Nycthemeral variations of the dissolved oxygen concentration in the turbidity maximum of three European estuaries: biological vs. physical processes

Nycthemeral variations in oxygen concentrations have been compared in the maximum turbidity zone of three European estuaries, the Elbe, the Westerschelde and the Gironde. It appears that oxygen concentration increases during the day in the Elbe and the Westerschelde due to biological processes, but not in the Gironde where physical processes dominate. The results are discussed in relation to the concentration of suspended particulate matter in the maximum turbidity zone and the difference in quality of the organic matter between the three estuaries.