Marine sponges can be classified as high microbial abundance (HMA) and low microbial abundance (LMA) species. In HMA sponges, the microbiome is more complex and densities might reach 1010 bacteria per gram of sponge wet weight, while in LMA this concentration is similar to natural seawater. Using 16S rRNA gene metabarcoding, the present study investigates the HMA-LMA status and microbial community assembly processes of eight species of sponges from the southeastern coast of Brazil (Sao Paulo state). It was expected that the microbial community structure of these species would be dominated by distinct phyla from those described in the literature and the microbiomes assembled by deterministic processes, without core members across all HMA and LMA sponges. The sequencing captured the majority of the diversity of all samples and the Bray-Curtis dissimilarity index showed three distinct groups: (i) Aplysina species and Cinachyrella alloclada, (ii) all other five species and seawater and (iii) sediments. The diversity of the HMA microbiomes were 0.98 x-1.30 x higher than in LMA, while the LMA microbiomes were 1.45 x-1.66 x richer than its counterpart. The assembly of both microbial communities was strongly driven by deterministic processes and none of the ASVs was identified as habitat generalists. This demonstrates that the enriched microbial groups associated with these southwestern Atlantic sponges is distinct from those detected so far elsewhere, and that the current paradigms and assumptions for HMA and LMA sponges might not be universal.