Fig. 4

Microbial proportions and community structure. a Depth profiles of the microbial community (Eukaryota, Bacteria, and Archaea) presented as relative proportions to each other, which was determined by relative pyrosequencing reads per microbial fraction. b NMDS ordination of the vertical sediment microbial community structure. The clusters from Fig. 1 are presented as standard deviation around the group centroid. The color scale of the dots represents sediment depth. Community composition was highly correlated with sediment depths (on axis 1; Mantel correlation: r=0.735,p<0.001). The three distinct clusters at different depths were significantly different (adonis, p=0.0005) with a reduced variance in cluster c (Tukey’s honest significant differences between groups, p<0.01). The principal components of “past” and “present” environmental parameters were correlated with the community matrix (Mantel correlation: “present” r=0.527,p<0.001 and “past” r=0.459,p<0.001) and with the ordination (envfit: “present” R ²=0.658,p<0.001 and “past” R ²=0.547,p<0.001)