Determining the biogeochemical transformations of organic matter composition in rivers using molecular signatures

BUSER-YOUNG, JESSICA Z.; GARCIA, PATRICIA E.; SCHRENK, MATTHEW O.; REGIER, PETER J.; WARD, NICHOLAS D.; BIÇE, KADIR; BROOKS, SCOTT C.; FREEMAN, ERIKA C.; LØNBORG, CHRISTIAN

Frontiers in Water

Frontiers Media S.A.

Año: 2023 vol. 5

Inland waters are hotspots for biogeochemical activity, but the environmentaland biological factors that govern the transformation of organic matter (OM)flowing through them are still poorly constrained. Here we evaluate data from acrowdsourced sampling campaign led by the Worldwide HydrobiogeochemistryObservation Network for Dynamic River Systems (WHONDRS) consortium toinvestigate broad continental-scale trends in OM composition compared tolocalized events that influence biogeochemical transformations. Samples fromtwo dierent OM compartments, sediments and surface water, were collectedfrom 97 streams throughout the Northern Hemisphere and analyzed to identifydierences in biogeochemical processes involved in OM transformations. By usingdimensional reduction techniques, we identified that putative biogeochemicaltransformations and microbial respiration rates vary across sediment and surfacewater along river continua independent of latitude (18◦N−68◦N). In contrast,we reveal small- and large-scale patterns in OM composition related to local(sediment vs. water column) and reach (stream order, latitude) characteristics.These patterns lay the foundation to modeling the linkage between ecologicalprocesses and biogeochemical signals. We further showed how spatial, physical,and biogeochemical factors influence the reactivity of the two OM pools in localreaches yet find emergent broad-scale patterns between OM concentrations andstream order. OM processing will likely change as hydrologic flow regimes shiftand vertical mixing occurs on dierent spatial and temporal scales. As our planetcontinues to warm and the timing and magnitude of surface and subsurface flowsshift, understanding changes in OM cycling across hydrologic systems is critical,given the unknown broad-scale responses and consequences for riverine O