German scientists publish satellite images showing algae spread in Oder

Experts from Brockmann Consult (a company for environmental data analysis and software located in Hamburg) - in close cooperation with the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) and the AG Modelling Methods in Remote Sensing at the University of Leipzig - have processed satellite data from the European Copernicus satellite Sentinel 2 and calculated chlorophyll concentrations, which serve as indicators of algal blooms.

The IGB institute said "the Sentinel 2 satellite carries an optical sensor that can be used to determine water color and infer which color-giving substances are in the water".

"Color-providing pigments such as the chlorophyll in algae change the incident sunlight, and the sensor onboard of the satellite can detect this change in the light. This means that also unusual high concentrations of algae can be detected," we read in an analysis of the satellite images at the IGB website.

For the purpose of this initial analysis, the experts examined three selected time periods. "The graph shows three profiles of chlorophyll concentrations in the Odra River in late July (24-25), early August (4-6) and mid-August 16-18). The yellowish colors indicate the particularly high chlorophyll concentrations," the scientists explained.

"At the end of July, the concentration of the entire river course is at about a medium level with a slight increase in the southern section of the river around the town of Opode. In early August, a jump in chlorophyll concentration is seen at the level of Wroclaw, and 10 to 12 days later the algal bloom has moved further downstream like a wave and spread to a larger area of the Odra River," we read in the analysis.

The satellite data have great potential to help further clarify the Oder disaster.

"The new results will help to better understand the ongoing toxic prymnesium algal bloom and to narrow down its origin in space and time. For this purpose, aquatic ecological monitoring data and water samples are combined with satellite data, which are also available from the time of the onset of the environmental disaster. These analyses are to be continued in the coming weeks," IGB said.