Characterization of in situ microbial community structure by non-metric multidimensional scaling (NMDS) in (a) control plots, (b) +2.25 °C plots, (c) +4.5 °C plots, (d) +6.75 °C plots and (e) +9 °C plots. Symbols represent averages of two samples collected from each plot/depth within each temperature treatment plot from pre-DPH (2014, closed symbols) and 13 months post-initiation of the DPH (2015, open symbols) experiment. Error bars represent 1 s.d. of replicate results. Circles represent results from the control (0°C) plots, squares represent results from the +2.25°C plots, diamonds represent results from the +4.5°C plots, triangles represent results from the +6.75°C plots, and inverted triangles represent results from the +9°C plots. Final sequence data were normalized by cumulative sum scaling (CSS) and beta diversity indices were estimated based on Bray–Curtis and weighted as well as unweighted Unifrac distances. Significant differences in beta diversity were analysed by a PERMANOVA test on weighted Unifrac distance metrics with 1,000 permutations followed by Bonferroni correction of P-values.