An account of epiphytic diatoms in mediterranean wetlands: comparing morphological and molecular assessments

Benthic diatoms are well known bioindicators of water quality, used in many aquatic ecosystems. Since diatom-based monitoring quality is required by European legislation, the search for methods that facilitate this task has become more relevant. The aim study was to test reliability DNA metabarcoding combined with high-throughput sequencing (HTS) techniques bioassessment 22 Mediterranean shallow ponds Spain. For each pond, Trophic Diatom Index (TDI) calculated from inventories obtained using light microscopy, and then molecular methods. Ponds were subsequently classified into five classes. Our results showed a good correspondence between both methods, especially after applying correction factor depending on biovolume cells. This led assignment same class 59% ponds. determination quantification valves or sequences one main pitfalls, mainly those related variability relative abundances some species. Accordingly, similar dominant species assigned class. Moreover, other difficulties leading discrepancies misidentification due presence semi-cryptic taxa, incompleteness reference database bioinformatic protocol. Therefore, validation DNA-based identification freshwater represents an important goal, as alternative traditional ones