Abstract
The Itaipu Hydroelectric Power Plant is the second largest in the world in power generation. The artificial barrier created by its dam imposes an obstacle for fish migration. Thus, in 2002, a fish pass system, named Piracema Channel, was built to allow fish to access areas upstream of the reservoir. We tested the potential of environmental DNA metabarcoding to monitor the impact of both the dam and associated fish pass system in the Paraná River fish communities and to compare it with traditional monitoring methods. Using a fragment of the 12S gene, we characterized richness and community composition based on amplicon sequence variants, operational taxonomic units, and zero-radius OTUs. We combined GenBank and in-house data for taxonomic assignment. We found that different bioinformatics approaches showed similar results. Also, we found a decrease in fish diversity from 2019 to 2020 probably due to the recent extreme drought experienced in southeastern Brazil. The highest alpha diversity was recorded in the mouth of the fish pass system, located in a protected valley with the highest environmental heterogeneity. Despite the clear indication that the reference databases need to be continuously improved, our results demonstrate the analytical efficiency of the metabarcoding to monitor fish species.
Highlights
The Itaipu Hydroelectric Power Plant, built at the border between Brazil and Paraguay, is the second largest in the world in power generation[1], second only to the Three Gorges Power Plant in China
Even with an incomplete DNA reference database, the use of molecular units, such taxonomic units clustered by similarity or unique sequences allows for diversity monitoring in the context of biodiversity assessment in megadiverse biomes
Most specimens were collected at the mouth of channel at Paraná River, with 2240 (51%) fishes belonging to 105 species
Summary
The Itaipu Hydroelectric Power Plant, built at the border between Brazil and Paraguay, is the second largest in the world in power generation[1], second only to the Three Gorges Power Plant in China. Even with an incomplete DNA reference database, the use of molecular units, such taxonomic units clustered by similarity (operational taxonomic units—OTUs22) or unique sequences (e.g. amplicon sequence variants—ASVs23, or zero-radius OTUs—ZOTUs24) allows for diversity monitoring in the context of biodiversity assessment in megadiverse biomes Such estimates without comprehensive species identification limit ecological conclusions but allowed for monitoring of natural and artificial impacts[16,25]. The metabarcoding approach has been successfully used for molecular identification of several vertebrate groups in temperate regions[26,27], monitoring of endangered species such as freshwater fish in Australia[28] and turtles in the United States[29], and to describe biodiversity even with limited taxonomic identification[30] In this context, our goal here is to describe an effective survey protocol for detecting fish assemblages through eDNA metabarcoding in an ecologically complex and highly diverse freshwater system, the Piracema channel, that connects the Paraná River with Itaipu Reservoir. We compare our metabarcoding results with the traditional sampling campaigns made between 2017 and 2021
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