NOVEL AND SUSTAINABLE APPROACH TO HYDROLOGICAL TRACING WITH SYNTHETIC DNA

ABSTRACT: Conventional hydrologic tracers such as salts and dyes may pose a risk to sensitive ecosystems as large quantities are often required for tracing experiments. Synthetic DNA has the potential to be used at large scales and in environmentally critical areas as small volumes can achieve sensitive detection and it poses no risk for the environment. Synthetic DNA also has the potential to aid in better understanding detection methods for environmental DNA (eDNA). eDNA is any genetic information shed from organisms into the environment and can be found in the form of free DNA, in cells, or as clusters of cells. The purpose of this research was to explore the potential for free (unbound) synthetic single-stranded DNA to be used as a hydrologic tracer and to assess its interdisciplinary value for ecological monitoring. The research methods included preliminary laboratory work where DNA analysis was optimized using quantitative polymerase chain reaction (qPCR). A field tracer experiment was then conducted where synthetic DNA was released into Washington Creek, in the Grand River subwatershed of Southern Ontario. Water samples (1 mL) were collected 100 meters and 350 meters downstream from the point of injection, immediately frozen on dry ice, then stored at -80degC and subsequent qPCR analyses were conducted. Breakthrough curves of DNA concentration in nanogram/microlitre versus time were plotted for each downstream site. The DNA tracer demonstrated advective and dispersive behaviour as it travelled downstream to each sampling site. Some sample degradation was noted during storage however degradation was proportional therefore the peak arrival time remained unchanged. The curves illustrated similar behaviour to conventional tracers and depicted the potential for synthetic free DNA to be used as a reliable tracer for field experiments. In terms of biological implications, free DNA was easily detected downstream which may help understand eDNA degradation and downstream movement.