21st April, 2010 - Tony Groves, Pam Tyning, Paul Hausler - Progressive AE
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 Isle2 and has since infested several Michigan lakes.3,4
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 a tendency to colonize deeper water and can form dense mats several feet thick. Starry stonewort can impede navigation and limit growth of more beneficial plants. Compared to many other aquatic plants, starry stonewort may begin growing later in the season and persist longer.2
It is unclear what effects starry stonewort may have on a lake’s fishery. The encroachment of starry stonewort into fish spawning beds may be a cause for concern. Nichols et al.2 noted that starry stonewort may be a food source or shelter for bottom-dwelling and juvenile fish in fall and winter when other plants are absent.
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.
- Schloesser D.W., P.L. Hudson, and J. Nichols. 1986. Distribution and habitat of Nitellopsis obtusa (Characeae) in the Laurentian Great Lakes. Hydrobiologia 133: 91-96.
- Nichols, S.J., D.W. Schloesser, and J.W. Geis. 1988. Seasonal growth of the exotic submerged macrophyte Nitellopsis obtusa in the Detroit River of the Great Lakes. Canadian Journal of Botany. 66: 116-118.
- Hill, R. 2006. Littorally speaking: Other aquatic invaders on Maine’s radar. The Water Column. 10(3): 5-7.
- Jackett, J. 2006. New exotic plant showing up in Oakland lakes. Oakland Lakefront.