Reclamation scientist Fred Nibling. “We’ll have a series of tests where we’re going to be testing off-line, off the river, so we can have the data to where we can apply for the permits to test elsewhere.

If the initial testing proves to be successful, the Bureau of Reclamation hopes to have a larger scale test approved by the Environmental Protection Agency.

The U.S. Bureau of Reclamation got the idea to use Pseudomonas fluorescens from Daniel Molloy, a researcher at the New York State Museum who discovered that both zebra and quagga mussels died if they ingest the bacterium. He confirmed the effect in 1998 and the method was patented by the museum. Eventually, the Californian firm Marrone Organic Innovations was awarded a National Science Foundation grant to commercialize the technology.

According to Molloy’s research, a mussel needs to ingest a high density of a strain of the bacteria in order for the bacteria to be lethal. If the density is high enough, a toxin inside the bacterium cell will efficiently devastate the digestive tract of the animal.

One advantage with Pseudomonas fluorescens compared to conventional anti-mussel treatments like chlorine is that mussels recognize chlorine as dangerous and close their feeding valves to keep the chemical out. They do however happily devour Pseudomonas fluorescens. Another important aspect is that research has found that Pseudomonas fluorescens does not kill fish or shellfish.

If large scale testing also proves successful, the Bureau of Reclamation say they wish to meet with municipal public works and water authority officials before the bacterium is put into general use. “We want to make sure they’re very comfortable and they have a chance to ask questions,” says Nibbling.

Zebra mussels