Ecological Risk Screening Summary - Water Flea (Daphnia lumholtzi) - 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.

Daphnia lumholtzi is a cladoceran native to parts of Africa, Asia, and Australia. It has become established in numerous locations in the United States, as well as scattered locations in Mexico, Brazil, and Argentina. D. lumholtzi has been associated with declines in the zooplankton Diaphanosoma. Although competition between D. lumholtzi and native Daphnia in the United States is reduced by differences in phenology, competition can occur in certain circumstances. D. lumholtzi is less available to juvenile fish predators than native Daphnia because of its larger size and prominent spines. The History of Invasiveness for this species is classified as High. D. lumholtzi is regulated in four States. The climate matching analysis for the contiguous United States indicates establishment concern for this species. The climate match was high across much of the contiguous United States. However, the Certainty of Assessment has been reduced to Medium due to varying conclusions about the seriousness of the impacts of introduction, and lack of impacts of introduction in some cases. The Overall Risk Assessment Category for D. lumholtzi in the contiguous United States is High.