Statistical properties of turbidity, oxygen and pH fluctuations in the Seine river estuary (France)

We consider here, the fluctuations of turbidity, oxygen and pH time series recorded from the MAREL system (Ifremer, France), which is based on the deployment of data buoys equipped with water analysis capabilities in an automated mode. We perform a spectral analysis (from 10 min to years) of these time series, and we estimate their probability density functions. Oxygen, turbidity and pH are important quantities for ecosystem studies and physics-biology couplings, and their fluctuations reveal the possible influence of environmental factors such as tides and turbulence. Turbidity variability is highly complex and does not appear to be directly coupled to turbulence, since no clear range is visible. On the other hand, oxygen percentage of saturation and pH data show remarkably nice scaling ranges, indicating an important coupling with turbulence, but also biological or chemical activity, since the statistics differ markedly from passive scalars. Several possible sources of this variability are discussed.