Integration of DNA-based approaches in aquatic ecological assessment using benthic macroinvertebrates

Benthic macroinvertebrates are among the most used biological quality elements for assessing the condition of all types of aquatic ecosystems worldwide (i.e., fresh water, transitional, and marine). Current morphology-based assessments have several limitations that may be circumvented by using DNA-based approaches. Here, we present a comprehensive review of 90 publications on the use of DNA metabarcoding of benthic macroinvertebrates in aquatic ecosystems bioassessments. Metabarcoding of bulk macrozoobenthos has been preferentially used in fresh waters, whereas in marine waters, environmental DNA (eDNA) from sediment and bulk communities from deployed artificial structures has been favored. DNA extraction has been done predominantly through commercial kits, and cytochrome c oxidase subunit I (COI) has been, by far, the most used marker, occasionally combined with others, namely, the 18S rRNA gene. Current limitations include the lack of standardized protocols and broad-coverage primers, the incompleteness of reference libraries, and the inability to reliably extrapolate abundance data. In addition, morphology versus DNA benchmarking of ecological status and biotic indexes are required to allow general worldwide implementation and higher end-user confidence. The increased sensitivity, high throughput, and faster execution of DNA metabarcoding can provide much higher spatial and temporal data resolution on aquatic ecological status, thereby being more responsive to immediate management needs.

This work was supported by the "Contrato-Programa" UIDB/04050/2020 and the project NIS-DNA (PTDC/BIA-BMA/29754/2017) funded by national funds through the FCT I.P (Foundation for Science and Technology). Financial support granted by the FCT to S.D. (CEECIND/00667/2017) and B.R.L. (PD/BD/127994/2016) is also acknowledged. A.F.F. was supported by the project FRESHING founded by the FCT and COMPETE (PTDC/AAGMAA/2261/2014-POCI-01-0145-FEDER356016824). M.J.F. was supported by FCT through MARE strategic project UIDB/04292/2020 and Norma Transitoria-DL57/2016.