Surface Water Chemistry as an Integrated Signal of Ecosystem Vectors and Critical Zone Reactors

Lying at the valley of nearly all critical zones is a freshwater ecosystem. Due to precipitation, gravity, and hydrological connectivity, the chemistry of these aquatic habitats provides an integrated signal of geologic, meteorologic, and biologic processes occurring within the landscape. Here we explore the intersection between ecosystem and critical zone science to develop a holistic multidimensional perspective of surface water chemistry. We leverage both foundational concepts from ecosystem ecology and geochemistry and discuss interactions between vectors of material transport throughout the critical zone and the ramifications for spatial and temporal variation in surface water chemistry. We then evaluate methods that can be applied at the watershed, ecosystem, and critical zone scale to characterize these integrated signals. We end by highlighting a series of open questions that are central to understanding the controls of surface water chemistry and water quality in a changing world.