Starry stonewort and other aliens invading US lakes

Authorities have confirmed the presence of starry stonewort, a type of invasive algae, in two Minnesota lakes. The algae is among a number of invasive species that conservationists say pose a threat to US waters.

Paul Skawinski/Wisconsin Department of Natural Resources
The invasive algae starry stonewort coats the bottom of a lake in this undated photo.

A stubborn, squatting species of algae has come to Minnesota’s lakes.

On Friday, the Minnesota Department of Natural Resources confirmed the presence of non-native starry stonewort in Lake Koronis and Mud Lake, producing dense mats that choke out other plants and form a wall between fish and their natural breeding grounds. The algae is one in a list of invasive pests that conservationists say pose serious risks to the nation’s water bodies in particular and its ecosystems in general.  

“Invasive species are a major threat to US biodiversity, second only to habitat loss and degradation,” according to the Virginia-based National Wildlife Federation. “Non-native plants and animals ... threaten native wildlife and ecosystems and are causing ecological havoc in many of our most sensitive habitats, pushing many of our native plants and animals to the brink of extinction.”

Invasive species also cost taxpayers in terms of damages to the environment, agriculture, and native species: Government estimates of their impact range from $74 billion to $120 billion annually.

Which is why such species are a concern across the United States. From the Northeast to the Southwest, non-native aquatic species disrupt local plant and animal communities, spurring local groups to act.

To encourage locals to report the appearance of invasive aquatic species, for instance, the Maine Department of Environmental Protection provides a list of plants – from Brazilian elodea to European frog-bit – infesting water bodies in the state.

Texas Invasives, a collaboration between conservation groups, government agencies, the academe, and others, warns of the dangers of zebra mussels – “a small, destructive invasive species that can spread across Texas by hitching a ride on boats and trailers.” The mussels multiply rapidly and lack natural predators in the area, which makes them prone to taking over habitats from native species, damaging boats, and clogging pipelines.

Among the nation’s most vulnerable regions are the Great Lakes, which have been troubled by at least 25 non-native species of fish since 1800 as well as alien species of mussels and mollusks, crustaceans, and plants.

The appearance of starry stonewort in Minnesota’s lakes have locals worried. Native to Europe and western Asia, the algae first appeared in Michigan and northern Indiana, likely via ballast water carried in ships. Authorities also recently confirmed the presence of starry stonewort in six lakes in southeast Wisconsin.

“It’s really hard to see this happening,” Karen Langmo, a member of the Koronis Lake Association, told the Minneapolis Star Tribune. “To me, this lake is sacred.”

Manual removal of starry stonewort is difficult, and effective biological control agents have yet to be identified. Still, conservationists, communities, and government agencies in the region have been coordinating in efforts to stem the algae’s spread.

In Wisconsin, for instance, the Department of Natural Resources (DNR) provides state funding for removal, control, and monitoring of invasive aquatic species, and to encourage innovation in preventing their spread.

“Adaptive management efforts that include the use of multiple prevention and control techniques are underway to prevent further spread and control existing populations,” according to the department. “Though not ruled out completely, chemical treatments have had little success in other states, so the DNR is exploring other control options including hand pulling and suction harvesting.”

This report contains material from the Associated Press.

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