Continental-aquatic mollusk hydrochemical occurrence patterns: Implications for population dynamics and paleoenvironmental reconstruction

Abstract Paired water and mollusk samples collected from 90 lakes, springs, and wetlands throughout the northwestern quarter of the United States suggest that, rather than just occupying discrete total dissolved solids (TDS) ranges as is often described, molluscan distribution is also related to solute types produced by solute evolution. This may explain why water bodies having similar environmental characteristics and TDS values have different molluscan assemblages. Therefore, continental-aquatic mollusk occurrences define solute and TDS fields that offer a means to assess past hydrology and climate. These relations also provide new insights into mollusk population dynamics. For example, molluscan distribution on the aquatic landscape is not a uniform continuum, but rather is a solute compositional mosaic, where taxa in adjoining lakes may be as isolated from each other as taxa on opposite sides of the continent. Knowledge regarding the relation of mollusk occurrence and solute composition can assist management decisions in sustaining threatened, sensitive, or endemic taxa, designing conservation programs, resolving wetland and spring mitigation issues, and determining the potential biological impacts from interbasin water transfers or ground water pumping.