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Abstract The interaction of climate change and increasing anthropogenic water withdrawals is anticipated to alter surface water availability and the transport of carbon (C), nitrogen (N), and phosphorus (P) in river networks. But how changes to river flow will alter the balance, or stoichiometry, of these fluxes is unknown. The Lower Flint River Basin (LFRB) is part of an interstate watershed relied upon by several million people for diverse ecosystem services, including seasonal crop irrigation, municipal drinking water access, and public recreation. Recently, increased water demand compounded with intensified droughts have caused historically perennial streams in the LFRB to cease flowing, increasing ecosystem vulnerability. Our objectives were to quantify how riverine dissolved C:N:P varies spatially and seasonally and determine how monthly stoichiometric fluxes varied with overall water availability in a major tributary of LFRB. We used a long‐term record (21–29 years) of solute water chemistry (dissolved organic carbon, nitrate/nitrite, ammonia, and soluble reactive phosphorus) paired with long‐term stream discharge data across six sites within a single LFRB watershed. We found spatial and seasonal differences in soluble nutrient concentrations and stoichiometry attributable to groundwater connections, the presence of a major floodplain wetland, and flow conditions. Further, we showed that water availability, as indicated by the Palmer Drought Severity Index (PDSI), strongly predicted stoichiometry with generally lower C:N and C:P and higher N:P fluxes during periods of low water availability (PDSI < −4). These patterns suggest there may be long‐term and significant changes to stream ecosystem function as water availability is being dramatically altered by human demand with consequential impacts on solute transport, in‐stream processing, and stoichiometric ratios.
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Continental‐scale seston stoichiometry reveals fundamental constraints on the elemental composition of particles transported by streams
Abstract Suspended particulate matter, or seston, represents an understudied flux of carbon (C), nitrogen (N), and phosphorus (P) in river networks. Here, we summarize riverine seston C : N : P stoichiometry data from 27 streams and rivers sampled regularly from 2014 to 2022 across the United States by the National Ecological Observatory Network (NEON). We examine relationships among seston C, N, and P content using standardized major‐axis (SMA) and ordinary least squares slopes to test congruence with a constant‐ratio model (scaling coefficient = 1), and hierarchical models to identify watershed‐level covariates of seston C : nutrient stoichiometric allometry. At the continental scale, C and N were tightly coupled and conformed to the constant‐ratio model, while seston C : P and N : P indicated weaker coupling and inconstant ratios across the range of C vs. P and N vs. P values. At the stream‐site scale, C : N, C : P, and N : P often exhibited slopes < 1, indicating that within individual streams seston becomes more nutrient‐rich as seston concentration increases. Watershed forest cover, season, and discharge helped explain stoichiometric allometry across streams, where forested sites in wetter climates had lower scaling slopes, and slopes decreased with low flows. Our study underscores the importance of suspended particles as a material flux in river networks and highlights the interplay between biotic and abiotic factors that drive the relative consistency of its C : nutrient stoichiometry during transport from local to continental scales.
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- PAR ID:
- 10593718
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Limnology and Oceanography
- Volume:
- 70
- Issue:
- 6
- ISSN:
- 0024-3590
- Format(s):
- Medium: X Size: p. 1755-1769
- Size(s):
- p. 1755-1769
- Sponsoring Org:
- National Science Foundation
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