Hydrological Transport and Biological Degradation of Dissolved Organic
Carbon in a Headwater Tributary of the Yangtze
River systems represent important drivers of carbon loading, utilization
and storage. However, underlying controls of hydrological transport and
biological degradation on fluvial dissolved organic carbon (DOC) have
yet to be revealed. Here, we explored spatiotemporal variability of DOC
concentrations, components and sources, as well as its biodegradability
in a headwater tributary of the Yangtze. We found that temporal rainfall
stimulated terrestrial inputs and increased terrigenous DOC abundance.
Hydrological transport was accompanied by biological generation and
utilization of DOC, resulting in reduced labile components and
accumulated recalcitrant components from tributaries to the main stem.
Biodegradable DOC (BDOC) notably responded to temperature gradients over
a 56-day laboratory incubation. Riverine DOC component, molecular weight
and source highly predicted its biodegradation. Particularly, partial
refractory (ultraviolet humic-like) fractions contributed to biological
degradation of DOC, which was incompletely degraded from high-molecular
to low-molecular weight compounds. The findings hope to supplement a new
understanding of carbon fate under global change.