Abstract
Our aim was to assess the environmental factors responsible for the degradation and persistence of environmental DNA (eDNA) over time in an environment that is not fully controlled. This was achieved by measuring the effects of these factors on the eDNA persistence of Limnoperna fortunei and Cordylophora sp. After a pilot experiment to determine DNA degradation in the field, the experimental phase began at two hydroelectric power plant, in Paraná, Brazil, EI, which was made with bottles contained DNA extract of L. fortunei and EII, which bottles contained water from the reservoir itself, with eDNA of both species. Temperature, luminosity, turbidity and transparency were monitored and DNA concentration was measured by qPCR. Sampling units consisted of two sets of sterile glass tubes for two treatments, one with transparent tubes and one with tubes covered with black tape, to prevent the influence of sunlight. The units were arranged in triplicate and attached to a guide rope held vertically in the water column where they were distributed at 0.0; 0.3; 0.6; 1.5; 3.0; 4.3, 7.0; and 10.0 m depths and remained submerged for 24, 72, 168 and 264 hours, respectively. We concluded that the presence of eDNA could still be detected after 12 days under different environmental conditions, but the degradation process of the molecule was clearly accentuated in the first 24 hours. The rapid degradation of eDNA in aquatic habitats allowed monitoring of species practically in real time, as the DNA identified was the result of a recent release.