G03_P03

Anthropogenic perturbations change the quality and quantity of terrestrial carbon flux to the coastal ocean

Wei B^1,2, Mollenhauer G^1,3,4, Kusch S⁴, Hefter J¹, Grotheer H¹, Schefuß E⁴, Geibert W¹, Ransby D¹, Jia G^1,6

¹Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany, ²State Key Laboratory of Marine Geology, Tongji University, Shanghai, China, ³Department of Geosciences, University of Bremen, Bremen, Germany, ⁴MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany, ⁵University of Cologne-Centre for Accelerator Mass Spectrometry, University of Cologne, Cologne, Germany, ⁶Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China

Rivers export organic carbon (OC) sourced from their watersheds, offering an opportunity to assess impacts of climatic change and anthropogenic perturbations on the transfer of terrestrial OC to the ocean. Using ¹³C and ¹⁴C compositions of OC exported by the Pearl River during the Industrial Age, we show that anthropogenic activities primarily control the quantity and quality of terrestrial OC fluxes to the coastal ocean. Damming the river and accelerating coal consumption have led to increasing burial flux of petrogenic OC, a rather stable carbon fraction. Man-made ecosystem changes including deforestation, cropland extension, urbanization, and river management increased fresh terrestrial biospheric OC burial, additionally contributing to the long-term carbon sink. Our data help identifying the drivers of sustained change in terrestrial OC export and reveal that human activities substantially enhance the transfer of petrogenic OC and fresh biospheric OC to the coastal ocean, acting as an important sink for anthropogenic CO₂.