Attaches to hard surfaces, sometimes completing covering the underside of docks and boats. Damages ecosystems by aggressively displacing native mussels. Adults 1-1/4″ to 1-1/2″ long. Juveniles about the size of peppercorns. Alternating dark and light colored stripes. Black to brownish D-shaped shell. Byssal threads used for attachment.
A related invasive mussel, the quagga mussel, has less pronounced stripes, which tend to fade near the hinge. Both the zebra and quagga mussels are native to inland lakes in Russia.
Found in waters up to 20 feet deep. May form dense mats in waters up to 15 feet deep. Interferes with fishing, boating and swimming. Three to five feathery leaves arranged in whorls (circles) on stems. Each leaf has 12-21 leaflet pairs. A native look-alike — northern watermilfoil — has only 5-10 leaflet pairs.
Forms weed mats that shade out native plants. Grows from the shore to depths up to 15 feet. Leaves somewhat stiff and crinkled, 1/2 inch wide, up to 2-3 inches long, arranged alternately around stem. Has small “teeth” visible along edge of leaf.
Starry stonewort is a bushy, bright green macro-algae. It produces a characteristic star-shaped bulbil.
Starry stonewort impacts:
Dense mats at the water’s surface inhibit water recreationists.
Overtakes habitat and outcompetes native aquatic plants, potentially lowering diversity.
Provides unsuitable shelter, food, and nesting habitat for native animals.