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Organic matter composition and C:N stoichiometry are main drivers of heterotrophic nitrate uptake in Mediterranean headwater streams. JGR:Biogeosciences
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| Created: | Jul 05, 2024 at 12:14 p.m. | |
| Last updated: | Jul 05, 2024 at 3:58 p.m. | |
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| Sharing Status: | Private (Accessible via direct link sharing) |
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Abstract
Heterotrophic bacteria can contribute to improve stream water quality by taking up nitrate (NO3-) from the water column, although microbial demand for this nutrient is usually lower than for other inorganic N forms, such as ammonium. Heterotrophic NO3- uptake has been related to the availability of dissolved organic carbon (DOC) relative to nutrients (DOC:nutrients). Yet, how dissolved organic matter (DOM) composition and specific microbial assemblages influence NO3- uptake remains poorly understood. We conducted laboratory incubations to investigate heterotrophic NO3- uptake kinetics in 9 Mediterranean freshwater ecosystems, primarily headwater streams, exhibiting wide variation in DOC:NO3 ratios (from 1.5 to 750). Moreover, we characterized DOM composition using spectroscopic indexes and its degradation via Reactivity Continuum model approach. Microbial community composition and functioning were assessed by analysing extracellular enzymatic activities and the potential abundance of N-cycling genes. Our results revealed that NO3- uptake rates (kNO3) were positively related with DOC:NO3 ratios (r2=0.3). Yet, our results showed that nutrient:nutrient stoichiometry also influence NO3- uptake, with soluble reactive phosphorus (SRP) availability (NO3:SRP ratio) constraining kNO3. Furthermore, kNO3 was negatively correlated to the humification index (r2=0.7), suggesting that aromatic compounds slow down heterotrophic NO3- uptake. A multivariate analysis pinpointed that DOC and nutrient availability, DOM composition and reactivity, and microbial composition and activity collectively contributed to explain the variability in kNO3 observed across treatments. Our findings suggest that heterotrophic NO3- uptake may show significant responsiveness to shifts towards more labile DOM sources and nutrient imbalances induced by global change.
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Funding Agencies
This resource was created using funding from the following sources:
| Agency Name | Award Title | Award Number |
|---|---|---|
| Next Generation EU (NGEU) | Europa Excelencia | EUR2023-143456 |
| Spanish Ministry of Science, Innovation, and Universities and AEI/FEDER UE | Generación de Conocimiento | PID2021-122817-NB-100 |
| Spanish Ministry of Science, Innovation, and Universities and AEI/FEDER UE | Generación de Conocimiento | CNS2023-144737 |
| Spanish Ministry of Science, Innovation, and Universities and AEI/FEDER UE | Ramón Y Cajal Fellowship | RYC-2017-22643 |
| Spanish Ministry of Science, Innovation, and Universities and AEI/FEDER UE | Ramón Y Cajal Fellowship | RYC-2021-033714-I |
| Spanish Ministry of Science and Innovation | PLAN DE RECUPERACIÓN, TRANSFORMACIÓN Y RESILIENCIA | CNS2022-135690 |
| Spanish Agency of Research (AEI-MICINN) | I+D+I Retos de la Sociedad | RTI2018-101205-B-I00 |
| Spanish Ministry of Science, Innovation, and Universities and AEI/FEDER UE | Generación de Conocimiento | PID2019-111803RB-I00 |
| Spanish Ministry of Science, Innovation, and Universities and AEI/FEDER UE | Generación de conocimiento | PID2022-143112NB-I00 |
Contributors
People or Organizations that contributed technically, materially, financially, or provided general support for the creation of the resource's content but are not considered authors.
| Name | Organization | Address | Phone | Author Identifiers |
|---|---|---|---|---|
| Carmen Gómez | ||||
| Carolina Jativa |
How to Cite
This resource is shared under the Creative Commons Attribution CC BY.
http://creativecommons.org/licenses/by/4.0/
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