Abstract

The w ay str ong envir onmental gradients shape m ultispecific assemb la ges has allowed us to examine a suite of ecological and evo- lutionar y hypotheses a bout structur e, r egulation and comm unity r esponses to fluctuating envir onments. But whether the highl y di v erse co-occurring micr oorganisms ar e shaped in similar w ays as macr oscopic organisms acr oss the same gradients has yet to be addressed in most ecosystems. Here , w e c har acterize intertidal biofilm bacteria communities, comparing zonation at both the "species"and community levels, as well as network attributes, with co-occurring macroalgae and invertebrates in the same rocky shore system. The results revealed that the desiccation gradient has a more significant impact on smaller communities, while both desiccation and submersion gradients (surge) affect the larger, macroscopic communities. At the community level, we also confirmed the existence of distinct communities within each intertidal zone for microorganisms, similar to what has been previously described for macroorganisms. But our results indicated that dominant microbial organisms along the same environmental gradient exhibited less differ entiation acr oss tidal lev els than their macr oscopic counterparts. Howev er, despite the substantial differ ences in richness, size and attributes of co-occurrence networks, both macro- and micro-communities respond to stress gradients, leading to the for- mation of similar zonation patterns in the intertidal r ock y shor e.