The most striking finding here is that the abalone digestive microbiota seems to be already established during the first year of life of the abalone and that seasonal variation, feed type, and quality only account for a small proportion of the variability of the microbiota. This is in agreement with the existence of a relatively stable digestive microbiota, inherent part of the holobiont. In the case of a healthy abalone holobiont, digestive gland conditions may control the composition of the microbiota, and in return, this microbiota may be adapted to seasonal variations. In addition, transient and rare algal epiphytic bacteria may remain in the niche, depending on their ability to assist in algal polysaccharide degradation. In the abalone holobiont, two non-exclusive scenarios may occur during digestion: (i) the dominant fermenters have acquired polysaccharide degrading genes by lateral gene transfer from aerobic epiphytic algal microbiota, and degrade and ferment algal polysaccharides themselves, (ii) the aerobic epiphytic algal microbiota cooperate with the dominant fermenters to transform algal polysaccharides to SCFA. To test these hypotheses and to elucidate further details on the functional plasticity of the dominant fermenters or the aerobic microbiota, we would need to investigate microbial genes associated with abalone digestion, using metagenomic tools or trying to isolate candidates and further analyze their genomes.