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Summary 1. Subtropical reservoirs of Australia are commonly subject to summer blooms of cyanobacteria. The potential for food web manipulation to control cyanobacterial blooms was investigated in Lake Maroon, south east Queensland using enclosures in which the density of the Australian gudgeon Hypseleotris spp. was manipulated. 2. Zooplankton biomass and community structure were strongly affected by fish density. A size dependent predation effect of Hypseleotris on zooplankton was observed at ambient fish densities, and the community shifted towards a dominance of copepod juveniles and nauplii. Substantial increases in the populations of Ceriodaphnia and calanoid copepods were observed at low fish densities and in the absence of fish. 3. At ambient fish densities total phytoplankton and the proportion of cyanobacteria were maintained at levels similar to those prevailing at day 0. Total phytoplankton and the proportion of cyanobacteria decreased substantially at low fish densities and in the absence of fish. Chlorophytes became dominant in the ‘no fish’ treatment and the grazing-resistant species Oocystis and Dictyosphaerium were significantly higher than at ambient fish densities. 4. The experiment demonstrated a strong positive relationship between Hypseleotris density and cyanobacteria, and the results suggest that subtropical reservoirs may be suited to food web manipulation as a means of controlling summer cyanobacterial blooms. [ABSTRACT FROM AUTHOR]

Summary 1. Planktivorous fish were hypothesised to influence the abundance of algal biomass in lakes by changing zooplankton grazing, affecting zooplankton nutrient recycling and by direct recycling of nutrients to phytoplankton. The relative roles of direct fish effects vs. zooplankton grazing were tested in mesocosm experiments by adding to natural communities large grazing zooplankton (Daphnia carinata) and small planktivorous fish (mosquitofish or juveniles of Australian golden perch). 2. The addition of Daphnia to natural communities reduced the numbers of all phytoplankton less than 30 µm in size, but did not affect total biomass of phytoplankton as large Volvox colonies predominated. 3. The addition of Daphnia also reduced the abundance of some small (Moina, Bosmina, Keratella) and large (adult Boeckella) zooplankton, suggesting competitive interactions within zooplankton. 4. The addition of mosquitofish to communities containing Daphnia further reduced the abundance of some small zooplankton (Moina, Keratella), but increased the numbers of Daphnia and adult Boeckella. In spite of the likely increase in grazing due to Daphnia, the abundance of total phytoplankton and dominant alga Volvox did not decline in the presence of mosquitofish but was maintained at a significantly higher level than in control. 5. The addition of juveniles of golden perch to communities containing Daphnia reduced the abundance of small zooplankton (Moina), increased the abundance of large zooplankton (adult Boeckella) but had no significant effect on Daphnia and total phytoplankton abundance. 6. The results of the present study suggest that some planktivorous fish can promote the growth of phytoplankton in a direct way, probably by recycling nutrients, and even in the presence of large grazers. However, the manifestation of the direct effect of fish can vary with fish species. [ABSTRACT FROM AUTHOR]

Paralytic shellfish poisons (PSPs) were detected in 24 of 31 bloom samples dominated by the cyanobacterium Anabaena circinalis Rabenhorst, collected from across Australia. The ability to produce PSPs has been maintained in several non-axenic strains of A. circinalis kept in culture, whereas strains that were non-toxin-producing when isolated have remaned as such. PSPs were detected and quantified by high-performance liquid chromatography (HPLC), and the structures were confirmed by electropray mass spectroscopy. The concentration of toxins in PSP positive samples ranged from 50 to 3400 μg-g[sup-1] dry weight. Toxin profiles were always dominated by the N-sulfocarbamoyl-11-hydroxysulfate C toxins, C1 and C2 (44-85 mol%), with the remainder consisting of gonyautoxins-2, -3, and -5, decarbamolygonyautoxins-2 and -3, saxitoxin, and decarbamoylsaxitoxin, N[sub1]-hydroxy PSPs, commonly found in marine dinoflagellates, were absent, suggesting that A. circinalis lacks the enzyme responsible for N[sub1]-hydroxylation. On a dry weight basis, the amount of toxin in cultured Anabaena circinalis (strain ACMB06) rose significantly (P < 0.05) over time from 570 to 3400 μg-g[sup-1] cells in late stationary phase. However, there was no significant trend in cellular toxin quota (toxin per cell) over the life of the culture; this may be explained by variation in cell mass. On average, batch cultures of Anabaena circinalis contained 19% extracellular toxin, which increased slightly over the growth cycle and had a composition similar to that of the intracellular toxins. As cultures aged, the formation of decarbamoyl toxins and increases in the α/β-epimer ratios of C toxins and gonyautoxins were observed. The variation in these components during stationary phase in culture was sufficient to explain the variation in relative PSP composition observed among natural bloom samples. Because decarbamoylgonyautoxins are much more toxic than C toxins on a molar basis, these transformations also lead to an increase in toxicity of the sample or bloom over time. The tranformation of PSPs, which occur during aging and sample storage, render the comparison of PSPs in HPLC unreliable for phenotyping Anabaena circinalis, unless strains are cultured, harvested, and analyzed under standard conditions. [ABSTRACT FROM AUTHOR]

A three year study of two sub-tropical water supply (potable and irrigation) reservoirs -- Baroon pocket and Leslie - aimed to develop an improved understanding and effective management strategy for the control of low level toxic cyanobacterial "blooms'. The two reservoirs appear to be typical of those elsewhere in tropical and sub-tropical Australia, being strongly stratified and monomictic if deep, or polymictic to monomictic (depending on inter-annual climatic variation) if shallow. In both reservoirs, thermal stratification appeared to he the key factor influencing the onset and demise of cyanobacterial blooms Hypolimnetic deoxygenation was rapid during periods of stratification, and high rates of nitrogen and phosphorus release from bottom sediments occurred during anoxia. External nutrient inputs were dominated by episodic storm in-flows following the passing of (sub)tropical depressions, carrying massive sediment and nutrient loads into the reservoirs. As a consequence of this, and coupled with the high degree of internal nutrient recycling and the low national targets for cyanobacterial control in Australia, we believe that reduction of external nutrient inputs alone, through improved catchment management, may not be sufficient to prevent cyanobacterial blooms. Therefore, more emphasis should be given to "in lake" control strategies such as destratification, biomanipulation and in situ sediment treatment. [ABSTRACT FROM AUTHOR]

The article focuses on the leadership skills of several emergency nurses and their ability to influence others, including Liz Cloughessy, executive director of the Australian College of Emergency Nursing, Olive Goodall, emergency department lead nurse and matron at Hope Hospital, and Helen Patterson, former senior sister in the accident & emergency department at the Royal Victoria Hospital in Belfast, Northern Ireland.

In a laboratory-scale trial, we studied the removal of saxitoxins from water by ozone, granular activated carbon (GAC) and H(2)O(2), and considered the implications of residual toxicity for compliance with the Australian drinking water standards. Cell-free extracts of Anabaena circinalis were added to raw, untreated drinking water obtained from a water supply reservoir to provide a toxicity of 30 microg (STX equivalents)l(-1). Ozone alone, or in combination with H(2)O(2), failed to destroy the highly toxic STX and GTX-2/3, and only partially destroyed dc-STX, and the low-toxicity C-toxins and GTX-5. In all cases, the toxicity of the water was reduced by less than 10%. GAC removed all of the STX, dc-STX and GTXs, but only partially removed the C-toxins. However, the residual toxicity was reduced to the suggested Australian drinking water guideline concentration of 3 microg (STX equivalents)l(-1) without O(3) pre-treatment. Modelling the spontaneous chemical degradation of residual C-toxins following treatment shows that residual toxicity could increase to 10 microgl(-1) after 11 d due to formation of dc-GTXs and would then gradually decay. In all, residual toxicity would exceed the Australian drinking water guideline concentration for a total of 50 d.