Starry Stonewort (Nitellopsis obtusa)
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Starry stonewort is a submerged aquatic macroalgae with many irregular branches. It is native to Europe and was likely introduced in ballast water to the Great Lakes. Fragments of starry stonewort can easily attach to the fur and feathers of mammals and birds, or attach to boats and fishing equipment allowing it to spread from one water body to another.
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Starry stonewort forms a dense, vertically thick mat that completely covers the lake bottom.
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Impacts of Starry Stonewort
Starry stonewort forms dense mats in lakes and can significantly reduce the diversity of other aquatic plants. Dense mats of vegetation can also impede the movement of fish, spawning activity, water flow, and recreational activities.
Starry stonewort forms dense mats in lakes and can significantly reduce the diversity of other aquatic plants. Dense mats of vegetation can also impede the movement of fish, spawning activity, water flow, and recreational activities.
Starry Stonewort Identification
Starry stonewort is soft with a light green hue. It often branches in whorls of 4-6, angled toward the tip of the growth. The branches are separated by long tube-like cells. Small white stars a couple millimeters across adorn clumps of the algae.
Starry stonewort is often confused with a native algae called muskgrass or Chara. Muskgrass is similar in appearance to starry stonewort, but is typically more bristly and has a bottom cover less than a foot tall. Muskgrass also lacks the small white stars of starry stonewort.
Starry stonewort is soft with a light green hue. It often branches in whorls of 4-6, angled toward the tip of the growth. The branches are separated by long tube-like cells. Small white stars a couple millimeters across adorn clumps of the algae.
Starry stonewort is often confused with a native algae called muskgrass or Chara. Muskgrass is similar in appearance to starry stonewort, but is typically more bristly and has a bottom cover less than a foot tall. Muskgrass also lacks the small white stars of starry stonewort.
Invasive Starry Stonewort Identification - Video
In this very helpful video, you will learn to identify starry stonewort (Nitellopsis obtusa) and distinguish it from several look-alike species. A production of the Wisconsin Lakes Partnership. |
Photos: Courtesy of Paul Skawinski, UW-Extension Lakes Program
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The Squeeze Test
Starry stonewort is often mistaken for other types of macroalgae like Chara. One test that may be used to distinguish Starry Stonewort from Chara is the “squeeze test.” In Starry Stonewort the protoplasm inside will pop out of the cell when squeezed. The remaining cell wall becomes a limp straw. In Chara, the protoplasm does not separate easily from the cell wall.
Starry stonewort is often mistaken for other types of macroalgae like Chara. One test that may be used to distinguish Starry Stonewort from Chara is the “squeeze test.” In Starry Stonewort the protoplasm inside will pop out of the cell when squeezed. The remaining cell wall becomes a limp straw. In Chara, the protoplasm does not separate easily from the cell wall.
What can you do to prevent the spread of this invasive species
- Learn to identify Starry stonewort.
- Inspect and remove aquatic plants and animals from boat, motor and trailer.
- Drain lake or river water from live well and bilge before leaving access.
- Rinse boat and equipment with high-pressure hot water (104° F), especially if moored for more than a day, or dry everything for at least 5 days before launching in a new body of water.
- Report sightings of Starry stonewort to Tip of the Mitt Watershed Council by calling (231) 347-1181 or by
e- mailing info@watershedcouncil.org . Please note the exact location in which you saw the species.
