Additional file 1:Figure S1. Alpha-diversity of the digestive microbiota of abalone, as described by the Shannon (left panels) and Simpson (right panels) indices. Figure S2. Fluctuations of the digestive microbiota between consecutive dates over 1 year. Figure S3. Relative abundance and taxonomical composition of the digestive microbiota at the phylum level for abalone fed on Palmaria palmata (A), Laminaria digitata (B), Ulva lactuca (C), and Saccharina latissima (D). Figure S4. Ecological patterns of the digestive microbiota explained by a model of contextual parameters. Figure S5. Experimental site and set up. Figure S6. In situ sampling procedure of abalone for each algal treatment. Figure S7. Experimental procedure for DNA extraction and library preparation for studying the abalone digestive microbiota. (DOCX 1944 kb) Additional file 2:Table S1. Wilcoxon test to compare Shannon or Simpson indices between algal diets for the whole data set or between sampling dates or seasons for each algal diet (multiple comparisons were corrected using FDR). (XLSX 22 kb) Additional file 3:Table S2. R value of the ANOSIM calculated for the whole dataset and for each algal diet dataset separately between sample groups according to season, sampling date, or algal diet. Numbers in bold indicate the significance of the comparison after Bonferroni correction. (XLSX 15 kb) Additional file 4:Table S3. Number of annotated genes for each glycoside hydrolase, polysaccharide lyase, and sulfatase family in all Vibrio, Mycoplasma, Polaribacter, Roseobacter, and Psychromonas genomes available at http://www.cazy.org/ and/or at http://abims.sb-roscoff.fr/sulfatlas/ on 19 May 2017 and in Zobellia galactanivorans DsijT (Barbeyron et al. 2017). GH, Glycoside hydrolases; PL, Polysaccharide lyases, CAZyme, Carbohydrate active enzyme. Sulfatase gene counts are indicated when available in the SulfAtlas database. (XLSX 160 kb) Additional file 5:Table S4. Genes belonging to families of glycoside hydrolases, polysaccharide lyases, or sulfatases and genes putatively involved in the pyruvate fermentation to acetate pathway in the genomes of Psychrilyobacter atlanticus DSM19335 (A), Vibrio halioticoli NBRC 102217 (B), and Mycoplasma mobile 163 K (C), when present. Annotations include gene identifiers (locus tags), closest characterized homologs with their UniProtKB ID number when available, EC numbers, and information on their functioning. The percentage of amino-acid sequence identity is indicated in parentheses. (XLSX 66 kb) Additional file 6:Table S5. Measures of abalone characteristics and algal composition from April 2012 to January 2013. See supplementary text for details. GDG, gonado-digestive gland; DG, digestive gland. (XLSX 33 kb) Additional file 7:Table S6. Fasta sequences of the pyruvate to acetate formation pathways, I, II, and IV, commonly found in Bacteria according to MetaCyc (https://metacyc.org/META/NEW-IMAGE?object=Super-Pathways&detail-level=3). (DOCX 61 kb) Additional file 8:Supplementary text. Supplementary information on methods used and results analysed for the study. (DOCX 43 kb)