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

Abstract

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

Predation, community asynchrony, and metacommunity stability in cyanobacterial mats

“…1b), conspicuous benthic consortia primarily comprised of members of the phyla Cyanobacteria, Proteobacteria, and Bacteroidetes, with a distinct lack of a robust eukaryotic phototrophic assemblage (i.e. minimal relative abundance of diatoms and multicellular microbial algae; Cissell & McCoy 2021, Cissell & McCoy in review; though see Biessy et al 2021). Composition among mats at a local scale (e.g.…”

“…within reef site beta diversity) displays remarkably minimal heterogeneity (Cissell & McCoy in review). At higher taxonomic rankings, mat composition is also seemingly well-conserved across broader geographic ranges (Biessy et al 2021), though biogeographic differences in the composition of the dominant cyanobacterial taxa in benthic mats have previously been proposed, mediated via local environmental context (Charpy et al 2012b, Echenique-Subiabre et al 2015). The taxonomic complexity of mats is complemented by a rich functional complexity encompassing both oxic and anoxic metabolisms, with ecophysiological and/or molecular evidence supporting mat contributions to the cycling of carbon, nitrogen, sulfur, and phosphorous on reefs (Charpy et al 2007, 2010, Brocke et al 2015b, 2018, den Haan et al 2016, Cissell and McCoy 2021).…”

“…Benthic cyanobacterial mats are dramatically increasing in abundance on coral reefs across the globe owing to the influence of both local and global stressors (reviewed in Ford et al 2018). Coral reef cyanobacterial mats are complex microbial consortia, composed primarily of diverse bacteria, archaea, microbial eukaryotes, and viruses (Cissell and McCoy 2021, Biessy et al 2021). Similar to typical microbial mat systems (Bolhuis et al 2014), cyanobacterial mats are strongly cooperative communities, reliant upon metabolic handoffs and physiological synchronicity for persistence (Cissell & McCoy in review).…”

Preferential consumption of benthic cyanobacterial mats by Caribbean parrotfishes

“…Conflicting evidence of BCM consumption may reflect geographic differences in the composition of these mat communities or the production of secondary metabolites within them. Few studies have investigated the taxonomic composition of BCMs (but see Biessy et al 2021; Cissell and McCoy 2021), and much of the research surrounding the chemical defenses of BCMs has focused on secondary metabolites isolated from a few mat-forming species (e.g., Lyngbya spp. ; Thacker et al 1997; Nagle and Paul 1999).…”

“…Few studies have investigated the taxonomic composition of BCMs (but see Biessy et al 2021;Cissell and McCoy 2021), and much of the research surrounding the chemical defenses of BCMs has focused on secondary metabolites isolated from a few mat-forming species (e.g., Lyngbya spp. ; Thacker et al 1997;Nagle and Paul 1999).…”