Högskolan i Skövde

Freshwater habitats and their quality have always been of utmost importance for human subsistence. Water quality assessment is an important tool, covering biological, chemical and hydromorphological aspects. Bioindicators such as the bivalves can be used as evidence for good water quality, but widespread groups such as species of the family Sphaeriidae Deshayes,1855 (1822) and genus Pisidium/Euglesa/Odhneripidisium also known as ‘pea clams’ are poorly known and lack taxonomic expertise. The situation is similar for many other benthic macroinvertebrate species used in biomonitoring. In this study, we tested if pea clams can be detected using eDNA metabarcoding methods applied to sediment and plankton samples from 15 lakes and rivers in Sweden. Additionally, we detected benthic macroinvertebrates, so-called indicator species used in freshwater monitoring, as well as rare or red-listed and invasive species. We created a COI reference barcode library of 22 species of Swedish freshwater molluscs, of which one species is new, and five species have less than five records on NCBI and BOLD. From 272 sediment and plankton samples, we detected 497 benthic macroinvertebrate indicator species, 20 mollusc species and 3 invasive species in 15 freshwater environments in Sweden using eDNA metabarcoding. We show that one of the sediment sampling methods (M42) can detect slightly more species in autumn compared to the plankton or sediment kick-net methods, or to collecting samples in spring. A clear advantage is that biological water quality indices formerly calculated using taxa identified to the family level can now be calculated using the species level, giving higher precision. We suggest that future freshwater monitoring efforts can be greatly improved and sped up through large-scale and strategic habitat screening using barcoding and metabarcoding methods to support decision-making and help fulfill the goals of the UN 2030 Agenda.