Available Dissolved Organic Carbon Alters Uptake and Recycling of Phosphorus and Nitrogen from River Sediments

Concurrent with nutrient pollution, agriculture has significantly impacted the quantity, composition, and bioavailability of catchment-derived dissolved organic carbon (DOC) in stream ecosystems. Based on the stoichiometric theory, we tested the hypothesis that bioavailable DOC will stimulate the heterotrophic uptake of soluble reactive P (SRP) and inorganic nitrogen in stream sediments. In a simplified laboratory column flow-through study, we exposed stream sediments to additions of glucose, nitrate, and phosphate alone and in combination (+C, +NP, +CNP), and calculated gross and net changes in DOC and nutrients via a mass balance approach. Our results show that glucose-C increased nutrient uptake, but also that NP additions resulted in the enhanced consumption of both native and added organic C. The effects of C addition were stronger on N than P uptake, presumably because labile C stimulated both assimilation and denitrification, while part of the P uptake was due to adsorption. Internal cycling affected net nutrient uptake due to losses of dissolved organically-complexed P and N (DOP and DON). Overall, our study shows that increases in the stoichiometric availability of organic carbon can stimulate N and P sequestration in nutrient-polluted stream sediments. Future studies are required to assess the effects of complex organic carbon sources on nutrient uptake in stream sediments under different environmental conditions, and whether these stoichiometric relations are relevant for ecosystem management.

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Column experiments show that cycling of both nitrogen and phosphorus is altered by dissolved organic carbon in river sediments

10.5194/egusphere-egu21-14774 ◽

2021 ◽

Author(s):

Marc Stutter ◽

Daniel Graeber ◽

Gabriele Weigelhofer

Keyword(s):

Organic Carbon ◽

Nutrient Uptake ◽

Inorganic Nitrogen ◽

River Sediments ◽

P Uptake ◽

Controlled Study ◽

Column Experiments ◽

Nitrogen And Phosphorus ◽

Organic C ◽

Riparian Trees

Since agriculture and wider development have altered simultaneously runoff, pollution and natural structures in catchments (e.g. wetlands, floodplains, soil drainage, riparian trees) aquatic ecosystems deviate from background concentrations of N and P, but also organic C (OC). Hence mechanistic studies coupling OC, N and P are needed and whilst data coupling OC:N is becoming more available and interpreted this is not yet the case for aquatic OC:P.&#160; Column flow experiments (excluding light) allow preliminary controlled study of microbial biogeochemical processes in benthic sediments exposed to factorial nutrients (here +C, +NP, +CNP using simple dissolved substrates glucose, nitrate, and phosphate).Based on the stoichiometric theory, we tested the hypothesis that bioavailable DOC will stimulate the heterotrophic uptake of soluble reactive P (SRP) and dissolved inorganic nitrogen in stream sediments. Glucose-C additions increased nutrient uptake, but also NP additions enhanced consumption of native and added OC. The effects of C addition were stronger on N than P uptake, presumably because labile C stimulated both assimilation and denitrification, while adsorption (unaffected by the presence or not of OC) formed a part of P uptake. Internal biogeochemical cycling lessened net nutrient uptake due to N and P recycling into dissolved organically-complexed forms (DOP and DON).Simple column experiments point to mechanisms whereby availability of organic carbon can stimulate N and P sequestration in the bed of nutrient-polluted streams. This should promote further studies coupling OC with N and, especially P, towards better knowledge and ability to incorporate coupled macronutrient cycles into nutrient models and, potentially, ecosystem management.

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Biodegradability of dissolved organic carbon in the Yukon River and its tributaries: Seasonality and importance of inorganic nitrogen

Global Biogeochemical Cycles ◽

10.1029/2012gb004342 ◽

2012 ◽

Vol 26 (4) ◽

pp. n/a-n/a ◽

Cited By ~ 124

Author(s):

K. P. Wickland ◽

G. R. Aiken ◽

K. Butler ◽

M. M. Dornblaser ◽

R. G. M. Spencer ◽

...

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Inorganic Nitrogen ◽

Yukon River

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Representation of dissolved organic carbon in the JULES land surface model (vn4.4_JULES-DOCM)

Geoscientific Model Development ◽

10.5194/gmd-11-593-2018 ◽

2018 ◽

Vol 11 (2) ◽

pp. 593-609 ◽

Cited By ~ 7

Author(s):

Mahdi Nakhavali ◽

Pierre Friedlingstein ◽

Ronny Lauerwald ◽

Jing Tang ◽

Sarah Chadburn ◽

...

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Land Surface ◽

Soil Column ◽

River System ◽

Terrestrial Ecosystems ◽

Surface Model ◽

Organic C ◽

C Cycle ◽

Doc Concentration

Abstract. Current global models of the carbon (C) cycle consider only vertical gas exchanges between terrestrial or oceanic reservoirs and the atmosphere, thus not considering the lateral transport of carbon from the continents to the oceans. Therefore, those models implicitly consider all of the C which is not respired to the atmosphere to be stored on land and hence overestimate the land C sink capability. A model that represents the whole continuum from atmosphere to land and into the ocean would provide a better understanding of the Earth's C cycle and hence more reliable historical or future projections. A first and critical step in that direction is to include processes representing the production and export of dissolved organic carbon in soils. Here we present an original representation of dissolved organic C (DOC) processes in the Joint UK Land Environment Simulator (JULES-DOCM) that integrates a representation of DOC production in terrestrial ecosystems based on the incomplete decomposition of organic matter, DOC decomposition within the soil column, and DOC export to the river network via leaching. The model performance is evaluated in five specific sites for which observations of soil DOC concentration are available. Results show that the model is able to reproduce the DOC concentration and controlling processes, including leaching to the riverine system, which is fundamental for integrating terrestrial and aquatic ecosystems. Future work should include the fate of exported DOC in the river system as well as DIC and POC export from soil.

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