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

Dissolved calcium concentration [Ca²⁺] 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 [Ca²⁺] in 168 water samples collected along ~100 river-km of the lower Columbia River, USA, between June 2018 and March 2020. We found [Ca²⁺] 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 [Ca²⁺]