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Lake Detroiters Association


VIDEO :: Identifying Starry Stonewort


Starry Stonewort (SSW) Photos:

starry stonewort 092515

PHOTO - Starry-stonewort-4

The 7-star bulbil is a unique identifierStarry-stonewort-7 - star-shaped bulbils give starry stonewort its name

SSW lakebed dense matstarry stonewort-minnesota


Bulbils are Small in Size Small SSW bulbil in hand

Starry Stonewort From a Rake Pull
starry+stonewort - Upper Red lake

SSW and Chara Comparisons with Labels1

The starry stonewort 7-point bulbils are very small and visible late summer and fall and they are unique to starry stonewort. 

2016 Lake Koronis wall of starry stonewort at depths of 12 feet                       2016 Lake Koronis starry stonewort - early spring  Koronis - Early Spring1

2016 Lake Koronis starry stonewort with additional algae attached
Koronis - Additional algae growing on the SSW - late season

Starry stonewort (SSW) is a grass-like algae that can produce dense mats which choke out native plants, limit motorized watercraft, and affect fish habitat. It is a very invasive aquatic invasive species (AIS) that Detroit Lake recreationalists have an opportunity to ward off.  There are no known treatment methods for SSW and may be more devastating to lakes than zebra mussels because of how navigation is limited through the SSW.

SSW is introduced to a lake by watercraft or water-related equipment with SSW fragments attached at the time of launch.  Because it is difficult to identify and can resemble native vegetation.  Extreme caution must be taken when launching watercraft or equipment into the lake.  Make sure that all equipment is free of any vegetation framents espeically on trailer carpet bunks and other nooks and crannies.  A very small fragment can multiply and become a huge infestation.  Sometimes SSW can initially be confused with chara.  Photos of a SSW mass at the surface and dense mats at the lakebed bottom:

PHOTO - Starry Stonewort - appearance in water

This is especially important for lake homeowners that have guests bringing boats, pontoons, jet skiis that have recently been in other Minnesota lakes and especially boats/trailers from areas outside of Minnesota.  For the most part, homeowners do not trailer watercraft to other waterbodies but caution should be taken if the need arises. 

For free professional watercraft inspection and decontamination prior to launch, please use the South public access during times inspectors are on duty.  A decontamination unit is always available when inspectors are working.  If a special situation arises and inspection and/or decontamination is necessary outside of scheduled times, please call Karl Koenig, Becker County AIS Coordinator at 218-849-6438.

Starry stonewort not considered a plant but a grass-like form of algae that are not native to North America. The plant was first confirmed in Minnesota in Lake Koronis (Stearns County) in late August of 2015 and followed by a second infestation August 2016 in Turtle Lake; Beltrami County. Fragments were probably initially brought into the state on a trailered watercraft from infested waters in another state.

Starry stonewort compromises the ability to use public waters for recreational activities because of the mass at the surface.  The filamentous algae acts like a ball of fishing line which makes using motorized watercraft difficult. 

Starry stonewort may be difficult for a citizen to identify and any suspicious infestation should be immediately be reported to the local DNR AIS specialist, Mark Ranweiler at 218-616-2117 or the Pelican River Watershed District at 218-846-0436s for identification.

The MN DNR website has more information on starry stonewort.
Known Starry Stonewort Infestations - MN - DRAFTcropped1
Starry stonewort ID laminate WI CLMN