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Abstract The northeast Pacific Coastal Temperate Rainforest (NPCTR) extending from southeast Alaska to northern California is characterized by high precipitation and large stores of recently fixed biological carbon. We show that 3.5 Tg‐C yr−1as dissolved organic carbon (DOC) is exported from the NPCTR drainage basin to the coastal ocean. More than 56% of this riverine DOC flux originates from thousands of small (mean = 118 km2), coastal watersheds comprising 22% of the NPCTR drainage basin. The average DOC yield from NPCTR coastal watersheds (6.20 g‐C m−2 yr−1) exceeds that from Earth's tropical regions by roughly a factor of three. The highest yields occur in small, coastal watersheds in the central NPCTR due to the balance of moderate temperature, high precipitation, and high soil organic carbon stocks. These findings indicate DOC export from NPCTR watersheds may play an important role in regional‐scale heterotrophy within near‐shore marine ecosystems in the northeast Pacific.
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Du Feu à l'Eau: Source and Flux of Dissolved Black Carbon From the Congo River
Abstract Pyrogenic organic residues from wildfires and anthropogenic combustion are ubiquitous in the environment and susceptible to leaching from soils into rivers, where they are known as dissolved black carbon (DBC). Here we quantified and isotopically characterized DBC from the second largest river on Earth, the Congo, using 12 samples collected across three annual hydrographs from 2010 to 2012. We find that the Congo River exports an average of 803 ± 84 Gg‐C as DBC per year, comprising 7.5% of the river's average annual dissolved organic carbon (DOC) flux (10.7 ± 1.2 Tg‐C yr−1). Concentrations of DBC were strongly correlated with discharge and DOC concentration, indicating transport limitation for DBC flux from the Congo River Basin. Stable carbon isotopic signatures of DBC revealed a seasonal shift in pyrogenic source from forest dominant to an increasing contribution from savannah biomass, which derives from the North‐South bimodal hydrologic regime within the basin. Our results also indicate that black carbon produced within the Congo Basin is exported by the river on relatively short time scales and that total DBC export will increase with climate change predictions for the central African region.
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- Award ID(s):
- 1756812
- PAR ID:
- 10455584
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Global Biogeochemical Cycles
- Volume:
- 34
- Issue:
- 8
- ISSN:
- 0886-6236
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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