This week, lakes in the Trondheim city forest are treated with rotenone to remove common roach (Rutilus rutilus). We know that all fish will be killed by rotenone, but previous studies indicate that macroinvertebrates in lakes are less affected than previously thought (Arnekleiv et al. 2015). In EBAI we will use eDNA and DNA barcoding of bulk macroinvertebrate samples to see how molecular tools can be used to monitor changes in the invertebrate communities after rotenone treatment. Will we detect a change in the invertebrate community? How long will it take until changes are detected as eDNA in water samples? Time will show.