Comparing OEUs and biogeochemical processes. We asserted that certain OEUs
are related to certain modelled biogeochemical processes by comparing the spatial
distributions of OEUs and modelled processes and by manual bioinformatic
inference. Average Euclidean distance to each process for all OTUs within an OEU
was calculated (Supplementary Fig. 8). OEUs containing the reference OTUs were
chosen to represent each modelled process because existing literature about the
reference OTU suggests that those OTUs perform that modelled process. To assign
an OEU to a process, we further required that the imputed process be one of the two
processes least distant from that OEU, as described above, except for methane
oxidation on oxygen, which is not within the lowest two distances for that OEU (see
‘Discussion’ section).
Linking taxonomic marker sequences with a functional gene. Data for 16S rRNA
gene fusion products with both selective (dsrB) and non-selective (barcode)
sequences experiments was obtained from a previous analysis26. Briefly, 7 ml of water
from both the 2 m and 21 m samples on 12 August 2013 was added to 7 ml of 50%
glycerol (25% final concentration) to preserve membrane integrity for single-cell
techniques, then was immediately placed on dry ice and stored at −80 °C. 16S rRNA
gene sequences were fused to a 20-bp droplet barcode to control for effects of the
protocol on limiting diversity. In a separate reaction, 16S rRNA gene sequences were