Tiny Pest Threatens the Las Vegas Lights

  • Hoover Dam's backside stretches more than 700 feet from top to bottom, but the dam's seeing trouble from the tiny aquatic zebra mussel. (Photo by Shawn Allee)

Hoover Dam generates some of the power that lights Las Vegas all night long. But there’s something
that’s making that job a bit more difficult. Shawn Allee found out, it’s a tiny aquatic pest:

Transcript

Hoover Dam generates some of the power that lights Las Vegas all night long. But there’s something
that’s making that job a bit more difficult. Shawn Allee found out, it’s a tiny aquatic pest:

The usual tour of Hoover Dam starts at the visitor’s center – way at the top.

Robert Walsh works with the federal agency that runs Hoover.

He says, go ahead – look over the edge.

Allee: “OK. That’s creepy. Seriously, that’s creepy.”

Walsh: “It’s spooky. Are you afraid of heights?”

Allee: “No, they don’t bother me at all.”

The dam stretches down 700 feet, and it holds an enormous reservoir – Lake Mead.

This tour is awesome, but Walsh says there’s another tour, too.

It’s, um, NOT so awesome.

It’s all about the trouble the tiny quagga mussel is causing Hoover and other nearby dams.

To get that tour, Walsh takes me to Leonard Willet.

Allee: “Where are we right now?”

Willet: “It’s kind of a work station where all the quagga mussel control activities take place
for Hoover Dam.”

Allee: “It’s quagga mussel central for this area?”

Willet: “Exactly.”

Willet first heard quagga mussels were growing in the nearby Lake Mead reservoir in 2007.

He called an expert for advice.

“First thing out of her mouth was, ‘I’m sorry to hear that.’ I knew it was a lot more serious.
And I asked her what we’re in for.”

Willet learned quickly enough – quagga mussels attach to nearly anything underwater.

He shows me a sandal that was in water – and is smothered in them.

They’re like clams the size of your pinky fingernail.

“We went from zero to THAT in seven months.”

And that’s the problem.

Hoover Dam uses water from Lake Mead to spin generators.

The water moves around in pipes – and quagga mussels can attach to them – just like on that sandal.

Allee: “What does that mean in a real practical sense?”

Willet: “Our intake towers would close off. Once you start closing off, you can’t spin the
generators. That’s just kind of the big view of it.”

Zero power generation.

That’s the worst-case scenario. It hasn’t happened – but it’s a fight to prevent it.

“Now, we’re going to go down to the third floor, which is the generator floor.”

The generators are inside broad metal cylinders.

Big water pipes turn the generators. Smaller ones cool them off.

“Well, we circulate cold water from those pipes. If those start to plug up with mussels, then
you can’t keep a generator cool, if those … it shuts down due to overheating.”

Right now, it takes a lot of scraping to keep everything clear.

All this effort’s adding up – Willet says he’ll spend 2 million dollars soon on new equipment.

Even with that, Willet is still a bit jittery about some pipes outside, at the very bottom of the dam.

“The one that’s probably the scariest of all is, we have a fireline that runs around here.
Mussels love it. Then, your firelines, when they’re needed, are plugged with mussels. So
that’s another area you have to really be careful of, safety-wise.”

This didn’t have to happen.

Quagga mussels invaded eastern rivers and the Great Lakes first.

Experts figure the mussels hitched a ride West on someone’s fishing boat.

Apparently – someone didn’t clean their boat properly – and mussels dropped into Lake Mead.

Allee: “When they built this amazing structure during the Depression, do you think they had
any idea that something like this could ever happen?”

Willet: “I think there was a lot of disagreement among professionals that a little mussel the
size of your finger nail could impact a large hydro facility, but we’re quickly learning a bunch
of them can impact water and power delivery.”

Willet says if boaters aren’t careful – they’ll spread quagga mussels to the Pacific Northwest, where
there’re lots of dams and hydro power plants.

After all, if it can happen at mighty Hoover Dam – it could happen anywhere.

For The Environment Report, I’m Shawn Allee.

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A Silver Bullet for Zebra Mussels?

  • Zebra mussels were discovered 20 years ago, and have since spread across the country (Photo courtesy of the US Fish and Wildlife Service)

Researchers say they’ve found something
that will kill invasive zebra and quagga mussels.
The mussels got into the US in the ballast of
foreign ships. Since then they’ve spread throughout
the country. Rebecca Williams reports:

Transcript

Researchers say they’ve found something
that will kill invasive zebra and quagga mussels.
The mussels got into the US in the ballast of
foreign ships. Since then they’ve spread throughout
the country. Rebecca Williams reports:

So, let’s say you have a nasty pest, an invasive species. Then someone says, we can get rid of that
pest and it looks like there’s no environmental downside.

“It kinda sounds like snake oil. But it’s true.”

That’s Dan Molloy with the New York State Museum lab. He’s come up with a
way to kill zebra and quagga mussels.

Molloy says a strain of common bacteria is toxic to zebra and quagga
mussels. And, even if the bacteria are dead, they can still kill the
mussels.

“You know maybe horror stories of people applying biocontrol agents. And it
had effects they didn’t anticipate. We’re applying dead cells. And they’re
just as effective live or dead.”

It’s great news for power plants, because the mussels clog up intake
pipes.

But it’s not clear if the bacteria can kill mussels in open water.

For The Environment Report, I’m Rebecca Williams.

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Zebra Mussels 20 Years Later

  • (Photo courtesy of the US Fish and Wildlife Service)

The invasive zebra mussel has disrupted food chains and
caused billions of dollars in damage across the country. This
year marks the twentieth anniversary of the discovery of zebra
mussels. Mark Brush reports:

Transcript

The invasive zebra mussel has disrupted food chains and
caused billions of dollars in damage across the country. This
year marks the twentieth anniversary of the discovery of zebra
mussels. Mark Brush reports:

The invasive mussels first arrived here in the ballast water of foreign ships. The mussels
are really good at filtering food out of the water column – such as algae and zooplankton –
food that would eventually go to fish.

David Jude is a research scientist at the University of Michigan. He says, 20 years later,
researchers are still fighting a perception that zebra mussels are good for the
environment. That’s because the mussels do make the water clearer.

“Well if you get clear water that means that some of the algae and some of the
zooplankton that are in that water, that are part of the food chain, that are fueling our fish are going to be destroyed, degraded and
damaged.”

The Great Lakes have been hit hard by the invasive zebra mussels – and by their close
cousins – known as quagga mussels. Jude says in many places popular sport fish such as
salmon and yellow perch are having a tough time finding enough food to survive.

For The Environment Report, I’m Mark Brush.

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The Invasion of the Quaggas

  • A close-up of the quagga mussel. Quaggas have spread in all of the Great Lakes except Lake Superior. (Photo courtesy of the Michigan Sea Grant Archives)

Whitefish is a main dish for everything from fish boils to fancy dinners all around the Great Lakes region. But in some areas of the Great Lakes, whitefish aren’t doing so well. Rebecca Williams reports on what’s happening to the fish many people love to eat:

Transcript

Whitefish is a main dish for everything from fish boils to fancy dinners all around the Great Lakes region. But in some areas of the Great Lakes, whitefish aren’t doing so well. Rebecca Williams reports on what’s happening to the fish many people love to eat:

(sound of knives getting sharpened and fish being filleted)

Mike Monahan sells fish from all over the world at his seafood market. But he says whitefish is a very popular seller.


“It’s been there forever, and everybody just expects it to be there, and it’s inexpensive. But really it’s a great fish, as far as a nice light delicate fish, I’d put it up against the soles and flounders.”


Monahan says he’s still getting good supplies of whitefish. So, for now, he’s happy.


But some of the people who catch whitefish are worried. Commercial fishers have been hauling in skinnier whitefish in some parts of the lakes. It’s taking whitefish longer to grow to a size worth selling. And in some cases, the fish aren’t fat enough to make a good fillet.


(sound of shorebirds)


Paul Jensen fishes for whitefish in Lake Michigan. He says lately, he’s had to move his boat to deeper waters. That’s because whitefish are hungry and they’re swimming out deeper. They aren’t finding their favorite food. It’s a little shrimp-like creature called Diporeia.


“Diporeia are probably like a Snickers bar to whitefish; they were high in fats, high in lipids and it was their main food – it was very nutritious for them and it affected their growth rate. Eating Diporeia a fish could reach maturity maybe in 18 months or 2 years. Now we’re looking at fish that may take 5 years to get there.”


Whitefish are not eating Diporeia because it’s vanishing. In some places, researchers used to find 10-thousand of the little critters in a square meter of sediment. Now there are very few, or none at all.


Tom Nalepa has been trying to figure out why. Nalepa is a biologist with the National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Lab.


“It’s a real scientific puzzle as to why Diporeia is declining. It’s definitely related to the spread of quagga mussels and zebra mussels but that exact negative relationship is kind of elusive at this point in time.”


But Nalepa says he’s sure the invasive mussels are to blame. The mussels got into the Lakes in the ballast tanks of foreign ships. And they’ve spread in all the lakes except Superior.


Tom Nalepa says he’s seen populations of Diporeia crash right around the time the mussels were booming. Nalepa says now, Diporeia’s gone from large areas in most of the Lakes.


That’s bad because Diporeia is an important food source for most of the fish in the Great Lakes.


But for whitefish it’s really crucial. Back in the good old days, Diporeia made up about 80% of their diet.


Tom Nalepa says whitefish are trying to find something else to eat. He’s seeing them switch to a snack food that could make them even skinnier.


They’re starting to eat quagga mussels.


“When whitefish feed on quagga mussels they have to deal with the shell which has no energy content at all and it has to pass the shells through its digestive system so basically the fish feels full when it’s not getting any energy source.”


Nalepa says to the fish, quagga mussels must seem like good food, because there are lots of them.


He says quagga mussels are booming, because they can live in harsher conditions than zebra mussels can. So biologists are predicting quaggas will be even worse for the lakes than zebra mussels.


“Where are things ultimately going to end up? People may just have to get used to fewer fish. Because basically now we’re trading the fish community for the mussel community. The lakes are loaded with mussels instead of fish now. It may be just the way it’s gonna be.”


Some fishermen are already seeing things change. One day last season, Paul Jensen pulled in some of his nets. He was expecting fish.


“It was kind of startling because the amount of quagga mussels that came up with those nets far exceeded the catch of fish. And we hadn’t really equipped the boat with a snow shovel to shovel quagga mussels out of the boat. The impacts are startling because you begin to wonder, if our little net caught these, how many are there and what are the impacts going to be down the road?”


Jensen says he wishes the invaders had never gotten into the lakes in the first place, because there’s no way to predict what effect they’ll have next.


But some scientists worry these changes at the bottom of the food chain will lead to a major collapse of the fish stocks that many people depend on.


For the Environment Report, I’m Rebecca Williams.

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