Larelle Fabbro

A two-part model linking multidimensional environmental gradients and seasonal succession of phytoplankton assemblages

Algal assemblages and their respective niches are analysed for a large riverine impoundment in semi-arid Australia. The extreme variability of the flow regime and the extensive period of low or no flow produced conditions including prolonged stratification akin to those of a lake during the dry season. Hierarchical agglomerative clustering of phytoplankton data and comparison with a principal component analysis of corresponding environmental data are used to demonstrate the linkage between steep environmental gradients and variations in the phytoplankton assemblages. The factor score plots separate the algal assemblages according to key environmental parameters including increasing clarity of the water column, temperature and modification of water chemistry. Assemblages normally contained cyanoprokaryotes (Oscillatoriales), euglenophytes or non-flagellated chlorophytes during flows followed by flagellated chlorophytes and cyanoprokaryotes (Nostocales) during the dry season. Species present during the period of reduced flow occupied conditions similar to those presented in the literature for temperate and/or tropical lakes. Common species included Pandorina morum, Eudorina elegans, Anabaena circinalis, Aphanizomenon issatschenkoi, Aphanizomenon aphanizomenioides and Cylindrospermopsis raciborskii. A two-part model is proposed which predicts the most likely genera of phytoplankton with respect to multidimensional environmental gradients.

Onset and persistence of cyanobacterial blooms in a large impounded tropical river, Australia

The dynamic interplay between physical, chemical and biological factors in the development and persistence of cyanobacterial blooms in impounded rivers is an important topic. Over a 3-year study period, variable climatic conditions were recorded in the Fitzroy River, Queensland, Australia, which is a typical, impounded lowland tropical river. Post-flood turbidity reduced the available light in the well-mixed water column to levels insufficient for cyanobacterial growth. Only when the water column stratified and the slowly sinking particles dropped from the surface layer did the ratio of surface mixed layer depth to euphotic depth approach 1, allowing cyanobacterial growth. By the time the light climate became favorable, most of the dissolved nutrients had been scavenged from the water column by settling particles or sequestered by fringing macrophytes and other biogeochemical processes. Cyanobacterial blooms dominated by Cylindrospermopsis raciborskii persisted for several months until the next flood flushed the system. The cyanobacterial species dominating that environment were very small and had high specific phosphorus uptake rates. Their nutrient requirement was met by transfer across the oxycline driven by regular high wind mixing events, entraining nutrient-rich bottom waters. Nutrient fluxes from the sediments into the anoxic bottom layer were sufficient to replace the bottom nutrients lost to the surface layer.

Incidence and Distribution of Microfungi in a Treated Municipal Water Supply System in Sub-Tropical Australia

Drinking water quality is usually determined by its pathogenic bacterial content. However, the potential of water-borne spores as a source of nosocomial fungal infection is increasingly being recognised. This study into the incidence of microfungal contaminants in a typical Australian municipal water supply was carried out over an 18 month period. Microfungal abundance was estimated by the membrane filtration method with filters incubated on malt extract agar at 25 °C for seven days. Colony forming units were recovered from all parts of the system and these were enumerated and identified to genus level. The most commonly recovered genera were Cladosporium, Penicillium, Aspergillus and Fusarium. Nonparametric multivariate statistical analyses of the data using MDS, PCA, BEST and bubble plots were carried out with PRIMER v6 software. Positive and significant correlations were found between filamentous fungi, yeasts and bacteria. This study has demonstrated that numerous microfungal genera, including those that contain species which are opportunistic human pathogens, populate a typical treated municipal water supply in sub-tropical Australia.

Investigations into the taxonomy, toxicity and ecology of benthic cyanobacterial accumulations in Myall Lake, Australia

Large benthic accumulations of cyanobacteria occur in sheltered embayments within Myall Lake, New South Wales, Australia. The lake is shallow, with the entire bottom within the euphotic zone, and it is generally considered pristine, having low nutrient concentrations. The accumulations are highly organic and contain a mix of species mainly from the order Chroococcales, with two forms of Aphanothece being dominant. However polymerase chain reaction (PCR) analysis indicates a close similarity to Microcystis flos-aquae. The cells appear to lack aerotopes and form sticky mucilaginous amalgamations, which may enhance their benthic habit. Although Chroococcales also dominate the planktonic cyanobacterial community, the benthic species are seldom, if ever, found entrained within the water column. Some hepatotoxicity was indicated by mouse bioassay, protein phosphatase inhibition assay, enzyme-linked immuno-sorbent assay (ELISA) for microcystins, PCR and by chromatographic evidence for a microcystin. Ecological aspects of the distribution, gross morphology of the organisms and management implications for recreational water-users are discussed.

Novel toxic effects associated with a tropical Limnothrix/Geitlerinema-like cyanobacterium

The presence of a toxic strain of a fine filamentous cyanobacterium belonging to the Oscillatorialean family Pseudanabaenacea was detected during a survey of cyanobacterial taxa associated with the presence of cylindrospermopsin in dams in Central Queensland (Australia). The strain, AC0243, was isolated and cultured, its genomic DNA extracted and 16S RNA gene sequenced. Phylogenetic analysis placed AC0243 with Limnothrix species, although this genus appears polyphyletic. Moreover, not all morphological characters are consistent with this genus but more closely fit the description of Geitlerinema unigranulatum (R.N. Singh) Komárek and Azevedo. The potential toxic effects of AC0243 extract were assessed chemically and biologically. Cell free protein synthesis was inhibited by the extract. Exposure of Vero cells to the extract resulted in a significant reduction in cellular ATP levels following 24–72 h incubation. The presence of cylindrospermopsin was excluded based on the nature of responses obtained in cell and cell‐free assays; in addition, (i) it could not be detected by HPLC, LC‐MS, or immunological assay, and (ii) no genes currently associated with the production of cylindrospermopsin were found in the genome. Other known cyanobacterial toxins were not detected. The apparent novelty of this toxin is discussed.

Distribution of the cyanobacterial toxins cylindrospermopsin and deoxycylindrospermopsin in a stratified lake in north-eastern New South Wales, Australia

This paper describes the vertical water column distribution of the cyanobacterial toxins cylindrospermopsin and deoxycylindrospermopsin in a water body containing the cyanobacteria Aphanizomenon ovalisporum and Cylindrospermopsis raciborskii. The study site was Cobaki Village Lake, a small stratified anthropogenic lake in north-eastern New South Wales, Australia. Water quality analysis indicated that stratification and oxygenation of the water column were significant in both the distribution of the cyanobacterial populations and their associated toxin concentrations. Toxin was distributed throughout the entire water column, but the highest concentrations were recorded in the hypolimnion. Maximum toxin concentrations were detected in February 2007 (38.2 μg L–1 cylindrospermopsin (CYN) and 42.2 μg L–1 deoxy-CYN). The relative distribution of CYN and deoxy-CYN paralleled the distribution of NH3H and NOX within the water column, with oxygenated chemical species dominating above 15 m and de-oxygenated chemical species dominating below 15 m. Cyanobacterial cell concentrations were highest in the oxic, warm and low conductivity waters of the epilimnion and cyanobacterial species succession was associated with nutrient and trace-metal depletion in this surface layer. These research findings are directly relevant to the management of water supplies affected by toxic blue-green algal blooms, particularly with respect to the considered placement of off-take devices to avoid layers of cyanobacterial cell and toxin concentrations.

Three Potential Sources of Microfungi in a Treated Municipal Water Supply System in Sub-Tropical Australia

Some microfungi are known to be opportunistic human pathogens, and there is a body of scientific opinion that one of their routes of infection may be water aerosols. Others have been implicated as causative agents of odours and off-tastes in drinking water. This study was undertaken to investigate three potential sources of microfungi in a treated, oligotrophic municipal water supply system in sub-tropical Australia. Formation of the microfungal component of developing biofilm on hard surfaces in water storage reservoirs was also assessed. Inside and outside air samples were collected from two reservoirs using two types of Burkard air samplers. Biofilm and soft sediment samples were collected from the inner surfaces of asbestos cement water pipes and from pipe dead ends respectively. These were analysed for microfungal growth and sporulation using Calcofluor White stain and epifluorescent microscopy. Artificial coupons of glass, PVC and concrete were immersed in two reservoirs to assess microfungal biofilm formation. This was analysed periodically using Calcofluor White stain and epifluorescent microscopy, cultures of coupon swabs and scanning electron microscopy. Fungal spores were recovered from all air samples. The number of colonies and the genera were similar for both inside and outside air. Microfungal filaments and sporulating structures were recovered from most of the pipe inner surface biofilm and dead end sediment samples, but were sparser in the biofilm than in the sediment samples. No recognisable, vegetative filamentous fungi were found in the slowly developing biofilm on coupons. This study indicates that airborne spores are an important potential source of microfungi found in water storage reservoirs. It has also demonstrated conclusively that filamentous microfungi grow and sporulate on water pipe inner surfaces and in soft sediments within the water distribution system.

Impacts of a toxic Microcystis bloom on the macroinvertebrate fauna of Lake Elphinstone, Central Queensland, Australia

The biological, physical and chemical properties of Lake Elphinstone were studied during a dense, toxic cyanoprokaryote bloom dominated by Microcystis. Decreases in total abundance and richness in macroinvertebrate communities coincided with increases in Microcystis toxicity. Water quality was characterized by high light attenuation values caused by abiogenic turbidity and shading and absorbance from thick algal scums. The study highlights the potential for multidimensional environmental impacts associated with toxic cyanoprokaryote blooms, and the consequent implications for the management of shallow, inland and tropical lakes that are susceptible to toxic blooms.

Diurnal activity patterns as a sensitive behavioural outcome in fish: effect of short-term exposure to treated sewage and a sub-lethal PPCP mixture

Sub‐lethal toxicological responses are common occurrences in aquatic animals exposed to sewage wastewater and organic wastewater contaminants. Behavioural alterations are particularly sensitive indicators of sub‐lethal toxicological stress in animals exposed to various pollutants, and often correlate with higher‐level outcomes. Diurnal activity patterns in many fish species are sensitive to changes in natural biotic factors, but few studies have explored how environmental pollutants influence such rhythms. We investigated diurnal activity patterns in the mosquitofish (Gambusia holbrooki), after exposure to UV‐treated sewage and a mixture of key contaminants identified through chemical analysis and subsequent risk‐based prioritization of the wastewater. Exposure to 50% and 100% wastewater abolished daytime activity levels in male, but not female fish. Chemical analysis identified fluoxetine, diazinon and triclosan above their reported predicted‐no‐effect‐concentrations (PNECs), and fish were thus exposed to a mixture of these compounds at 1, 10 and 100 μg l–1. Behavioural responses were highly consistent between fish exposed to wastewater and the contaminant mixture, indicating that these prioritized contaminants are indeed likely contributing to the observed effects. Effective concentrations of the mixture were considerably lower than those reported as eliciting behavioural effects in previous studies exploring each of these compounds alone. Results warn of the potential for negative higher‐level consequences associated with exposures of fish to common organic wastewater contaminants, as altered diurnal activity patterns could conceivably scale‐up to influence performance including foraging success and predator avoidance. Further research is necessary to increase our understanding of linkages between alterations to diurnal activities and effects at the population level. Copyright

Behaviour, development and metal accumulation in striped marsh frog tadpoles (Limnodynastes peronii) exposed to coal mine wastewater

Coal mining generates large quantities of complex effluent, and this often contains high levels of dissolved solids, suspended solids, metals, hydrocarbons, salts and other compounds. Substantial volumes of mine wastewater are periodically discharged into the environment, through both planned and accidental releases, and this raises concerns about the potential for adverse impacts on aquatic wildlife. There have been few attempts to explore sub-lethal effects of coal mine wastewater on amphibians compared to other organisms, and this is particularly true for Australian species. To address existing knowledge gaps, we exposed striped marsh frog (Limnodynastes peronii) tadpoles to 25, 50 and 100% coal mine wastewater collected from two holding dams (CMW1 and CMW2) located at an open cut mine in Central Queensland, Australia. The exposure lasted for four weeks, after which survival, growth and development, swimming behaviour, and concentrations of metals and metalloids in tail and liver tissues were assessed. Physico-chemical parameters varied considerably between sites, with higher turbidity, nutrients, total and dissolved organic carbon, alkalinity and arsenic (As) concentrations at CMW1, and higher conductivity, salinity, dissolved solids, hardness and sulfate levels at CMW2. There was no mortality in controls and less than 5% mortality in CMW1 treatments, whereas survival was significantly decreased in tadpoles exposed to CMW2 with 40 and 55% mortality in the 50 and 100% treatments, respectively. Development was significantly delayed in 100% CMW1 wastewater, but tadpole size (growth) was not influenced by the exposure. Hepatosomatic indices were significantly increased in tadpoles exposed to 25 and 50% CMW1 but not the 100% treatment group. Exposed tadpoles (predominantly those exposed to CMW1) exhibited increased activity after very short-term exposure (24h), but this did not persist as animals approached metamorphic climax. At the end of the experiment, tadpoles exposed to both wastewaters had elevated levels of selenium (Se), cobalt (Co) and As in tail and liver tissue compared to controls. Manganese (Mn) levels were also elevated in livers and tails of CMW2 exposed tadpoles. Hepatic tissue accumulated 8-9 times higher concentrations of Co, Mn and Se compared to tail tissue, irrespective of treatments. Future research is warranted to explore possible relationships between metal bioaccumulation, morpho-physiological effects during development, and subsequent higher-level outcomes related to individual performance and population fitness.