The change occurs below 17.5 cm where low quantities of extractable DNA and RNA, and significantly lower bacterial diversity and richness indicate low microbial biomass (Fig. 3, Supplementary TTaybpliec aSl2s,uFlpigh.a Ste1r)e. dAudciencgretaasxea,insuTchAaasnHdaNloHde4s+ual...