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Calcium chloride pollution mitigates the negative effects of an invasive clam

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Invasive bivalves can drastically alter freshwater ecosystems and affect ecosystem services, but they can be influenced by external factors including calcium concentrations. When a common road salt, calcium chloride (CaCl2), enters freshwater ecosystems, it may be toxic to organisms or facilitate bivalves by serving as a calcium source. Therefore, CaCl2 could benefit invasive mollusks tolerant to chloride that require calcium to grow. We used mesocosms to investigate the impacts of CaCl2 (35–187 mg Ca2+ L−1) and invasive bivalves (Asian clams, Corbicula fluminea; zebra mussels, Dreissena polymorpha) on a native lake food web. We hypothesized that invasive bivalves facilitate benthic algae because they reduce phytoplankton and excrete waste. These changes in primary producers would subsequently impact consumers. We also hypothesized that low to moderate CaCl2 concentrations promote the survival, growth, and reproduction of native and invasive mollusks, while causing few toxic effects. If so, we hypothesized that invaded communities exposed to CaCl2 experience stronger impacts from the invasive bivalves. We found that invasive bivalves decreased phytoplankton, which led to decreases in periphyton, zooplankton, and native clams. They caused increases in filamentous algae and isopods. While zebra mussels survived poorly in all treatments, moderate concentrations of CaCl2 substantially reduced Asian clams, which reduced their community effects. Our highest CaCl2 treatments also reduced zooplankton densities. Thus, while freshwater salinization from road salts poses a concern, we observed no indication that CaCl2 road salt will benefit Asian clams and zebra mussels. However, the community-wide consequences from Asian clams at low CaCl2 emphasize the extensive effects that invasive bivalves can have on freshwater communities and the immense concern surrounding their invasions.

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Availability of data and materials

Data are available via request from K. D. Coldsnow (corresponding author).

Code availability

Relevant code is available via request from K. D. Coldsnow (corresponding author).


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We thank Laurie Ahrens, Daniela Arriola, Hannah Barrett, Bianca Bigit, Skylar Carter, Reily Cooper, Amelia Cummings, Laurel Dean, Ryan Dicks, Frank Erickson, Emily Giff, Jorge Guarin, Devin Jones, Brian Mattes, Sherese Morgan, Joseph Mruzek, Jeevan Narendran, Elizabeth Nelligan, Justin Rappold, Kelsey Sudol, and Erika Yates for help with conducting the experiment and processing the samples. We also thank the associate editors for the handling of our manuscript and the three anonymous reviewers for comments that greatly improved our manuscript.


This study was funded by the Jefferson Project at Lake George, which is supported by Rensselaer Polytechnic Institute, International Business Machines (IBM), and The Fund for Lake George. K.D. Coldsnow was supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE 1744655.

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KC, WH, MS, AS, and RR formulated the idea. KC and RR designed the experiment. KC, WH, MS, and AS performed the experiment. KC analyzed the data and wrote the manuscript. WH, MS, AS, and RR provided editorial advice.

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Correspondence to Kayla D. Coldsnow.

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Institutional and national guidelines for the care and use of animals were followed.

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Coldsnow, K.D., Hintz, W.D., Schuler, M.S. et al. Calcium chloride pollution mitigates the negative effects of an invasive clam. Biol Invasions 23, 1349–1366 (2021).

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