A new paper by Spoof et al. in Environmental Science and Pollution Research reports a series of experiments where lysis of cyanobacteria in abstracted lake water was induced by the use of hydrogen peroxide.
From the abstract:
This paper reports a series of experiments where lysis of cyanobacteria in abstracted lake water was induced by the use of hydrogen peroxide and the fate of released MCs was followed. The hydrogen peroxide–treated water was then used for spray irrigation of cultivated spinach and possible toxin accumulation in the plants was monitored. The water abstracted from Lake Köyliönjärvi, SW Finland, contained fairly low concentrations of intracellular MC prior to the hydrogen peroxide treatment (0.04 μgL −1 in July to 2.4 μgL −1 in September 2014). Hydrogen peroxide at sufficient doses was able to lyse cyanobacteria efficiently but released MCs were still present even after the application of the highest hydrogen peroxide dose of 20 mg L−1. No traces of MC were detected in the spinach leaves. The viability of moving phytoplankton and zooplankton was also monitored after the application of hydrogen peroxide. Hydrogen peroxide at 10 mg L−1 or higher had a detrimental effect on the moving phytoplankton and zooplankton.
The paper acknowledges CYANOCOST.
Spoof, L., Jaakkola, S., Važić, T. Važić, T., Häggqvist, K., Kirkkala, T., Ventelä, A-M., Kirkkala, T., Svirčev, Z., Meriluoto, J. Elimination of cyanobacteria and microcystins in irrigation water—effects of hydrogen peroxide treatment. Environ Sci Pollut Res (2020). https://doi.org/10.1007/s11356-019-07476-x
Abstract of a new paper by Major et al., published in Environmental Science and Pollution Research:
“The composition and abundance of cyanobacteria and their toxins, microcystins (MCs), and cylindrospermopsins (CYN) were investigated using samples collected at monthly intervals from the Amudde side of Koka Reservoir from May 2013 to April 2014. Cyanobacteria were the most abundant and persistent phytoplankton taxa with Microcystis and Cylindrospermopsis species alternately dominating the phytoplankton community of the reservoir and accounting for up to 84.3 and 11.9% of total cyanobacterial abundance, respectively. Analyses of cyanotoxins in filtered samples by HPLC-DAD and LC-MS/MS identified and quantified five variants of MCs (MC-LR, MC-YR, MC-RR, MC-dmLR, and MC-LA) in all samples, with their total concentrations ranging from 1.86 to 28.3 μg L−1 and from 1.71 to 33 μg L−1, respectively. Despite the presence and occasional abundance of Cylindrospermopsis sp., cylindrospermopsin was not detected. Redundancy analysis (RDA) showed that the environmental variables explained 82.7% of the total variance in cyanobacterial abundance and microcystin concentration. The presence of considerably high levels of MCs almost throughout the year represents a serious threat to public health and life of domestic and wild animals”.
Environ Sci Pollut Res https://doi.org/10.1007/s11356-018-2727-2
From the abstract of a paper by Simiyu et al., published in Toxins:
The human health risks posed by exposure to cyanobacterial toxins such as microcystin (MC) through water and fish consumption remain poorly described. During the last two decades, coastal regions of Lake Victoria such as Nyanza Gulf (Kisumu Bay) have shown severe signs of eutrophication with blooms formed by Microcystis producing MC. In this study, the spatial variability in MC concentration in Kisumu Bay was investigated which was mostly caused by Microcystis buoyancy and wind drifting. Small fish (<6 cm) mainly composed of Rastrineobola argentea were examined for MC content by means of biological methods such as ELISA and protein phosphatase inhibition assay (PPIA) and partly by chemical-analytical methods such as LC-MS/MS. Overall, the MC content in small fish was related to the MC content observed in the seston. When comparing the MC content in the seston in relation to dry weight with the MC content in small fish the latter was found three orders of magnitude decreased. On average, the ELISA-determined MC contents exceeded the PPIA-determined MC contents by a factor of 8.2 ± 0.5 (SE) while the MC contents as determined by LC-MS/MS were close to the detection limit. Using PPIA, the MC content varied from 25–109 (mean 62 ± 7) ng/g fish dry weight in Kisumu Bay vs. 14 ± 0.8 ng MC/g in the more open water of L. Victoria at Rusinga channel. Drying the fish under the sun showed little effect on MC content, although increased humidity might indirectly favor photocatalyzed MC degradation.
Benard Mucholwa Simiyu, Steve Omondi Oduor, Thomas Rohrlack , Lewis Sitoki and Rainer Kurmayer (2018).Microcystin Content in Phytoplankton and in Small Fish from Eutrophic Nyanza Gulf, Lake Victoria, Kenya. Toxins 10(7), 275. doi:10.3390/toxins10070275
The City of Salem, Oregon USA, has issued a drinking water advisory on May 29, related to the presence of cylindrospermopsin and microcystin in the water supplies. The cyanotoxins originate from the Detroit Reservoir that is used as source.
The advisory concerns infants, young children and other vulnerable individuals, stating that “children under the age of six, people with compromised immune systems, people receiving dialysis treatment, people with pre-existing liver conditions, pets, pregnant women or nursing mothers, or other sensitive populations should follow this advisory. At this time, people not on this list may continue to drink the water unless additional messaging is received.”
Updates of the advisory will follow on https://www.cityofsalem.net/ .
From the abstract of a recent paper by Greer et al. in Scientific Reports:
“To understand the uptake and processing of MC-LR in humans, the pig was chosen as an animal model. This was assessed by repeated exposure for 13 weeks of eight animals dosed daily with MC-LR at 0.04 µg/kg bw, repeated with six animals over five weeks at a dose 50 times higher at 2 µg/kg bw. An analytical method was developed for MC-LR in porcine serum and also to analyse levels of free MC-LR in harvested porcine tissues, with Lemieux Oxidation employed to determine bound MC-LR in these tissues. MC-LR was not detected in the serum of treated animals from either experiment but free MC-LR was observed in the large intestine and kidney from two animals from the higher dosed group at levels of 1.4 and 1.9 µg/kg dry weight (dw) respectively. The results indicated 50% of higher dosed animals accumulated bound MC-LR in liver tissue, averaging 26.4 µg, approximately 1.1% of the dose administered. These results point to the potential uptake and accumulation of MC-LR in human liver tissue exposed chronically to sub-acute doses.”
Brett Greer, Julie P. Meneely & Christopher T. Elliott (2018). Uptake and accumulation of Microcystin-LR based on exposure through drinking water: An animal model assessing the human health risk. Scietific Reports 8, 4913. DOI:10.1038/s41598-018-23312-7
From the abstract of a recent paper by Hercog et al. in Chemosphere:
“Increased eutrophication of water bodies promotes cyanobacterial blooming that is hazardous due to the production of various bioactive compounds. Microcystin-LR (MCLR) is among the most widespread cyanotoxins classified as possible human carcinogen, while cylindrospermopsin (CYN) has only recently been recognized as health concern. Both cyanotoxins are genotoxic; however, the mechanisms of their action differ. They are ubiquitously present in water environment and are often detected together. Therefore, we studied genotoxic potential of the binary mixture of these cyanotoxins. Human hepatoma cells (HepG2) were exposed to a single dose of MCLR (1 μg/mL), graded doses of CYN (0.01-0.5 μg/mL), and their combinations. Comet and Cytokinesis block micronucleus assays were used to detect induction of DNA strand breaks (sb) and genomic instability, respectively, along with the transcriptional analyses of the expression of selected genes involved in xenobiotic metabolism, immediate/early cell response and DNA-damage response. MCLR induced DNA sb that were only transiently present after 4 h exposure, whereas CYN, after 24 h exposure, induced DNA sb and genomic instability. The MCLR/CYN mixture induced DNA sb after 24 h exposure, but to lesser extent as CYN alone. On the other hand, induction of genomic instability by the MCLR/CYN mixture was comparable to that induced by CYN alone. In addition, patterns of changes in the expression of selected genes induced by the MCLR/CYN mixture were not significantly different from those induced by CYN alone. Our results indicate that CYN exerts higher genotoxic potential than MCLR and that genotoxic potential of the MCLR/CYN mixture is comparable to that of CYN alone.”
Klara Hercog, Sara Maisanaba, Metka Filipič, Ángeles Jos, Ana M. Cameán, Bojana Žegura (2017). Genotoxic potential of the binary mixture of cyanotoxins microcystin-LR and cylindrospermopsin, Chemosphere, Volume 189, Pages 319-329, https://doi.org/10.1016/j.chemosphere.2017.09.075.
The Steering Group (SG) of CYANOCOST has submitted comments to the European Commission about the inclusion of MC-LR in the proposed revision of the Drinking Water Directive (DWD). Based on the facts presented in this response the SG proposes the inclusion of all microcystins in the Drinking Water Guideline in the following manner: the reference to the parameter “microcystin-LR” in the proposed Drinking Water Directive should be replaced by “sum of all detected microcystin variants”. The parametric value should stay at 1.0 µg/l.
You can read the CYANOCOST comments in the EC webpage (download the file with feedback).
From the abstract of a new paper by Jungblut et. al (2018) published in European Journal of Phycology :
Microcystins (MCN), β-N-methylamino-L-alanine (BMAA) and anatoxin-a were investigated in Antarctic cyanobacterial mats collected from Ross Island and the McMurdo Ice Shelf, East Antarctica during Captain Scott’s ‘Discovery’ National Antarctic Expedition (1901–1904). Ultra-performance liquid chromatography-photodiode array detection (UPLC-PDA) and tandem mass spectrometry (MS/MS) analysis were used to quantify the cyanotoxins in seven cyanobacterial mat samples. MCNs were identified in six of the mat samples at concentrations from 0.5 to 16.1 µg g–1 dry weight. BMAA was found in one sample (528 ng g–1 dry weight, total BMAA), as well as two BMAA isomers, 2,4-diaminobutyric acid (DAB) and N-(2-aminoethyl) glycine (AEG) in six samples up to 6.56 and 6.79 μg g–1 dry weight, respectively. No anatoxin-a was detected. The findings confirm that MCNs, BMAA and BMAA isomers are preserved under dry herbarium conditions. The ‘Discovery’ cyanobacterial mat samples represent the oldest polar cyanobacterial samples found to contain cyanotoxins to date and provide new baseline data for cyanotoxins in Antarctic freshwater cyanobacterial mats from prior to human activity in Antarctica, the development of the ozone hole and current levels of climatic change.
Read the story by Katie Pavid in the Natural History Museum, UK website.
Highlights from a paper by Walls et al. (2017) in Science of the Total Environment:
– Toxin release from harmful cyanobacteria increases with warming.
– In-situ and laboratory studies showed elevated microcystin release between 20 and 25 °C.
– Elevated toxin release was coupled with a decline in cyanobacteria biomass.
– Water temperature could be used to forecast harmful algal bloom severity.
Jeremy T. Walls, Kevin H. Wyatt, Jason C. Doll, Eric M. Rubenstein, Allison R. Rober (2017).
“Hot and toxic: Temperature regulates microcystin release from cyanobacteria”, Science of The Total Environment 610–611, pp. 786-795. https://doi.org/10.1016/j.scitotenv.2017.08.149.
Abstract from the Myhre et al. (2018) paper in Scientific Reports:
“The cyanobacterial toxins β-methylamino-L-alanine (L-BMAA) and microcystin-LR (MC-LR; a potent liver toxin) are suspected to cause neurological disorders. Adult male C57BL/6JOlaHsd mice aged approximately 11 months were subcutaneously injected for five consecutive days with L-BMAA and microcystin-LR alone, or as a mixture. A dose-range study determined a tolerable daily dose to be ~31 µg MC-LR/kg BW/day based on survival, serum liver status enzymes, and relative liver and kidney weight. Mice tolerating the first one-two doses also tolerated the subsequent three-four doses indicating adaptation. The LD50 was 43–50 μg MC-LR/kg BW. Long-term effects (up to 10 weeks) on spatial learning and memory performance was investigated using a Barnes maze, were mice were given 30 µg MC-LR/kg BW and/or 30 mg L-BMAA/kg BW either alone or in mixture for five consecutive days. Anxiety, general locomotor activity, willingness to explore, hippocampal and peri-postrhinal cortex dependent memory was investigated after eight weeks using Open field combined with Novel location/Novel object recognition tests. Toxin exposed animals did not perform worse than controls, and MC-LR exposed animals performed somewhat better during the first Barnes maze re-test session. MC-LR exposed mice rapidly lost up to ~5% body weight, but regained weight from day eight.”
Oddvar Myhre, Dag Marcus Eide, Synne Kleiven, Hans Christian Utkilen & Tim Hofer (2018), Scientific Reports 8, Article number: 2308. doi:10.1038/s41598-018-20327-y