JEFFREY BROWN: And next, the story of a tiny invader doing big damage to the Great Lakes.
Ash-har Quraishi of WTTW Chicago reports.
ASH-HAR QURAISHI, WTTW Chicago: 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.
MAN: Our mainstay of our fishery here in Baileys Harbor is whitefish, Lake Michigan whitefish.
ASH-HAR QURAISHI: Today, Hickey's lucky. He won't be battling the elements to bring in a catch. It is 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.
MAN: Looks like the hearts have quite a bit of moss and slime in them again.
ASH-HAR QURAISHI: The slime is a type of alga called Cladophora, 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.
TOM NALEPA, Great Lakes Environmental Research Lab: To me it's one of the worst, if not the worst.
ASH-HAR QURAISHI: Tom Nalepa is a research biologist with the Great Lakes Environmental Research Lab 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.
TOM NALEPA: They find conditions very suitable and just explode in terms of population numbers. And during the period of exponential growth, they wreak havoc on other organisms. They take away resources, outcompete native species.
ASH-HAR QURAISHI: Henry Henderson is director of the National Resources Defense Council.
HENRY HENDERSON, National Resources Defense Council: 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. You can see it happen in Lake Erie. It's on the edge of collapse.
ASH-HAR QURAISHI: 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.
MAN: These are typical quagga mussels in Lake Michigan. They have the striping, as zebra mussels do. They have a little flatter shell.
ASH-HAR QURAISHI: 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.
Nalepa estimates there are now 437 trillion in Lake Michigan alone. And the reason scientists say 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.
TOM NALEPA: 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. So it's led to a cascading effect from one species to the other throughout the food web.
ASH-HAR QURAISHI: In addition to altering the food chain in the Great Lakes, these mussels attach to all types of surfaces, like 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 from 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.
KIRK KLEIST, Chicago Harbors: They load up so much. They cause problems.
ASH-HAR QURAISHI: 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.
KIRK KLEIST: Thirty years ago, you had five foot of visibility at the max. Now I have seen 40 to 60 foot of visibility.
ASH-HAR QURAISHI: But scientists say clear water in this clear is in fact a bad thing.
TOM NALEPA: 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.
So, if you like clear water, certainly, when you look out at Lake Michigan, you have it. But clear water also means that there's no food in the water for all the other organisms.
ASH-HAR QURAISHI: The other side effect of excess clarity caused by the quagga's filtering is that it encourages explosive algal blooms like Cladophora and toxic algae known as Microcystis.
HENRY HENDERSON: 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 a threat to our public health and safety.
ASH-HAR QURAISHI: These images taken by NOAA and the U.S. Geological Survey last month reveal just how overwhelming the algae have become in the Great Lakes. 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 ever recorded.
MICHAEL MURRAY, National Wildlife Federation: When the Cladophora wash up on beaches, they often harbor problematic bacteria, including botulism, which then can negatively impact fish and birds that consume somewhere in the food web.
ASH-HAR QURAISHI: Michael Murray is a staff scientist with the National Wildlife Federation's Great Lakes office in Ann Arbor, Mich., and co-authored 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.
MICHAEL MURRAY: So, the overall effect is, were still seeing a lot of -- still a nutrients in near-shore areas, major problems with algal blooms, Cladophora, those types of problems, and then in the offshore areas, not enough nutrients and major problems with the fisheries there.
ASH-HAR QURAISHI: Because of the drastic changes in the Great Lakes over the last two decades, commercial fishermen say they have had to adapt. Today, they're forced to go further and further out into the lake just to get a good catch.
When the wind blows, fisherman Dennis Hickey says 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.
MAN: Well, it gets worse every year. It's been -- the last five years, I say, it's been increasing.
ASH-HAR QURAISHI: Scrawny fish and too much algae have become game-changers for many small commercial fishermen in the area.
MAN: The smaller fishermen just plain decided to sell out and get out of the business.
ASH-HAR QURAISHI: And the future of commercial fisheries looks bleak, because scientists say removing the mussels from the lake is impossible.
TOM NALEPA: Quagga mussels are going to be with us now forever, I think. It's just a matter of, at what abundance does the population stabilize? And that's the key.
ASH-HAR QURAISHI: 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 under way by the quagga mussel now serves as a painful cautionary tale.