Ecological Risk Screening Summary - Grass Kelp (Ulva flexuosa) - High Risk

Species that are considered high risk have a well-documented history of invasiveness in at least one location globally, and a high or medium climate match to the contiguous United States.

Ulva flexuosa is a cryptogenic aquatic macroalgae that is globally distributed. U. flexuosa primarily a marine and coastal species but it is tolerant to freshwater conditions and a variety of climates. It has uses as a bioindicator of contamination, antibacterial materials, and bioremediation. The history of invasiveness is high. It has been reported in Lake Michigan starting in 2003, with no previous records in the Great Lakes basin, with negative impacts to abundance of epiphytic diatoms. The climate match with the contiguous United States is high. The climate match was high in coastal areas where this species is possibly native and in the Great Lakes basin where it has been introduced. It was also high in parts of the west that do not have any reports of this species’ presence. The certainty of assessment is high. The overall risk assessment category is high.