Microbial community compositions were determined for three soil horizons and drain sediments within an anthropogenically disturbed coastal acid sulfate landscape using 16S rRNA gene tagged 454 pyrosequencing. Diversity analyses were problematic due to the high microbiological heterogeneity between each geochemical replicate. Taxonomic analyses combined with measurements of metal(loid) bioaccessibility identified significant correlations to genera (5% phylogenetic distance) abundances. A number of positive correlations between genera abundance and bioaccessible metals concentrations were observed, indicating that metal(loid) tolerance influences microbial community compositions in these types of landscapes. Of note, Mn was highly bioaccessible (≤24% total soil Mn); and Mn bioaccessibility positively correlated to Acidobacterium abundance, but negatively correlated to Holophaga abundance. Two unidentified archaeal genera belonging to Crenarchaeota were also correlated to bioaccessible Mn concentrations, suggesting these genera can exploit Mn redox chemistry.