The quagga mussel discoveries in January set off a flurry of calls and meetings among park staff, state game officials, and scientists of all sorts, but definitive answers were hard to find. There are plenty of experts on invasive mussels in the Great Lakes; there are experts on the inner workings of Lake Mead. But the invasion of quagga mussels into the Colorado River Basin began an unintentional experiment, and no one is sure of the results.
“I think we have about a year before we’re going to really find out,” says Jim LaBounty, a lake ecologist for the Southern Nevada Water Authority and a longtime student of Lake Mead. “But we’ve got an ideal set of conditions.” Lake Mead isn’t nearly as rich in algae as the Great Lakes. But reservoirs are, of course, rivers trapped within lakes, and LaBounty surmises that the constant flow of water in Lake Mead will carry plenty of nutrients to the reservoir’s newest filter feeders.
No one could call Lake Mead pristine. Held in place by Hoover Dam, the reservoir is dominated by introduced sport fish, such as striped and largemouth bass. But it and Lake Mohave still harbor a handful of endangered razorback suckers, and Mohave is also home to a few endangered bonytail chub. Exactly how the mussels will affect them and the rest of the food web in the Colorado Basin remains largely unknown, especially since most research on invasive mussels has focused on zebras. Paul Hebert, the biologist whose students discovered zebra mussels in Lake St. Clair, supplies a rule of thumb: “You should prepare for broader consequences than you expect.”
Though zebra and quagga mussels can be controlled at water intakes with chemical treatments, and driven out of very limited areas with poisons, high-pressure hoses, and other shock-and-awe tactics, eradication on any scale is expensive: Last winter, state officials in Virginia spent more than $400,000 on potassium chloride treatments for a 12-acre quarry.
There is still some talk of eradication at Lake Mead, despite its enormous size and complex topography. “I don’t think we know enough to say it’s impossible,” says Andrew Cohen, a senior scientist at the San Francisco Estuary Institute and a member of the lake’s quagga mussel advisory team. While the park will never eliminate every mussel, he says, a well-funded effort could bury, overheat or poison enough mussels to interfere with the species’ famous fecundity. Considering the potential future costs of the mussel’s spread, such an undertaking could even make economic sense. But most agree that the lake’s primary concern is containment.
“Some lakes, because they receive so much boat traffic, can become what epidemiologists call super-spreaders,” says David Lodge, a researcher at the University of Notre Dame who works with the 100th Meridian Initiative. “Lake Mead will become such a lake.”
Lake Powell, which many expected would be first in line for a mussel invasion, now requires boats fresh from mussel-infested states to get a free hot-water wash, courtesy of park concessionaires. But these thorough scrubdowns won’t be practical this summer, when visitors begin hauling their boats from one Southwestern reservoir to the next. “Last year, we washed 45 high-risk boats. This year, we could easily be dealing with 4,500,” says Glen Canyon National Recreation Area aquatic ecologist Mark Anderson.
Quaggas could already be headed overland from Lake Mead to the West Coast. Two houseboat-rental operations on lakes Mead and Mohave also rent boats on lakes Trinity and Shasta in Northern California, and workers do move boats between the Nevada and California reservoirs. That means the quaggas might already have access to salmon watersheds, a prospect that worries many in the Pacific Northwest. The Columbia River could easily host a mussel infestation, and researchers foresee a raft of problems for the region’s salmon, ranging from disruption of the food web to encrustation of the ladders designed to allow salmon to migrate around dams.
In San Francisco Bay, which Cohen and his colleague James Carlton have called “the most invaded aquatic ecosystem in North America,” the precipitous recent decline of several fish species has been blamed on another invasive bivalve, a type of Asian clam that dominates the northern reaches of the bay. With the industrious clam consuming much of the algae and other plant matter in the bay itself, many species rely on an infusion of nutrients from the Sacramento-San Joaquin river delta. But if the quagga mussel were to invade the delta’s fresh waters, it could vacuum up the bay’s remaining food supply.
“The thought of another massively filter-feeding bivalve upstream, in the delta, is causing great concern,” says Cohen. “We might end up with a system that’s good for a couple species of clams, and things that feed on clams, but not much else.”
The 100th Meridian Initiative’s Colorado Basin Team meeting in late January draws about 80 people — a record crowd — to Las Vegas from all over the region, including the Pacific Northwest. Wen Baldwin displays an extra-large jug of quagga mussels, newly scraped from a submerged metal cart in the Las Vegas Boat Harbor, and Lake Mead staff and state agency representatives report their discoveries and progress.
California has assembled a three-person “incident command” team, the same authority structure it uses for earthquakes and oil spills. Emergency funding is keeping three of its state agricultural inspection stations near the Colorado River open around the clock, an effort — some say a quixotic one — to resist the continuing propagule pressure from Lake Mead.
With only two findings of quagga mussels within its borders so far, and no quagga carriers nabbed at its inspection stations, California officials remain optimistic that its mussels will get out and stay out. The Metropolitan Water District, whose board recently approved $180,000 for quagga decontamination and sampling equipment, hopes that a previously scheduled draining of the Colorado River Aqueduct in March will dry up any resident mussels. But quagga monitoring in California has already taken a tragic turn: On Feb. 7, two Department of Water Resources divers drowned while searching for quagga mussels at a pumping plant along the California Aqueduct. State officials are investigating the deaths, and as of Feb. 22, diver surveys at the department’s facilities remained suspended.
Throughout the Colorado Basin, most of the early response to the mussel invasion is underfunded and overtaxed. “We’re all dealing with very small pots of money,” says Tina Proctor, an aquatic nuisance species coordinator for the Fish and Wildlife Service. Press coverage has been spotty, and political attention is inconsistent: Gov. Janet Napolitano, D, of Arizona is receiving regular briefings on the issue, but a spokesperson for Gov. Jon Huntsman Jr., R, of Utah indicates that it isn’t high on his agenda, pointing out that “Lake Mead isn’t actually in Utah.” So while “there’s an immediate need to do something,” as one audience member at the 100th Meridian meeting puts it, well-provisioned, strongly coordinated action is scarce.