EPA’s Great Lakes National Program Office and their Great Lakes Biology Monitoring Program cooperators at Cornell University have confirmed the presence of two newly documented non-native zooplankton species in the Great Lakes once believed to be C. strenuus: Cyclops sibiricus in the St Marys River and Cyclops divergens in western Lake Erie. C. sibiricus and C. divergens are very small crustaceans (approximately 2 mm in length) known as cyclopoid copepods. C. sibiricus is a cold-water species native to the northern regions of North America, Asia, and Europe. C. divergens has a native range that spans Europe and central Asia. Only one native species of Cyclops (C. scutifer) is known to the Great Lakes.
Cyclops copepods are rare in the Great Lakes and are difficult to distinguish, which has led to uncertainty about historically documented instances of C. strenuus in the Great Lakes. Taking advantage of improvements in genetic sequencing and taxonomic keys in recent years, Cornell taxonomists reexamined all known archived specimens that were originally identified as C. strenuus. Both species are extremely rare in the Great Lakes. Only 13 specimens of C. sibiricus have been collected and archived from the St. Marys River in 1972 and 1995, and only 4 total specimens of C. divergens have been collected from western Lake Erie by the GLBMP annual sampling in 2013, 2014, and 2019.
According to the U.S. Fish and Wildlife Service (USFWS), the ecosystem risk from C. sibiricus and C. divergens is uncertain because there is no history or projection of harm from these species in the Great Lakes, and their means of introduction is uncertain. This study highlights the taxonomic expertise of Cornell University zooplankton taxonomists and the ability of the Great Lakes Biology Monitoring Program to detect non-native zooplankton species that occur at low abundances. The Great Lakes Biology Monitoring Program was initiated in 1983 by EPA to assess the heath of the Great Lakes food web. The Great Lakes Biology Monitoring Program is funded through the Great Lakes Restoration Initiative.