Abstract
The frequency and intensity of cyanobacterial blooms continue to increase in freshwater systems across the globe. Cyanobacteria can release toxins and several bioactive secondary metabolites and analytical methods are needed to effectively assess their concentrations in surface waters. Since booms can evolve rapidly in parts of a lake, high resolution of spatial and temporal sampling increases the complexity of monitoring efforts. Here, we present the validation of an automated, online-solid phase extraction (SPE) high performance liquid chromatography (HPLC)-high resolution tandem mass spectrometry (HRMS/MS) method. This online-SPE HPLC-HRMS/MS methods enables quantitative monitoring of surface waters for 17 cyanobacterial peptides (cyanopeptides), spanning 5 distinct cyanopeptide classes, including: microcystins, anabaenopeptins, nodularins, cyclamides and cyanopeptolins. The method can quantify these cyanopeptides in the low ng/L-range with high accuracy (85-116%) and low relative matrix effects (<25%). We demonstrated its application to Swiss lake waters (Zürichsee, Hallwilersee, Greifensee), which also highlighted the value of adding cyanopeptides beyond common microcystins when monitoring surface waters for cyanobacteria.
Highlights
Cyanobacteria can produce toxins and compromise water quality, especially during dense bloom events.[1,2] With increasing nutrient input and changes in thermal and hydrological conditions, cyanobacterial blooms are becoming more frequent and intense, posing risks to human and animal health, and disrupting activities of socio-economic importance associated with affected water bodies.[3]
We evaluated the performance of an online-solid phase extraction (SPE)–high performance liquid chromatography (HPLC)-HRMS/MS method as a tool for monitoring multi-class cyanopeptides in lake waters, including 10 microcystins, 3 anabaenopeptins, 2 cyanopeptolins, aerucyclamide A and nodularin-R
Samples from 2019 in lake Hallwilersee are in agreement with previous data of anabaenopeptin A, anabaenopeptin B, oscillamide Y and [d-Asp3,(E)-Dhb7]MC-RR detected in concentrated biomass samples in 2002–2005.[4e]. Qualitatively, we identified the same cyanopeptides in the three lakes, which are known to be inhabited by the same cyanobacterium; Planktothrix rubescens.[4e,6b,26] The results obtained for Swiss lakes are in line with findings for other European lakes inhabited by Planktothrix rubescens where demethylated microcystin-RR variants were regularly identified.[27]
Summary
Cyanobacteria can produce toxins and compromise water quality, especially during dense bloom events.[1,2] With increasing nutrient input and changes in thermal and hydrological conditions, cyanobacterial blooms are becoming more frequent and intense, posing risks to human and animal health, and disrupting activities of socio-economic importance associated with affected water bodies.[3]. Swiss waters are affected by seasonal increases in cyanobacterial loads, including the peri-alpine lakes, lake Zürichsee, lake Greifensee and lake Hallwilersee.[4e,6] Stakeholders concerned with the use and management of water resources are prompted to develop strategic action plans to react to bloom events These strategies include monitoring of cyanobacterial cell counts and toxin concentrations in the water.[7]. Determination of methodological limits of detection and quantification (mLOD and mLOQ), accuracy, intra- and inter-day precision, matrix effects (in lake water), recovery and carryover, based on calibration curves ranging between ≈ 1-1000 ng/L. determination of methodological limits of detection and quantification (mLOD and mLOQ), accuracy, intra- and inter-day precision, matrix effects (in lake water), recovery and carryover, based on calibration curves ranging between ≈ 1-1000 ng/L We applied this method to quantify cyanopeptides directly in water samples collected from three Swiss lakes, with the results emphasizing the benefits of including additional cyanopeptides beyond known toxins for strategic monitoring and risk assessment of cyanobacteria
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