Ecological Risk Screening Summary - Spiny naiad (Najas marina) - High Risk

Species that are considered high risk have a well-documented history of invasiveness in at least one location globally and are of establishment concern for the contiguous United States based on a climate matching analysis.

Najas marina, Spiny Naiad, is an aquatic plant native to Asia, Africa, Europe, and Australia. It may also be native to parts of North America and South America. Multiple subspecies and varieties of N. marina have been described, with some work indicating more than one species may have been included in this species complex historically. This species has been reported as introduced and expanding range in the Great Lakes with a few additional known introductions in Sri Lanka, Greece, and the Bahamas. The History of Invasiveness for Najas marina is classified as Highdue to the multiple documented impacts of introductions, including forming dense stands of vegetation that alter dissolved oxygen and sedimentation. Dissolved oxygen fluctuations related to N. marina infestations may be responsible for fish kills in Sri Lanka. In the Great Lakes, N. marina is of concern as a nuisance to recreation and ecosystems. The climate matching analysis for the contiguous United States indicates establishment concern for this species outside its native range.High climate match was found across the contiguous United States with small patches of low match along the Pacific Coast, Cascade Mountains, and Sierra Nevada. The Certainty of Assessment for this ERSS is classified as Medium mainly due to conflicting information on the taxonomic status and species range. The Overall Risk Assessment Category for Najas marina in the contiguous United States is High.