Seasonal patterns in riverine carbon form and export from a temperate forested watershed in Southeast Alaska

• Published in: Biogeochemistry Vol. 167; no. 11; pp. 1353 - 1369
• Main Authors: Delbecq, Claire, Fellman, Jason B., Bellmore, J. Ryan, Whitney, Emily J., Hood, Eran, Fitzgerald, Kevin, Falke, Jeffrey A.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.11.2024; Springer Nature B.V
• Subjects: Alkalinity; Aquatic ecosystems; Biogeosciences; Carbon; Carbon cycle; Dissolved organic carbon; Earth and Environmental Science; Earth Sciences; Ecosystems; Environmental Chemistry; Food chains; Food quality; Food webs; Forest watersheds; High frequency; Hydroclimate; Inorganic carbon; Invertebrates; Life Sciences; Low flow; Organic matter; Particulate organic carbon; Seasonal variations; Temperate forests; Watersheds; United States > US; Alaska; Organic matter stoichiometry; Hydrology; Biogeochemistry; Riverine carbon export
• ISSN: 0168-2563; 1573-515X
• DOI: 10.1007/s10533-024-01175-7

Riverine export of carbon (C) is an important part of the global C cycle; however, most riverine C budgets focus on individual forms of C and fail to comprehensively measure both organic and inorganic C species in concert. To address this knowledge gap, we conducted high frequency sampling of multiple C forms, including dissolved organic C (DOC), inorganic carbon (as alkalinity), particulate organic C (POC), coarse particulate organic C (CPOC), and invertebrate biomass C across the main run-off season in a predominantly rain-fed watershed in Southeast Alaska. Streamwater concentrations were used to model daily watershed C export from May through October. Concentration and modeled yield data indicated that DOC was the primary form of riverine C export (8708 kg C/km 2 ), except during low flow periods when alkalinity (3125 kg C/km 2 ) was the dominant form of C export. Relative to DOC and alkalinity, export of particulate organic C (POC: 992 kg C/km 2 ; CPOC: 313 kg C/km 2 ) and invertebrates (40 kg C/km 2 ) was small, but these forms of organic matter could disproportionately impact downstream food webs because of their higher quality, assessed via C to nitrogen ratios. These seasonal and flow driven changes to C form and export likely provide subsidies to downstream and nearshore ecosystems such that predicted shifts in regional hydroclimate could substantially impact C transfer and incorporation into aquatic food webs.