Exploring benthic cyanobacterial diversity and co-occurring potentially harmful dinoflagellates in six islands of the South Pacific

Cyanobacteria represent a potential risk to human health, as they can produce an array of toxic compounds. Proliferations of potentially toxic benthic marine cyanobacteria are predicted to increase in frequency and spread geographically with climate change and eutrophication, especially in tropical lagoons. Benthic cyanobacterial mats harbour many species of other bacteria and eukaryotic organisms, some of which have been linked to human poisonings after consumption of contaminated seafood. Metabarcoding was used to characterize the taxonomic diversity of 66 benthic cyanobacteria-dominated mats collected from six islands in three different countries of the South Pacific: French Polynesia, the Cook Islands and Kingdom of Tonga. Twenty-five potentially toxic cyanobacteria genera were recorded. Although core bacterial communities (excluding cyanobacteria) remained constant amongst mats, there were significant differences both within and between islands, even when the mats were dominated by the same cyanobacteria genera. Dinoflagellata and Ciliophora were the most dominant eukaryotes and seven potentially toxic genera of dinoflagellates co-occurred in the mats. This is the first baseline survey to use metabarcoding to demonstrate the co-occurrence of potentially toxic marine cyanobacteria and dinoflagellates in the Pacific. The results highlight that further research is needed to evaluate the toxicity of the mats in these regions.

Automated summary

The study used metabarcoding to characterize the taxonomic diversity of benthic marine cyanobacteria-dominated mats in the South Pacific. It found multiple potentially toxic cyanobacteria genera in these mats, with consistent core bacterial communities but significant differences between mats from different islands. The results emphasize the need for further research on the toxicity of these mats in the region.