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article imageAssessing the ‘health’ of rivers using DNA analysis

By Tim Sandle     Apr 23, 2017 in Environment
How healthy is a river? One answer is to assess the biodiversity of the waterway. This involves assessing the biodiversity. Current methods involve multiple testing, assessing microscopic marine life. A new method has been proposed based on DNA.
The new method has been proposed by researchers working at the University of Geneva) in Switzerland. The method is based on a measure of the DNA sequences of diatoms, and then using the data to construct a ‘water quality’ index.
Diatoms are a major group of algae and they are common phytoplankton. The organisms are unicellular and they are producers within the food chain. Diatom cells are enclosed within a cell wall made of silica (hydrated silicon dioxide). The new approach is to use diatom communities as means for monitoring environmental conditions, especially water quality.
The reason why diatoms are useful is because they are very sensitive to changes in water conditions. This means they function as effective bioindicators of water pollution levels. The usefulness of the new approach is that it avoids the need to assess biodiversity by screening for each individual species; a composite DNA analysis allows a collection of species to be examined at the same time.
The new approach was verified by collecting 90 different samples of diatoms taken from different rivers in Switzerland. The ecological status was assessed using the Swiss diatom index, which is a form of molecular index based on DNA sequences. When verified against manual counting methods an accuracy rate of close to 80 percent was obtained.
Discussing the approach, lead researcher Laure Apothéloz-Perret-Gentil told Laboratory Roots: “The whole range of DNA sequences revealed in each sample corresponds to a specific DI-CH quality index.”
The researcher adds: “Furthermore, each sequence identified has a different distribution and is detected in variable amounts from one sample to another. By integrating all these data, we were able to calculate an ecological value for each sequence, without having to identify the species to which it belongs.”
The new approach has been reported to the journal Molecular Ecology Resources. The research paper is titled “Taxonomy-free molecular diatom index for high-throughput eDNA biomonitoring.”
More about Rivers, river health, Waterways, Diatoms, Algae
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