Tracking Extensive Portfolio of Cyanotoxins in Five-Year Lake Survey and Identifying Indicator Metabolites of Cyanobacterial Taxa

Cyanobacterial blooms require monitoring, as they pose
a threat
to ecosystems and human health, especially by the release of toxins.
Along with widely reported microcystins, cyanobacteria coproduce other
bioactive metabolites; however, information about their dynamics in
surface waters is sparse. We investigated dynamics across full bloom
successions throughout a five-year lake monitoring campaign (Greifensee,
Switzerland) spanning 150 sampling dates. We conducted extensive suspect
screening of cyanobacterial metabolites using the database CyanoMetDB.
Across all 850 samples, 35 metabolites regularly co-occurred. Microcystins
were present in 70% of samples, with [d-Asp3,(E)-Dhb7]MC-RR reaching concentrations of 70 ng/L.
Anabaenopeptins, meanwhile, were detected in 95% of all samples with
concentrations of Oscillamide Y up to 100-fold higher than microcystins.
Based on LC-MS response and frequency, we identified indicator metabolites
exclusively produced by one of three cyanobacteria isolated from the
lake, these being [d-Asp3,(E)-Dhb7]MC-RR from Planktothrix sp. G2020, Microginin
761B from Microcystis sp. G2011, and Ferintoic acid
B from Microcystis sp. G2020. These indicators showed
distinct temporal trends and peaking seasons that reflect the variance
in either the abundance of the producing cyanobacteria or their toxin
production dynamics. Our approach demonstrates that selecting high
LC-MS response and frequent and species-specific indicator metabolites
can be advantageous for cyanobacterial monitoring.