Fig. 3

Effect of juvenile water treatment on relative abundance of bacterial phyla. We analyzed the bacterial community of the gut a and skin b of juveniles, as well as that of the gut of adults c. Water treatments include pond water (PW), sterile pond water only (SPW), sterile pond water and short-term antibiotics (STAB), or sterile pond water and long-term antibiotics (LTAB). For juvenile guts a, mean relative abundance of phylum Proteobacteria was three times higher for individuals from sterile pond water only (GLM, χ ² = 25.09, df = 3, P < 0.0001), Firmicutes was three times higher for individuals from pond water and short-term antibiotics (χ ² = 13.92, df = 3, P = 0.003), and Chloroflexi was higher for individuals from pond water (χ ² = 25.11, df = 3, P < 0.0001) compared to individuals from the other treatments. For juvenile skin b, relative abundance of phylum Actinobacteria was 20 times higher for individuals from long-term antibiotic water compared to the other three treatments (χ ² = 70.42, df = 3, P < 0.0001) and Bacteroidetes was three times higher for individuals from pond water compared to individuals from long-term antibiotic water (χ ² = 11.89, df = 3, P = 0.008). For adult guts, relative abundance of phylum Actinobacteria was five times higher for adults reared in sterile pond water compared to adults reared in long-term antibiotic water (GLMM, χ ² = 10.05, df = 3, P = 0.02), Spirochaetes was generally higher in adults reared in pond water but was only significantly higher compared to adults reared in short- and long-term antibiotic water (χ ² = 14.39, df = 3, P = 0.002), and Cyanobacteria was lower for adults reared in long-term antibiotic water compared to adults reared in pond water and short-term antibiotic water (χ ² = 12.23, df = 3, P = 0.007). Numbers above the bars are the number of replicates (tanks) per treatment