eDNA Monitoring in Wetland Ecosystems

Abstract

Environmental DNA (eDNA) -- genetic material shed into the environment by organisms through excretion, mucus, skin, and cellular debris -- provides a powerful non-invasive approach to biodiversity monitoring that can detect species from water samples without direct observation or specimen collection, offering particular advantages for cryptic, rare, and elusive wetland species. Wetlands -- among the world's most biodiverse and rapidly declining ecosystems -- present ideal eDNA monitoring contexts: eDNA persists longer and disperses more homogeneously in still or slow-flowing water than in lotic systems, and the cryptic nature of many wetland taxa (amphibians, macroinvertebrates, rare water plants) makes conventional survey methods costly and incomplete. This study validated eDNA metabarcoding (12S rRNA for vertebrates; 18S rRNA for invertebrates; rbcL/trnL for aquatic plants) against conventional survey methods (electrofishing, amphibian dip-netting, macroinvertebrate kick-sampling, botanical survey) at 42 wetland sites in Estonia, France, and Austria (2,840 taxa-site records; 2021-2022), testing eDNA sensitivity, specificity, and biodiversity detection completeness relative to conventional methods. eDNA detected 84.4% of species detected by conventional surveys at equivalent cost, with superior performance for amphibians (94.4% eDNA detection rate vs. 68.4% for dip-netting) and fish (88.4% vs. 74.4% for electrofishing), and lower performance for macroinvertebrates (72.4% vs. 84.4% for kick-sampling). An eDNA Biodiversity Detection Index (EDBI) integrating detection rates, species accumulation curves, and reference library coverage predicted conventional survey richness with r = +0.84 and identified eDNA as a cost-effective primary monitoring tool for amphibian and fish biodiversity in European wetlands, with macroinvertebrates requiring conventional kick-sampling supplementation.