Figure 4

Impact of acidification on the association between the sponge Hemimycale columella and calcibacteria. The bar plot (a) reports the number of bacterial cells per gram of sponge dry weight, as determined by CARD-FISH on calcibacteria extracted from fresh H. columella sponge tissues. Average values and standard deviations are shown for samples collected at the end of the experiment (86 d) from acidified and non-acidified mesocosms containing low-biodiversity assemblages (i.e., only 6 families), or high-biodiversity assemblages (i.e., 11 families). The epifluorescence microscopy images show sections of the corresponding samples of H. columella sponge tissues from which calcibacteria were extracted, analyzed in parallel by CARD-FISH. (b), control (low-biodiversity, 6 families); (c), control (high-biodiversity, 11 families); (d), Acidified (low-biodiversity, 6 families); E, acidified (high-biodiversity, 11 families). Scale bar: 40 µm. Greek letters are used to highlight the significant differences (p < 0.01) among the reported values, with α > β > γ.