Remediation Strategies to Control Toxic Cyanobacterial Blooms: Effects of Macrophyte Aqueous Extracts on Microcystis aeruginosa (Growth, Toxin Production and Oxidative Stress Response) and on Bacterial Ectoenzymatic Activities.

Increasing toxic cyanobacterial blooms in freshwater demand environmentally friendly solutions to control their growth and toxicity, especially in arid countries, where most drinking water is produced from surface reservoirs. We tested the effects of macrophyte allelochemicals on Microcystis aeruginosa and on the fundamental role of bacteria in nutrient recycling. The effects of Ranunculus aquatilis aqueous extract, the most bioactive of four Moroccan macrophyte extracts, were tested in batch systems on M. aeruginosa growth, toxin production and oxidative stress response and on the ectoenzymatic activity associated with the bacterial community. M. aeruginosa density was reduced by 82.18%, and a significant increase in oxidative stress markers was evidenced in cyanobacterial cells. Microcystin concentration significantly decreased, and they were detected only intracellularly, an important aspect in managing toxic blooms. R. aquatilis extract had no negative effects on associated bacteria. These results confirm a promising use of macrophyte extracts, but they cannot be generalized. The use of the extract on other toxic strains, such as Planktothrix rubescens, Raphidiopsis raciborskii and Chrysosporum ovalisporum, caused a reduction in growth rate but not in cyanotoxin content, increasing toxicity. The need to assess species-specific cyanobacteria responses to verify the efficacy and safety of the extracts for human health and the environment is highlighted.

An ultra performance liquid chromatography coupled with high resolution mass spectrometry method for the screening of cianotoxins content in drinking water samples.

The incidence of cyanobacterial harmful algal blooms (CHABs) and their potentially toxic secondary metabolites is increasing in Italy and worldwide and several studies demonstrated that the climate change may be playing a role. The method described in this work allows to detect simultaneously 21 cyanotoxins of different classes (including 12 Microcystins, 5 Microginins, 2 Cyanopeptolins, and 2 Anabaenopeptins) in water samples for human consumption by an Ultra Performance Liquid Chromatography coupled with a Q-TOF mass spectrometer. Water samples were freezed, filtered, spiked with Nodularin used as internal standard (I.S.) and then extracted with a SPE Carboghaph 4 cartridge. The extracted sample were analysed injecting 10 µL into the UPLC-HRMS/MS system: the chromatographic separation was obtained using acetonitrile and water as mobile phases, both containing 10 mM formic acid, and a UPLC C18 column, acquiring the experiments in positive ionization and Sensitivity Mode. The described method allows to separate and detect all the selected analytes in short time of analysis (16 minutes) with a good resolution for all the analytes.•simultaneous determination of 21 cyanotoxins belonging to different classes in water sample•low injection volume•short time of analysis.

Multi-residue Ultra Performance Liquid Chromatography-High resolution mass spectrometric method for the analysis of 21 cyanotoxins in surface water for human consumption.

The presence of cyanobacteria and their toxins in water used as drinking water or for recreational purposes may represent a risk for human health. This work describes the development of an advanced analytical method for simultaneous determination of 21 cyanotoxins (including Microcystins, Cyanopeptolins, Anabaenopeptins and Microginins) in drinking water based on Ultra Performance Liquid Chromatography coupled with a Q-TOF mass spectrometer. Water samples, spiked with Nodularin as internal standard at 1 µg/L, were extracted using Carbograph 4 SPE cartridge and 10 µL of the extracted sample were injected into the UPLC-HRMS/MS system. Analytes separation was obtained using a UPLC C18 column, acetonitrile and water as mobile phases, both containing 10 mM formic acid, and operating in positive ionization mode and sensitivity mode. The method has been proven to be robust, precise and accurate with recovery percentages above 85% and with relative standard deviations ≤16% and LODs between 0.002 and 0.047 µg/L, fitting for the intended purposes at the concentrations of interest. This method was applied during a monitoring activity in an Italian volcanic lake in Viterbo (Lazio Region, Italy), due to a severe algal proliferation in January 2018-March 2019 period and for the assessment of cyanobacteria proliferation risk and of cyanotoxin production in drinking water chain.

Management of a toxic cyanobacterium bloom (Planktothrix rubescens) affecting an Italian drinking water basin: a case study.

An extraordinary bloom of Planktothrix rubescens, which can produce microcystins (MCs), was observed in early 2009 in the Occhito basin, used even as a source of drinking water in Southern Italy. Several activities, coordinated by a task force, were implemented to assess and manage the risk associated to drinking water contaminated by cyanobacteria. Main actions were: evaluation of analytical protocols for screening and confirmatory purpose, monitoring the drinking water supply chain, training of operators, a dedicated web site for risk communication. ELISA assay was considered suitable for health authorities as screening method for MCs and to optimize frequency of sampling according to alert levels, and as internal control for the water supplier. A liquid chromatography-tandem mass spectrometric method able to quantify 9 MCs was optimized with the aim of supporting health authorities in a comprehensive risk evaluation based on the relative toxicity of different congeners. Short, medium, and long-term corrective actions were implemented to mitigate the health risk. Preoxidation with chlorine dioxide followed by flocculation and settling have been shown to be effective in removing MCs in the water treatment plant. Over two years, despite the high levels of cyanobacteria (up to 160 × 10(6) cells/L) and MCs (28.4 µg/L) initially reached in surface waters, the drinking water distribution was never limited.