This project leveraged extensively upon a diving season run by a project partner, the Australian Antarctic Division, which took place in the Austral summer of 2014/2015. During this period the Marie Curie Individual Fellow (MCIF) who was the recipient of this award (in 2017) was employed as a scientific diver. During the diving season the MCIF was involved in collecting data and samples from various dive sites around Casey Station, Antarctica, as well as collecting samples and data during an experiment conducted under the sea-ice, that manipulated the acidity of seawater in chambers on the seafloor, called antFOCE. It was during this period the MCIF collected the environmental DNA samples used as the basis for this project. They consisted of seawater and seawater/sediment filtered through syringe filters with very small holes only microns wide. These filters can capture very small particles as well as large molecules, such as DNA.
During the project, the MCIF extracted DNA from the syringe filters and amplified small stretches of DNA that could be used to identify the organisms that the DNA came from. Once the DNA was extracted and amplified, it was sequenced, resulting in over 60 gigabytes of DNA sequence data, representing over 90 million short DNA sequences. This DNA sequence data was then processed to assign specific DNA sequences to specific samples, to remove errors etc, and then to identify the likely organism (or broader group or organisms) that specific DNA sequences came from. These data were then statistically analysed so that relationships between samples, sampling sites and sampling mediums could be understood. The MCIF also performed sequencing of DNA from representative individual organisms from the benthic ecosystems being studied, so that DNA from the eDNA syringe filters could be matched to specific organisms that were underrepresented in current DNA sequence databases.
The results so far indicate eDNA can indeed be a powerful indicator for the biodiversity present in these ecosystems. They show that eDNA signals vary according to the medium sampled (seawater Vs. seawater/sediment from the seafloor) and the location of the sampled medium. The results also show that samples collected closer to one another are more similar to samples collected further away from one another and the nature of this relationship. This is an important step towards understanding the use of eDNA to study these ecosystems. The data also showed some differences in eDNA signals from different experimental treatments of the antFOCE experiment, which may lead to insights into how these ecosystems will respond to ocean acidification in the future.
