Anatoxins in cyanobacterial mat field samples from Atlantic Canada by direct analysis in Real Time–High Resolution Tandem Mass Spectrometry

Toxic freshwater benthic cyanobacterial mats are increasingly linked to animal fatalities worldwide, often due to the production of high concentrations of anatoxins (ATXs). Considering the high spatial and temporal variability of mat occurrence and concentrations of ATXs, suitable analytical methods are required to enable large-scale field studies in these systems. Here, a rapid, direct analysis in real time–high resolution tandem mass spectrometry (DART–HRMS/MS) method for analysis of anatoxin-a, homoanatoxin-a, and dihydroanatoxin-a including a simple sample preparation procedure and isotope dilution calibration, is investigated to address this challenge. The developed method was applied to three sets of cyanobacterial mat samples collected in Atlantic Canada in the summers of 2018-2020. Samples from all sets showed positive detection of ATXs ranging from <100 ng mL^-1 to > 70,000 ng mL^-1 in mat lysates. One large mat sample collected from the Wolastoq (Saint John River) in New Brunswick, Canada, was used to demonstrate the application of DART–HRMS/MS to study the intra-mat variability of ATXs. This initial work showed the method could be successfully used for the analysis of ATXs in field samples, which will be useful in ongoing studies of this emerging issue in Atlantic
Canada and beyond.