Molecular-level exploration of spatiotemporal dynamics of fluvial particulate organic carbon sources during storm events: Using a high-temporal resolution multi-biomarker approach

Authors: KIM, JIEUN - Northwestern University; BLAIR, NEAL - Northwestern University; Papanicolaou, Athanasios

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2025
Publication Date: 1/17/2025
Citation: Kim, J., Blair, N., Papanicolaou, A.N. 2025. Molecular-level exploration of spatiotemporal dynamics of fluvial particulate organic carbon sources during storm events: Using a high-temporal resolution multi-biomarker approach. Science of the Total Environment. 963. https://doi.org/10.1016/j.scitotenv.2025.178447.
DOI: https://doi.org/10.1016/j.scitotenv.2025.178447

Interpretive Summary: Rivers and streams serve as critical links between land and water environments. Fluvial systems collect and integrate particulate organic carbon (POC) from in-channel and adjacent landscapes, including hillslopes and floodplains, and subsequently transport it downstream. These transport processes are closely linked with the diverse sources of POC which often have distinct biogeochemical traits and varying degrees of bioavailability. The biogeochemical properties of POC in turn govern the structure and function of stream ecosystems as well as the carbon cycling within the system. Therefore, unravelling the origins of POC and the mechanisms underlying their transport is critical to preserving ecosystem health and understanding the roles of rivers and streams in the regional and global carbon cycle. Such information is valuable to watershed managers to identify the most suitable combination of management practices and optimal locations within a watershed to be placed for addressing ecosystem sustainability.

Technical Abstract: Identifying the origins of storm event fluvial particulate organic carbon (POC) provides information about the hydrological connectivity within the river corridor and the roles of this terrestrial-aquatic interface in the carbon cycle. However, our current understanding of storm-induced POC source dynamics is constrained by observations limited in space and time. This study presents a unique approach that integrates higher spatial and temporal resolution sampling with a multi-biomarker analysis to better understand the sources of storm POC and the timing in inputs across spatial and temporal scales. High-temporal resolution (~2 hr intervals) storm POC samples were collected at three locations along the flow trajectory of an agricultural stream and characterized for their concentrations, C and N contents, stable C isotopes, and biomarker contents. Six storm events with varied storm characteristics and seasonality were investigated to explore the intra- and inter-event, as well as inter-site, variability in POC response. Our results showed a transition in POC sources from in-stream algal production during the early stages of events to surface soils with vascular plant signatures during peak precipitation and discharge across events and stations. However, no two storm responses were identical in detail in terms of the timing or the character of the inputs. The variability was traceable to environmental factors such as storm trajectory, antecedent hydrologic conditions, and vegetation cover. By taking the approach that was employed, the evolution of the storm pulse POC as it responds to stream corridor processes could be visualized both temporally and spatially.