Reflection on SPM eDNA
Isolating eDNA from SPM is a really interesting idea that raises a lot of questions. I think a lot of my class mates had been wondering whether suspended particulate matter was a viable source of eDNA, and this week’s paper did a good job of demonstrating that it is. One opportunity this paper gives rise to is careful integration of different eDNA sources to answer different questions. Water samples can give fine resolution spatially and temporally due to faster degradation of eDNA in the water column. Sediments give a much broader resolution as sediment could have been transported from miles upstream, and eDNA is much more stable in sediment. SPM may provide a middle ground. Genetic material could be preserved to some degree in SPM, but perhaps not to the degree that it is in sediment. The paper does not quite get into the question of eDNA degradation rates in SPM, as it’s really more of a pilot study, but that would be an interesting next step. The authors note that electrofishing surveys were able to identify more species than their study, however there really isn’t a fair comparison. The electrofishing survey took place in different areas and have been ongoing for years. It would have been nice if the authors had done their own electrofishing survey at the same spots they had sediment traps in order to get a better comparison. This would do a better job of supporting their argument that their technique is better than the standard survey technique.