eDNA metabarcoding from aquatic biofilms allows studying spatial and temporal fluctuations of fish communities from Lake Geneva

Abstract Fish communities are now studied non‐invasively using environmental DNA (eDNA) recovered from water samples. The objective of this study is to evaluate the possibility of surveying these communities using fish eDNA passively “captured” by aquatic biofilms. To this end, biofilm samples developing on natural and artificial substrates were collected every 2 weeks for a year and a half in a large lake (Lake Geneva). DNA was extracted from biofilms and fish communities were targeted using a standard 12S barcode with a metabarcoding approach. The fish eDNA signal recovered from biofilms revealed temporal and spatial changes in fish communities. These changes were linked to fish habitat preferences and spawning season. Peaks in the eDNA signal of some taxa fitted with their spawning period reported in the literature. We evidenced that the nature of the biofilm's substrate (natural or artificial) does not affect the image obtained of the fish community composition. Furthermore, by using biofilms grown on artificial substrates, the studied temporal window of the eDNA signal can be controlled. With biofilms acting as environmental passive samplers, our results open up the possibility to accurately monitor fish communities and their temporal and spatial changes with eDNA in a faster and less expensive way than with the classical water filtration approach.