Calcium concentrations in the lower Columbia River, USA , are generally sufficient to support invasive bivalve spread

Abstract Dissolved calcium concentration [Ca 2+ ] is thought to be a major factor limiting the establishment and thus the spread of invasive bivalves such as zebra ( Dreissena polymorpha ) and quagga ( Dreissena bugensis ) mussels. We measured [Ca 2+ ] in 168 water samples collected along ~100 river‐km of the lower Columbia River, USA, between June 2018 and March 2020. We found [Ca 2+ ] to range from 13 to 18 mg L −1 during summer/fall and 5 to 22 mg L −1 during the winter/spring. Previous research indicates that [Ca 2+ ] < 12 mg L −1 are likely to limit the establishment and spread of invasive bivalves. Thus, our results indicate that there is sufficient Ca 2+ 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 ( Corbicula fluminea ) 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.