Environmental DNA (eDNA): an eco-friendly approach for conservation of Indian freshwater diversity-a review

Freshwater ecosystems have been among the most vulnerable habitats worldwide for the last 50 years. It has been experiencing varying degrees of decline across the planet due to combination of global changes, including anthropogenic activities and climate change in recent decades. As a result, monitoring the diversity of freshwater ecosystems and their biota has emerged as a hotspot area of research in light of this diminishing variety. Environmental DNA (eDNA) has demonstrated its utility in biodiversity studies, particularly for identifying fish species and measuring fluctuations in species richness, owing to its numerous advantages. eDNA represents an environmentally sustainable and cost-effective approach that can identify and quantify a broad spectrum of taxa from any ecosystem without adversely impacting native species or their habitats. These genetic material consists of short DNA fragments or cellular components released by aquatic organisms through various means, including skin, urine, faeces, mucus, and cellular debris, into environments such as water, air, soil, or sediment. The potential of eDNA is further enhanced by next-generation sequencing (NGS), which allows for simultaneous analysis of all DNA present in single run. Our systematic review of eDNA research (2008 to 2024) showed that 32.79% of studies focused on freshwater ecosystems, with 30.2% targeting fish diversity assessment. The analysis also reveals a steady increase in eDNA-related publications, reflecting growing global interest in its application for biodiversity assessment and conservation (38.92%). Through this present review, Indian researchers, as well as non-molecular biologists, can gain better understanding of eDNA metabarcoding concept and its methodological overview.