Michael D. Burch

Taihu Lake Not to Blame for Wuxi's Woes

The algal bloom observed in Taihu lake in the summer of 2007 and sensationalized in a News Focus story (“Doing battle with the green monster of Taihu Lake,” 31 August 2007, p. [1166][1]) is certainly a serious environmental and ecological problem. However, the issue that drew public attention to

The impact of conventional water treatment processes on cells of the cyanobacterium microcystis aeruginosa

Cyanobacteria can produce toxins, tastes and odors which significantly impair water quality. Removal of intact cyanobacterial cells with their intracellular compounds during water treatment would potentially reduce the concentration of taste, odor and toxic cell metabolites present in the treated water. In this study, the effect of conventional water treatment processes using aluminum sulphate (alum) on the integrity of cells of toxic Microcystis aeruginosa was evaluated using both jar tests and pilot plant studies. Removal of M. aeruginosa cells by alum flocculation using a jar test apparatus indicated all cells were removed without damage to membrane integrity. Thus the chemical treatment and mechanical action did not damage the cultured M. aeruginosa cells and, more importantly, did not result in additional release of cell metabolites above background concentrations. For pilot plant experiments, which consisted of coagulation/flocculation–sedimentation–filtration, most of the cells were removed intact and no additional microcystin was found in the finished water.

Health effects of exposure to cyanobacteria (blue–green algae) during recreational water–related activities

Abstract: The aim of this study was to investigate effects on health of exposure to cyanobacteria as a result of recreational water activities. Participants, who were aged six years and over, were interviewed at water recreation sites in South Australia, New South Wales and Victoria on selected Sundays during January and February 1995. Telephone follow–up was conducted two and seven days later to record any subsequent diarrhoea, vomiting, flu–like symptoms, skin rashes, mouth ulcers, fevers and eye or ear irritations. On the Sundays of interview, water samples from the sites were collected for cyanobac–terial cell counts and toxin analysis. There were 852 participants, of whom 75 did not have water contact on the day of interview and were considered unexposed. The 777 who had water contact were considered exposed. No significant differences in overall symptoms were found between the unexposed and exposed after two days. At seven days, there was a significant trend to increasing symptom occurrence with duration of exposure (P = 0.03). There was a significant trend to increasing symptom occurrence with increase in cell count (P = 0.04). Participants exposed to more than 5000 cells per mL for more than one hour had a significantly higher symptom occurrence rate than the unexposed. Symptoms were not correlated with the presence of hepatotoxins. These results suggest symptom occurrence was associated with duration of contact with water containing cyanobacteria, and with cyanobacterial cell density. The findings suggest that the current safety threshold for exposure of 20 000 cells per mL may be too high. (Aust N Z J Public Health 1997; 21: 562–6)

Destruction of cyanobacterial peptide hepatotoxins by chlorine and chloramine

Toxic cyanobacteria (blue-green algae) are becoming recognized as a greater water quality problem as blooms become more common in waters affected by increasing nutrient levels, and knowledge of the properties of the toxin increases. Of particular importance are the hepatotoxic cyclic peptides produced by certain strains of Microcystis species and by Nodularia spumigena. The effects of chlorine and chloramine on these hepatotoxins in both freeze-dried and intact material were investigated. The destruction of the toxins was monitored using HPLC analysis. In a number of cases mouse bioassays were used for confirmation of the destruction of the toxins and to ensure that toxic by-products, not detectable by HPLC, were not formed. Contrary to evidence reported in the literature, chlorine was effective in destroying toxins, as long as sufficient chlorine was used. Toxins were destroyed under conditions such that a chlorine residual of at least 0.5 mg/l was present after 30 min contact time. The destruction of toxins was pH dependent; chlorinating agents such as calcium and sodium hypochlorite were not as effective at high dose rates due to elevation of pH. Chloramination had little effect on toxins. Although the degradation mechanisms have yet to be established, the results show that chlorination may be an effective and practical method for the removal of cyanobacterial peptide toxins from drinking water.

Use of artificial neural networks for modelling cyanobacteria Anabaena spp. in the River Murray, South Australia

The use of artificial neural networks (ANNs) for modelling the incidence of cyanobacteria in rivers was investigated by forecasting the occurrence of a species group of Anabaena in the River Murray at Morgan, Australia. The networks of backpropagation type were trained on 7 years of weekly data for eight variables, and their ability to provide a 4-week forecast was evaluated for a 28-week period. They were relatively successful in providing a good forecast of both the incidence and magnitude of a growth peak of the cyanobacteria within the limits required for water quality monitoring. The use of lagged versus unlagged inputs was evaluated in the implementation and performance of the networks. Lagged inputs proved far superior in providing a fit to the actual data. Sensitivity analysis of input variables was performed to evaluate their relative significance in determining the forecast values. The analysis indicated that for this data set for the River Murray, flow and temperature were the predominant variables in determining the onset and duration of cyanobacterial growth. Water colour was the next most important variable in determining the magnitude of the population growth peak. Plant nutrients nitrogen, phosphorus and iron, and turbidity were less important for this time period.

Development of health alerts for cyanobacteria and related toxins in drinking water in South Australia

Cyanobacterial blooms occur intermittently in various reservoirs, rivers, and lakes in South Australia. Well‐documented human and animal health effects related to blooms and the associated cyanotoxins have led health and water authorities in this state to recognize the need for establishing health alert (acute exposure) values for these cyanobacteria and their toxins. Distinct from lifetime drinking‐water guideline values, these health alerts take into account known and possible acute health effects. Operationally, water authorities involved in monitoring the quality of water resources are required to contact the health authorities immediately if a health alert condition is detected. This then triggers a rapid assessment of potential health consequences of continued water use and sets in motion an appropriate management response. This article outlines the development of proposed health alerts for microcystin‐LR‐eq toxicity (10 μg/L), nodularin (10 μg/L), and saxitoxins (3 μg STX‐eq/L). Corresponding cell densities for Microcystis aeruginosa (50,000 cells/mL), Nodularia spumigena (50,000 cells/mL), and Anabaena circinalis (20,000 cells/mL) are also provided for use as health alert indicators prior to determination of toxin concentration. In practice, it is likely that cell densities well below these values render drinking water unpalatable. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 203–209, 1999

Odorous compounds associated with algal blooms in south australian waters

Abstract Identification of volatile odorous compounds is reported from blooms of the Cyanobacteria Oscillatoria, Anabaena and Microcystis and the Chrysophyte Synura in South Australian reservoirs and River Murray water. Chemical “fingerprinting” of this kind may be used to assist in the development of removal or treatment techniques to minimise or eliminate the aesthetically unpleasant effects of algal blooms on drinking water quality. Volatiles were concentrated using the closed loop stripping (CLS) method and analysed by gas chromatography/mass spectrometry (GC/MS). Compounds isolated from the Cyanobacteria included geosmin, 2-methylisoborneol, sesquiterpenes, β-cyclocitral, 3-methyl-1-butanol and 6-methyl-5-hepten-2-one. The compound responsible for the dominant cucumber odour of Synura petersenii was identified for the first time as trans -2, cis -6-nonadienal.

Use of FDA and flow cytometry to assess metabolic activity as an indicator of nutrient status in phytoplankton

This study reports the use of a technique to determine nutrient limitation of cultured and natural phytoplankton. The technique, an FDA-activity assay, which is usually used to assess cell viability, was used to measure metabolic activity in response to nutrient addition; the metabolic activity of phytoplankton was determined as the rate of hydrolysis of fluorescein diacetate (FDA), by intracellular esterases, to fluorescein, which was detectedusing a flow cytometer. Replacement of the limiting nutrient to nitrogen- or phosphorus-limited cultures and field populations resulted in an increase in metabolic activity that was detectable 24 h after nutrient addition. By flow cytometry, the natural phytoplankton community can be divided into different taxonomic groups; the response of these to FDA could be determined individually to allow identification of the nutrients limiting each type of phytoplankton. This would be more specific than the assessment of a whole-community response, which may mask subtle differences among taxa.

Does toxic Microcystis aeruginosa affect aquatic plant establishment

Germination and establishment of aquatic plants in response to the addition of toxic and nontoxic cultures of Microcystis aeruginosa cells, the toxin, microcystin, or both nontoxic cells and dissolved microcystin was investigated in two glasshouse experiments and an in vitro germination experiment. The presence of high densities of cyanobacterial cells had a negative effect on aquatic plant establishment when cell densities were greater than 109 cells mL−1. Plants that were shaded with 20% shade cloth also had reduced establishment compared to the control. The most sensitive plants were species of Chara and Nitella. There was no evidence that dissolved microcystin (as cyanobacterial cell‐free extracts) alone had a deleterious effect on aquatic plant germination and establishment. Dense cyanobacterial blooms may, therefore, have a role in preventing the establishment of aquatic plants through shading. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 97–109, 1999

Acute skin irritant effects of cyanobacteria (blue-green algae) in healthy volunteers.

Objective: To assess the skin irritant potential of a range of laboratory grown cyanobacterial species using skin‐patch testing on human volunteers.