Every month, we will put a spotlight on an aquatic invasive species (AIS) in a re-occurring monthly article. Check it out! This month, we highlight an emerging threat to Wisconsin lakes: Starry Stonewort!
Starry Stonewort
Starry stonewort (Nitellopsis obtusa) is a submerged macro alga that has recently invaded several inland lakes in southeast Wisconsin as well as coastal areas of Green Bay and Lake Michigan within the Door County Peninsula. Starry stonewort is native to Eurasia and is found from Europe to Japan. It was brought to the United States in the ballast water of a cargo ships with the first invasive population found in the St. Lawrence River in 1970’s. It was first found in Wisconsin in Little Muskego Lake in Waukesha County in 2014 and has since been detected in a few neighboring counties as well as Door County.
Starry Stonewort Bulbil
Starry stonewort is loosely rooted in the bottom of waterbodies. It grows long branches from stems that are variable in length. The plant has been found to grow as large as 6 feet in 29 feet of water in a Michigan lake. Starry stonewort is light green and can form dense mats at the bottom of invaded waterways. The most identifiable portion of the plant are the star-shaped bulbils (a small bulb-like reproductive structure of a plant) that are about the size of a grain of rice. That’s where the plant gets its name!
Nitellopsis obtusa grows in slow moving water and can grow in depths where there are few other plants. It has a large tolerance to salt and is believed to have therefore survived in ballast water of a trans-Atlantic ship that arrived in the Great Lakes. In invaded areas in the U.S., the algae grows best from July to September before decomposing in the following March. Small pieces of the plant can break off and grow new plants in different locations. The star-shaped bulbils (where the plant gets its name) can easily be transported by wildlife and humans.
Starry stonewort has not invaded the Winnebago Waterways. Make sure to be extra attentative when checking your gear! The small bulbils are very small and can be tricky to spot!
Starry stonewort bulbil on anchor
In places where starry stonewort has invaded, there have been reports of a decrease in fish spawning activities in the algae compared with spawning in native plants. Starry stonewort can outcompete many native plant species and has even been reported to out-compete other invasive plant species such as curly leaf pondweed and Eurasian watermilfoil. This is due to starry stonewort’s ability to block other plants from growing due to its dense mat growth. In addition, starry stonewort accumulates phytotoxins in the sediment around the algae such that other plants cannot grow.
In Wisconsin, starry stonewort is classified as Prohibited in all counties.
Want to help? HELP PREVENT THE SPREAD!
Every time you come off the water, make sure to follow these steps to stop the spread of faucet snails and other aquatic invasive species:
* Inspect boats, trailers, push poles, anchors, and other equipment for attached aquatic plants or animals.
* Remove all attached plants or animals
* Drain all water from boats, motors, livewells and other equipment
* Never move live fish away from a waterbody
* Never release aquarium plants or animals into your local waterways
Follow the Fox Wolf Watershed Alliance’s Winnebago Waterways Program on our Winnebago Waterways Facebook page or @WinnWaterways on Twitter! You can also sign-up for email updates at WinnebagoWaterways.org.
Questions? Comments? Contact Chris Acy, the AIS Coordinator for the Winnebago Waterways Program covering Fond du Lac, Calumet, and Winnebago Counties at (920) 460-3674 or chris@fwwa.org!
Winnebago Waterways is a Fox-Wolf Watershed Alliance program. The Fox-Wolf Watershed Alliance is an independent nonprofit organization that identifies and advocates effective policies and actions that protect, restore, and sustain water resources in the Fox-Wolf River Basin.
Photo Credit: Paul Skawinski, Brad Steckart, Chris Acy
