Heat-map showing abundance (rDNA-based survey) and relative activity (rRNA/rDNA ratio) of the 100 most abundant OTUs (representing more than 92% of all the reads) detected between 2013 and 2015.

Positive versus negative ratios can be used as an indication of relative cell activity. Negative rRNA:rDNA ratio indicates low cell activity, in contrast to positive ratio which corresponds to higher cells activity (for example, a ratio of -40 corresponds to an OTU having 40-time more rDNA reads than rRNA reads).