Saginaw Bay CISMA
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Starry Stonewort

Starry stonewort (Nitellopsis obtusa) is a microalgae from Eurasia that was likely introduced to the US accidentally in ballast water. Starry stonewort first appeared in the US in 1978 in the St. Lawrence River between New York and Ontario, and has since spread throughout the Great Lakes basin into Michigan, Indiana, Wisconsin and Minnesota. Starry stonewort has been identified along the shoreline of the Saginaw Bay in Tuscola, Bay, Huron and Arenac counties. 

When left unchecked, starry stonewort grows in large underwater mats that harm natural ecosystems, and make fishing, swimming or boating nearly impossible. Starry stonewort can reproduce sexually or asexually from fragmentation, making them difficult to control. The stonewort takes its name from the white, star-shaped bulbils at the branch nodes. The bulbils set the starry stonewort apart from similar native species, making the invasive plant easy to identify. 

Like many other aquatic invasive species, starry stonewort spreads through waterways on boats and aquatic gear. Plants can regrow from very small fragments, so preventing the spread of fragments is crucial. You can prevent the spread of starry stonewort by washing off boating and recreational gear when leaving any freshwater body.
​​
Picture
Starry stonewort form large pillowy masses that prevent fish movement and damage natural ecosystem functions. Photo: Barbara Tokarska-Guzik, University of Silesia, Bugwood.org
Identification:
  • Whorls of 4-6 branchlet with blunt tips
  • Star-shaped bulbils at nodes
  • Can reach up to 33 inches in length. 
Habitat:
Invades lakes, ponds, reservoirs, and slow moving rivers. Will inhabit freshwater habitats from 3 to 95 feet in depth.

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Starry stonewort spreads through waterway through fragmentation. Even very small fragments are enough to regrow a whole plant. Photo: Scott Brown, Michigan Lake and Stream Association
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White bulbils at the branch nodes give the starry stonewort its distinctive characteristic. Photo: Paul Skawinski
​Additional Resources
Starry Stonewort Collaborative
Starry Stonewort Status and Strategy
Starry Stonewort Boater's Beware Card
​Michigan Invasive Species Website
​MISIN Species Training Module
Report Starry Stonewort
Banner Credit: Michael Shephard USDA Forest Service

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4490 W. M-61
Standish, MI 48658
P: (989)-846-4565 ext. 5
Hours of Operation: 
Mon-Fri, 8:00-4:30
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This project was funded by the Michigan Invasive Species Grant Program (Michigan.gov/Invasives).

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  • Home
  • About Us
    • Strategic Plan
    • Steering Committee
    • Partners
  • Invasive Species
    • Invasive Species Profiles >
      • Japanese Knotweed
      • Giant Knotweed
      • Phragmites
      • Spongy Moth
      • European Frog-bit
      • Invasive Swallow-wort
      • Starry Stonewort
      • Flowering Rush
    • Watch List Species
  • Events
    • National Invasive Species Awareness Week
  • Projects
    • Shoreline Phragmites Treatments 2022
    • Roadside Treatment
    • Hampton Township Treatment
    • Au Gres River European Frog-Bit
  • Resources
    • Landowner Resources
    • Outreach and Education
    • Contractors
    • Tool Crib Rental
  • Contact Us
    • Employment
    • Volunteer