The people of Australia are very familiar with toxic cyanobacterial blooms, as they have been a long-standing problem for agricultural and human drinking water supply, as well as for the recreational use of water. Livestock poisoning by cyanobacteria was first described in the last century near Adelaide, and the names of water-courses such as \'Poison Waterhole Creek\' across the country reflect the hazard from cyanobacteria. More recently 1,000km of the Darling River carried a massive bloom of PSP containing Anabaena which killed an estimated 10.000 livestock and required emergency water supplies for several towns.This year (and last) in the centre of the City of Adelaide the Torrens Lake (no longer used for water supply) had a heavy bloom of toxic Microcystis, with waterfowl deaths. While livestock poisoning is relatively common,cases of human and wildlife poisoning are however rare, more through avoiding drinking evil-smelling water than to an absence of toxicity in cyanobacterial blooms.Effective assessment of the risk to human health requires data which relate the dose of toxin to the clinical effects in a population. When ,in the past, an adverse health effect from a cyanobacterial bloom has been observed in the population, no measurements of toxin in the water supply have been made. Even in the recent case of deaths of 50 dialysis patients in Brazil ,the best that could be achieved was retrospective analysis of post-mortem samples for toxin. As a result animal toxicity data are used for risk assessment, incorporating safety factors, to derive Guideline Values for a safe water supply.WHO has just announced the first of these values for cyanobacterial toxins, for the toxin microcystin,of 1.0 mg/litre of water.The other major potential hazards in water supplies in Australia are cylindrospermopsin from the tropical Cylindrospermopsis, and PSPs from Anabaena. All three toxic cyanobacteria occur in water supply reservoirs as intermittent blooms, often controlled by the supply authority by copper sulphate application.This lyses the bloom liberating toxins free into the water.Children tend to be more vulnerable than adults to toxins in the drinking water, partly because they have less choice of what they drink.Blooms usually occur in summer,when water consumption is high and swimming is popular.These hazards are recognised,bloom warnings are given on the radio and by erection of signs by rivers and lakes.Monitoring for blooms in reservoirs and rivers is essential to reduce the risks to the population and is undertaked widely in Australia.

Microcystin (MCYST) toxins produced by the water bloom forming cyanobacterium Microcystis aeruginosa are chemically stable compounds which have both acute and chronic health effects on mammals, including cattle and humans. Cattle will drink water containing lethal cell concentrations of M. aeruginosa. When cattle consume sub-lethal doses of microcystins, the ultimate fate of those toxins is unknown. We undertook a study to examine the transmission of microcystins from drinking water containing environmentally realistic concentrations of M. aeruginosa (strain MASH01-A19) through lactating dairy cattle to determine if the MCYST-LR toxins present in the cyanobacteria, could subsequently be detected in milk produced by those cattle. During the course of the study, cattle consumed up to 15mg of highly hepatotoxic MCYST-LR over a three week period. In this talk we will release the outcomes of our findings and the implications for contamination of milk products by microcystins resulting from ingested cyanobacteria.

Where are the harmful algae? Thin layers of phytoplankton, and their implications for understanding the dynamics of harful algal blooms

 

J.E.B. Rines, J.M. Sullivan, P.L. Donaghay and M.M. Dekshenieks University of Rhode Island, Graduate School of Oceanography South Ferry Road, Narragansett, Rhode Island 02882 USA

The toxin, cylindrospermopsin, has been shown to be produced in Australia by the cyanobacteria, Cylindrospermopsis raciborskii and Aphanizomenon ovalisporum. A. ovalisporum is infrequently detected and has thus far only been found in Queensland. By contrast, C. raciborskii is widely distributed in freshwater systems in Queensland and to a lesser extent in other states. Concentrations of cylindrospermopsin in water bodies have been shown to exceed 100mg/L under heavy bloom conditions with both organisms. The main toxic mechanism of cylindrospermopsin is believed to be inhibition of protein synthesis. The liver is the main target organ with substantial fatty vacuolation occurring. In addition to liver toxicity, other organs affected include the kidney, thymus and spleen. A thrombohaemorrhagic lesion in the eye orbit is also seen in some dosed animals Studies with radiolabelled cylindrospermopsin has shown that a proportion of the cylindrospermopsin is strongly bound in the liver as a metabolite. Studies using cell lines also indicate that cylindrospermopsin is metabolically activated in order to produce inhibition of protein synthesis. In addition, studies with cylindrospermopsin dosed mice have shown that covalent binding occurs in liver DNA. The acute intraperitoneal 1 day LD50 for cylindrospermopsin in mice is 2mg/kg , while the 5 day LD50 is 0.2mg/kg which demonstrates the time course of cylindrospermopsin intoxication. The acute oral LD50 is approximately 6mg/kg.. In mice dosed daily via drinking water for a period of 90 days, the NOAEL was approximately 0.15mg/kg/day. A risk assessment using suitable safety factors suggests that a guideline value of 15mg/L would apply based on this data. If demonstrated DNA binding was to be considered, and if cylindrospermopsin was classified as a genotoxin, then a guideline value of 1.5mg/L would be applicable. Considering the levels of cylindrospermopsin found in water reservoirs in Queensland, it is essential that suitable treatment techniques be employed to remove this toxin to levels of less than 1mg/L when water is to be used for human consumption

Occurrence of toxic cyanobacteria in drinking water supplies has become an important problem for the water authorities. Recent research demonstrated that cyanobacterial toxins such as microcystin LR, cylindrospermopsin and saxitoxin are successfully degraded to below the detection limit if the water is treated with chlorine, providing a residual free chlorine concentration greater 0.5 mg L-1 is maintained for sufficient time. The aim of this study was to determine formation of chlorinated byproducts during the treatment of water spiked with environmentally relevant concentrations of cylindrospermopsin and microcystin. Experiments were set-up in which water (20 - 60 L) was spiked with cell free extract material of toxic Microcystis and Cylindrospermopsis. The water samples, including control samples (nonchlorinated water with no algae, chlorinated water with no algae and nonchlorinated water with algae) were then filtered and/or passed through a XAD-2 solid phase cartridge under vacuum. For chlorophenols the water was acidified (pH < 2) prior to sampling. Samples were then subject to GC-MS analysis. Results showed that formation of lower chlorinated phenols (mono - trichlorophenol) during the treatment of the water which contained the cell free extract material has occurred.

Toxin producing cyanobacteria are becoming more abundant in drinking water reservoirs around the World. Cylindrospermopsis raciborskii is a potential toxin producing cyanobacterium commonly found in drinking water reservoirs in South East Queensland. This cyanobacterium produces the cyclic hepatotoxin cylindrospermopsin. With potentially lethal effects on humans, cylindrospermopsin must be removed from drinking water. Typical treatment methods (flocculation, sedimentation and filtration) are effective in cellular removal, however, such processes often result in cell lysis and hence the release of intracellular toxins. It is important to remove the dissolved cyanotoxin from the water. Several methods of removal have been examined including, oxidation by chlorine and ozone, and ultra violet degradation with the addition of titanium dioxide. Each method is effective in cylindrospermopsin removal under various conditions. Chlorination is pH dependent and ultra violet degradation is more efficient with the addition of titanium dioxide.

During August 2-12 1999, development of a surface bloom dominated by the cyanobacterium Nodularia spumigena was followed in the western Gulf of Finland, the Baltic Sea. Intense surface scums of aggregated Nodularia existed on calm days. The low-nutrient Nodularia-dominated water mass was separated by a front from the nutrient-rich Aphanizomenon flos aquae-dominated mass in the Gulf area. Due to inadequate mixing of the two water masses, it is likely that the Nodularia growth was based on the use of internal phosphorus storage (surface water phosphate concentrations between 0 and 0.05 µM). Signs of cell decay were observed on August 5 and the degree of empty filaments in the community grew higher towards the end of the survey period. A high number of the diatoms Nitzschia was recorded within the Nodularia aggregates on August 8, suggesting nutrient leakage from the Nodularia filaments. On-board, toxin analysis was carried out with HPLC and ELISA. The results from these tests indicated that decay of Nodularia or a decrease in the proportion of Nodularia cells in dry material resulted in decreasing concentrations of cell-bound nodularin (from 2.1 to 0.5 g kg-1 dw; HPLC). Results obtained with rapid ELISA kits correlated (r = 0.92, n=7) with HPLC results. On the average, ELISA provided 50% higher results than HPLC. No clear temporal trends in nodularin water concentration(<<0.5-2.6m g l-1; ELISA) was observed. The bloom was probably linked to a fish kill during the same time. Dead three-spine sticklebacks (Gasterosteus aculeatus) were found floating on the surface. According to ELISA, the sticklebacks contained approximately 35-170 mg toxin kg-1 dw (MC-LR equivalents). Empty Nodularia cells and traces of nodularin were also found in surficial sediments collected from the study area which indicated that toxic Nodularia may reach the seafloor.