Zebra Mussels

photo: USFWS

Some of these things just don't belong here -- invasive species such as zebra mussels and Asian carp are living pollution that can hurt fisheries, degrade water quality and otherwise disrupt nature's balance.

At first glance, zebra mussels look pretty harmless. They're small, freshwater mollusks with stripy, triangular shells, the kind a kid might like to pick up at the beach. In the Great Lakes, however, these little mussels are ruthless invaders, clogging up water pipes, gobbling up the food supply and rapidly altering the ecology of the lakes, which supply one-fifth of world's fresh water.


Invasive Species 101

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Thom Cmar explains the impact of invasive species like Asian Carp and Zebra mussels on the Great Lakes and other waterways.

A multi-million dollar nightmare

Zebra mussels are tough, reproduce rapidly and have few natural predators. When they arrived in the Great Lakes, their population exploded. Today, along with their cousins, the quagga mussels, they've become the most numerous life form in Lake Michigan. They clog up water treatment facilities, water intake pipes for power plants and boat engines. Invasive species are an annual $200 million dollar drain on the regional economy, and the fight to keep zebra and quagga mussels out of municipal water systems and infrastructure is by far the biggest cost.

The mussels also suck up so much plankton that the nutrient-rich waters of Lake Michigan are turning clear. Sunlight can now reach the bottom of the lake, allowing large algal blooms, which form an unhealthy muck that's a haven for disease-causing bacteria like E. coli.

The next threat

Asian carp at Shedd Aquarium

photo: Kate.Gardiner via Flickr Asian carp in the Shedd Aquarium.

Zebra mussels are not native to the Great Lakes region. They come from the Black Sea in Russia and probably hitched a ride to the Midwest in ballast water dumped from ocean-going ships. They're just one of more than 180 invasive species that have made their way into the Great Lakes, including the sea lamprey, spiny flea, bloody red shrimp, and viral hemorrhagic septicemia (also known as "fish Ebola").

One of the newest threats to the fragile Great Lakes ecosystem is Asian carp. These big, aggressive invaders out-eat the native competition and can even injure people with their acrobatic leaps. Boaters and jet-skiiers along the Illinois and Mississippi rivers have reported cuts, bruises and broken bones after being hit by flying carp, which can weigh 100 pounds.

Asian carp were originally imported into the southern United States for aquaculture, and escaped into the Mississippi River system during flooding in the 1990s. Now the invasive fish are within miles of a canal that would give them access to Lake Michigan and the entire Great Lakes ecosystem. Once in, they could destroy the region's $7 billion fishing industry and further strain the quality of the water supply for 40 million people. The latest tests suggest that the carp may have already made it through.

Fighting to close the door


Invasive species are a national problem. The Great Lakes are a gateway to freshwater ecosystems across the country, as demonstrated by the rapid spread of zebra and quagga mussels to the central and southwestern United States, where they now pose a threat to Lake Mead and Hoover Dam. Chesapeake Bay, San Francisco Bay, and other coastal areas nationwide have also been affected by the advance of invasive species.

Tougher water ballast laws are critical to keeping these harmful invaders out, and NRDC is defending such laws in court. We’re also fighting for the integrity of the Great Lakes ecosystem. Our Chicago office is lobbying for infrastructure changes in a series of canals that connect the Great Lakes to the carp-infested Mississippi River system.

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