Environmental DNA, good or bad proxy for macroinvertebrate abundance? Allometric scaling and trait category do benefits

Macroinvertebrates play a crucial role as bioindicators of freshwater ecosystem health due to their sensitivity to pollution and human activities. Environmental DNA (eDNA) metabarcoding is a promising tool for monitoring biodiversity but faces challenges in accurately quantifying species abundance. In this study, we tested the effectiveness of eDNA methods in controlled laboratory conditions with ten macroinvertebrate species of varying sizes and body structures. We found that eDNA read abundance was strongly correlated with species abundance but not with biomass. Body structure and size significantly influenced eDNA detection, with smaller species even producing higher read counts. Using allometric scaling models, we improved the prediction of species abundance from eDNA data. These findings support the use of eDNA metabarcoding as a reliable approach for assessing macroinvertebrate diversity and abundance, with potential applications in ecological monitoring and conservation.