written by Susan Daniel
The New Zealand Mud Snail (NZMS; Potamopyrgus antipodarum) is an invasive snail that was first reported in Lake Ontario in 1991, followed by Lake Superior in 2001, Lake Erie in 2005, and Lake Michigan in 2006. In 2022, we found a small population in the North Channel, representing the first record of this snail in Lake Huron. This global invader, found in 39 countries and five continents (Geist et al., 2022), has been ranked 42nd as one of the “more than 100 worst” alien species in Europe (Nentwig et al., 2018). The invasive ability of this snail is mainly due to its tolerance of pollution, brackish waters, and a variety of habitat types. Additionally, invasive populations are nearly entirely composed of asexually reproducing females, so they can produce offspring individually and a single female can give rise to a population (Wallace 1985).
To understand the status of this species in the Great Lakes, Research Scientist Susan Daniel and coauthors from the GLC combined data from the U.S. EPA Great Lakes National Program Office sampling efforts, publications, regional reports, and online databases. In the last three decades, the NZMS has spread to all of the Great Lakes, and the number of official sightings per year increased 4-fold during the last decade. The highest abundance was observed in Lake Michigan, followed by Lakes Ontario, Erie, and Huron. In Lake Michigan in 2021, NZMS lake-wide density increased 56-fold compared to 2015, comprising 93% of the total gastropod density and 79% of biomass. This spread may have been facilitated by invasive quagga mussels (Dreissena rostriformis bugensis) through stimulation of bottom algae and periphyton growth. While the NZMS is still spreading in Lakes Michigan and Huron, its abundance remains stable in other lakes. However, the current recorded densities in the Great Lakes are much lower than in streams and rivers.
While we are still uncertain about the effect of NZMS on native snails and other native communities, existing local and regional monitoring programs and environmental agencies should adjust survey efforts to follow the invasion, understand species preferences and community effects, and to prevent their spread into new, particularly lotic, habitats within and outside the Great Lakes region.
The research will soon be available in "Invasion dynamics of New Zealand mud snail (Potamopyrgus antipodarum) in the Laurentian Great Lakes," by Daniel, S.E., L.E. Burlakova, A.Y. Karatayev, and L.E. Denecke, in press at Hydrobiologia.
Image caption: New Zealand mud snails.
