Health risks caused by freshwater cyanobacteria in recreational waters

Multiplatform optical monitoring of eutrophication in temporally and spatially variable lakes

Representative spatial patterns of eutrophication variables cannot be produced using traditional in situ sampling techniques. Spatial heterogeneity complicates the study of seasonal and long-term trends and the evaluation of water management policies. Remote sensing, however, with its broad view has the potential to deliver the relevant information. This paper will address the added value of synoptic eutrophication maps to the standard monitoring program of two large, spatially and temporally variable lakes in the Netherlands, Lakes IJssel and Marken. Remote sensing images were obtained from SeaWiFS; and combined with hyperspectral reflectance data from the airborne EPS-a sensor and the shipboard PR-650 spectroradiometer. The PR-650 data were used in selecting the most appropriate algorithms for SeaWiFS and EPS-a. A special algorithm for case II waters with high chlorophyll content was applied to SeaWiFS data to obtain chlorophyll concentrations. Synoptic maps of suspended matter were retrieved using inversion of a model for irradiance reflectance. For the airborne sensor inversion of reflectance was used for both suspended matter and chlorophyll. Satellite and airborne sensors clearly are complementary to each other. Comparison of satellite data with the airborne data and the (scarcely available) in situ data reveal underlying problems with: (i) validation of remote sensing images; and (ii) comparing data at different spatial and temporal scales. In our study, we found a reasonable agreement between different data sources at seasonal time scales, but at shorter time scales the differences can be (much) larger. In situ data suffer from poor reproducibility, related to the natural variability at small spatial scales (patchiness), combined with a significant temporal variability. The standard in situ monitoring program in Lakes IJssel and Marken lacks both the necessary spatial coverage as well as an appropriate sampling frequency. This indicates that for reliable monitoring, a synoptic data set, sampled at a high frequency is required. Remote sensing can partially fulfil this demand but still lacks the demanded frequency, mainly due to regular cloud cover. The answer may be in a multiplatform monitoring approach, as used in our study (combining in situ data with shipboard, airborne and satellite optical data) and in combining monitoring data with models. Satellite remote sensing is most powerful in determining properties that are inherent to the whole lake system, like the overall mean chlorophyll-a concentration. Computational models may meet the demand for a sufficiently high sampling frequency by deterministic interpolation of the data in time.

Comparative toxicity evaluation of cyanobacterial cyclic peptide toxin microcystin variants (LR, RR, YR) in mice

The cyclic peptide toxins microcystins and nodularins are the most common and abundant cyanotoxins present in diverse water systems. They have been the cause of human and animal health hazards and even death. Over 60 microcystin variants have been reported so far. We report here the results of our study on comparative toxicity evaluation of three most predominant microcystins, MC-LR, MC-RR and MC-YR in mice. The mice were administered one LD(50) dose of MC-LR, RR and YR (43, 235.4 and 110.6 micro g/kg body weight, respectively), and biochemical and histological variables were determined at 30 min post-treatment and mean time to death (MTD). Significant increase in liver body weight index was induced by all three variants. There was marginal increase in serum levels of hepatic enzymes viz. AST, ALT and gamma-GT at 30 min post-treatment but 3-4 fold increase was observed at MTD. In contrast, enhanced LDH leakage, DNA fragmentation and depletion of hepatic glutathione was observed at 30 min post treatment in all three variants. There was no change in levels of serum protein, albumin and albumin/globulin ratio. Liver histology showed time dependent severe pathological lesions like congestion, haemorrhage, portal mononuclear cell infiltration and obliteration of chromatin material. Lung lesions were predominantly in bronchi and parenchyma. Though qualitatively lesions were identical in all three microcystin variants, degree of liver and lung lesions varied quantitatively with the toxin. The breathing pattern and respiratory frequency of the mice after i.p. administration of the toxin showed uniform pattern for 90 min followed by abrupt change in the respiratory pattern and instantaneous death. Based on biochemical and histological studies, MC-LR was found to be the most potent toxin followed by MC-YR and MC-RR.

Liquid chromatography-electrospray ionisation-mass spectrometry based method for the simultaneous determination of algal and cyanobacterial toxins in phytoplankton from marine waters and lakes followed by tentative structural elucidation of microcystins

A liquid chromatography (LC)-based method with mass spectrometric (MS) detection was developed for simultaneous determination of various algal and cyanobacterial toxins extracted from phytoplankton occurring world-wide in marine waters and lakes. The method enables quantification of saxitoxin, anatoxin-A, domoic acid, nodularin, microcystins, okadaic acid and dinophysistoxin-1 with a single chromatographic run. In addition, the applied chromatographic conditions allow isolation and identification of substances suspected to be "new" microcystins (cyclic peptides) by fraction collection, hydrolysis, derivatisation of resulting free amino acids with the modified chiral Marfey's reagent N-alpha-(2,4-dinitro-5-fluorophenyl)-L-valinamide (L-FDVA) and enantioselective analysis of the amino acid derivatives by LC-ESI-MS.

The influence of microcystin-LR and hepatotoxic cyanobacterial extract on the water plant Spirodela oligorrhiza

The eutrophication of the Sulejów Reservoir dam in Poland is related to toxicity from cyanobacterial blooms. The main species responsible for hepatotoxic bloom formation is Microcystis aeruginosa. The aim of this study was to evaluate the influence of toxic cyanobacterial extract on the growth and morphology of the water plant Spirodela oligorrhiza, compared with commercial-grade microcystin-LR (MC-LR). It was found that after 96 h of incubation the highest concentration of cyanobacterial extract, containing 0.344 mg MC-LR/L, reduced the number of fronds by about 50% in comparison with the control. The extract effected a reduction in the frond mass and a decrease in chlorophyll (a + b) concentration. A reduction in the number of fronds was also observed after the first 24 h of incubation in the presence of 0.2 and 0.1 microg/L of commercial-grade MC-LR. Changes in activity of constitutive acid phosphatase and RNase after 7 days of incubation with commercial-grade MC-LR were observed. The results confirm the toxicity of cyanobacterial hepatotoxins to Spirodela oligorrhiza, which can be used as a sensitive bioindicator.

Genotoxicity of cyanobacterial extracts containing microcystins from Polish water reservoirs as determined by SOS chromotest and comet assay

Toxicity of cyanobacterial blooms, an increasing problem around the world, is connected to the increase in bloom samples containing microcystins, caused by excessive eutrophication of drinking- and recreational water reservoirs. Microcystins are the most common group of cyanobacterial hepatotoxins. In Poland they are produced mainly by the Microcystis genus. The toxicity of microcystins has been well documented, but investigation into their genotoxicity has been insufficient relative to the study of their overall toxicity. Therefore, the aim of this study was the estimation and comparison of the genotoxicity of cyanobacterial extracts with microcystins (CEMs) using the SOS chromotest (bacterial test) with Escherichia coli PQ37 and the comet assay with human lymphocytes. Cyanobacterial bloom samples were collected in the summer months from two Polish water reservoirs, one at Sulejów and one at Jeziorsko. The SOS chromotest, which used prokaryotic cells (without metabolic activation), and the comet assay, which used eukaryotic cells, both indicated the potential genotoxic effect of CEMs. Cyanobacterial extracts caused DNA damage in human lymphocytes in vitro. The maximum level of DNA damage was observed after 12 h incubation with CEMs. The bacterial test indicated a dependence of the degree of CEM genotoxicity, the composition, and the concentration of microcystins in each bloom sample examined with the time of exposure. Differences between the genotoxicity of cyanobacterial extract and the standard microcystin-LR were noticeable. This was probably caused by the interaction of different microcystin variants. The results showed that CEMs from Polish water reservoirs were genotoxic, which was reflected by the stimulation of the SOS repair system in bacterial cells (SOS chromotest) and by the damage induced in DNA in human lymphocytes (comet assay).