Sedimentary aDNA

The DNA binds to the sediments and layer by layer the sediment archive builds up. But how did the DNA of a sheep or a goat get into the lake? Finding plant remains and their DNA, as well as micro fossils and DNA of any aquatic organism once living in a specific lake might not sound that far fetched, however imagining how the genetic material of land living animals might end up in a lake might not be that straightforward. Essentially, DNA and remains of animals and plants can be washed into the lake. Depending on the size of the lake, the so-called "catchment area" is bigger or smaller, as the area from which water might flow in varies. Animal herds moving or even staying close to a lake, will leave their DNA in the surrounding though defecation, blood and decay of dead individuals. This now environmental DNA of these individuals will likely be washed into the lake with the next rain. In the lake the DNA binds to the lake sediments and can be preserved.

Lake sediment cores for scientific analysis are usually taken at the deepest point of the lake, as this point tends to have the best archive. The cores are taken to a clean laboratory and split in half. Layers throughout the entire core are sampled for radiocarbon dating and DNA analysis. This allows us to put a date to the analysed DNA. The DNA is extracted and then identified. Identifying ancient DNA can be tricky, due to its chemical degradation and fragmentation, but as the techniques of ancient DNA developed so did the bioinformatic tools to analyse the retrieved data.

The extraction and identification of ancient DNA from lake sediments is a relatively new and exciting technique that allows us to identify the changes in plant animal communities over time. As with palynology, cores are taken in lakes, and samples carefully prepared in clean laboratories. Cores can date back to several thousand years and allow us to reconstruct the environment around the lake and its use, based on the retrieved sedimentary ancient DNA.

Katharina Dulias started work on this work-package in March 2019.