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Hot springs are characterised by water temperatures above 36.7 °C. Temperature decreases with distance in flow away from spring vents; this natural gradient provides a unique opportunity to investigate the influence of water temperature on aquatic biota. This study investigated the relationship between water temperature and the aquatic invertebrates and benthic diatoms in outflows from a hot spring complex in tropical north Queensland, Australia. Water temperature ranged from 62.7 °C at the vents to 26.0 °C at the location furthest downstream. Richness of benthic diatoms and aquatic invertebrates increased linearly in response to decreasing temperature, with no species present in the hot vents. Multivariate analysis showed that both community assemblages had a response to the temperature gradient. A drop in aquatic invertebrate richness and a change in assemblage composition occurred between 40 °C and 42 °C, indicating a threshold at this temperature. The nearby Einasleigh River has experienced several contemporary peaks in water temperature over 40 °C, which corresponds to this threshold level. The relationships indicate that consistent increases in water temperature expected under climate change could decrease biological richness and precipitate changes in the aquatic invertebrate and benthic diatom taxa of tropical aquatic ecosystems.

Abstract Cyanobacteria can produce groups of structurally and functionally unrelated but highly potent toxins. Cyanotoxins are used in multiple research endeavours, either for direct investigation of their toxicologic properties, or as functional analogues for various biochemical and physiological processes. This paper presents occupational safety guidelines and recommendations for personnel working in field, laboratory or industrial settings to produce and use purified cyanotoxins and toxic cyanobacteria, from bulk harvesting of bloom material, mass culture of laboratory isolates, through routine extraction, isolation and purification. Oral, inhalational, dermal and parenteral routes are all potential occupational exposure pathways during the various stages of cyanotoxin production and application. Investigation of toxicologic or pharmacologic properties using in vivo models may present specific risks if radiolabelled cyanotoxins are employed, and the potential for occupational exposure via the dermal route is heightened with the use of organic solvents as vehicles. Inter- and intra-national transport of living cyanobacteria for research purposes risks establishing feral microalgal populations, so disinfection of culture equipment and destruction of cells by autoclaving, incineration and/or chlorination is recommended in order to prevent viable cyanobacteria from escaping research or production facilities.

Three populations of the freshwater filamentous cyanobacterium Lyngbya wollei (Farlow ex Gomont) Speziale and Dyck have been putatively identified from north-eastern Australia and found to produce the potent cyanotoxin cylindrospermopsin ( CYN) and its analog deoxy-cylindrospermopsin (deoxy- CYN). We investigated the phylogeny and toxicology of strains and mats isolated from two of these populations using a combination of molecular and morphological techniques. Morphologically the strains corresponded to the type description, however, the frequency of false-branching was low, and variable over time. Strains and mat samples from both sites were positive for the cyrF and cyrJ genes associated with CYN biosynthesis. Phylogenetic analysis of these genes from Australian L. wollei sequences and comparable cyanobacterial sequences revealed that the genes in L. wollei were more closely related to homologous genes in Oscillatoria sp. PCC 6506 than to homologs in Nostocalean CYN-producers. These data suggest a common evolutionary origin of CYN biosynthesis in L. wollei and Oscillatoria. In both the 16S rRNA and nifH phylogenies, the Australian L. wollei strains formed well-supported clades with United States L. wollei (= Plectonema wollei) strains. Pair-wise sequence similarities within the 16S rRNA clade containing all eleven L. wollei strains were high, ranging from 97% to 100%. This group was distantly related (<92% nucleotide similarity) to other taxa within the group previously considered under the genus Lyngbya sensu lato (C. Agardh ex Gomont). Collectively, these results suggest that this toxigenic group is evolutionarily distinct and sufficiently distant as to be considered a separate genus, which we have described as Microseira gen. nov. and hence transfer to it the type M. wollei comb. nov. [ABSTRACT FROM AUTHOR]

A new epipelic freshwater cyanobacterium, Komvophoron kgarii sp. nov., was identified from a perennial wallum stream on Fraser Island, northeastern Australia. Komvophoron kgariiv/as the first species in Komvophoron that was described on the basis of combined morphological, ultrastructural and phylogenetic attributes. The new taxon was distinguished by virtue of its obtuse-conical apical cells that became conically elongated and narrowed toward the ends as they matured. Additionally, trichome separation into hormogonia was preceded by preapical cells beginning to differentiate on either side of the fragmentation point before separation, a feature not previously recorded in this genus. Ultrastructural examination showed that thylakoids formed irregularly arranged blocks of lamellae in both longitudinal and cross-sections. Phylogenetic analysis revealed that the isolated material shared less than 91% 16S ribosomal RNA nucleotide sequence similarity with any other cyanobacterial sequence and formed a novel branch. [ABSTRACT FROM AUTHOR]

Human-induced environmental change threatens freshwater ecosystems, and knowing how these systems have responded to past variability can inform management decisions. Palaeoenvironmental reconstructions provide insight, although their low temporal resolution may mask short-term responses. Hence, a combination of short-term, high-resolution contemporary data and long-term, low-resolution palaeoenvironmental data can offer greater understanding of system behaviour., We demonstrate this approach by examining the response of a lake on North Stradbroke Island, Australia, to environmental change, by investigating hydrological and water quality variation at different temporal scales. The data include daily lake discharge, monthly water quality, modelled annual lake discharge over a 117-year period and comparisons of aerial photographs and lake bathymetry over the past 65 years. A palaeoenvironmental reconstruction of the last c. 7500 years used pollen, stable isotopes, macrofossils and diatoms to provide a long-term perspective., Despite variability in regional climate over recent decades, the depth and water chemistry of Blue Lake displayed little variation. At millennial timescales, there is clear evidence of catchment change in response to a marked shift in climate around 4500 years ago. However, diatom analysis indicates that Blue Lake has exhibited exceptional stability and resistance to change, compared to other Australian Holocene lake records. This suggests that Blue Lake has been an important climate refuge for aquatic biota in the past and, with appropriate management, should continue in this capacity into the future., This study highlights the benefits of a combined, multi-temporal approach to inform understanding of the structure and function of freshwater ecosystems and their responses to environmental change. Such scientific understanding of system requirements is critical to achieving sustainable management objectives. [ABSTRACT FROM AUTHOR]

The occurrence of the cyanobacteriumCylindrospermopsis raciborskii(Woloszynska) Seenayya and Subba Raju is a global water quality issue. The misidentification ofC. raciborskiiin the past is a major concern for water quality users, considering the reported cases of human and livestock poisonings associated with the cyanobacterium. Many of the available taxonomic descriptions for this species provide little or no detail of the morphology of early developmental phases that may assist with identification. Therefore, typifying the morphological changes throughout the entire life cycle for such a species requires urgent attention. In this study, five distinct morphological phases identified using a new culturing technique are reported for the process of akinete germination inC. raciborskii. Before the terminal emergence of three to four cell germlings through a ruptured akinete envelope (phase 3), mature akinetes (phase 1) elongated and the endospore separated from the akinete envelope (phase 2). After the association with the envelope was lost, four-cell germlings (phase 4a) matured into young trichomes of more than four cells (phase 4b). Throughout the process of germination, internal granular structures decreased in size and were irregular in shape in germlings and young trichomes. The culturing technique, which used a Sedgwick-Rafter cell, was successful in its application but was limiting in that the development of young trichomes after phase 4b could not be monitored. [ABSTRACT FROM AUTHOR]