Calcium concentrations in Lake Superior and south shore tributaries and the implications for dreissenid mussel establishment in the Apostle Islands area: 2014–2017
Lafrancois BM, McCartney M, Lafrancois T, Delvaux J. 2018. Calcium concentrations in Lake Superior and south shore tributaries and the implications for dreissenid mussel establishment in the Apostle Islands area: 2014–2017. Natural Resource Report. NPS/APIS/NRR—2018/1827. National Park Service. Fort Collins, Colorado
Zebra and quagga mussels (dreissenids) have caused substantial economic and ecological damage in invaded habitats, but to date have not established extensive populations in Lake Superior. However, dreissenids have recently been detected in low densities in the Apostle Islands National Lakeshore, suggesting that local conditions may be more favorable to their establishment than previously expected. Because low calcium concentrations can limit dreissenid mussel growth and development, calcium conditions can be a useful tool for understanding dreissenid risk. We compiled calcium data from multiple studies and sites in and around the Apostle Islands from 2014–2017, and related calcium concentrations to literature-based thresholds for dreissenid mussel growth and development. All Lake Superior sites had mean concentrations greater than 12 mg/L, suggesting moderate risk of invasive mussel establishment. Further, calcium concentrations were elevated in tributaries relative to Lake Superior, with nearly all river samples exceeding the 15 mg/L threshold and almost half of the river samples exceeding the high-risk 20 mg/L threshold. River plumes likely serve to elevate calcium concentrations in nearshore Lake Superior waters. Given the trend toward increasing calcium concentrations in Lake Superior and the increasing intensity of precipitation and runoff events in this region, continued dreissenid mussel monitoring and prevention work is warranted.
- Type
- Published Report
- Authors
- Lafrancois, Brenda; McCartney, Mike; Lafrancois, Toben; Delvaux, Josh
- Date of Issue
- 2018-11
- Publisher
- National Park Service
- Units
- APIS , NRSS
- Keywords
- Apostle Islands, calcium, Dreissena, Dreissenid, GLKN General, Great Lakes, invasive species, Lake Superior, mussels