The continuous decline in Earth’s biodiversity is a major concern in the 21st century. Anthropogenic disturbances have affected the populations of flora and fauna and some of the species are on the verge of extinction. The species are depleting more rapidly compared to prehistory and it is the biggest threat to the sustainability of our planet. We can halt this depletion by conserving biodiversity. To realize that an effective biodiversity monitoring tool is needed and Environmental DNA (eDNA) has come up as one of the best options.
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Table of Contents
Problems in traditional approaches of biodiversity monitoring
Traditionally different species are monitored using physical identification based on morphological characters. Two distinct species may look similar in the early stage of their life and this might result in an error-prone survey. Some traditional approaches to biodiversity monitoring use the sampling method (such as canopy fogging, quadrat sampling, transect sampling, and netting). Some of these methods are a threat to the life of the organism under monitoring. To overcome these limitations of traditional biodiversity monitoring we need an alternative as well as an effective approach. These problems are answer to the question as to why do we need Environmental DNA biodiversity monitoring.
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What is Environmental DNA?
Environmental DNA or eDNA is defined as an organismal DNA obtained from a variety of environmental samples like soil, seawater, snow, or air. Organisms while interacting with the aquatic or terrestrial environment give out cellular material in the form of feces, shed skin, gametes, mucus, carcasses, and hair. The DNA (deoxyribonucleic acid) contains hereditary information of an organism and that can be extracted using various DNA sequencing methods. The results obtained thus are used in biodiversity monitoring.
The availability of environmental DNA after its release varies broadly from several days to several years. For this behavior, eDNA has a wide scope in fundamental research of areas relating to molecular biology, ecology, paleontology, and environmental sciences.
How does environmental DNA monitoring work?
Workflow for environmental DNA (eDNA) study is consists of several steps. These steps are briefly explained below –
- Environmental DNA Sampling: eDNA Sampling is taken from different environments (such as glaciers, permafrost/tundra, aquatic sediments, lakes and streams, terrestrial habitats, oceans). This is represented with the blue color in the workflow diagram.
- Environmental DNA Extraction: eDNA extraction is done using a specific technique designated for a particular type of environmental sample. Good quality of eDNA is obtained in sufficient quantity using eDNA extraction. This process is represented with the green color.
- Polymerase Chain Reaction amplification and sequencing: PCR amplification is done to amplify an eDNA sequence. This step is mentioned in orange in the flow diagram. There are two approaches of amplification, the single-species approach using specific primers and the multiple-species approach using generic primers. For comprehensive biodiversity monitoring, next-generation sequencing (NGS) technologies are applied in which a multiple-species approach is followed such as eDNA metabarcoding.
- Data Processing: In the final step, depicted in red, bioinformatic data processing is done by employing software. Elimination of errors, sorting of sequences, and identification of the taxonomy are done in this step.
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Environmental DNA Metabarcoding
eDNA metabarcoding is a quick and advanced method of biodiversity assessment. Metabarcoding is a multiple-species approach in which many taxa are identified from a single sample simultaneously. Barcoding is different from metabarcoding as barcoding is a single-species approach to monitoring. the workflow for the eDNA metabarcoding is the same as explained above. The following image differentiates between barcoding and metabarcoding as well as the processing.
As eDNA metabarcoding is an emerging field and the research is underway on its scope, there are some very useful applications of metabarcoding for ecosystem and biodiversity assessment. These are –
- Reconstructing ancient ecosystems from the eDNA
- Studying the relation between plants and pollinators
- Diet analysis of species without physical observation
- For identifying invasive species
- Understanding pollution response
- Check air quality
Current events in science and technology–
- Polarized Image of Black Hole
- NASA’s Chandra X-ray Observatory
- Nobel Prize in Physics for 2020
- Stephen Hawking’s theory of Dark Matter
Environmental DNA advantages and disadvantages
Environment DNA is a new method of biodiversity monitoring and measurement. Compared to the classical methods of a biodiversity survey, eDNA is more comprehensive in its approach as it can be employed in detecting rare species as well.
It is to be noted that the population quality information ( sex ratios & body conditions) can not be determined with eDNA that can be detected with the traditional approach. This is the first drawback of eDNA monitoring. Hence, we can say that eDNA can not completely replace the traditional biodiversity survey mechanism but it can be complemented with them for improved efficiency.
The second drawback of eDNA monitoring is the degradation of eDNA, some amount of eDNA is damaged and is not the actual eDNA.
The third drawback is linked to the deviation of spatiotemporal trends. As the eDNA travels through different environmental conditions after its release.
Even after all the limitations, eDNA accounts for certain advantages as well. These are –
- Standardization of environmental samples
- Non-invasive method of monitoring
- Efficient in monitoring invasive, cryptic, endangered, or probably extinct species of conservation concern.
- Cost-effective compared to traditional survey techniques
- Independent from weather conditions
Conclusion
From the above text, this is evident that environmental DNA is an effective technique for biodiversity research and monitoring. It can be complemented to the existing methods for efficient surveying results. Global initiatives for DNA databases can assist in extensive research on various species. Limitations experienced in eDNA measurement processes are needed to be overcome to make it a full-fledged biodiversity assessment tool.
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