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Concentration-discharge (C-Q) relationships of total suspended solids (TSS), total dissolved solids (TDS), particulate organic carbon (POC), and dissolved organic carbon (DOC) were investigated in the tributaries and main-stems of two mountainous river systems with distinct watershed characteristics (Eel and Umpqua rivers) in Northern California and central Oregon (USA). Power-law (C = a × Q b) fits to the data showed strong transport-limited behavior (b > 1) by TSS and POC, moderate transport limitation of DOC (b > 0.3) and chemostatic behavior (b < 0) by TDS in most streams. These contrasts led to significant compositional differences at varying discharge levels, with particle-bound constituents becoming increasingly important (relative abundances of 50% to >90%) at high-flow conditions. Organic carbon contents of TSS displayed marked decreases with discharge whereas they increased in TDS during high-flow conditions. Daily and cumulative material fluxes for different coastal streams were calculated using the C-Q relationships and showed that the delivery of transport-limited constituents, such as TSS and POC (and DOC to a lesser degree), was closely tied to high-discharge events and occurred primarily during the winter season. The coherence between winter fluxes and high wave-southerly wind conditions along the coast highlights how seasonal and inter-annual differences in fluvial discharge patterns affect the fate of land-derived materials delivered to coastal regions.
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Dissolved Organic Carbon Chemostasis in Antarctic Polar Desert Streams
Abstract Dissolved organic carbon (DOC) is a key variable impacting stream biogeochemical processes. The relationship between DOC concentration (C) and stream discharge (q) can elucidate spatial and temporal DOC source dynamics in watersheds. In the ephemeral glacial meltwater streams of the McMurdo Dry Valleys (MDV), Antarctica, the C‐qrelationship has been applied to dissolved inorganic nitrogen and weathering solutes including silica, which all exhibit chemostatic C‐qbehavior; but DOC‐qdynamics have not been studied. DOC concentrations here are low compared to temperate streams, in the range of 0.1–2 mg C l−1, and their chemical signal clearly indicates derivation from microbial biomass (benthic mats and hyporheic biofilm). To investigate whether the DOC generation rate from these autochthonous organic matter pools was sufficient to maintain chemostasis for DOC, despite these streams' large diel and interannual fluctuations in discharge, we fit the long‐term DOC‐qdata to a power law and an advection‐reaction model. Model outputs and coefficients of variation characterize the DOC‐qrelationship as chemostatic for several MDV streams. We propose a conceptual model in which hyporheic carbon storage, hyporheic exchange rates, and net DOC generation rates are key interacting components that enable chemostatic DOC‐qbehavior in MDV streams. This model clarifies the role of autochthonous carbon stores in maintaining DOC chemostasis and may be useful for examining these relationships in temperate systems, which typically have larger sources of bioavailable autochthonous organic carbon than MDV streams but where this autochthonous signal could be masked by a stronger allochthonous contribution.
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- Award ID(s):
- 1637708
- PAR ID:
- 10419177
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Biogeosciences
- Volume:
- 127
- Issue:
- 7
- ISSN:
- 2169-8953
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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