Plants and Animals

How DNA Evidence Could Be A Game-Changer In Monitoring Freshwater Fish

The Conversation

Water may well be everywhere, but freshwater lake ecosystems are among some of the most vulnerable on Earth. In recent decades, freshwater species have suffered double the rate of decline of land species. And nearly 50% of fresh water lakes, rivers and streams across Europe failed to meet the EU Water Framework Directive, which aimed to achieve “good ecological status” of freshwater in Europe by 2015.

Part of the problem is that current tools used to monitor the so called “health” of a lake can be costly, time consuming, inefficient, and in some cases, lethal to the organisms they are sampling. Which is why our new research is pioneering a new way of monitoring water species – using techniques more familiar to fans of crime TV shows.

Environmental DNA, also known as eDNA works in the same way as regular DNA testing, but rather than using saliva or hair, samples of water, soil or even air are taken and tested. The method works because every creature in freshwater leaves behind traces of its eDNA as it swims around, shedding minute flakes of skin, eggs, sperm or in the case of plants, pollen or seeds.

The majority of eDNA studies so far have focused on detecting single species using highly specific DNA-based procedures which focus on detecting one species at a time. Our study instead used a form of DNA testing called “metabarcoding”. This is where a single region of DNA called a “barcode” is simultaneously sequenced from a whole community of organisms. This enabled us to analyse millions of DNA sequences from water samples, identifying the DNA of a broad range of species and looking at whole communities of organisms – rather than just detecting single species.

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