Reflection on SPM Sampling
Something that continues to surprise me in this course is the many ways in which you can sample and analyze eDNA. Learning about these different methods, despite the fact that it further muddies the already complex sampling design decision-making process, is always exciting to me. The more I learn, the more I see the many possible applications and benefits of eDNA research.
Diaz et al. (2020) and their analysis of suspended particulate matter (SPM) as a source of eDNA is no exception. What excited me the most about this approach was the possibility for long-term analysis of a system and the power of archived samples to show temporal shifts in species. In the context of a changing marine ecosystems like the Damariscotta River Estuary, SPM may be a way to see species regime shifts or identify when invasive species were first introduced. I also appreciated that SPM produces such high concentrations of eDNA to allow for repeated subsampling now and in the future.
As with all the methods we have discussed so far, there are caveats concerning their applications and potential concerns about contamination. For example, in a commercially active system like the Damariscotta aquaculture dredging, or even tidal flow, could contaminate samples. Further, degradation of the samples in the field collectors also raises questions about how fine of a temporal scale can be analyzed and how often samples should be collected. All in all, though, SPM is an eDNA source and method that I would like to continue to discuss, especially in the context of long-term monitoring programs in systems like the Damariscotta.