Community structure of the digestive microbiota of the abalone over 1 year. Samples were grouped a posteriori according to one of the four monospecific algal diets (a) or a sampling date (b). The Bray-Curtis dissimilarity index was calculated after Hellinger transformation of the metabarcoding data set at the OTU level. The low stress value of 18% validates the goodness-of-fit of the two-dimensional representation compared with the original matrix. Significance between groupings of samples according to algal diet, sampling date, or season was tested using ANOSIM (Additional file 3: Table S2)