Environmental associations of CB and SB/SW vOTUs, respectively. For the CB ( B ) and SB/SW ( D ) vOTUs that clustered (i.e., shared VCs/genera) with viruses from environmental metagenomes, the distribution of environmental habitats was evaluated and illustrated by a heatmap. The gradient colors in the heatmap represent the percentage of vOTUs (weighted by the associated vOTUs) that were associated with the different ecosystems. Each cell in the last column (i.e., labeled as Total) indicates the total percentage of vOTUs detected from each of the tested environments on the right-side legend, while each cell in the other columns (i.e., the 12 columns in the left rectangle) indicates the percentage of vOTUs that were detected from both of the two environments suggested at the top- and right-side legend of the heatmap. For example, the cells associated with both Arctic and Deep ocean water showed that 1020% ( B ) and 510% ( D ) of the 52 CB and 2628 SB/SW vOTUs, respectively, were detected from both of the Arctic and Deep ocean water environments. Most of the CB and SB/SW viruses were associated with seawater viruses from the Arctic
