Representation of sequencing reads relative to biomass per sample. Relative representation is calculated as the log-ratio between relative read abundance and relative abundance in biomass of each species in each replicate. A higher log-ratio indicates that the species is over-represented in the metabarcoding dataset, while a lower value indicates that the species is under-represented in relation to its relative abundance in biomass in the mock community. Each community’s replicates are indicated in the following order: B1.LT1.P1, B1.LT1.P2, B1.LT2.P1, B1.LT2.P2, B2.LT1.P1, B2.LT1.P2, B2.LT2.P1, and B2.LT2.P2. No reads were recovered for COI from sample C-B2.LT2.P1.