Ecological changes caused by humans affect natural biodiversity. For example, the eutrophication of Greifensee and Lake Constance in the 1970s and 1980s led to genetic changes in a species of water flea which was ultimately displaced. Despite the fact that water quality has since been significantly improved, this species has not been re-established. This was demonstrated by researchers from Eawag and from two German universities (Frankfurt and Konstanz), who analysed genetic material from Daphnia eggs up to 100 years old.