Sampling marine environmental DNA to find out who was there
Date of publication: Oct 3, 2023

All organisms leave a trace of DNA in the environment that they inhabit, including those living in the ocean. We call this type of DNA, environmental DNA (eDNA). Example sources of eDNA include, but are not limited to, faeces, mucus, gametes, shed skin and dead cells. We can sample this DNA and analyse it to figure out who was there! In our case, we will use eDNA to study the biodiversity in coastal forests such as eelgrass and brown algal habitats.  To sample it, we simply take a bottle of water from the area we want to study and pump it through a filter. The filter has a small enough mesh, so that when the water passes through, the DNA is captured. In these images you can see student Lydia Rysavy collect a sample in the field by pumping water through a filter. We use bottled water as “blank” samples to make sure that no DNA from the air or from our equipment is contaminating the filters.

Left: Lydia Rysavy working with our portable laboratory in the field; Centre: Lydia pumping water through a filter using our battery powered pump; Right: Lydia extracting DNA from the filters, in the laboratory.

Back in the lab, Lydia retrieves the DNA from the filter in a process called “extraction”. She is very careful not to expose the filter to DNA from the lab. After this process, the samples are ready to be sequenced and analysed further.

Written by Thomas Dahlgren, NORCE