FISHY FINGERPRINTS HOW eDNA WORKS

Environmental DNA, or eDNA, is the genetic material left in the environment as animals move around, feed and mate. eDNA can be used to identify which organisms are present in a particular environment without the need to physically observe, capture or kill them.

STEP 1 Seawater is collected in pre-sterilised containers dropped to various depths at set locations.

STEP 2 eDNA is isolated from the seawater through very fine mesh filters before being extracted and purified.

STEP 3 A common eDNA workflow involves the amplification of eDNA using PCR (the same process used to detect Covid-19) to target species-specific genetic markers. The resulting copies of DNA are then sequenced.

STEP 4 A second machine, called a qPCR, tests how much of a particular type of DNA is within the sample. The more DNA, the greater the presence of that species.

STEP 5 eDNA can also be “shotgun” sequenced where all the DNA in the sample is sequenced – a method useful for biodiversity analysis, to discover which organisms are present in that environment – provided you have a good reference genome DNA database to match these short sequences against (see below).

STEP 6 eDNA samples can be stored in -80C freezers for several years – important when researchers need to revisit samples.

A REFERENCE LIBRARY OF SPECIES’ DNA

1. The full characterisation of ocean wildlife using eDNA relies on a library of DNA reference genomes.

2. A reference genome is generated by sequencing the complete set of genetic information of each individual species – requiring high quality DNA isolated from a piece of tissue or blood.

3. Only 200 of the 20,000 known species of fish have had their genome sequenced.

4. In collaboration with partners, Minderoo‘s OceanOmics lab will develop and publicly release a library of DNA reference genomes for thousands of species.