Insights into the representativeness of biodiversity assessment in large reservoir through eDNA metabarcoding

orders, namely Cichliformes, Characiformes, Chondrichthyes, Cypriniformes, Eupercaria, Gymnotiformes, Myliobatiformes, Siluriformes, and Synbranchiformes. The Cichliformes and Characiformes orders were the most abundant in almost all stations (Fig 4A), followed by Gymnotiformes, represented here by species of the genus Gymnotus, exhibiting significant presence, especially in station C01. The order Clupeiformes, represented by a single species (Platanichthys platana), was found in the pilot sampling, and identified in three other stations (C03, C04, and C15). Chondrichthyes species were detected in several stations, but in low fre- quencies, ranging between 3% and 8% per sample. Station C01 exhibited higher variability in terms of the number of taxa and also had higher MOTU frequencies compared to all other stations, accounting for ~54% of all species found across all locations, including the pilot sampling. It also erevealed some exclusive species, such as Acestrorhynchus lacustris, Pimelodella avanhandavae, and Gymnotus carapo. The only autoch- thonous species identified was the Siluriforme Pimelodus maculatus. The other six species are allochthonous (originally from other basins) such as the Plagioscion squamosissimus (Corvina) and the three cichliforms (Cichla piquiti, C. kelberi, and C. ocellaris) all native to the Amazon. From the six native fish species known to be introduced annually into the TI reservoir as part of a local restocking program, Brycon orbygnianus (Piracanjuba) and Prochilodus lineatus

(Curimbata´) were detected by eDNA metabarcoding at nine and seven sampling stations, respectively. The other four species that are part of the restocking program Piaractus mesopo- tamicus (Pacu-guac¸u), Pseudoplatystoma corruscans (Pintado), Salminus brasiliensis (Dour- ado) and Leporinus elongatus (Piapara) were not detected with eDNA. Diversity variation among samples from the same station is greater than across stations Despite being collected only minutes apart, diversity indexes, i.e. richness and Shannon’s H, of the ichthyofauna communities showed greater variation among samples from the same station Fig 4. Alpha diversity results for ichthyofauna taxa detected in the Três Irmãos (TI) reservoir. Based on fish Molecular Operational Taxonomic Units (MOTUs) identified through eDNA per sampling station, A) the barplot displays all orders found within the Três Irmãos (TI) reservoir. Colors indicate the orders as shown in the legend. The TI reservoir is shown at the top with all sampled stations C1-C4 and C6-C15. Stations abbreviations as in S1 Table. B) Richness and Shannon’s H index (y-axis) were computed for each station (x-axis). Each diamond represents one sample collected at the respective station. https://doi.org/10.1371/journal.pone.0314210.g004 PLOS ONE eDNA metabarcoding reservoir PLOS ONE | https://doi.org/10.1371/journal.pone.0314210 January 24, 2025 11 / 22