The raw data come from the European environmental satellite Sentinel 2, which is part of the Copernicus program. The Leibniz Institute for Freshwater Ecology and Inland Fisheries in Berlin (IGB) announced on Saturday that they were analyzed by the Hamburg environmental data analysis company Brockmann Consult, IGB researchers and the working group on modeling processes in remote sensing at the University of Leipzig.

The satellite’s camera and software can measure chlorophyll concentrations in the river, which allows conclusions to be drawn about the concentration of algae. The analysis shows that massive algal growth began in late July at a point – where the injection of growth-promoting substance may have occurred – and then continued with the flow down the river. It is not certain that it is Prymnesium, but it is considered probable. These algae are microorganisms that require high levels of salinity not normally found in river water.

Like plants, they carry out photosynthesis and use it to obtain the energy they need for growth. They give off plenty of oxygen. The algal bloom and a toxic death of the aquatic animals could also partially explain the high oxygen concentrations measured. Because if the oxygen is not absorbed to the normal extent by fish and other animals, it accumulates.

According to information from the Environment Ministry of the State of Brandenburg, experts assume that the fish die-off was caused by a “multi-causal” event. High salt concentrations, for which discharges on the Polish side are possible causes, could have promoted the growth of algae. In addition, fish could have been killed directly as a result, since freshwater fish physiologically cannot tolerate high salt concentrations and, above all, sudden changes in salt concentration. In addition, there may be the effect of a herbicide recently detected in samples, as well as stress from high temperatures and also mercury compounds released locally from the sediment.

The cause or causes, but above all the lessons learned from the disaster, will largely determine how quickly and how permanently the river can recover.