Diversity of toxin-producing benthic cyanobacterial proliferations from the Gulf Coast of Florida (USA)

Overgrowth of benthic cyanobacterial mats (BCMs) is prevalent in marine environments, partly driven by nutrient loading and climate change. Reports of BCMs occurring on both Florida coasts have increased, demonstrating a need to understand the diversity involved in the blooms and potential toxicity of the BCMs. As an initial survey on this environmental health threat, benthic proliferations were sampled on the Florida Gulf Coast in summer 2021. Cyanobacterial mats were collected, DNA was extracted, and the 16S rRNA of both bacteria and cyanobacteria were amplified using respective specific primers. The homocytous filamentous Dapis, Okeania, Planktothricoides, Salileptolyngbya, and Sirenicapillaria dominated BCMs. Additionally, the most abundant bacterial orders included Chitinophagales, Cytophagales, Flavobacteriales, and Rhodobacterales. LC-MS/MS analyses detected high concentrations of anatoxin-a, dihydroanatoxin-a and BMAA and low concentrations of cylindrospermopsin, within both the water column and mat material. Large benthic marine mats are often reported in Florida from Sarasota Bay to Charlotte Harbor and we observed similar microbial communities and toxicity among proliferations. Results from this study indicate a need to further assess the spatial and temporal aspects of these blooms, in addition to their community structure, influencing factors and the production of toxic compounds.