Invasion dynamics of New Zealand mud snail (Potamopyrgus antipodarum) in the Laurentian Great Lakes

The New Zealand mud snail (Potamopyrgus antipodarum) is an invasive mollusk that was first reported in Lake Ontario, a Laurentian Great Lake, in 1991. In 2022, we found a small population in the North Channel representing the first record of this snail in Lake Huron. To understand the status of this species in the Great Lakes, we combined data from the U.S. EPA Great Lakes National Program Office sampling efforts, data from publications, regional reports, and online databases. In the last three decades P. antipodarum has spread to all Great Lakes, and the number of official sightings per year increased fourfold during the last decade. The highest density was observed in Lake Michigan, followed by lakes Ontario, Erie, and Huron. In Lake Michigan in 2021, P. antipodarum 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 Dreissena spp. through stimulation of bottom algae and periphyton growth. While P. antipodarum is still spreading in lakes Michigan and Huron, its abundance remains stable in other lakes. Further monitoring is needed to understand the patterns of spread and P. antipodarum effects on Great Lakes benthic communities.