Reflection - Wk4
During class this week we read Díaz et al’s 2020 paper, “Aquatic suspended particulate matter as source of eDNA for fish metabarcoding”. This paper is particularly interesting to me this week because I had the opportunity to accompany Maine-eDNA researchers in the field as they collected eDNA water samples through the ice at Damariscotta Lake. Afterwards we used an underwater drone ROV to explore the sediment at the bottom of the lake’s floor. We operated the drone close to the bottom, which according to the depth finder, was approximately 43 feet directly below our hole in the ice. We ran the drone at approximately 37-39 feet and the temperature recorded by the drone ranged from 36F at the surface, 37F at ~3.5 feet, and 39-40F at 37-38 feet. As we allowed the drone to quietly drift (no motors/props running) with the nose tilted to view the bottom, with one light running (the other blew out as we tested it at 15 feet), it was slowly pushed and bumped through the water column by some force (a current?, a spring?). At times the drone would pass by suspended particulate matter or tiny bubble streaks.
The article and class discussions about sediments and the opportunities for species discovery through metabarcoding resonated with me as I’ve been looking through the drone footage. My reflection this week is full of questions as I wondered (and continue to wonder), what is the story behind those particles floating past the drone, or the bottom fluff kicked up by the drone? What can the top layers of sediment tell us about who lives (or lived) in the lake? How old is the top layer of sediment on the floor, 3-5 years? Younger? Older? (And how does one determine the height of that layer?) What are best methods for collecting sediment and not causing a lot of disturbance to the sediment or to the environment? I am curious about the possibilities for sediment collection in the Maine-eDNA project. What would metabarcoding from particulate matter tell us about a site, a particular location over time? Compared with water sampling? What will we be able to learn from our samples collected now, in the next years to come (if we save some of the samples), as the technology advances?