Advances in genomic sequencing technologies resulted in massive microbial diversity data (16S ribosomal gene sequences, rDNA) being generated in every possible environment.However, the majority of microorganisms have never been cultured, and therefore, nor cataloged. This poses a problem for molecular microbial ecologists because a large portion of the marker sequences can not be taxonomically resolved past the phylum taxon level.This tells very little about who or what these microorganisms are doing in relation to their environment. Our study describes an approach to assist in drawing ecological information from a sample when the taxon resolution is poor. We generated 16S rDNA libraries from a hypersaline marine sediment (coastal Sabkha) and saline mangrove soil in Abu Dhabi and then compared the compositional features to a database of 20,470 publicly available microbial community profiles (comprising the entire Earth Microbiome Project, EMP) that were annotated with terms from the Environmental Ontology (EnvO). An accurate taxonomic classification was not possible for 80% of the Sabkha operational taxonomic units (OTUs) beyond phylum level with widely used taxonomy classification tools, but habitat profiling performed on the community revealed strong links to bacterial assemblages of soil and marine origins. To capture the notion of generalist vs. specialist formally, we developed an algorithm to derive empirical probability distributions of OTUs over ecosystems from observed occurrences in the sample database, which then give rise to OTU-specific ecosystem entropies. We observed very low average ecosystem entropy of the Sabkha in contrast to other environmental samples. Based on this concept, the Sabkha community, while of midrange alpha diversity, presented largely specialist characteristics, with most OTUs identified to be unique to the Sabkha habitat. This finding is further corroborated by the observation that the Sabkha sample is unique with respect to the EMP-derived dataset (which contains 74 hypersaline and thousands of marine samples), as PeerJ Preprints | https://doi.org/10.7287/peerj.preprints.3286v1 | CC BY 4.0 Open Access | recABSTRACT 15 Advances in genomic sequencing technologies resulted in massive microbial diversity data (16S ribosomal gene sequences, rDNA) being generated for samples from wide-ranging environments. However, the majority of microorganisms have never been cultured, and therefore, are not reflected in current public databases. This poses a problem for molecular microbial ecologists because a large portion of the marker sequences can not be taxonomically resolved past the phylum taxon level. This tells very little about who or what these microorganisms are doing in relation to their environment. Our study describes an approach to assist in drawing ecological information from a sample even when the taxon resolution is poor. We generated 16S rDNA libraries from a hypersaline marine sediment (coastal sabkha) and a moderately hypersaline mangrove soil in Abu Dhabi. Intuitively, our ...