eDNA Primer · For newcomers · Launching January 2027
New to eDNA? Start here.
A short, plain-language introduction to environmental DNA: what it is, how it works, what it can and can't tell you, and where to learn more. We're not the authority on eDNA. The researchers and practitioners who built this field are, and we point to their work throughout.
Who this is for
Media
Get the basics right before you write the story.
Government
Understand what eDNA can support in a monitoring program.
Consultants
Scope eDNA work with confidence.
Academia
A starting point for students and researchers entering the field.
General public
Learn how a cup of water can reveal what lives nearby.
What is eDNA?
Every living thing sheds DNA into its surroundings through skin, mucus, waste, and other material. Environmental DNA is that genetic material, collected from a sample of water, soil, or sediment rather than from the organism itself. By filtering a water sample and analyzing the DNA it contains, scientists can identify which species were recently present, often without seeing, catching, or disturbing them.
Two ways to use eDNA
Looking for specific species.
Targeted methods, usually qPCR or dPCR, test for the DNA of one or a few species: an endangered fish, an invasive mussel, a pathogen. Highly sensitive and well suited to yes-or-no management questions.
Describing the whole community.
Metabarcoding sequences DNA from many species at once to build a picture of the community in a water body: fish, amphibians, invertebrates, and more.
From water sample to species list.
- 01
Collect
Water, soil, or sediment is sampled in the field.
- 02
Filter and preserve
DNA is captured on a filter and preserved for transport.
- 03
Extract
The lab isolates DNA from the filter.
- 04
Amplify and sequence
Target DNA is amplified, then detected or sequenced.
- 05
Identify
Sequences are matched against a reference database to assign species names.
Every step involves choices (filter type, replicates, controls, software, reference database), and those choices affect results.
What eDNA can and can't tell you
What it does well
- Detects species at low numbers, including rare and hidden ones
- Surveys without disturbing animals or habitat
- Covers many species from a single sample (metabarcoding)
- Gives early warning of invasive species and pathogens
What to keep in mind
- DNA can travel: a detection shows DNA was present, not exactly where the organism was
- A detection doesn't confirm an organism is alive or breeding
- No detection doesn't prove absence
- Results depend on sampling design and lab methods, so results from different labs or years may not be directly comparable
Key terms
- eDNA
- Genetic material collected from an environmental sample rather than an organism
- qPCR / dPCR
- Methods that detect and measure the DNA of specific target species
- Metabarcoding
- Sequencing DNA from many species at once to describe a community
- Replicate
- A repeated sample or analysis used to check consistency
- Control (or blank)
- A sample with no expected DNA, used to detect contamination
- Reference database
- A library of known DNA sequences used to identify species
- FASTQ
- The standard raw data file produced by DNA sequencers
Ready to hire an eDNA lab?
Our free RFP Builder turns your monitoring question into a request for proposals that asks every lab the same questions, so you can compare bids on more than price.
RFP BuilderLaunching January 2027
Learn from the people who built this field.
These resources go far deeper than this primer. We're grateful to the researchers and agencies behind them.
- eDNA Resources (Washington State University)Practitioner-focused guidance on eDNA methods for aquatic monitoring.(opens in a new tab)
- National Aquatic eDNA StrategyThe US federal strategy for advancing eDNA in aquatic monitoring.(opens in a new tab)
- Environmental DNA (journal)Peer-reviewed research across the field.(opens in a new tab)
- “What is eDNA method standardisation and why do we need it?” (Metabarcoding and Metagenomics, 2025)A clear overview of terminology and the state of standardization.(opens in a new tab)
Launching January 2027
eDNA Primer
This page is a first draft. In January 2027 we'll launch a free, expanded edition for newcomers and practitioners: field guides, plain-language explainers, a living glossary, and procurement tools. Every page will show who wrote it, when it was last reviewed, and what changed.
Standing on existing work
eDNA Resources, Washington State University
Researchers at Washington State University built one of the field's most useful practitioner guides to eDNA methods for aquatic monitoring. Anyone starting out should read it. If you've built eDNA training or guidance and want to see it maintained and reach a new generation of practitioners, we'd welcome the conversation.
Visit eDNA Resources(opens in a new tab)