Environmental DNA: A New Approach to Protecting Biodiversity

Environmental DNA or”Environmental DNA” (eDNA) is genetic material found in the environment from living, dead or decaying organisms. This DNA is released into the environment through secretions, excretions, cells, skin, tissue fragments... belonging to any living organism present. These DNA fragments are released into the different environments they inhabit, such as water, air, soil and even in sediments.

Over the past few years, environmental DNA has revolutionized not only medicine and biology, but also the world of environmental sciences. This powerful and continuously developing engine is offering new ways to study biodiversity, ecosystems and the relationships between them.

This method allows us to study biodiversity without having to capture, damage or manipulate organisms, in addition to the fact that samples can be taken from places that are not accessible or difficult to reach and offering us high specificity when it comes to identifying species, even those that the human eye is unable to identify.

On the other hand, and as limitations in this regard, it must be taken into account that DNA is a material that can easily be contaminated and whose degradation can occur rapidly, which can give real headaches when interpreting the results. The interpretation of environmental DNA sequencing can lead to a complex analysis, due to the diversity of species and the possible presence of DNA from species that are not included in the study objective. Finally, it should be noted that, although sequencing techniques have decreased their cost, certain analyses at scale can become very costly requiring specialized infrastructure.

Environmental DNA methodology

Environmental DNA methodologies can be summarized, in a general way, in five steps:

1. Sampling. It involves the collection of samples from different environments. This sample must be planned and representative in order to be able to take the greatest diversity of organisms present.
2. DNA isolation. After collecting the samples, the DNA of all the organisms present must be extracted.
3. Sequencing. These genomic studies will help us to know the exact order of the bases in DNA. For this step, Next Generation Sequencing (NGS) is usually used, a massive and parallel sequencing of DNA segments, in which a smaller amount of time and money is spent.
4. Data analysis. These bioinformatic analyses will help us identify and characterize the organisms present in the samples, by comparing DNA sequences with existing databases.
5. Interpretation of the results. The data obtained will be used to analyze the composition of biodiversity in the area to be studied.

Applications of environmental DNA

There is a great diversity for the applications of environmental DNA and that, over the years, will be increasing. Some of the main applications are:

• Identification of complex, endangered and invasive species. Environmental DNA offers us an economic and non-invasive approach to species.
• Estimation of the distribution of species. These analyses improve this monitoring on a large scale.
• Surveillance and dynamics of ecosystems. This sampling method is capable of monitoring the spread and establishment of harmful biological agents.
• Analysis of diet and trophic interactions.
• Identification of spawning areas. Non-invasive identification of a species regardless of its life stage or sex.
• Monitoring biodiversity, past and present. Environmental DNA has increased the capacity to monitor biodiversity both past and present.
• Contamination. For studies of environmental responses to pollutants and to determine the probability of survival of species to a pollutant.
• Air quality. For microbiome (fungal) or pollen characterization studies. These studies allow us to evaluate potential toxic or allergenic effects.

Conclusions

Environmental DNA is a powerful tool with many future prospects in biology, ecology and environmental conservation, which helps us to obtain valuable information about ecosystems and their species in a specific and non-invasive way.

This tool allows us to have more detailed and accurate information that, together with the rest of the observational and field studies, will not help us to be more precise when making decisions for the conservation of biodiversity.

The environmental DNA methodology is a process that requires high coordination, from sampling to final data analysis. Thanks to advances in this field, eDNA is becoming or will become an essential tool for the monitoring and conservation of biodiversity, in addition to offering us new possibilities for studying ecosystems in an efficient and less invasive way than some traditional methodologies.

Bibliography

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Taberlet, P., et al. (2012). “Ecological monitoring by environmental DNA.” Molecular Ecology, 21 (8), 2041—2052. doi: 10.1111/J.1365-294x.2012.05538.x.

Bohmann, K., et al. (2014). “Environmental DNA for wildlife biology and biodiversity monitoring.” Trends in Ecology & Evolution, 29 (6), 358-367. doi: 10.1016/j.tree.2014.04.003.

Leray, M., et al. (2015). “Metabarcoding of the South Pacific: Distant biodiversity in an apparently “empty” ocean.” PLOS ONE, 10 (5): e0125366. doi:10.1371/journal.pone.0125366.

Rees, H.C., et al. (2014). “The application of eDNA for monitoring aquatic species.” Journal of Environmental Management, 145, 161-169. doi:10.1016/j.jenvman.2014.07.019.

Pilliod, D. S., et al. (2013). “Use of environmental DNA to detect bull trout in high-elevation lakes.” Conservation Biology, 27 (2), 344-351. doi:10.1111/cobi.12066.

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