John A. Harrison Marc G. Kramer Gretchen Rollwagen-Bollens Timothy D. Counihan Salvador B. Robb-Chavez Sean T. Nolan Stephen M. Bollens 2021 <p><span>Dissolved calcium concentration [Ca</span>²⁺<span>] is thought to be a major factor limiting the establishment and thus the spread of invasive bivalves such as zebra (</span><i>Dreissena polymorpha</i><span>) and quagga (</span><i>Dreissena bugensis</i><span>) mussels. We measured [Ca</span>²⁺<span>] in 168 water samples collected along ~100 river-km of the lower Columbia River, USA, between June 2018 and March 2020. We found [Ca</span>²⁺<span>] to range from 13 to 18 mg L</span>⁻¹<span>&nbsp;during summer/fall and 5 to 22 mg L</span>⁻¹<span>&nbsp;during the winter/spring. Previous research indicates that [Ca</span>²⁺<span>] &lt; 12 mg L</span>⁻¹<span>&nbsp;are likely to limit the establishment and spread of invasive bivalves. Thus, our results indicate that there is sufficient Ca</span>²⁺<span>&nbsp;in most locations in the lower Columbia River to support the establishment of invasive dreissenid mussels, which could join the already widespread and abundant Asian clam (</span><i>Corbicula fluminea</i><span>) as the newest invader to an already heavily invaded Columbia River ecosystem. These new data provide important measurements from a heretofore undersampled region of the Columbia River and have important implications for the spread of invasive bivalves and, by extension, the conservation and management of native species and ecosystems.</span></p> application/pdf 10.1002/rra.3804 en Wiley Calcium concentrations in the lower Columbia River, USA, are generally sufficient to support invasive bivalve spread article