Written by Industry Expert Shannon Junior, Aquatic Ecologist and Senior Business Development Consultant
Starry stonewort (Nitellopsis obtusa) is a species of macroscopic green algae in the Characeae family. It was first discovered in the United States in 1978 in the St. Lawrence River, but has since spread to Michigan, New York, Indiana, Pennsylvania, Wisconsin, Minnesota and Vermont. When the algae were first discovered in new areas, they were often misidentified as less invasive native species of macroscopic algae. However, the growth habit of starry stonewort is much more aggressive and robust, and can reach nuisance abundances. These nuisance plants can reduce the growth of desirable aquatic vegetation, reduce suitable fish habitat and cause fishing frustration. Although the algae are non-vascular and have no true plant structures, they have been found to grow as much as eight feet tall. The blooms have severe negative impacts on the habitats where they occur, and have posed unique challenges for lake managers in these areas.
Now that the presence of starry stonewort has become more familiar to lake managers, it is actually quite easy to identify. The blooms appear more “raggedy” than other macroscopic algae species, and have much greater height and biomass. They are also characterized by distinctive “starry” rhizoids, also known as bulbils, which are the reproductive structures of the pond algae. The blooms are very transient, and are subject to a “boom and bust” phenomenon where large blooms will crash suddenly and unpredictably. This can cause hazardous low dissolved oxygen conditions in the waterbodies where it occurs.