Using Community Science to Reveal Global Chemogeography of River Metabolomes

Abstract:

Organic matter cycling in aquatic ecosystems is a key uncertainty in modelling global biogeochemistry. River corridor metabolomes can address this knowledge gap by providing useful insight into the organic matter that drives aquatic biogeochemical processes. In particular, ultrahigh resolution mass spectrometry has opened new doors into describing and understanding aquatic metabolomes, and recent work has highlighted the power of these data for predicting river corridor metabolism. Yet, there has been no comprehensive investigation of the global chemogeography of river corridor metabolomes. Here, we describe a community science effort conducted during July-August 2019 by the Worldwide Hydrobiogeochemistry Observation Network for Dynamic River Systems (WHONDRS) research consortium to characterize global metabolomes in surface waters and sediments spanning a range of ecotones, stream orders, climates, and geomorphological features. We used Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS) to characterize metabolomes and collected a suite of complementary data including geochemical and hydrologic attributes. We describe the global distribution of key aspects of metabolomes including inferred elemental composition, chemical classes, descriptor indices, biochemical transformations, and associated microbial metabolisms. Among other results, we show that molecular formula pools significantly differ across surface water and sediment samples, with sediment pools being substantially more constrained. We also show significant spatial variation within the United States between east and west coast pools with regard to derived characteristics and elemental composition. Our work not only provides a basis for understanding global patterns in river corridor organic matter cycles but also demonstrates that community science endeavors can enable global research projects that are unfeasible with traditional research models.