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

Material and methods Study area The Três Irmãos (TI) hydroelectric power plant reservoir is located at the lower Tietê River basin, in São Paulo State in the Southeastern region of Brazil (Fig 1A). A 9,600 m long artificial channel called Pereira Barreto—the second-largest freshwater canal in the world—connects the TI HPP reservoir to the nearby Ilha Solteira HPP reservoir on the São Jose´ dos Dourados River (Fig 1A). This enables coordinated water management of the two reservoirs and inte- grated energy operation of the two hydroelectric plants, both of which drain into the Parana´ River. Três Irmãos is the largest power plant on the Tietê River. Its operation began in November 1993 (CESP 2013). The reservoir spans 133 km in length, with a main central water channel width of about 5 km. Its largest arm stretches 23 km in one direction and extends another 20 km in the opposite direction. It covers a surface area of 815 square km and holds 13.4 billion cubic meters of water. The reservoir has a flooded area of 817 km2, a volume of 13,800 x 106 m3, and an average depth of 17 meters. Inflow into the TI reservoir is limited primarily by the Fig 1. Três Irmãos (TI) reservoir and hydrodynamic modeling compartments. A) The TI and all sampling sites are shown. Purple circle shows the pilot sampling location. Blue circles labeled C1-C4 and C6-C15 designate the positions of the 14 sampling stations along the TI reservoir. Stations abbreviations as in S1 Table. White circles (PS1 and PS2)

indicate where fish restocking programs are conducted. Orange circles (JNA, JAC, JBA, SLUICES and JTI) show the locations where the traditional taxonomic surveys are conducted by the hydroelectric company. Black trapezoid bars represent the positions of the Três Irmãos (UHE TI) and Nova Avanhandava (UHE NA) hydroelectric dams. Black star shows the Pereira Barreto service channel that connects the TI and IS reservoirs. B) For water renewal computations by hydrodynamic modeling, the reservoir was divided into 14 compartments. Red bars delineate the boundaries of the compartments. Compartment numbers are in red; the blue numbers are the control sections in which time series flows were calculated with the hydrodynamic model. https://doi.org/10.1371/journal.pone.0314210.g001 PLOS ONE eDNA metabarcoding reservoir PLOS ONE | https://doi.org/10.1371/journal.pone.0314210 January 24, 2025 3 / 22