LAUSR

In this report, I describe a method for rapid measurement of total adenylate (ATP+ADP+AMP) in marine sediment samples for estimating microbial biomass. A simple 'boil and dilute' method is described here, whereby adding boiled MilliQ water to sediments increases the detection limit for ATP+ADP+AMP up to 100-fold. The lowered detection limit of this method enabled the detection ATP+ADP+AMP in relatively low-biomass subseafloor sediment cores with 104 16S rRNA gene copies per g. Concentrations of ATP+ADP+AMP correlated with 16S rRNA gene concentrations from Bacteria and Archaea across six different sites that range in water depth from 1 - 6,000 m indicating that the ATP+ADP+AMP method can be used as an additional biomass proxy. In deep sea microbial communities, the subseafloor ratio of ATP+ADP+AMP concentrations to 16S rRNA genes >1 meter below seafloor was significantly lower compared to communities in the upper 30 cm of sediment, which may be due to reduced cell sizes and or lower ATP+ADP+AMP concentrations per cell in the deep sea subseafloor biosphere. The boil and dilute method for ATP+ADP+AMP is demonstrated here to have a detection limit sufficient for measuring low biomass communities from deep sea subseafloor cores. The method can be applied to frozen samples, enabling measurements of ATP+ADP+AMP from frozen sediment cores stored in core repositories from past and future international drilling campaigns.