Ecological Risk Screening Summary - Thermocyclops crassus (a copepod, no common name) - Uncertain Risk

Species that are considered uncertain risk need a more in-depth assessment beyond the Risk Summary to better define the species’ risk to U.S. environments.

Thermocyclops crassus is a copepod that is native to Europe, Asia, Africa, and Australia. T. crassus is tolerant of a broad range of habitats and environmental conditions, although it prefers eutrophic waters. This species can feed on cyanobacteria, particularly Microcystis. T. crassus has been established in Lake Champlain, Vermont, since the 1990s. It has recently been introduced into the Great Lakes, where it is considered established in Lake Erie and Lake Michigan. There are no species-specific state regulations. T. crassus is hypothesized to be introduced to non-native regions through ballast water, natural dispersal through canals, via aquaculture, or overland via recreational vessels. However, the exact means by which past introductions occurred remain unknown. The History of Invasiveness for Thermocyclops crassus is classified as Data Deficient due to there being a lack of data on realized impacts resulting from introductions outside its native range. The climate matching analysis for the contiguous United States indicates establishment concern for this species. Locations with the highest climate match were in the Great Lakes basin, the Midwest, and the northern Northeast, around the locations where T. crassus is already recorded as established. The Certainty of Assessment for this ERSS is classified as Low due to the lack of data regarding T. crassus’s history of invasiveness. The Overall Risk Assessment Category for Thermocyclops crassus in the contiguous United States is Uncertain.