Kumud Acharya, Ph.D. has worked in Southern Nevada for the last four years studying the changing climate and its effect on the state’s water. Since coming to Las Vegas his focus has shifted to another problem, invasive species specially those living in Lake Mead.

Dr. Kumud Acharya holding a Quagga mussel from Lake Mead.
Click photo to enlarge.

“The quagga mussels are a big problem, they have begun to damage the ecosystem of the lake and are rapidly expanding to other aquatic systems in Arizona, Utah and Southern California,” Acharya said. “You can see the beaches and Lake bottom covered with the mussels.”

Lake Mead is the largest reservoir in the United States and one of the most important water resources in the West. In January of 2007, Quagga mussels (Dreissena bugensis) were discovered in Lake Mead, for the first time in the west. This invasive species and the related Zebra mussel (Dreissena polymorpha) have disrupted ecosystems in a number of waterways elsewhere in the U.S. and have cost billions of dollars in control efforts.

“Given the seriousness of the recent Quagga mussel invasion for the ecology and economy of the broader region, and for the overall management of water resources, the primary goal of DRI's research is to study the ecology and biology of Quagga mussels and their impact on aquatic biodiversity and water quality in Lake Mead,” Acharya added.

Until now the Quagga and its equally mischievous and more common close relative, the Zebra mussel, have been found primarily east of the Mississippi River, particularly in the Great Lakes. There, their massive colonies have clogged water intake and outfall pipes and altered basic aquatic food webs.

The problem may not seem to be a big deal but Acharya warns us that the mollusks could be poisoning the Lake.

Years before the invasive species showed up in Southern Nevada, researchers working in the Great Lakes found that an increase in the Quagga populations correlated with increases in dangerous toxins. A recently completed study at Acharya’s laboratory suggested that Lake Mead mussel tissues showed significantly higher levels of arsenic than found in the sediments and water indicating bioaccumulation of arsenic in the tissue.

“So thoroughly do the mussels filter microscopic food from the water that in areas where they are abundant, the water has increased clarity. But the suggestion of cleanliness is misleading. As waste (feces and psuedofeces) from the feeding process decomposes, it uses up oxygen and releases toxic byproducts.”
Quaggas can relocate nutrients from pelagic to benthic areas by disproportionately recycling and creating nitrogen limited zones which facilitates shifts in algal composition to more harmful cyanobacteria and can turn swaths of open lake into cyanobacteria-filled dead zones. Cyanobacteria are not the preferred food choice for mussels due to their toxins. Lake Mead had small levels of cyanobacteria algae even before the quagga invasion. But the Quaggas, by eating up all the other algae, are making space for the cyanobacteria.

The mussels’ presence in Lake Mead and quick expansion to the entire Lower Colorado River signals its western arrival, an event wildlife and water officials had been able to stave off so far.

Acharya has begun testing the bacteria strain Pseudomonas fluorescens, which has been shown to successfully kill zebra and quagga mussels without killing other native species in the ecosystem. To date, tests on Pseudomonas been limited to attacking mussels in pipes and industrial equipment, but new research is beginning to see if it could be effective in open waters.