Microbial community and network responses across strong environmental gradients: How do they compare to macroorganisms?. Microbial communities across strong environmental gradients in the intertidal rocky shore

The way strong environmental gradients shape multispecific assemblages has allowed us to examine a suite of ecological and evolutionary hypotheses about structure, regulation, and community responses to fluctuating environments. But whether the highly diverse co-occurring and free-living microorganisms are shaped in similar ways as macroscopic organisms across the same gradients has yet to be addressed in most ecosystems. Here we characterize the structure of intertidal biofilm communities and compare the intensity of zonation at the ‘species’ and community level and network attributes with those observed in co-occurring macroalgae and invertebrates. At the level of species and Amplicon Sequence Variants (ASVs), for dominant macro and microorganisms, respectively, our results partially support the idea that microbes are less affected by environmental variability, suggesting they perceive a more homogeneous environment and/or are more resistant to the associated stress. At the community-level, microbes and macroorganisms showed that the proportion of ‘habitat specialists’ and their positive co-occurrences in different tidal zones were remarkably similar, taxonomic richness and diversity followed similar trends, and network analyses showed similar connectivity and transitivity, suggesting that despite orders of magnitude differences in richness and size, these two systems respond similarly to stress gradients, giving rise to the same zonation patterns.