Survival of cyanobacteria in rivers following their release in water from large headwater reservoirs.

Cyanobacterial survival following their release in water from major headwaters reservoirs was compared in five New South Wales rivers. Under low flow conditions, cyanobacterial presence disappeared rapidly with distance downstream in the Cudgegong and Hunter Rivers, whereas the other three rivers were contaminated for at least 300 km. Cyanobacterial survival is likely to be impacted by the geomorphology of each river, especially the extent of gravel riffle reaches (cells striking rocks can destroy them) and by the different turbulent flow conditions it produces within each. Flow conditions at gauging stations were used to estimate the turbulent strain rate experienced by suspended cyanobacteria. These indicate average turbulent strain rates in the Cudgegong and Hunter Rivers can be above 33 and 83 s-1 while for the Murray, Edward and Macquarie Rivers average strain rate was estimated to be less than 30 s-1. These turbulent strain rate estimates are substantially above published thresholds of approximately 2 s-1 for impacts indicated from laboratory tests. Estimates of strain rate were correlated with changes in cyanobacterial biovolume at stations along the rivers. These measurements indicate a weak but significant negative linear relationship between average strain rate and change in cyanobacterial biomass. River management often involves releasing cold deep water with low cyanobacterial presence from these reservoirs, leading to ecological impacts from cold water pollution downstream. The pollution may be avoided if cyanobacteria die off rapidly downstream of the reservoir, allowing surface water to be released instead. However high concentrations of soluble cyanotoxins may remain even after the cyanobacterial cells have been destroyed. The geomorphology of the river (length of riffle reaches) is an important consideration for river management during cyanobacterial blooms in headwater reservoirs.

Detection of the suspected neurotoxin ß-methylamino-l-alanine (BMAA) in cyanobacterial blooms from multiple water bodies in Eastern Australia.

The emerging toxin ß-methylamino-l-alanine (BMAA) has been linked to the development of a number of neurodegenerative diseases in humans including amyotrophic lateral sclerosis (ALS), Alzheimer's disease, and Parkinson's disease. BMAA has been found to be produced by a range of cyanobacteria, diatoms, and dinoflagellates worldwide, and is present in freshwater, saltwater, and terrestrial ecosystems. Surface scum samples were collected from waterways in rural and urban New South Wales, Australia and algal species identified. Reverse phase liquid chromatography-tandem mass spectrometry was used to analyse sixteen cyanobacterial scum for the presence of BMAA as well as its toxic structural isomer 2,4-diaminobutyric acid (2,4-DAB). BMAA was detected in ten of the samples analysed, and 2,4-DAB in all sixteen. The presence of these toxins in water used for agriculture raises concerns for public health and food security in Australia.

An evaluation of a handheld spectroradiometer for the near real-time measurement of cyanobacteria for bloom management purposes.

A commercially available handheld spectroradiometer, the WISP-3, was assessed as a tool for monitoring freshwater cyanobacterial blooms for management purposes. Three small eutrophic urban ponds which displayed considerable within-pond and between-pond variability in water quality and cyanobacterial community composition were used as trial sites. On-board algorithms provide field measurements of phycocyanin (CPC) and chlorophyll-a (Chl-a) from surface reflectance spectra measured by the instrument. These were compared with laboratory measurements. Although significant but weak relationships were found between WISP-3 measured CPC and cyanobacterial biovolume measurements and WISP-3 and laboratory Chl-a measurements, there was considerable scatter in the data due likely to error in both WISP-3 and laboratory measurements. The relationships generally differed only slightly between ponds, indicating that different cyanobacterial communities had little effect on the pigment retrievals of the WISP-3. The on-board algorithms need appropriate modification for local conditions, posing a problem if it is to be used extensively across water bodies with differing optical properties. Although suffering a range of other limitations, the WISP-3 has a potential as a rapid screening tool for preliminary risk assessment of cyanobacterial blooms. However, such field assessment would still require adequate support by sampling and laboratory-based analysis.

Use of three monitoring approaches to manage a major Chrysosporum ovalisporum bloom in the Murray River, Australia, 2016.

An unusual bloom of Chrysosporum ovalisporum (basionym Aphanizomenon ovalisporum) occurred for the first time in the Murray River and distributary rivers in New South Wales, Australia, from mid-February to early June 2016. At its greatest extent, it contaminated a combined river length of ca. 2360 km. Chrysosporum ovalisporum usually comprised >99% of the total bloom biovolume at most locations sampled, which at times exceeded 40 mm3 l-1. The origins of the bloom were most likely reservoirs on the upper Murray River, with cyanobacterial-infested water released from them contaminating the river systems downstream. An integrated approach using three analytical methods: (1) identification and enumeration by microscopy, (2) multiplex quantitative polymerase chain reaction (qPCR), and (3) toxin analysis, was used to obtain data for the assessment of risk to water users and management of the bloom. qPCR indicated some cyrA and stxA genes responsible for cylindrospermopsin and saxitoxin biosynthesis respectively were present, but mostly below the level of quantification. No mcyE genes for microcystin biosynthesis were detected. Toxin analysis also revealed that cylindrospermopsin, saxitoxin and microcystin were all below detection. Lack of measurable toxicity in a species usually considered a cylindrospermopsin producer elsewhere meant the possibility of relaxing management guidelines; however, high (Red) alerts needed to be maintained due to risk to water users from other biohazards potentially produced by the cyanobacteria such as contact irritants. A three-tiered monitoring strategy is suggested for monitoring cyanobacterial blooms to provide enhanced data for bloom management.

Assessment of in situ fluorometry to measure cyanobacterial presence in water bodies with diverse cyanobacterial populations.

A YSI EXO2 water quality sonde fitted with fluorometric sensors for chlorophyll-a (Chl-a) and phycocyanin (CPC) was used to determine its applicability in cyanobacterial quantification in three small urban ponds in Sydney, Australia displaying considerable variations in cyanobacterial community composition and abundance, as well as eukaryotic algae, turbidity and chromophoric dissolved organic matter. CPC and Chl-a measured in situ with the instrument was compared against laboratory measures of cyanobacterial biovolume over two summer sampling periods. A good correlation was found between CPC and total cyanobacterial biovolume in two of the three ponds. The poor correlation in the third was due to the frequent dominance of picoplanktonic sized cyanobacteria. CPC did not correlate well with cell counts, and Chl-a was a poor measure of cyanobacterial presence. The relationship between CPC measured by fluorometry varied according to the dominant cyanobacterial taxa present in the ponds at any one time. Fluorometry has good potential for use in environmental monitoring of cyanobacterial biovolume, but may need to be based on predetermined relations applicable to local water bodies. Management guidelines based on CPC concentrations would also enhance the usefulness of in situ CPC measurements.

Microbial communities reflect temporal changes in cyanobacterial composition in a shallow ephemeral freshwater lake.

The frequency of freshwater cyanobacterial blooms is at risk of increasing as a consequence of climate change and eutrophication of waterways. It is increasingly apparent that abiotic data are insufficient to explain variability within the cyanobacterial community, with biotic factors such as heterotrophic bacterioplankton, viruses and protists emerging as critical drivers. During the Australian summer of 2012-2013, a bloom that occurred in a shallow ephemeral lake over a 6-month period was comprised of 22 distinct cyanobacteria, including Microcystis, Dolichospermum, Oscillatoria and Sphaerospermopsis. Cyanobacterial cell densities, bacterial community composition and abiotic parameters were assessed over this period. Alpha-diversity indices and multivariate analysis were successful at differentiating three distinct bloom phases and the contribution of abiotic parameters to each. Network analysis, assessing correlations between biotic and abiotic variables, reproduced these phases and assessed the relative importance of both abiotic and biotic factors. Variables possessing elevated betweeness centrality included temperature, sodium and operational taxonomic units belonging to the phyla Verrucomicrobia, Planctomyces, Bacteroidetes and Actinobacteria. Species-specific associations between cyanobacteria and bacterioplankton, including the free-living Actinobacteria acI, Bacteroidetes, Betaproteobacteria and Verrucomicrobia, were also identified. We concluded that changes in the abundance and nature of freshwater cyanobacteria are associated with changes in the diversity and composition of lake bacterioplankton. Given this, an increase in the frequency of cyanobacteria blooms has the potential to alter nutrient cycling and contribute to long-term functional perturbation of freshwater systems.

Community composition, toxigenicity, and environmental conditions during a cyanobacterial bloom occurring along 1,100 kilometers of the Murray River.

A cyanobacterial bloom impacted over 1,100 km of the Murray River, Australia, and its tributaries in 2009. Physicochemical conditions in the river were optimal to support a bloom at the time. The data suggest that at least three blooms occurred concurrently in different sections of the river, with each having a different community composition and associated cyanotoxin profile. Microscopic and genetic analyses suggested the presence of potentially toxic Anabaena circinalis, Microcystis flos-aquae, and Cylindrospermopsis raciborskii at many locations. Low concentrations of saxitoxins and cylindrospermopsin were detected in Anabaena and Cylindrospermopsis populations. A multiplex quantitative PCR was used, employing novel oligonucleotide primers and fluorescent TaqMan probes, to examine bloom toxigenicity. This single reaction method identified the presence of the major cyanotoxin-producing species present in these environmental samples and also quantified the various toxin biosynthesis genes. A large number of cells present throughout the bloom were not potential toxin producers or were present in numbers below the limit of detection of the assay and therefore not an immediate health risk. Potential toxin-producing cells, possessing the cylindrospermopsin biosynthesis gene (cyrA), predominated early in the bloom, while those possessing the saxitoxin biosynthesis gene (sxtA) were more common toward its decline. In this study, the concentrations of cyanotoxins measured via enzyme-linked immunosorbent assay (ELISA) correlated positively with the respective toxin gene copy numbers, indicating that the molecular method may be used as a proxy for bloom risk assessment.