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Be on the lookout for Starry Stonewort!

Be On the Lookout For Starry Stonewort

By Emily Staychock, Finger Lakes Institute Aquatic Invasive Species Education Coordinator


Photo credit: https://adkwatershed.wordpress.com/2014/10/23/starry-stonewort-nitellopsis-obtusa/


Residents of the Finger Lakes region are becoming increasingly aware of the threat that aquatic invasive species pose to our beautiful lakes and the water recreation-based tourism that supports our local economies. The Finger Lakes Institute and the Finger Lakes PRISM work to engage citizens in invasive species monitoring and management in order to enhance the region’s capacity to respond to this threat. We’d like to introduce a high-profile aquatic invasive species to add to the radar in the hopes that community members can assist in identifying new infestations: starry stonewort, or Nitellopsis obtusa. Interest in this species has been growing over the past several years as partners have become aware of its presence in New York and have identified it in water bodies across the state.


Starry stonewort is a macroalgae that has stem-like and leaf-like structures, giving it the appearance of a plant. It’s bright green and has branchlets that are arranged in whorls of 4-6 growing around the stem. Starry stonewort is anchored to the substrate by hair-like filaments, or rhyzoids, that contain several dozen 4-5 mm star-shaped bulbils which inspired its name. All documented starry stonewort in the US are male, so there is no known sexual reproduction by seed. All known reproduction in the US occurs by sprouts from the bulbils or by fragmentation. Nodes located along the stem can turn into bulbils in late autumn. Starry stonewort can grow to several feet long at depths of 3-20 feet in lakes or slow moving rivers.


Starry stonewort was most likely introduced to North America in the ballast waters of ships coming from its native waters in Europe and Asia. It was first discovered in the St. Lawrence River in 1978 and has since spread throughout the upper Midwest and New York. It is similar in appearance to the native macroaglae Chara, also known as muskgrass, which may cause it to be initially overlooked and prevent early detection. The easiest way to tell these species apart is the rough texture and musky smell associated with Chara, and the white star-shaped bulbils on starry stonewort. Since 2005, different agencies and organizations have confirmed starry stonewort at locations around Lake Ontario and the Finger Lakes region, including Canandaigua, Keuka, Owasco, Cayuga, Oneida, Duck, Tully, and Upper Little York Lakes, as well as Lake Como.


Starry stonewort presents an ecological concern because it grows in dense stands and crowds out native vegetation and interferes with the habitat needs of native animal species, including fish spawning. Dense stands can foul boat motors and can impede swimming and fishing. It fragments easily and can be spread by boats and trailers.


The upper Midwest has been studying and attempting to manage starry stonewort for years and there is valuable information that we can gain from efforts in the states of WI, MI, IN and MN. Management of starry stonewort in the US has shown that common algaecides containing copper and endothall based compounds can be effective when the infestations are low in height. Once the starry stonewort grow taller the algaecides typically kill only the top part, while the lower part survives. There is no known biological control, and mechanical treatments are difficult due to population density and its ability to reproduce by fragmentation. In addition, mechanical treatments must be sure to remove the bulbils that are rooted in the substrate as well.


Finger Lakes Institute and the Finger Lakes PRISM will work with the NYS Department of Environmental Conservation and partners in New York State as well as contacts in the upper Midwest to better understand this species’ range in the region, impacts, and management. You can help! Learn how to identify starry stonewort and report any identifications in new locations to the Finger Lakes PRISM: 315-781-4385. Visit the PRISM website http://fingerlakesinvasives.org/ for information about starry stonewort and other invasive species, and to find out how to get involved in invasive species initiatives and events in the Finger Lakes region.

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