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Detecting fish and bacteria through eDNA analysis

We can determine fish populations on the basis of DNA traces. DNA techniques also make it possible to establish the presence of the pathogenic Leptospira in surface water.

The eDNA characterisations are the subject of two articles in the latest edition of the ‘Water Matters’ knowledge journal of the H2O magazine. The eDNA methodology is based on identifying DNA traces left behind in the water by animals, plants and bacteria. The analysis of this eDNA is a cheap and efficient way of demonstrating what living organisms are present in the water. The application of eDNA techniques is rapidly gaining popularity in water management.

Characterising the fish population

KWR recently developed the NL-Fish Population Scan. This technique makes it possible to characterise the species composition of the fish population by analysing DNA traces in the water. In principle, this is cheaper, more accurate and also more animal-friendly than capturing the fish. A test was conducted for the Limburg Waterboard, which involved taking seven samples on a single day from the Roer river. The eDNA of 33 different fish species was detected. This one-day sampling found only eight fewer fish species than have been detected through daily sampling at a fish ladder in Roermond over a period of five years. One species, the schneider, was not caught in the fish ladder but was detected through its eDNA.

Leptospira and brown rat

The (e)DNA methods developed have made it possible to show the presence of Leptospira and the brown rat in outdoor bathing water. Leptospira is the agent responsible for Weil’s disease, and brown rats play a role in spreading this bacterium. The eDNA analysis showed the presence of both Leptospira and of the brown rat in samples taken at bathing locations, indicating that the rat is the source of the Leptospira. In those cases where no traces of the rat are found, other agents, such as rodents or livestock, are the possible source. By combining several samples per location, and testing for several animals, one can obtain a precise picture of the infection sources and thus take targeted management initiatives.

H2O’s Water Matters knowledge magazine, also includes, besides the above research projects, other articles on a variety of water-sector subjects, from antibiotic-resistant bacteria in urban waters to the cheaper processing of sewage sludge. Here’s an overview of the contents:

  • Spreading veterinary pharmaceuticals in the soil and water through manure applications
  • Antibiotic-resistant bacteria in urban water due to sewer misconnections
  • Insight into the emission of pharmaceutical residues into wastewater
  • The effect of the rotation of maize and grass on nitrate leaching
  • Are WFD targets achievable through more ecological agriculture?
  • Cheaper processing of sewage sludge through the addition of cations
  • Monitoring stream water temperature with fibre-optic cables

Water Matters is a publication of the Royal Dutch Waternetwerk (KNW), and is made possible by ARCADIS, Deltares, KWR Watercycle Research Institute, the Netherlands Water Partnership (NWP), Royal HaskoningDHV, the Foundation for Applied Water Research and Wageningen Environmental Research (Alterra).