Abstract
The Gironde estuary (S-W France) is one of the largest European macrotidal estuaries. In the tidal Garonne River, its main tributary, episodes of low (<5 mg L−1) to hypoxic (<2 mg L−1) dissolved oxygen (DO) concentrations have been occasionally recorded close to Bordeaux, about 100 km from the mouth. Projected long-term environmental changes (increase in temperature and population, decrease in river discharge) suggest the establishment of summer chronic oxygen deficiency in the tidal Garonne River in the next decades. Assessing and managing the risk of hypoxia on such a large, hyper-turbid fluvio-estuarine system is complex, due to the different forcing factors (temperature, river discharge, turbidity, urban wastes) acting over a wide range of temporal and spatial scales. In this context, we show the interest of a real-time, high-frequency monitoring of the water quality, the MAGEST network, which continuously records since 2005 temperature, salinity, turbidity, and dissolved oxygen in surface waters in Bordeaux. Through the analysis of the 10-year DO records, we demonstrate the interest of a high-frequency, long-term database to better document DO variability and to define the controlling factors of DO concentrations. This real-time monitoring is also of great interest for the development of manager’s oriented tools and the follow-up of DO objectives in the tidal Garonne River.
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Acknowledgments
This network is funded by the following organisms: AEAG (Agence de l’Eau Adour-Garonne), SMIDDEST (Syndicat MIxte pour le Développement Durable de l’ESTuaire de la Gironde), SMEAG (Syndicat Mixte d’Etudes et d’Aménagement de la Garonne), EPIDOR (Etablissement Public Interdépartemental de la Dordogne), EDF, GPMB (Grand Port Maritime de Bordeaux), CUB (Communauté Urbaine de Bordeaux), Conseil Régional Aquitaine, CG-33 (Conseil Général de Gironde), IRSTEA, CNRS, and Université de Bordeaux.
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Schmidt, S., Bernard, C., Escalier, JM. et al. Assessing and managing the risks of hypoxia in transitional waters: a case study in the tidal Garonne River (South-West France). Environ Sci Pollut Res 24, 3251–3259 (2017). https://doi.org/10.1007/s11356-016-7654-5
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DOI: https://doi.org/10.1007/s11356-016-7654-5