June 23, 2008
Weekly News UpdateMussels Wreaking Havoc in the Colorado River
While biologists were busy trying to control populations of invasive zebra mussels, another non-native mussel species sneaked in under the radar. Quagga mussels, bivalves native to Ukraine, has quietly been taking over waterways from the Great Lakes to the Colorado River. And, just like their zebra mussel relatives, quagga mussels hold tightly to whatever they latch on to, including water intake pipes—which can be a major problem for hydroelectric plants. This is especially problematic given the amount of people who rely on the Colorado River as their primary source or water.
While the mussels cause major problems for humans, their impact on the ecosystems that they invade are even more far-reaching. Mussels are filter feeders. When they feed, mussels clear the water of debris. The clear water lets in more sunlight, which leads to algal blooms and increased growth of weeds. This massive growth of algae and plants in turn causes oxygen-depleted dead zones. When mussels filter feed, they also accumulate toxins in their bodies. Such an accumulation of toxins has led to increased cases of botulism poisoning. In the Great Lakes ecosystem, biologists have noted that cases of avian botulism have risen at an exponential rate. A massive die-off of loons has been particularly distressing.
Like zebra mussels, quagga mussels out-compete the native species in the ecosystems that they invade. Two endangered fish species native to the Colorado River, the bonytail chub and the razorback sucker, are considered to be especially vulnerable to competition by the mussels. Quagga mussels are so prolific that they have even displaced the zebra mussel in much of the Great Lakes ecosystem.
Resource managers have taken a number of steps to combat the spread of the invasive mussels. Nine thousand gallons of chlorine are added to the Colorado River Aqueduct daily to kill mussel larvae. Because mussels are often spread from one waterway to another through larvae-contaminated bilge pumps and live bait wells, the inspection of recreational boats has become commonplace. In California, inspectors with the Fish and Game Department even use mussel-sniffing dogs to inspect boats before they enter the water.
The spread of quagga mussels—which occured at a time when biologists were actively monitoring for the spread of a different mussel species—highlights how quickly invasive species can spread and remain undetected. The spread of Eurasian quagga mussels in waterways across the United States illustrates the fact that there is no such thing as geographic isolation when it comes to invasive species.