Dissolved organic carbon export in a small, disturbed peat catchment: Insights from long-term, high-resolution, sensor-based monitoring

Understanding dissolved organic carbon (DOC) export dynamics from carbon-rich environments is critical. Peatlands act as terrestrial carbon stores, and consequently supply substantial amounts of DOC to drainage. This DOC flux is temporally heterogeneous and subject to long- and short-term variability. Ultrahigh temporal resolution sampling (< hourly) is still in-frequent in peatland catchments. We used a field-deployable -ultraviolet-visible light spectrometer (Spectro::lyser (TM)) and monitored DOC flux from a temperate peatland over 31 months to examine seasonal and event dynamics. DOC concentration varied from 6.8 to 63.5 mg L-1, in the higher reported range for peatlands and showed clear seasonal (high-summer, low-winter) variability coinciding with elevated biological productivity in the peatland. Discharge was an unreliable predictor of instantaneous DOC concentration overall, with antecedent water temperatures proving the most reliable predictor overall. Discharge drove total DOC export in the catchment, where the top 10% of flow events, accounted for 41.3% of all DOC exported-increasing to 84.6% in the top 50% of flow events. Total estimated catchment DOC flux was sensitive to measurement frequency: increasing from every 30 min to daily altered export estimates by < 1%, increasing to > 10% at 1-week intervals. The variation in estimated flux increased approximately linearly with reduced sampling frequency, reaching > 40% at monthly intervals. High-resolution data reveal the large amount of within-site complexity of DOC export dynamics in a temperate peatland and provide evidence on the subsequently recommended sampling frequency for the future elucidation of detailed DOC budgets in these environments.

Automated summary

Understanding the dynamics of dissolved organic carbon (DOC) export from carbon-rich environments is crucial. This study monitored DOC flux from a temperate peatland over 31 months using ultrahigh temporal resolution sampling, and found seasonal and event dynamics in DOC concentration. Discharge was not a reliable predictor of instantaneous DOC concentration, while water temperature showed the most consistent predictability. High-resolution data revealed the complexity of DOC export dynamics and provided insights for future sampling frequency in these environments.