Cyanobacteria and their secondary metabolites in three freshwater reservoirs in the United Kingdom

Daria Filatova,Martin R Jones,Marinella Farré,Elisabeth M.-L Janssen,John A Haley,Oscar Núñez

doi:10.1186/s12302-021-00472-4

Abstract

BackgroundBloom-forming cyanobacteria occur globally in aquatic environments. They produce diverse bioactive metabolites, some of which are known to be toxic. The most studied cyanobacterial toxins are microcystins, anatoxin, and cylindrospermopsin, yet more than 2000 bioactive metabolites have been identified to date. Data on the occurrence of cyanopeptides other than microcystins in surface waters are sparse.ResultsWe used a high-performance liquid chromatography–high-resolution tandem mass spectrometry/tandem mass spectrometry (HPLC–HRMS/MS) method to analyse cyanotoxin and cyanopeptide profiles in raw drinking water collected from three freshwater reservoirs in the United Kingdom. A total of 8 cyanopeptides were identified and quantified using reference standards. A further 20 cyanopeptides were identified based on a suspect-screening procedure, with class-equivalent quantification. Samples from Ingbirchworth reservoir showed the highest total cyanopeptide concentrations, reaching 5.8, 61, and 0.8 µg/L in August, September, and October, respectively. Several classes of cyanopeptides were identified with anabaenopeptins, cyanopeptolins, and microcystins dominating in September with 37%, 36%, and 26%, respectively. Samples from Tophill Low reservoir reached 2.4 µg/L in September, but remained below 0.2 µg/L in other months. Samples from Embsay reservoir did not exceed 0.1 µg/L. At Ingbirchworth and Tophill Low, the maximum chlorophyll-a concentrations of 37 µg/L and 22 µg/L, respectively, and cyanobacterial count of 6 × 104 cells/mL were observed at, or a few days after, peak cyanopeptide concentrations. These values exceed the World Health Organization’s guideline levels for relatively low probability of adverse health effects, which are defined as 10 µg/L chlorophyll-a and 2 × 104 cells/mL.ConclusionsThis data is the first to present concentrations of anabaenopeptins, cyanopeptolins, aeruginosins, and microginins, along with microcystins, in U.K. reservoirs. A better understanding of those cyanopeptides that are abundant in drinking water reservoirs can inform future monitoring and studies on abatement efficiency during water treatment.

Highlights

Bloom-forming cyanobacteria occur globally in aquatic environments
The World Health Organization (WHO) has set a guideline threshold value of 2 × 104 cyanobacterial cells/mL for recreational waters that would pose a relatively low probability of adverse health effects, which may correspond to a concentration of 20 μg/L microcystins for a Microcystis bloom [4]
To the best of our knowledge, this is the first time that anabaenopeptins, cyanopeptolins, aeruginosins, and microginins have been quantified in U.K. waters along with microcystins and anatoxin-a

Summary

Introduction

Bloom-forming cyanobacteria occur globally in aquatic environments They produce diverse bioactive metabolites, some of which are known to be toxic. The most studied cyanobacterial toxins are microcystins, anatoxin, and cylindrospermopsin, yet more than 2000 bioactive metabolites have been identified to date. Filatova et al Environ Sci Eur (2021) 33:29 absorbing across a wide light spectrum), buoyancy, nitrogen fixation, production of dormant cells, and formation of colonies or filaments [2] These advantages allow cyanobacteria to form high-density communities termed, blooms [3]. One major issue associated with bloom-forming cyanobacteria is the production of bioactive secondary metabolites, some of which are identified as toxins These cyanotoxins include microcystins, cylindrospermopsin, anatoxins, and saxitoxins. Anatoxin-a has been detected in several lakes in Ireland reaching a maximum of 112 μg/L [20]

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Results

Conclusion