| Tiny, Clingy and Destructive, Mussel Makes Its Way West |
 |
|
 |
| By John Collins Rudolf, NY Times |
|
Published June 17, 2008
LAKE MEAD, Nev. Kneeling at the edge of the dock, Wen Baldwin began
hauling on a length of nylon rope that disappeared into the depths
of Lake Mead. One after another, an odd assemblage of objects a water
bottle, a chunk of concrete, a pair of flip-flops, a steel anchor emerged
from the emerald-green waters.
The conditions here are ideal for these things, absolutely ideal,
said Mr. Baldwin, 70, a retired design engineer and a National Park Service
volunteer.
The mussel-coated debris is unmistakable evidence of an event
occurring silently and largely out of sight the colonization of the
Colorado River by the quagga mussel, a fingernail-size Eurasian bivalve with an
astonishing sex drive and a nasty reputation for causing economic and
ecological havoc.
Like the closely related zebra mussel, the quagga can cling
tenaciously to hard surfaces, like the equipment of the many hydroelectric and
water-supply plants along the lower Colorado.
Theyre going to be all over the pipes, all over the intakes,
said Gary L. Fahnenstiel, senior ecologist with the Great Lakes Environmental
Research Laboratory of the National Oceanic and Atmospheric
Administration. Its going to be devastating.
Dr. Fahnenstiel ought to know. The quagga has carpeted much of the
Great Lakes, largely displacing the better-known zebra. Its invasion of the
Colorado, presumably after crossing the Rockies on recreational boats
hitched to trailers, foretells major disruptions not just for
utilities, but also for the entire ecology of the lower river.
By stripping nutrients and microorganisms from the water, the
mussel could do grave damage to a wide variety of species, including small
invertebrates, fish and birds. This is one bad hombre, Dr.
Fahnenstiel said. Its almost your worst-case scenario for affecting the
entire food chain.
The quaggas introduction in the Colorado can hardly be a surprise.
For almost 10 years, a small chorus has warned of ruinous consequences if the
mussels crossed into the West.
In 1998, a group called the 100th Meridian Initiative brought together
biologists, wildlife officials, water managers, environmentalists and
others with the goal of preventing invasive species from crossing
the 100th meridian, a historical boundary separating East and West. For seven
years, Mr. Baldwin has been the groups sentinel at Lake Mead.
In 2001, Mr. Baldwin, then president of the Lake Mead Boat Owners
Association, heard a presentation by a biologist from the
initiative on the zebra mussel. The zebra invaded the Great Lakes from Ukraine in the
1980s and spread to major rivers and more than 800 lakes.
Mr. Baldwin lobbied officials at the Lake Mead National Recreation
Area for more inspections of recreational boats, which carry mussels in
bilge pumps and live bait wells. He distributed brochures and spoke widely on the
threat. I started researching it and put on some programs, trying
to get people to pay attention. Some did. Most didnt.
He even built monitoring stations on docks around the lake, but found
nothing. In January 2007, however, Mr. Baldwin received a call from a
maintenance worker who had spotted a suspicious-looking mussel
clinging to a steel cable below a Lake Mead dock. It was a quagga. Investigation
quickly found colonies throughout the lake, at depths much greater
than usual for zebras. We were monitoring for zebras, and the quaggas
snuck right in beneath us, he said.
At Lake Mead, a deep, narrow reservoir hundreds of miles long
created by the Hoover Dam, quaggas appear well on the way to taking over.
Within a year of discovery, it was apparent that they were
lakewide, and in areas they were really numerous, said Kent Turner, chief of
resource management for the park service at the recreation area. Sampling
the lake bottom has found mussel concentrations in the thousands per square
meter, he said.
Like the zebra, the quagga breeds externally, forming clouds of
veligers, microscopic, free-swimming larvae that can float up to five weeks
before settling on any surface that strikes their fancy.
By riding the current, quagga veligers have floated hundreds of miles
downstream. Adult mussels have been found as far south as the
Imperial Dam, near the Mexican border.
They have not stopped there. At the Lake Havasu reservoir, on the
California-Arizona border, giant pumping stations pull millions of
gallons of water a day for cities and farms. Drawn into the Colorado River
Aqueduct and the Central Arizona Project canal, veligers have journeyed as
far east as Phoenix and Tucson and as far west as San Diego.
Wherever the river takes them, they have gone, said Alexia
Retallack, a spokeswoman for the California Fish and Game Department.
The infiltration of the Colorado poses a major challenge for a
water system already strained by record drought. Las Vegas is particularly
reliant on the river, drawing 90 percent of its drinking water from Lake Mead.
The Metropolitan Water District, which provides water to 26 cities in
Southern California, regularly deploys scuba divers to clear mussels from
its intake pumps on Lake Havasu. To kill the mussel larvae, 9,000
gallons of chlorine, equal to two trailer tanks, are added to the Colorado
River Aqueduct daily. What we want to do is contain them, said Ric de
Leon, a microbiologist who directs quagga control for the district. So
far, were doing fairly well.
California officials have begun aggressive boat inspections, even
enlisting canine units trained to find mussels.
We have the first quagga-sniffing dogs on the planet, Ms.
Retallack said.
Lined with dams, reservoirs, canals and pipelines, the Colorado more
closely resembles a giant plumbing project than a wild river,
giving the mussels ample opportunity for mayhem. David Pimentel, a professor of
ecology at Cornell and an expert on the economic effects of invasive
species, said the maintenance and control costs might run into the
billions, as it has been in the East.
More alarming to some experts are the potential ecological effects.
Dr. Fahnenstiel called the mussels explosive growth the most significant
ecological disruption in modern Great Lakes history. Its a huge
perturbation, he said. I dont think that can be understated.
In Lake Michigan, fish populations have plummeted as quaggas strip the
water of nutrients. The fish are taking a hit because theres no
food for them, said Tom Nalepa, a research biologist with the Great Lakes
laboratory. All the food is being sucked out by the mussels. What
were seeing is the replacement of the fish by the mussels.
By filtering the water, quaggas can increase clarity, letting in
sunlight that leads to algae blooms and explosive weed growth. That can, in
turn, result in oxygen-starved dead zones, observed recently in Lake
Erie. By accumulating toxins filtered from the water, the mussels have also
contributed to botulism.
In the Great Lakes, weve seen avian botulism go through the
roof, Dr. Fahnenstiel said. Weve had huge die-offs of loons, which are one
of the most beloved species here.
In the Colorado River, two native fish species, the bonytail chub and
razorback sucker, are considered particularly vulnerable to mussel
competition, and avian botulism may threaten bald eagles around
Lake Mead.
Biologists also warn that the vector behind the quaggas spread, to
the Great Lakes by oceanic freighter and to the West on recreational
boats, remains open to exploitation by other potentially destructive
species. An estimated 180 alien species have reproducing populations in the
Great Lakes Basin, with new ones added almost yearly. Most recently, viral
hemorrhagic septicemia, a European virus that can cause large fish kills, has
spread to three Great Lakes: Huron, Michigan and Ontario.
Everybody in North America needs to be concerned about what
species come into the Great Lakes, Dr. Fahnenstiel said. Theres no system thats
geographically isolated anymore. Were all linked.
###
|
|
| |
|
|
