Sediment core from the bottom of Kermadec Trench. Sediment samples are of immense value for the researchers. Photo: Anni Glud.
Viral abundance and activity at hadal depths have not been investigated. Generally, the abundance of viruses correlates positively with microbial abundance and activity and we expect, that the activity and relative importance of viruses will be high at these anticipated hot spots of microbial activity.
There is, however, currently no generally accepted method for reliable quantification of viral abundance and production sediments. Different approaches have provided highly variable viral counts.
Quantification of viral production is associated with even larger challenges as all currently applied methods, in addition to recovery, involve manipulation of the sediment samples by homogenization and incubation with or without slurrying.
Maybe microbes and viruses evolved together
Here we aim to test current approaches systematically and develop robust protocols for extraction of viruses and microbes from hadal sediments, and subsequently to optimize flow cytometric quantification of their abundance.
Combined with the in situ fixation strategy this will allow us to provide accurate estimates of viral and microbial abundances from the trench locations and reference stations, and to compare these data with results obtained by traditional methodology.
We hypothesize that co-evolution of microbial and viral communities in hadal environments have selected for unique viral communities with genetic and life cycle properties adapted to perform in this environment.
Collecting samples from Kermadec Trench. Photo: Ashley Rowden.
Challenge: Testing without destroying
It is impossible to collect a microbe sample on 10.000 m depth and bring it to the surface without harming or killing it. Many of the microorganisms adapted to life at extreme depths will die when pressure and temperature change.
HADES project has developed and tested instruments that autonomously can perform preprogrammed measuring routines directly on the seabed.