Document: KAR-3-74-14

Response of aquatic macrophyte communities to rusty crayfish (Orconectes rusticus) invasion: Contrasting results from long-term vs. multiple lake data.

WILSON, K.A.* and J.J.MAGNUSON

University of Wisconsin, Madison, WI, 53706 ¹

Abstract:
The distribution of aquatic macrophytes has historically been attributed to physical and chemical characteristics of water bodies. However, in northern Wisconsin lakes the presence of the exotic rusty crayfish in many lakes and streams has had detrimental effects on aquatic macrophyte communities. Observational data in a suite of Northern Wisconsin Lakes demonstrates a strong negative relationship between macrophyte species richness and rusty crayfish abundance. In this paper, we compare long-term changes in an aquatic macrophyte community in one lake to macrophyte communities in 24 area lakes with a gradient of native and rusty crayfish abundances to answer the general question: Can we predict the macrophyte community composition in lakes with and without invasive crayfish? In Trout Lake, WI, rusty crayfish invaded sometime between 1979 and 1981, taking over 15 years to disperse around the lake shore. During this time macrophyte species richness dropped from 15 to 3 species in sites occupied by rusty crayfish for the greatest amount of time and at the highest sustained abundances. In addition, species were lost over time in a predictable pattern: More delicate, annual species first, followed by more robust perennial species. This pattern is consistent with macrophyte communities in lakes differing in rusty crayfish abundance. However, the relationships are more complex due to lake landscape position which influences both water chemistry and lake accessibility for crayfish and plant propagules.

Keywords: aquatic macrophytes, invasion, rusty crayfish, space vs. time

This abstract is being presented at: 8:30 AM in session:
Oral Session #7: Aquatic Ecology: Shellfish to Snails.