Environmental DNA (eDNA)

Environmental DNA (eDNA) : Recently, scientists have moved beyond traditional methods like catching animals or counting plants and are increasingly using environmental DNA (eDNA) to study biodiversity.

• About eDNA : Refers to genetic material that organisms shed into their surroundings during their life or after death. It originates from cellular material such as skin cells, feces, saliva, or decomposed tissue, which gets deposited in water, soil, or air.

o Working : Scientists collect a few litres of water (or soil/air samples) from the environment.

- The DNA fragments present are filtered and sequenced to detect the presence of different organisms.

- This method can identify a broad spectrum of life forms, including: Microorganisms (bacteria, viruses, archaea), Fungi, plants, insects, birds, fish, amphibians, and mammals.

• Key Advantages: Non-invasive and eliminates the need to capture or count organisms.

o Highly sensitive, detecting both rare and cryptic species that are hard to observe directly.

o Useful in early detection of invasive species and in forensic identification (e.g., detection of human remains).

o Faster, cheaper, and scalable to large marine and freshwater ecosystems.

• Recent Study: Kashi River Basin, China: eDNA metabarcoding in the Kashi River found 166 fish species across 21 sites, far exceeding the 27 species recorded in earlier net surveys.

o The study also showed how seasonal changes and human interventions (like hydropower) affect biodiversity.