Table 2 Conceptual categories established according to the study objectives and their description

Biodiversity assessment (BA)

Studies that assess diversity, composition, distribution, abundance and richness

Antibiotic resistance genes (ARG)

Studies focused in the identification, detection and characterization of bacterial resistance genes to antibiotics through NGS

Functional traits/physiology (PHY)

Focused on determinate functional potential or dominant metabolism-type in a system

Diseases detection (DIS)

Studies focused on detection of virus, and other microorganisms that are considered of medical importance for humans

Monitoring (MON)

Focused on a single species, and its presence/absence in the ecological system and distribution range

Seasonal changes (SEA)

Description of spatiotemporal changes in species composition, population trends, diversity, and their presence

Comparison vs conventional surveys (COMP)

Focused on making a comparison between the use of eDNA methodology vs conventional methodologies, monitoring programs, and identification procedures

Quality assessments (QUA)

Studies that try to determine quality, health or system conditions based on the use of eDNA. This includes effects of pollution on quality of rivers

Exotic/invasive species (EXIV)

Studies focused on identifying through use of eDNA, presence of exotic and/or invasive species that could degrade the system

eDNA degradation/perdurance (DEPE)

Research about eDNA degradation process, rates, persistence and their role on biological studies

Techniques evaluation (TEC)

Evaluation of effectiveness, cost, sample effort, resolution, and generated information of eDNA over other techniques

Community assemblages (COMA)

Focused on characterize a group community (fishes, crustaceans, bacteria, etc.) assemblages

eDNA modelling (MOD)

Models’ construction that try to predict eDNA transport, sites with more eDNA concentration, and other eDNA processes

Species at risk (RIS)

Studies whose objective is to detect, monitor and assess through eDNA, presence, absence, biomass estimation, etcetera of species at risk categories

Bioindicators (IND)

Pollution (POL)

Proposal of use some species as bioindicators, based on their eDNA sampling and processing studies that tried to document the pollution effects on a single species or a community level