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Ormond, Australia

Kohli G.S.,University of New South Wales | Kohli G.S.,University of Technology, Sydney | Murray S.A.,University of Technology, Sydney | Murray S.A.,Sydney Institute of Marine Science | And 8 more authors.
Harmful Algae | Year: 2014

Species of the genus Gambierdiscus are epiphytic dinoflagellates well known from tropical coral reef areas at water temperatures from 24 to 29°C. Gambierdiscus spp. are able to produce ciguatoxins (CTXs) known to bioaccumulate in fish, and the ingestion of tropical fish that accumulated CTXs and possibly also maitotoxins (MTXs) can cause ciguatera fish poisoning (CFP) in humans. In Australia, ciguatera poisonings have been reported in tropical parts of Queensland and the Northern Territory. Here, we report for the first time the seasonal abundance (April-May 2012/13) of Gambierdiscus spp. (up to 6565-8255cellsg-1 wet weight algae) from Merimbula and Wagonga Inlets in temperate southern New South Wales, Australia (37°S) at water temperatures of 16.5-17°C. These are popular shellfish aquaculture and recreational fisheries areas with no reports of ciguatera poisoning. Sequencing of a region of the 28S rRNA gene led to the conclusive identification of Gambierdiscus carpenteri. The cells differed however from the Belize type description, including the absence of a thecal groove, dorsal rostrum and variable hatchet- to rectangular-shaped 2' plate, and were morphologically more similar to Gambierdiscus toxicus. To study the dinoflagellate community structure in detail, a pyrosequencing approach based on the 18S rRNA gene was applied, which confirmed the presence of a single Gambierdiscus species only. Neither CTXs nor MTXs were detected in natural bloom material by LC-MS/MS; however, the extracts were found to be toxic via mouse-bioassay, with symptoms suggestive of poisoning by MTX-like compounds. Understanding the abundance of Gambierdiscus populations in areas with no apparent human health impacts is important towards defining the alternate conditions where sparse populations can create ciguatera problems. © 2014 Elsevier B.V. Source

Ajani P.,Macquarie University | Ajani P.,Sydney Institute of Marine Science | Murray S.,Sydney Institute of Marine Science | Murray S.,University of Technology, Sydney | And 3 more authors.
Phycological Research | Year: 2013

Pseudo-nitzschiaH. Peragallo is a marine diatom genus found worldwide in polar, temperate, subtropical and tropical waters. It includes toxigenic representatives that produce domoic acid (DA), a neurotoxin responsible for Amnesic Shellfish Poisoning. In this study we characterized two species of Pseudo-nitzschia collected from Port Stephens and the Hawkesbury River (south eastern Australia) previously unreported from Australian waters. Clonal isolates were sub-sampled for (i) light and transmission electron microscopy; (ii) DNA sequencing, based on the nuclear-encoded partial large subunit ribosomal RNA gene and internal transcribed spacer (ITS)-ITS1, 5.8S and ITS2 rDNA regions and, (iii) DA production as measured by liquid chromatography-mass spectrometry. Morphological and molecular data unambiguously revealed the species to be Pseudo-nitzschia microporaPriisholm, Moestrup & Lundholm (Port Stephens) and Pseudo-nitzschia hasleanaLundholm (Hawkesbury River). This is the first report of the occurrence of these species from the Southern Hemisphere and the first report of P. micropora in warm-temperate waters. Cultures of P. micropora, tested for DA production for the first time, proved to be non-toxic. Similarly, no detectable toxin concentrations were observed for P. hasleana. Species resolution and knowledge on the toxicity of local Pseudo-nitzschia species has important implications for harmful algal bloom monitoring and management. © 2013 Japanese Society of Phycology. Source

Ajani P.,Macquarie University | Ajani P.,Sydney Institute of Marine Science | Murray S.,Sydney Institute of Marine Science | Murray S.,University of Technology, Sydney | And 7 more authors.
Journal of Phycology | Year: 2013

Species belonging to the potentially harmful diatom genus Pseudo-nitzschia, isolated from 16 localities (31 sampling events) in the coastal waters of south-eastern Australia, were examined. Clonal isolates were characterized by (i) light and transmission electron microscopy; (ii) phylogenies, based on sequencing of nuclear-encoded ribosomal deoxyribonucleic acid (rDNA) regions and, (iii) domoic acid (DA) production as measured by liquid chromatography-mass spectrometry (LC-MS/MS). Ten taxa were unequivocally confirmed as Pseudo-nitzschia americana, P. arenysensis, P. calliantha, P. cuspidata, P. fraudulenta, P. hasleana, P. micropora, P. multiseries, P. multistriata, and P. pungens. An updated taxonomic key for south-eastern Australian Pseudo-nitzschia is presented. The occurrence of two toxigenic species, P. multistriata (maximum concentration 11 pg DA per cell) and P. cuspidata (25.4 pg DA per cell), was documented for the first time in Australia. The Australian strains of P. multiseries, a consistent producer of DA in strains throughout the world, were nontoxic. Data from 5,888 water samples, collected from 31 oyster-growing estuaries (2,000 km coastline) from 2005 to 2009, revealed 310 regulatory exceedances for "Total Pseudo-nitzschia," resulting in six toxic episodes. Further examination of high-risk estuaries revealed that the "P. seriata group" had highest cell densities in the austral summer, autumn, or spring (species dependent), and lowest cell densities in the austral winter, while the "P. delicatissima group" had highest in winter and spring. © 2013 Phycological Society of America. Source

Murray S.A.,Sydney Institute of Marine Science | Murray S.A.,University of New South Wales | Wiese M.,Sydney Institute of Marine Science | Wiese M.,University of New South Wales | And 5 more authors.
Harmful Algae | Year: 2012

The three Alexandrium species A. tamarense, A. fundyense and A. catenella include strains that can be potent producers of the neurotoxin saxitoxin (STX) and its analogues, the causative agents of paralytic shellfish poisoning (PSP). These three species are morphologically highly similar, differing from each other only in the possession of a ventral pore, or in the ability to form chains. The appropriateness of these morphological characters for species delimitation has been extensively debated. A distinctive clade of this species complex, Group V, Tasmanian clade, is found in southern Australia, and occasionally occurs in bloom proportions. This clade has been considered non-toxic, and no PSP toxins have been found in shellfish following blooms of this species. In the present study, we report on a Tasmanian strain of A. tamarense, Group V that produces STX and possesses the gene, sxtA that is putatively involved in STX production. The toxin profile was determined and is unusual, including a high proportion of GTX5 and a small amount of STX, and differs from that of co-occurring A. catenella (Group IV). A putative bloom of A. tamarense that occurred in October 2010, and the subsequent finding of STX in Sydney Rock Oysters (. Saccostrea glomerata), may suggest that some naturally occurring strains of this species could produce STX. © 2012 Elsevier B.V. Source

Murray S.A.,Sydney Institute of Marine Science | Murray S.A.,University of New South Wales | Wiese M.,Sydney Institute of Marine Science | Wiese M.,University of New South Wales | And 5 more authors.
Applied and Environmental Microbiology | Year: 2011

The recent identification of genes involved in the production of the potent neurotoxin and keystone metabolite saxitoxin (STX) in marine eukaryotic phytoplankton has allowed us for the first time to develop molecular genetic methods to investigate the chemical ecology of harmful algal blooms in situ. We present a novel method for detecting and quantifying the potential for STX production in marine environmental samples. Our assay detects a domain of the gene sxtA that encodes a unique enzyme putatively involved in the sxt pathway in marine dinoflagellates, sxtA4. A product of the correct size was recovered from nine strains of four species of STX-producing Alexandrium and Gymnodinium catenatum and was not detected in the non-STX-producing Alexandrium species, other dinoflagellate cultures, or an environmental sample that did not contain known STX-producing species. However, sxtA4 was also detected in the non-STX-producing strain of Alexandrium tamarense, Tasmanian ribotype. We investigated the copy number of sxtA4 in three strains of Alexandrium catenella and found it to be relatively constant among strains. Using our novel method, we detected and quantified sxtA4 in three environmental blooms of Alexandrium catenella that led to STX uptake in oysters. We conclude that this method shows promise as an accurate, fast, and cost-effective means of quantifying the potential for STX production in marine samples and will be useful for biological oceanographic research and harmful algal bloom monitoring. © 2011, American Society for Microbiology. Source

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