Tracking a broad inventory of cyanotoxins and related secondary metabolites using UHPLC-HRMS

Abstract

Rising temperatures caused by global warming and elevated nutrient influx promote the growth of harmful cyanobacteria in freshwater ecosystems affecting human and environmental health. In this work, UHPLC-HRMS was used to simultaneously determine 7 common microcystins and 18 additional cyanobacterial metabolites in natural freshwater samples. Therefore, the particulate material of the water from Lake Stechlin in northern Brandenburg (Germany) was collected, extracted, and analyzed. The chromatographic method for the separation of cyanotoxins was optimized to enable the quantification of common toxins. By investigating additional cyanotoxins for which standards are unavailable, two more microcystins, three cyanopeptolins, five anabaenopeptins, one aeruginosin, and three additional secondary metabolites could be identified. In addition to these molecules, five unknown metabolites were detected and could be linked to Planktothrix rubescens, a native species in Lake Stechlin. Applying the proposed method yielded insights on cyanotoxin prevalence in northern German lowland Lake Stechlin and will enable further studies to elucidate additional coherences. Furthermore, by correlating additional biological, hydrodynamic, and ecological data with information on the distribution and productivity of cyanobacteria, the proposed method with the expanded toxin inventory can provide important information in risk assessment about the quality and toxicity of the ecosystem in and around the water.