Great Lakes Invasion

Quagga Mussels Wreak Havoc on Ecosystem

Algae blooming in Lake Erie. Image credit: NOAA/USGSOn Tuesday, the U.S. House of Representatives passed legislation backed by the shipping industry that prevents states from establishing their own tougher regulation of ballast water. Scientists say it is that ballast water from ocean freighters that imports dangerous, invasive species into U.S. waters.

While the battle between the shipping industry and environmentalists rages on Capitol Hill, a tiny invader is already living in the Great Lakes and is wrecking the food chain and the commercial fishing industry.

It’s just after dawn in Northern Wisconsin. Commercial Fisherman Dennis Hickey is getting ready to take his fishing boat out on Lake Michigan.

Hickey’s family has fished these waters for more than a century. 

The Great Lakes currently support a $7 billion a year commercial and recreational fishing industry.

“Our mainstay of our fishery in Bailey’s Harbor is Whitefish,” Hickey said. “Lake Michigan Whitefish.”

Today, Hickey is lucky. He won’t be battling the elements to bring in a catch. It’s unseasonably warm on this late autumn morning. But he does have to deal with a problem that increasingly plagues fishermen throughout the Great Lakes and threatens their livelihoods.

Hickey pulls up one of his fishing nets which are covered in a green film.

“Looks like the hearts have quite a bit of moss and slime in them again,” he said.

The slime is a type of alga called Cladaphora, and some scientists think its extraordinary increase in the Great Lakes is related to recent and irreparable changes in the marine ecosystem.

The culprit, they say, is a tiny invasive mollusk called the Quagga mussel. Quagga Mussel. Image credit: NOAA

“To me, it’s one of the worst, if not the worst,” said Tom Nalepa, research biologist with the Great Lakes Environmental research laboratory at the National Oceanic and Atmospheric Administration.

For the last 20 years, Nalepa and his team have been assessing population trends and the impact of the mussel invasion on the Great Lakes.

“They find conditions very suitable and just explode in terms of population numbers,” said Nalepa. “During the period of exponential growth, they wreak havoc on other organisms; they take away resources and out-compete native species.”

Scientists believe the Quagga mussel first stowed away in the ballast water on transoceanic ships from the Caspian Sea. The mussels made their way into the lakes when that ballast water was purged.

The tiny fingernail-sized mussels closely related to another invasive, known as the Zebra mussel, first appeared in lake waters here in 1988.

The Quagga mussel is now the most pervasive and destructive invasive species ever to enter the Great Lakes. Over the last 15 years, the Quagga population has exploded, eclipsing the Zebra mussel and infecting all five of the Great Lakes.

Fishermen examine a pile of Quagga mussels. Image credit: NOAANalepa estimates there are now 437 trillion in Lake Michigan alone.

Scientists say the reason this dominating mussel is so destructive is that it is wiping out critical food at the bottom of the food chain; organisms like plankton, the main food source for a shrimp-like organism known as Diporeia.

“It’s a very important fish food organism, hence this has led to declines in the growth and condition of fish populations that once depended upon Diporeia as a food source,” said Nalepa. “So it’s led to kind of a cascading effect from one species to another throughout the food web.”

In addition to altering the food chain in the Great Lakes, these mussels attach to all types of surfaces, including boats, buoys and docks. They clog water intake pipes, sometimes cutting off drinking water supplies that require expensive remediation.  Which is why the financial impact of these tiny invaders is staggering.  
 
The U.S. Fish and Wildlife Service estimates the economic losses over the last decade at about $5 billion within the Great Lakes region alone.

At the DuSable Harbor on Chicago’s Lakeshore, Operations Manager Kirk Kleist pulls up a dock anchor chain to show just us how pervasive the mussels have become in near shore areas. The chains are encrusted with a thick layer of the tiny mollusks. 

“They load up so much. They cause problems,” he said.

Kleist, who has been a diver for over three decades, says he’s seen the dramatic changes in the lake water caused by mussel filtering.

“Thirty years ago, you had five feet of visibility at the max, now I’ve seen 40 to 60 feet of visibility,” he said.

But scientists say clear water, in this case, is in fact a bad thing. Algae blooming in Lake Erie. Image credit: NOAA/USGS

“The water clarity has increased two- or three-fold, just because of the ability of mussels to filter all the particles out of the water which they use as food,” said Nalepa. “So, if you like clear water, certainly when you look out at Lake Michigan, you have it. But clear water also means there’s no food in the water for all the other organisms.”

The other side effect of excess clarity caused by the Quagga’s filtering is that it encourages explosive algal blooms like Cladaphora and a toxic algae known as Microcystis.

“They allow, for the first time in the life of the Great Lakes, sunlight to pierce all the way down to the bottom of the lake…from Erie on, and that creates the ability for toxic algae to grow; which is poisonous and it’s retro to public health and safety,” said Henry Henderson, Director of the Natural Resources Defense Council.
 
Satellite images taken last month reveal just how overwhelming the algae have become in the Great Lakes, indicating massive swirls of green algae all along coastal areas.

A report published by the National Wildlife Federation called the toxic algal bloom that infested Lake Erie’s western basin this year and caused mass beach closings, “the most harmful in recorded history.”

“When the Cladophora washes up on beaches, they often harbor problematic bacteria including botulism toxin which then can negatively impact fish and birds that consume somewhere in the food web,” said Michael Murray, staff scientist with the National Wildlife Federation’s Great Lakes office in Ann Arbor, Michigan and co-author of the report.

Murray says the Great Lakes are experiencing both feast and famine because while algae is growing in record amounts in coastal areas, there is also the formation of nutrient deserts in offshore waters; which scientists say contribute to the steep decline in fish populations.

“The overall effect is, we’re still seeing a lot of nutrients in the near-shore areas, major problems with algal blooms, Cladophora, those types of problems,” Murray said. “And then in the offshore areas not enough nutrients, and major problems with the fisheries there.”

Because of the drastic changes in the Great Lakes over the last two decades, commercial fishermen say they’ve had to adapt. Today, they’re forced to go further and further out into the lakes just to get a good catch.

When the wind blows, fishermen like Hickey say the algae load up their live entrapment nets, making it easier for fish to see and avoid.

Hickey and his crew have to spend precious time and money to pull out the nets and clean them.

“Well, it gets worse every year. The last five years it’s been increasing,” he said.

Scrawny fish and too much algae have become game-changers for many smaller commercial fishermen in the area.

“The smaller fisherman, just plain decided to sell out…and just get out of the business,” said Hickey.

And the future of commercial fisheries looks bleak because scientists say removing the mussels from the lake is impossible.

“Quagga mussels are going to be with us now forever,” said Nalepa. “It’s just a matter of, at what abundance does the population stabilize, and that’s the key."

"They wreck the life that’s in there and create a new ecosystem that is dangerous for our health and safety in fundamentally devastating ways," said Henderson. "You can see it happening in Lake Erie. It’s on the edge of collapse.”

Scientists and activists say that while the focus must shift to preventing the introduction and spread of new invasive species into the Great Lakes, the destruction underway by the Quagga mussel now serves as a painful cautionary tale.

For more information on Quagga mussels and the environment, please visit the PDFs and links below.