Botrel, M. et Hudon, C. et Heffernan, J. B. et Biron, P. M. et Maranger, R. (2022). Climate-Driven Variations in Nitrogen Retention From a Riverine Submerged Aquatic Vegetation Meadow. Water Resources Research , 58 (10). pp. 1-21. DOI: 10.1029/2022WR032678.
Ce document n'est pas hébergé sur Bibliothèque Électronique Lac Saint-Pierre.Résumé
Large rivers can retain a substantial amount of nitrogen (N), particularly in submerged aquatic vegetation (SAV) meadows that may act as disproportionate control points for N retention. However, the temporal variation of N retention in large rivers remains unknown since past measurements were snapshots in time. Using high-frequency plants and NO3− measurements over the summers 2012–2017, we investigated how the climate variation influenced N retention in a SAV meadow (∼10 km2) at the confluence zone of two agricultural tributaries entering the St. Lawrence River. Distinctive combinations of water temperature and level were recorded between years, ranging from extreme hot-low (2012) and cold-high (2017) summers (2°C and 1.4 m interannual range). Using an indicator of SAV biomass, we found that these extreme hot-low and cold-high years had reduced biomass compared to hot summers with intermediate levels. In addition, changes in main stem water levels were asynchronous with the tributary discharges that controlled NO3− inputs at the confluence. We estimated daily N uptake rates from a moored NO3− sensor and partitioned these into assimilatory and dissimilatory pathways. Measured rates were variable but among the highest reported in rivers (median 576 mg N m−2 d−1, range 60–3,893 mg N m−2 d−1) and SAV biomass promoted greater proportional retention and permanent N loss through denitrification. We estimated that the SAV meadow could retain up to 0.8 kt N per year and 87% of N inputs, but this valuable ecosystem service is contingent on how climate variations modulate both N loads and SAV biomass.
| Type de document: | Article scientifique |
|---|---|
| Mots-clés libres: | Nitrogen pollution, Aquatic vegetation, Nitrogen retention, Biomass retention, Nitrate uptake rates, Denitrification, Climatic conditions |
| Sujets: | 1. Laboratoire de développement durable > 1.7. Environnement, écologie, écosystème 3. Végétation, milieux humides 6. Milieu humain > 6.2. Agriculture 8. Impacts et monitoring > 8.1. Qualité de l’eau 9. Nouvelles pressions > 9.1. Changement climatique |
| Date de dépôt: | 07 mai 2025 14:39 |
| Dernière modification: | 07 mai 2025 14:40 |
| URI: | https://belsp.uqtr.ca/id/eprint/1670 |
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