Long-term analysis of turbidity patterns in Danube Delta coastal area based on MODIS satellite data

The monitoring of coastal areas is becoming an urgent necessity in the context of increased pressure over these ecosystems due to climate change and human activities. Long term evaluation of specific parameters regarding water quality can now be achieved, thanks to the increased number of archived Earth Observation satellite data, now covering decades. Within this study, 12years of MODIS information were used to compute surface water turbidity products that were further temporal binned into composite datasets (e.g. monthly, annual). A regional algorithm, based on local in situ measurements, was used in order to inverse remote sensing reflectance values into turbidity units. The interpretation of the final maps revealed important characteristics of the processes that play a major role in the regional turbidity dynamics. Observations were made regarding the relation between surface water turbidity and Danube River's discharge rates, winds, currents and also the bottom sedimentary characteristics of the shelf area. We discuss how different regions are affected by various external factors, depending on their geographical location, and we reinforce the idea that the river solid input is not the only parameter controlling water clarity in the Danube Delta coastal area, resuspension processes playing also an important role. •Long time series of satellite data were processed, covering 12years.•A regional algorithm for turbidity retrieval was used.•Dynamics of water turbidity over different periods of time was analysed.•Turbidity evolution patterns are discussed in correlation with controlling factors.