Phylogenetic diversity of cyanobacteria from Qatar coastal waters

A major consequence of the sustained degradation of the coastal environment is the progressive eutrophication, which makes Harmful Algal Blooms (e.g. cyanobacteria) more likely to happen and with potential production of cyanotoxins which may create health hazards. Qatar concerns have been rising following the observations of blooms in the last years. Identifying relevant cyanobacteria species that grow in the extreme environment of Qatar would help in keeping records of their diversity as well as finding the strains that have several positive biotechnological applications or negative effects such as harmful algal blooms (HABs) where environmental mitigation and/or adaptation measures are needed. We aimed in this work to better understand the diversity of the cyanobacterial natural communities found in Qatari marine environment through a genotypic characterization (phylogenetic analysis) with the objectives to a) assess the local diversity, and b) provide consistent reference for future comparative analysis, biotechnological applications, and monitoring. In this study, Qatar University Culture Collection of Cyanobacteria and Microalgae (QUCCCM) strains collected from Qatar’s coastal regions were used to amplify fragments of the 16S rRNA gene followed by phylogenetic analysis. The obtained phylogenetic trees helped in branching the isolates by computing the differences (distances) among the isolates and compared them to known (published) cyanobacteria. This allowed the accurate identification and detection of the relevant Qatari cyanobacteria diversity and evolutionary relationship. Qatari marine cyanobacteria populations showed a high species richness. Indeed, we identified 28 taxa among them Geitlerinema sp., Euhalothece sp., and Geminocystis sp. have never been reported from Qatari waters. Additionally several isolates are potentially newly identified strains with low relationship to known cyanobacteria species. We were able to distinguish between populations in geographically separate regions along the Qatari coasts identifying where potentially toxic cyanobacteria may occur. Within the identified 28 species, we conducted a bibliographic analysis about their potential toxicity or toxin production. Eighteen strains are belonging to potentially toxic marine cyanobacteria. A regular monitoring of the occurrence and potential toxicity of the cyanobacteria in the coastal zone is recommended to timely identify potential environmental and human health hazards. Indeed, six isolates belonged to the potentially toxic marine cyanobacteria Geitlerinema sp., producer of a cytotoxic response to human lung tumor cells and other six isolates belonged to the marine cyanobacteria Chroococcidiopsis sp. and are known to produce a neurotoxic amino acid.