Environmental Nucleic Acids: A Toolkit for Monitoring Diversity, Conservation, and Environmental/Population Health

The Amazon basin comprehends several aquatic environments and a great diversity of ichthyofauna, with a high rate of endemism. The number of species found in the region, combined with its extension, makes the identification and monitoring of biodiversity a problem, which might be solved with the application of the environmental nucleic acid technique, such as eDNA and eRNA. The eDNA technique uses aquatic or terrestrial environmental samples, where there are genetic traces of the organisms that frequent the local. This method can be used for the identification of target species, for the study of diversity of several taxa, and for the identification of invasive species, minimizing the stress of the organisms once it is not an invasive technique. In addition, environmental genetic analyses can still use other tools, such as the analysis of environmental mRNA and microRNA, where, through the expression of specific genes, it is possible to identify genes already known to respond to different stresses, such as pollution, thermal stress, and natural variation in dissolved oxygen levels, generally determining the possible pressures that organisms are exposed in their environment. As it is a technique under development, its application in the Amazon water basin still faces problems, such as the physical-chemical conditions of the aquatic environments and the lack of a genetic database for the species of such a diverse environment. Despite this, there are prospects of development applications in biodiversity monitoring, in addition to the identification of environmental genetic parameters related to human and animal health. In this chapter, we will discuss the applications of the environmental DNA technique for the Amazon region, the main results found with the technique, so far, and a comparison with studies that used traditional approaches to assess diversity. Finally, we will list the several perspectives for its future applications, both those concerning the monitoring of environmental and those concerning human health.