Starry stonewort (Nitellopsis obtusa) looks like a rooted plant but it is actually an algae. The plant is native to Europe and Asia and was first discovered in the St. Lawrence River in 1978 (1). In 1983, it was found in the Detroit River near Belle Isle (2) and as of 2014, has been observed in about 150 inland lakes in Michigan.
Starry stonewort resembles the native aquatic plant Chara. Starry stonewort has tiny, star-shaped, tan-colored reproductive structures called “bulbils” that are firm to the touch when compared to its soft branches. The presence of bulbils is one way to distinguish between starry stonewort and Chara. Unlike Chara, which is generally considered to be a beneficial plant, starry stonewort has several nuisance characteristics. Starry stonewort has a tendency to colonize deeper waters and can form dense nearly impenetrable mats several feet thick. In many infested lakes, starry stonewort impedes navigation, limits growth of beneficial plants, and covers valuable fish habitat and spawning areas.
Both algaecides and mechanical harvesting appear to be somewhat effective in controlling starry stonewort. Because it lacks roots, starry stonewort can be dislodged from the bottom without much difficulty.