Behrendt, L, Larkum, AWD, Trampe, E, Norman, A, Sorensen, SJ & Kuhl, M 2012, 'Microbial diversity of biofilm communities in microniches associated with the didemnid ascidian Lissoclinum patella', ISME JOURNAL, vol. 6, no. 6, pp. 1222-1237.
View/Download from: Publisher's site
View description>>
We assessed the microbial diversity and microenvironmental niche characteristics in the didemnid ascidian Lissoclinum patella using 16S rRNA gene sequencing, microsensor and imaging techniques. L. patella harbors three distinct microbial communities spatially separated by few millimeters of tunic tissue: (i) a biofilm on its upper surface exposed to high irradiance and O-2 levels, (ii) a cloacal cavity dominated by the prochlorophyte Prochloron spp. characterized by strong depletion of visible light and a dynamic chemical microenvironment ranging from hyperoxia in light to anoxia in darkness and (iii) a biofilm covering the underside of the animal, where light is depleted of visible wavelengths and enriched in near-infrared radiation (NIR). Variable chlorophyll fluorescence imaging demonstrated photosynthetic activity, and hyperspectral imaging revealed a diversity of photopigments in all microhabitats. Amplicon sequencing revealed the dominance of cyanobacteria in all three layers. Sequences representing the chlorophyll d containing cyanobacterium Acaryochloris marina and anoxygenic phototrophs were abundant on the underside of the ascidian in shallow waters but declined in deeper waters. This depth dependency was supported by a negative correlation between A. marina abundance and collection depth, explained by the increased attenuation of NIR as a function of water depth. The combination of microenvironmental analysis and fine-scale sampling techniques used in this investigation gives valuable first insights into the distribution, abundance and diversity of bacterial communities associated with tropical ascidians. In particular, we show that microenvironments and microbial diversity can vary significantly over scales of a few millimeters in such habitats; which is information easily lost by bulk sampling
Behrendt, L, Schrameyer, V, Qvortrup, K, Lundin, L, Sorensen, SJ, Larkum, AWD & Kuehl, M 2012, 'Biofilm Growth and Near-Infrared Radiation-Driven Photosynthesis of the Chlorophyll d-Containing Cyanobacterium Acaryochloris marina', APPLIED AND ENVIRONMENTAL MICROBIOLOGY, vol. 78, no. 11, pp. 3896-3904.
View/Download from: Publisher's site
View description>>
The cyanobacterium Acaryochloris marina is the only known phototroph harboring chlorophyll (Chl) d. It is easy to cultivate it in a planktonic growth mode, and A. marina cultures have been subject to detailed biochemical and biophysical characterization. In natural situations, A. marina is mainly found associated with surfaces, but this growth mode has not been studied yet. Here, we show that the A. marina type strain MBIC11017 inoculated into alginate beads forms dense biofilm-like cell clusters, as in natural A. marina biofilms, characterized by strong O-2 concentration gradients that change with irradiance. Biofilm growth under both visible radiation (VIS, 400 to 700 nm) and near-infrared radiation (NIR, similar to 700 to 730 nm) yielded maximal cell-specific growth rates of 0.38 per day and 0.64 per day, respectively. The population doubling times were 1.09 and 1.82 days for NIR and visible light, respectively. The photosynthesis versus irradiance curves showed saturation at a photon irradiance of E-k (saturating irradiance) >250 mu mol photons m(-2) s(-1) for blue light but no clear saturation at 365 mu mol photons m(-2) s(-1) for NIR. The maximal gross photosynthesis rates in the aggregates were similar to 1,272 mu mol O-2 mg Chl d(-1) h(-1) (NIR) and similar to 1,128 mu mol O-2 mg Chl d(-1) h(-1) (VIS). The photosynthetic efficiency (alpha) values were higher in NIR-irradiated cells [(268 +/- 0.29) x 10(-6) m(2) mg Chl d(-1) (mean +/- standard deviation)] than under blue light [(231 +/- 0.22) x 10(-6) m(2) mg Chl d(-1)]. A. marina is well adapted to a biofilm growth mode under both visible and NIR irradiance and under O-2 conditions ranging from anoxia to hyperoxia, explaining its presence in natural niches with similar environmental conditions.
Brading, P, Warner, ME, Davey, P, Smith, DJ, Achterberg, EP & Suggett, DJ 2012, 'Erratum: Differential effects of ocean acidification on growth and photosynthesis among phylotypes of Symbiodinium (Dinophyceae)', Limnology and Oceanography, vol. 57, no. 4, pp. 1255-1255.
View/Download from: Publisher's site
Buxton, L, Takahashi, S, Hill, R & Ralph, PJ 2012, 'VARIABILITY IN THE PRIMARY SITE OF PHOTOSYNTHETIC DAMAGE IN SYMBIODINIUM SP (DINOPHYCEAE) EXPOSED TO THERMAL STRESS', JOURNAL OF PHYCOLOGY, vol. 48, no. 1, pp. 117-126.
View/Download from: Publisher's site
View description>>
Exposure to elevated temperature is known to cause photosynthetic inhibition in the coral symbiont Symbiodinium sp. Through the use of the artificial electron acceptor, methyl viologen, this study identified how reduced photosynthetic capacity occurs as a result of inhibition up- and/or downstream of ferredoxin in Symbiodinium sp. in hospite and in culture. Heterogeneity between coral species and symbiont clades was identified in the thermal sensitivity of photosynthesis in the symbionts of the scleractinian corals Stylophora pistillata and Pocillopora damicornis, as well as among Symbiodinium cultures of clades A, B, and C. The in hospite symbionts of S. pistillata and the cultured clade C Symbiodinium both exhibited similar patterns in that their primary site of thermal inhibition occurred downstream of ferredoxin at 32 degrees C. In contrast, the primary site of thermal inhibition occurred upstream of ferredoxin in clades A and B at 32 degrees C, while at 34 degrees C, all samples showed combined up- and downstream inhibition. Although clade C is common to both P. damicornis and S. pistillata, the manner of thermal inhibition was not consistent when observed in hospite. Results showed that there is heterogeneity in the primal site of thermal damage in Symbiodinium among coral species and symbiont clades.
Ceh, J, Raina, J-B, Soo, RM, van Keulen, M & Bourne, DG 2012, 'Coral-Bacterial Communities before and after a Coral Mass Spawning Event on Ningaloo Reef', PLoS ONE, vol. 7, no. 5, pp. e36920-e36920.
View/Download from: Publisher's site
View description>>
Bacteria associated with three coral species, Acropora tenuis, Pocillopora damicornis and Tubastrea faulkneri, were assessed before and after coral mass spawning on Ningaloo Reef in Western Australia. Two colonies of each species were sampled before and after the mass spawning event and two additional samples were collected for P. damicornis after planulation. A variable 470 bp region of the 16 S rRNA gene was selected for pyrosequencing to provide an understanding of potential variations in coral-associated bacterial diversity and community structure. Bacterial diversity increased for all coral species after spawning as assessed by Chao1 diversity indicators. Minimal changes in community structure were observed at the class level and data at the taxonomical level of genus incorporated into a PCA analysis indicated that despite bacterial diversity increasing after spawning, coral-associated community structure did not shift greatly with samples grouped according to species. However, interesting changes could be detected from the dataset; for example, a-Proteobacteria increased in relative abundance after coral spawning and particularly the Roseobacter clade was found to be prominent in all coral species, indicating that this group may be important in coral reproduction.
Clifton, J, Etienne, M, Barnes, DKA, Barnes, RSK, Suggett, DJ & Smith, DJ 2012, 'Marine conservation policy in Seychelles: Current constraints and prospects for improvement', Marine Policy, vol. 36, no. 3, pp. 823-831.
View/Download from: Publisher's site
View description>>
The marine assets of Seychelles are fundamental to the national economy through generating income derived from tourism and fisheries. Marine management institutions and policies have undergone radical changes since 2008, reflecting a number of drivers and initiatives at international and national levels. Through using the example of Curieuse Marine National Park in the inner Seychelles, we demonstrate how these are affecting marine conservation with respect to coastal development, governance of marine protected areas and livelihood security within resource-dependent communities. These issues are of significance with respect to the current and future viability of marine conservation and resource management in Seychelles. Potential mitigating strategies are suggested which could lead to more effective governance and conservation of marine protected areas in Seychelles and similar small island developing states. © 2011 Elsevier Ltd.
Dunn, SR, Pernice, M, Green, K, Hoegh-Guldberg, O & Dove, SG 2012, 'Thermal Stress Promotes Host Mitochondrial Degradation in Symbiotic Cnidarians: Are the Batteries of the Reef Going to Run Out?', PLoS ONE, vol. 7, no. 7, pp. e39024-e39024.
View/Download from: Publisher's site
View description>>
The symbiotic relationship between cnidarians and their dinoflagellate symbionts, Symbiodinium spp, which underpins the formation of tropical coral reefs, can be destabilized by rapid changes to environmental conditions. Although some studies have concluded that a breakdown in the symbiosis begins with increased reactive oxygen species (ROS) generation within the symbiont due to a decoupling of photosynthesis, others have reported the release of viable symbionts via a variety of host cell derived mechanisms. We explored an alternative model focused upon changes in host cnidarian mitochondrial integrity in response to thermal stress. Mitochondria are often likened to being batteries of the cell, providing energy in the form of ATP, and controlling cellular pathway activation and ROS generation. The overall morphology of host mitochondria was compared to that of associated symbionts under an experimental thermal stress using confocal and electron microscopy. The results demonstrate that hyperthermic stress induces the degradation of cnidarian host mitochondria that is independent of symbiont cellular deterioration. The potential sites of host mitochondrial disruption were also assessed by measuring changes in the expression of genes associated with electron transport and ATP synthesis using quantitative RT-PCR. The primary site of degradation appeared to be downstream of complex III of the electron transport chain with a significant reduction in host cytochrome c and ATP synthase expression. The consequences of reduced expression could limit the capacity of the host to mitigate ROS generation and maintain both organelle integrity and cellular energy supplies. The disruption of host mitochondria, cellular homeostasis, and subsequent cell death irrespective of symbiont integrity highlights the importance of the host response to thermal stress and in symbiosis dysfunction that has substantial implications for understanding how coral reefs will survive in the...
Exton, DA, Suggett, DJ, Steinke, M & McGenity, TJ 2012, 'Spatial and temporal variability of biogenic isoprene emissions from a temperate estuary', Global Biogeochemical Cycles, vol. 26, no. 2, pp. n/a-n/a.
View/Download from: Publisher's site
View description>>
Isoprene is important for its atmospheric impacts and the ecophysiological benefits it affords to emitting organisms; however, isoprene emissions from marine systems remain vastly understudied compared to terrestrial systems. This study investigates for the first time drivers of isoprene production in a temperate estuary, and the role this production may play in enabling organisms to tolerate the inherently wide range of environmental conditions. Intertidal sediment cores as well as high and low tide water samples were collected from four sites along the Colne Estuary, UK, every six weeks over a year. Isoprene concentrations in the water were significantly higher at low than high tide, and decreased toward the mouth of the estuary; sediment production showed no spatial variability. Diel isoprene concentration increased with light availability and decreased with tidal height; nighttime production was 79% lower than daytime production. Seasonal isoprene production and water concentrations were highest for the warmest months, with production strongly correlated with light (r2 = 0.800) and temperature (r2 = 0.752). Intertidal microphytobenthic communities were found to be the primary source of isoprene, with tidal action acting as a concentrating factor for isoprene entering the water column. Using these data we estimated an annual production rate for this estuary of 681 μmol m−2 y−1. This value falls at the upper end of other marine estimates and highlights the potentially significant role of estuaries as isoprene sources. The control of estuarine isoprene production by environmental processes identified here further suggests that such emissions may be altered by future environmental change.
Feito, R, Valcárcel, Y & Catalá, M 2012, 'Biomarker assessment of toxicity with miniaturised bioassays: diclofenac as a case study', Ecotoxicology, vol. 21, no. 1, pp. 289-296.
View/Download from: Publisher's site
Gilbert, JA, Hill, R, Doblin, MA & Ralph, PJ 2012, 'Microbial consortia increase thermal tolerance of corals', MARINE BIOLOGY, vol. 159, no. 8, pp. 1763-1771.
View/Download from: Publisher's site
View description>>
This study examined the response of a coral holobiont to thermal stress when the bacterial community was treated with antibiotics. Colonies of Pocillopora damicornis were exposed to broad and narrow-spectrum antibiotics targeting coral-associated α and γ-Proteobacteria. Corals were gradually heated from the control temperature of 26 to 31 °C, and measurements were made of host, zooxanthellar and microbial condition. Antibiotics artificially reduced the abundance and activity of bacteria, but had minimal effect on zooxanthellae photosynthetic efficiency or host tissue protein content. Heated corals without antibiotics showed significant declines in F V/F M, typical of thermal stress. However, heated corals treated with antibiotics showed severe tissue loss in addition to a decline in F V/F M. This study demonstrated that a disruption to the microbial consortium diminished the resilience of the holobiont. Corals exposed to antibiotics under control temperature did not bleach, suggesting that temperature may be an important factor influencing the activity, diversity and ecological function of the holobiont bacterial community. © 2012 Springer-Verlag.
Green, BC, Suggett, DJ, Hills, A & Steinke, M 2012, 'Optimisation of a fast DMS sensor (FDS) for real time quantification of dimethyl sulfide production by algae', Biogeochemistry, vol. 110, no. 1-3, pp. 163-172.
View/Download from: Publisher's site
View description>>
Production of dimethyl sulfide (DMS) from marine samples is often quantified using gas chromatography techniques. Typically, these are labour intensive and have a slow sample turnover rate. Here we demonstrate the use of a portable fast DMS sensor (FDS) that utilises the chemiluminescent reaction of DMS and ozone to measure DMS production in aqueous samples, with a maximum frequency of 10 Hz. We have developed a protocol for quantifying DMS production that removes potential signal interference from other biogenic trace gases such as isoprene (2-methyl-1,3-butadiene) and hydrogen sulfide. The detection limit was 0. 89 pM (0. 02 ppbv) when using a DMS standard gas mixture. The lowest DMS production rates quantified with the FDS and verified using conventional gas chromatography with flame photometric detection (GC-FPD) were around 0. 01 nmol min -1. There was a strong correlation in DMS production when comparing the FDS and GC-FPD techniques with a range of marine samples (e. g., r 2 = 0. 94 for Emiliania huxleyi). However, the combined dataset showed the FDS measured 22% higher DMS production than the GC-FPD, with the differences in rates likely due to interfering gases, for example hydrogen sulfide and isoprene. This possible overestimation of DMS production is smaller than the two-fold difference in DMS production between day and night samples from a culture of E. huxleyi. The response time of the instrument to changes in DMS production is method dependent (e. g., geometry of incubation vessel, bubble size) and was approximately 4 min under our conditions when using a culture of E. huxleyi (800 ml) with aeration at 100 ml min -1. We suggest the FDS can reduce sample handling, is suitable for short- and long-term measurements of DMS production in algal cultures, and will widen the range of DMS research in marine environments. © 2011 Springer Science+Business Media B.V.
Gupta, V, Bijo, AJ, Kumar, M, Reddy, CRK & Jha, B 2012, 'Detection of Epigenetic Variations in the Protoplast-Derived Germlings of Ulva reticulata Using Methylation Sensitive Amplification Polymorphism (MSAP)', Marine Biotechnology, vol. 14, no. 6, pp. 692-700.
View/Download from: Publisher's site
View description>>
Regeneration of protoplasts into de novo plants was reported for a large number of seaweed species. The regeneration of protoplasts into different morphotypes as a result of epigenetic variations was discussed for the first time in this study. The loci assessed for methylation modifications in normal filamentous thalli showed a frequency of 32. 43% as unmethylated DNA, 24. 32% as a hemimethylated, and 20. 27% as a methylation of internal cytosine at both the strands. The corresponding methylation values for disk-type thalli were 27. 02%, 32. 43%, and 14. 86%, respectively. The hypermethylation condition was apparent in the disk-type thalli with methylation ratio of 72. 97% compared to that of normal filamentous thalli with 67. 56%. The frequency of methylation polymorphic sites among the two morphotypes was 53%. The present study reveals the distinct expression of cytosine methylation and is thus correlated to differential morphogenesis of plants regenerated from cultured cells. The number of protoplasts regenerating into filamentous thalli declined with increasing temperature from 15°C, 20°C, 25°C, and 30°C. The disk-type variant had higher thermal stability at 30°C over normal filamentous thalli. Further, this variant could maintain itself for more than a year in the laboratory indicating its suitability for in vitro germplasm maintenance and propagation. © 2012 The Author(s).
Hallegraeff, GM, Blackburn, SI, Doblin, MA & Bolch, CJS 2012, 'Global toxicology, ecophysiology and population relationships of the chainforming PST dinoflagellate Gymnodinium catenatum', HARMFUL ALGAE, vol. 14, pp. 130-143.
View/Download from: Publisher's site
View description>>
Increasing scientific awareness since the 1980s of the chain-forming dinoflagellate Gymnodinium catenatum has led to this species being reported with increased frequency in a globally increasing number of countries (23 at present). G. catenatum exhibits little molecular genetic variation in rDNA over its global range, in contrast to RAPD fingerprinting which points to high genetic variation within regional populations even between estuaries 50. km apart. All Australian and New Zealand strains possess a thymine nucleotide (T-gene) near the start of the 5.8S rRNA whereas all other global populations examined to date possess cytosine-nucleotide (C-gene), except for southern Japan which harbours both C-gene and T-gene strains. Together with cyst and plankton evidence this strongly suggests that both Australian and New Zealand populations have derived from southern Japan. Global dinoflagellate populations and cultures exhibit an extraordinary variation in PST profiles (STX and 21 analogues), but consistent regional patterns are evident with regard to the production of C1,2; C3,4; B1,2; and neoSTX analogues. PST profiles of cyst-derived cultures are deemed unrepresentative. Distinct ecophysiological differences exist between tropical (21-32°C) and warm-temperate ecotypes (12-18°C), but these appear unrelated to ITS genotypes and PST toxin phenotypes. On current evidence, cyst germination appears to play a minimal role in the bloom dynamics of this species, while seasonal and inter-annual bloom variations result from the physical constraints (temperature and light) on the growth of the dinoflagellates in the water column. G. catenatum exhibits a capacity to utilize many forms of nitrogen. Its chain formation and strong motility allow it to undergo retrieval migrations to exploit light and nutrient resource gradients in both stratified and mixed environments. Subtle strain-level variations in micronutrient (Se, humics) requirements and interaction with associat...
Hill, R, Larkum, AWD, Prasil, O, Kramer, DM, Szabo, M, Kumar, V & Ralph, PJ 2012, 'Light-induced dissociation of antenna complexes in the symbionts of scleractinian corals correlates with sensitivity to coral bleaching', CORAL REEFS, vol. 31, no. 4, pp. 963-975.
View/Download from: Publisher's site
View description>>
Elevated temperatures in combination with moderate to high irradiance are known to cause bleaching events in scleractinian corals, characterised by damage to photosystem II (PSII). Photoprotective mechanisms of the symbiont can reduce the excitation pressure impinging upon PSII. In the bleaching sensitive species, Acropora millepora and Pocillopora damicornis, high light alone induced photoprotection through the xanthophyll cycle, increased content of the antioxidant carotenoid, β-carotene, as well as the dissociation of the light-harvesting chlorophyll complexes. The evidence is compatible with either the membrane-bound chlorophyll a-chlorophyll c2-peridinin-protein (acpPC) complex or the peripheral peridinin-chlorophyll-protein complex, or both, disconnecting from PSII under high light. The acpPC complex potentially showed a state transition response with redistribution towards photosystem I to reduce PSII over-excitation. This apparent acpPC dissociation/reassociation was promoted by the addition of the xanthophyll cycle inhibitor, dithiothreitol, under high irradiance. Exposure to thermal stress as well as high light promoted xanthophyll de-epoxidation and increased β-carotene content, although it did not influence light-harvesting chlorophyll complex (LHC) dissociation, indicating light, rather than temperature, controls LHC dissociation. Photoinhibition was avoided in the bleaching tolerant species, Pavona decussata, suggesting xanthophyll cycling along with LHC dissociation may have been sufficient to prevent photodamage to PSII. Symbionts of P. decussata also displayed the greatest detachment of antenna complexes, while the more thermally sensitive species, Pocillopora damicornis and A. millepora, showed less LHC dissociation, suggesting antenna movement influences bleaching susceptibility. © 2012 Springer-Verlag.
Hoeksema, BW, Matthews, JL & Yeemin, T 2012, 'The 2010 coral bleaching event and its impact on the mushroom coral fauna of Koh Tao, western Gulf of Thailand', Phuket Marine Biological Center Research Bulletin, vol. 71, pp. 71-81.
View description>>
During two surveys of the mushroom coral fauna of Koh Tao, a total of 20 species was recorded. The first survey (June 2010) was during a coral bleaching event caused by elevated seawater temperatures. Bleaching in mushroom corals appeared to be depth-dependent at the deepest sites with less bleaching occurring below 20 m depth. Some fungiid species, like Ctenactis echinata, appeared to be less susceptible to bleaching than others. This species was affected very little and was represented by regularly coloured individuals among many bleached specimens of other mushroom coral species. Few corals of Fungia fungites showed bleaching on the shallow reef flats but many were bleached on the slopes. During the second survey (February 2011), Koh Tao's mushroom coral fauna appeared to have recovered and no trace of thermal bleaching was visible anymore.
Humphreys, W, Tetu, S, Elbourne, L, Gillings, M, Seymour, J, Mitchell, J & Paulsen, I 2012, 'Geochemical and microbial diversity of bundera sinkhole, an anchialine system in the eastern Indian ocean', Natura Croatica, vol. 21, no. SUPPL.1, pp. 59-63.
View description>>
The anchialine system at Bundera sinkhole, Australia, exhibits pronounced hydrogeochemical structure through depth that is reflected in the composition and distribution of the fauna. It is a strongly structured microbial ecosystem the components of which also change with depth and which is dominated by sulfur bacteria and chemolithotrophic microbial classes.
Jeffries, TC, Seymour, JR, Newton, K, Smith, RJ, Seuront, L & Mitchell, JG 2012, 'Increases in the abundance of microbial genes encoding halotolerance and photosynthesis along a sediment salinity gradient', BIOGEOSCIENCES, vol. 9, no. 2, pp. 815-825.
View/Download from: Publisher's site
View description>>
Biogeochemical cycles are driven by the metabolic activity of microbial communities, yet the environmental parameters that underpin shifts in the functional potential coded within microbial community genomes are still poorly understood. Salinity is one of the primary determinants of microbial community structure and can vary strongly along gradients within a variety of habitats. To test the hypothesis that shifts in salinity will also alter the bulk biogeochemical potential of aquatic microbial assemblages, we generated four metagenomic DNA sequence libraries from sediment samples taken along a continuous, natural salinity gradient in the Coorong lagoon, Australia, and compared them to physical and chemical parameters. A total of 392483 DNA sequences obtained from four sediment samples were generated and used to compare genomic characteristics along the gradient. The most significant shifts along the salinity gradient were in the genetic potential for halotolerance and photosynthesis, which were more highly represented in hypersaline samples. At these sites, halotolerance was achieved by an increase in genes responsible for the acquisition of compatible solutes-organic chemicals which influence the carbon, nitrogen and methane cycles of sediment. Photosynthesis gene increases were coupled to an increase in genes matching Cyanobacteria, which are responsible for mediating CO2 and nitrogen cycles. These salinity driven shifts in gene abundance will influence nutrient cycles along the gradient, controlling the ecology and biogeochemistry of the entire ecosystem. © 2012 Author(s).
Jimenez, IM, Larkum, AWD, Ralph, PJ & Kuehl, M 2012, 'Thermal effects of tissue optics in symbiont-bearing reef-building corals', LIMNOLOGY AND OCEANOGRAPHY, vol. 57, no. 6, pp. 1816-1825.
View/Download from: Publisher's site
View description>>
Reflectance spectroscopy and microscale temperature measurements were used to investigate links between optical and thermal properties of corals. Coral tissue heating showed a species-specific linear correlation to the absorptance of incident irradiance. Heat budgets estimated from absorptance and thermal boundary layer measurements indicated differences in the relative contribution of convection and conduction to heat loss in Porites lobata and Stylophora pistillata, and a higher heat conduction into the skeleton of the thin-tissued branching S. pistillata as compared to the massive thick-tissued P. lobata. Decreasing absorptance associated with bleaching resulted in decreased surface warming of coral tissue. Action spectra of coral tissue heating showed elevated efficiency of heating at wavelengths corresponding to absorption maxima of major zooxanthellae photopigments. Generally, energy-rich radiation (, 500 nm) showed the highest heating efficiency. Speciesspecific relationships between coral tissue heating and absorptance can be strongly affected by differences in the thermal properties of the skeleton and/or tissue arrangement within the skeletal matrix, indicating a yet unresolved potential for coral shape, size, and tissue thickness to affect heat dissipation and especially the conduction of heat into the coral skeleton.
Jimenez, IM, Larkum, AWD, Ralph, PJ & Kuhl, M 2012, 'In situ thermal dynamics of shallow water corals is affected by tidal patterns and irradiance', MARINE BIOLOGY, vol. 159, no. 8, pp. 1773-1782.
View/Download from: Publisher's site
View description>>
We studied the diel variation of in situ coral temperature, irradiance and photosynthetic performance of hemispherical colonies of Porites lobata and branching colonies of Porites cylindrica during different bulk water temperature and tidal scenarios on the shallow reef flat of Heron Island, Great Barrier Reef, Australia. Our study presents in situ evidence that coral tissue surface temperatures can exceed that of the surrounding water under environmental conditions typically occurring during low tide in shallow reef or lagoon environments. Such heating may be a regular occurrence on shallow reef flats, triggered by the combined effects of high irradiance and low water flow characteristic of low Spring tides. At these times, solar heating of corals coincides with times of maximum water temperature and high irradiance, where the slow flow and consequent thick boundary layers impede heat exchange between corals and the surrounding water. Despite similar light-absorbing properties, the heating effect was more pronounced for the hemispherical P. lobata than for the branching P. cylindrica. This is consistent with previous laboratory experiments showing the evidence of interspecific variation in coral thermal environment and may result from morphologically influenced variation in convective heat transfer and/or thermal properties of the skeleton. Maximum coral surface warming did not coincide with maximum irradiance, but with maximum water temperature, well into the low-tide period with extremely low water flow in the partially drained reef flat, just prior to flushing by the rising tide. The timing of low tide thus influences the thermal exposure and photophysiological performance of corals, and the timing of tidally driven coral surface warming could potentially have different physiological impacts in the morning or in the afternoon.
Krull, CR, Ranjard, L, Landers, TJ, Ismar, SMH, Matthews, JL & Hauber, ME 2012, 'Analyses of sex and individual differences in vocalizations of Australasian gannets using a dynamic time warping algorithm', The Journal of the Acoustical Society of America, vol. 132, no. 2, pp. 1189-1198.
View/Download from: Publisher's site
View description>>
The study of the evolution of sexual differences in behavioral and morphological displays requires analyses of the extent of sexual dimorphism across various sensory modalities. In the seabird family Sulidae, boobies show dramatic sexual dimorphism in their vocalizations, and gannet calls have also been suggested to be dimorphic to human observers. This study aimed to evaluate the presence of sexually dimorphic calls in the Australasian gannet (Morus serrator) through the first comprehensive description of its vocalizations recorded at two localities; Cape Kidnappers, where individuals were banded and sexed from DNA samples, and at the Muriwai gannetry, both on the North Island of New Zealand. Calls were first inspected using basic bioacoustic features to establish a library of call element types for general reference. Extensive multivariate tests, based on a dynamic time warping algorithm, subsequently revealed that no sexual differences could be detected in Australasian gannet calls. The analyses, however, indicated extensive and consistent vocal variation between individuals, particularly so in female gannets, which may serve to signal individual identity to conspecifics. This study generates predictions to identify whether differences in Australasian gannet vocalizations play perceptual and functional roles in the breeding and social biology of this long-lived biparental seabird species.
Kuehl, M, Behrendt, L, Trampe, E, Qvortrup, K, Schreiber, U, Borisov, SM, Klimant, I & Larkum, AWD 2012, 'Microenvironmental ecology of the chlorophyll b-containing symbiotic cyanobacterium Prochloron in the didernnid ascidian Lissoclinum patella', FRONTIERS IN MICROBIOLOGY, vol. 3, pp. 1-18.
View/Download from: Publisher's site
View description>>
The discovery of the cyanobacterium Prochloron was the first finding of a bacterial oxyphototroph with chlorophyll (Chl) b, in addition to Chl a. It was first described as Prochloron didemni but a number of clades have since been described. Prochloron is a conspicuously large (7â25mm) unicellular cyanobacterium living in a symbiotic relationship, primarily with (sub-) tropical didemnid ascidians; it has resisted numerous cultivation attempts and appears truly obligatory symbiotic. Recently, a Prochloron draft genome was published, revealing no lack of metabolic genes that could explain the apparent inability to reproduce and sustain photosynthesis in a free-living stage. Possibly, the unsuccessful cultivation is partly due to a lack of knowledge about the microenvironmental conditions and ecophysiology of Prochloron in its natural habitat.We used microsensors, variable chlorophyll fluorescence imaging and imaging of O2 and pH to obtain a detailed insight to the microenvironmental ecology and photobiology of Prochloron in hospite in the didemnid ascidian Lissoclinum patella. The microenvironment within ascidians is characterized by steep gradients of light and chemical parameters that change rapidly with varying irradiances. The interior zone of the ascidians harboring Prochloron thus became anoxic and acidic within a few minutes of darkness, while the same zone exhibited O2 super-saturation and strongly alkaline pH after a few minutes of illumination. Photosynthesis showed lack of photoinhibition even at high irradiances equivalent to full sunlight, and photosynthesis recovered rapidly after periods of anoxia.We discuss these new insights on the ecological niche of Prochloron and possible interactions with its host and other microbes in light of its recently published genome and a recent study of the overall microbial diversity and metagenome of L. patella.
Kumar, M, Bijo, AJ, Baghel, RS, Reddy, CRK & Jha, B 2012, 'Selenium and spermine alleviate cadmium induced toxicity in the red seaweed Gracilaria dura by regulating antioxidants and DNA methylation', Plant Physiology and Biochemistry, vol. 51, pp. 129-138.
View/Download from: Publisher's site
View description>>
The protective role of exogenously supplied selenium (Se) and polyamines (PAs) such as putrescine (Put) and spermine (Spm) in detoxifying the cadmium (Cd) induced toxicity was studied in the marine red alga Gracilaria dura in laboratory conditions. The Cd exposure (0.4 mM) impede the growth of alga while triggering the reactive oxygen species (ROS viz. O 2•- and H 2O 2) generation, inhibition of antioxidant system, and enhancing the lipoxygenase (LOX) activity, malondialdehyde (MDA) level and demethylation of DNA. Additions of Se (50 μM) and/or Spm (1 mM) to the culture medium in contrast to Put, efficiently ameliorated the Cd toxicity by decreasing the accumulation of ROS and MDA contents, while restoring or enhancing the level of enzymatic and nonenzymatic antioxidants and their redox ratio, phycobiliproteins and phytochelatins, over the controls. The isoforms of antioxidant enzymes namely superoxide dismutase (Mn-SOD, ∼ 150 kDa; Fe-SOD ∼120 kDa), glutathione peroxidase (GSH-Px, ∼120 and 140 kDa), glutathione reductase (GR, ∼110 kDa) regulated differentially to Se and/or Spm supplementation. Furthermore, it has also resulted in enhanced levels of endogenous PAs (specially free and bound insoluble Put and Spm) and n-6 PUFAs (C20-3, n-6 and C20-4, n-6). This is for the first time wherein Se and Spm were found to regulate the stabilization of DNA methylation by reducing the events of cytosine demethylation in a mechanism to alleviate the Cd stress in marine alga. The present findings reveal that both Se and Spm play a crucial role in controlling the Cd induced oxidative stress in G. dura. © 2011 Elsevier Masson SAS.
Larkum, AWD, Chen, M, Li, Y, Schliep, M, Trampe, E, West, J, Salih, A & Kuhl, M 2012, 'A Novel Epiphytic Chlorophyll d-containing Cyanobacterium Isolated from a Mangrove-associated Red Alga', JOURNAL OF PHYCOLOGY, vol. 48, no. 6, pp. 1320-1327.
View/Download from: Publisher's site
View description>>
A new habitat and a new chlorophyll (Chl) d-containing cyanobacterium belonging to the genus Acaryochloris are reported in this study. Hyperspectral microscopy showed the presence of Chl d-containing microorganisms in epiphytic biofilms on a red alga (Gelidium caulacantheum) colonizing the pneumato-phores of a temperate mangrove (Avicennia marina). The presence of Chl d was further proven by high performance liquid chromatography (HPLC)-based pigment analysis and by confocal imaging of cultured cells. Enrichment of mangrove biofilm samples under near-infrared radiation (NIR) yielded the new Acaryochloris sp. MPGRS1, which was closely related in terms of 16S rRNA gene sequence to an isolate from the hypertrophic Salton Sea, USA. The new isolate used Chl d as its major photopigment; Chl d and Chl a contents were ~98% and 1%-2% of total cellular chlorophyll, respectively. These findings expand the variety of ecological niches known to harbor Chl d-containing cyanobacteria and support our working hypothesis that such oxyphototrophs may be ubiquitous in habitats depleted of visible light, but with sufficient NIR exposure. © 2012 Phycological Society of America.
Larkum, AWD, Ross, IL, Kruse, O & Hankamer, B 2012, 'Selection, breeding and engineering of microalgae for bioenergy and biofuel production', Trends in Biotechnology, vol. 30, no. 4, pp. 198-205.
View/Download from: Publisher's site
View description>>
Microalgal production technologies are seen as increasingly attractive for bioenergy production to improve fuel security and reduce CO2 emissions. Photosynthetically derived fuels are a renewable, potentially carbon-neutral and scalable alternative reserve. Microalgae have particular promise because they can be produced on non-arable land and utilize saline and wastewater streams. Furthermore, emerging microalgal technologies can be used to produce a range of products such as biofuels, protein-rich animal feeds, chemical feedstocks (e.g. bio-plastic precursors) and higher-value products. This review focuses on the selection, breeding and engineering of microalgae for improved biomass and biofuel conversion efficiencies.
Lavery, TJ, Roudnew, B, Seymour, J, Mitchell, JG & Jeffries, T 2012, 'High Nutrient Transport and Cycling Potential Revealed in the Microbial Metagenome of Australian Sea Lion (Neophoca cinerea) Faeces', PLoS ONE, vol. 7, no. 5, pp. e36478-e36478.
View/Download from: Publisher's site
View description>>
Metagenomic analysis was used to examine the taxonomic diversity and metabolic potential of an Australian sea lion (Neophoca cinerea) gut microbiome. Bacteria comprised 98% of classifiable sequences and of these matches to Firmicutes (80%) were dominant, with Proteobacteria and Actinobacteria representing 8% and 2% of matches respectively. The relative proportion of Firmicutes (80%) to Bacteriodetes (2%) is similar to that in previous studies of obese humans and obese mice, suggesting the gut microbiome may confer a predisposition towards the excess body fat that is needed for thermoregulation within the cold oceanic habitats foraged by Australian sea lions. Core metabolic functions, including carbohydrate utilisation (14%), protein metabolism (9%) and DNA metabolism (7%) dominated the metagenome, but in comparison to human and fish gut microbiomes there was a significantly higher proportion of genes involved in phosphorus metabolism (2.4%) and iron scavenging mechanisms (1%). When sea lions defecate at sea, the relatively high nutrient metabolism potential of bacteria in their faeces may accelerate the dissolution of nutrients from faecal particles, enhancing their persistence in the euphotic zone where they are available to stimulate marine production. © 2012 Lavery et al.
Lu, J, Martin, J, Lu, Y, Zhao, J, Yuan, J, Ostrowski, M, Paulsen, I, Piper, JA & Jin, D 2012, 'Resolving Low-Expression Cell Surface Antigens by Time-Gated Orthogonal Scanning Automated Microscopy', Analytical Chemistry, vol. 84, no. 22, pp. 9674-9678.
View/Download from: Publisher's site
View description>>
We report a highly sensitive method for rapid identification and quantification of rare-event cells carrying low-abundance surface biomarkers. The method applies lanthanide bioprobes and time-gated detection to effectively eliminate both nontarget organisms and background noise and utilizes the europium containing nanoparticles to further amplify the signal strength by a factor of ∼20. Of interest is that these nanoparticles did not correspondingly enhance the intensity of nonspecific binding. Thus, the dramatically improved signal-to-background ratio enables the low-expression surface antigens on single cells to be quantified. Furthermore, we applied an orthogonal scanning automated microscopy (OSAM) technique to rapidly process a large population of target-only cells on microscopy slides, leading to quantitative statistical data with high certainty. Thus, the techniques together resolved nearly all false-negative events from the interfering crowd including many false-positive events. © 2012 American Chemical Society.
Macreadie, PI, Allen, K, Kelaher, BP, Ralph, PJ & Skilbeck, CG 2012, 'Paleoreconstruction of estuarine sediments reveal human-induced weakening of coastal carbon sinks', GLOBAL CHANGE BIOLOGY, vol. 18, no. 3, pp. 891-901.
View/Download from: Publisher's site
View description>>
Human activities in coastal areas frequently cause loss of benthic macrophytes (e.g. seagrasses) and concomitant increases in microalgal production through eutrophication. Whether such changes translate into shifts in the composition of sediment detritus is largely unknown, yet such changes could impact the role these ecosystems play in sequestrating CO2. We reconstructed the sedimentary records of cores taken from two sites within Botany Bay, Sydney the site of European settlement of Australia to look for human-induced changes in dominant sources of detritus in this estuary. Cores covered a period from the present day back to the middle Holocene (6000years) according to 210Pb profiles and radiocarbon (14C) dating. Depositional histories at both sites could not be characterized by a linear sedimentation rate; sedimentation rates in the last 3050years were considerably higher than during the rest of the Holocene. C:N ratios declined and began to exhibit a microalgal source signature from around the time of European settlement, which could be explained by increased nutrient flows into the Bay caused by anthropogenic activity. Analysis of stable isotopic ratios of 12C/13C showed that the relative contribution of seagrass and C3 terrestrial plants (mangroves, saltmarsh) to detritus declined around the time of rapid industrial expansion (1950s), coinciding with an increase in the contribution of microalgal sources. We conclude that the relative contribution of microalgae to detritus has increased within Botany Bay, and that this shift is the sign of increased industrialization and concomitant eutrophication.
Mansell, PJ, Suggett, DJ & Smith, DJ 2012, 'Management of marine resources; combining industry and research', Journal of the Marine Biological Association of the United Kingdom, vol. 92, no. 4, pp. 643-646.
View/Download from: Publisher's site
McMinn, A, Ashworth, C, Bhagooli, R, Martin, A, Salleh, S, Ralph, P & Ryan, K 2012, 'Antarctic coastal microalgal primary production and photosynthesis', MARINE BIOLOGY, vol. 159, no. 12, pp. 2827-2837.
View/Download from: Publisher's site
View description>>
Primary production in coastal Antarctica is primarily contributed from three sources: sea ice algae, phytoplankton, and microphytobenthos. Compared to other eastern Antarctic sites, the sea ice microalgal biomass at Casey Station, in spring 2005 was rela
Mondal, AK, Wang, B, Su, D, Wang, Y, Zhang, X & Wang, G 2012, 'Preparation and Enhanced Electrochemical Performance of MnO2 Nanosheets for Supercapacitors', Journal of the Chinese Chemical Society, vol. 59, no. 10, pp. 1275-1279.
View/Download from: Publisher's site
View description>>
AbstractMnO2 nanosheets have been synthesized by using a redox reaction of manganese nitrate tetrahydrate and potassium permanganate without any surfactants. The morphology and microstructure of the as‐prepared material were characterized by field emission scanning electron microscopy, transmission electron microscopy and X‐ray diffraction (XRD). Electrochemical performances as electrode materials for supercapacitor were evaluated using cyclic voltammetry and galvanostatic charge‐discharge in 1 M Na2SO4 aqueous electrolyte. It was found that MnO2 nanosheets showed an excellent capacitive behaviour with good cycling stability. The specific capacitance of the MnO2 nanosheet electrode can reach up to 332.8 Fg−1 at a current density of 500 mA/g and a stable cycling performance.
Oxborough, K, Moore, CM, Suggett, DJ, Lawson, T, Chan, HG & Geider, RJ 2012, 'Direct estimation of functional PSII reaction center concentration and PSII electron flux on a volume basis: a new approach to the analysis of Fast Repetition Rate fluorometry (FRRf) data', Limnology and Oceanography: Methods, vol. 10, no. 3, pp. 142-154.
View/Download from: Publisher's site
View description>>
Phytoplankton primary productivity is most commonly measured by 14C assimilation although less direct methods, such as O2 exchange, have also been employed. These methods are invasive, requiring bottle incubation for up to 24 h. As an alternative, Fast Repetition Rate fluorometry (FRRf) has been used, on wide temporal and spatial scales within aquatic systems, to estimate photosystem II (PSII) electron flux per unit volume (JVPSII), which generally correlates well with photosynthetic O2 evolution. A major limitation of using FRRf arises from the need to employ an independent method to determine the concentration of functional photosystem II reaction centers ([RCII]); a requirement that has prevented FRR fluorometers being used, as stand‐alone instruments, for the estimation of electron transport. Within this study, we have taken a new approach to the analysis of FRRf data, based on a simple hypothesis; that under a given set of environmental conditions, the ratio of rate constants for RCII fluorescence emission and photochemistry falls within a narrow range, for all groups of phytoplankton. We present a simple equation, derived from the established FRRf algorithm, for determining [RCII] from dark FRRf data alone. We also describe an entirely new algorithm for estimating JVPSII, which does not require determination of [RCII] and is valid for a heterogeneous model of connectivity among RCIIs. Empirical supporting evidence is presented. These data are derived from FRR measurements across a diverse range of microalgae, in parallel with independent measurements of [RCII]. Possible sources of error, particularly under nutrient stress conditions, are discussed.
Pernice, M & Boucher‐Rodoni, R 2012, 'Occurrence of a specific dual symbiosis in the excretory organ of geographically distant Nautiloids populations', Environmental Microbiology Reports, vol. 4, no. 5, pp. 504-511.
View/Download from: Publisher's site
View description>>
SummaryNautilus is one of the most intriguing of all sea creatures, sharing morphological similarities with the extinct forms of coiled cephalopods that evolved since the Cambrian (542–488 mya). Further, bacterial symbioses found in their excretory organ are of particular interest as they provide a great opportunity to investigate the influence of host–microbe interactions upon the origin and evolution of an innovative nitrogen excretory system. To establish the potential of Nautilus excretory organ as a new symbiotic system, it is, however, necessary to assess the specificity of this symbiosis and whether it is consistent within the different species of present‐day Nautiloids. By addressing the phylogeny and distribution of bacterial symbionts in three Nautilus populations separated by more than 6000 km (N. pompilius from Philippines and Vanuatu, and N. macromphalus from New Caledonia), this study confirms the specificity of this dual symbiosis involving the presence of betaproteobacteria and spirochaete symbionts on a very wide geographical area. Overall, this work sheds further light on Nautiloids excretory organ as an innovative system of interaction between bacteria and cephalopods.
Petrou, K, Kranz, SA, Doblin, MA & Ralph, PJ 2012, 'PHOTOPHYSIOLOGICAL RESPONSES OF FRAGILARIOPSIS CYLINDRUS (BACILLARIOPHYCEAE) TO NITROGEN DEPLETION AT TWO TEMPERATURES', JOURNAL OF PHYCOLOGY, vol. 48, no. 1, pp. 127-136.
View/Download from: Publisher's site
View description>>
The photosynthetic efficiency and photoprotective capacity of the sea-ice diatom, Fragilariopsis cylindrus (Grunow) W. Krieg., grown in a matrix of nitrogen repletion and depletion at two different temperatures (-1°C and +6°C) was investigated. Temperature showed no significant effect on photosynthetic efficiency or photoprotection in F. cylindrus. Cultures under nitrogen depletion showed enhanced photoprotective capacity with an increase in nonphotochemical quenching (NPQ) when compared with nitrogen-replete cultures. This phenomenon was achieved at no apparent cost to the photosynthetic efficiency of PSII (F V/F M). Nitrogen depletion yielded a partially reduced electron transport chain in which maximum fluorescence (F M) could only be obtained by adding 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). reoxidation curves showed the presence of Q B nonreducing PSII centers under nitrogen depletion. Fast induction curves (FICs) and electron transport rates (ETRs) revealed slowing of the electrons transferred from the primary (Q A) to the secondary (Q B) quinone electron acceptors of PSII. The data presented show that nitrogen depletion in F. cylindrus leads to the formation of Q B nonreducing PSII centers within the photosystem. On a physiological level, the formation of Q B nonreducing PSII centers in F. cylindrus provides the cell with protection against photoinhibition by facilitating the rapid induction of NPQ. This strategy provides an important ecological advantage, especially during the Antarctic spring, maintaining photosynthetic efficiency under high light and nutrient-limiting conditions. © 2011 Phycological Society of America.
Puill-Stephan, E, Willis, BL, Abrego, D, Raina, J-B & van Oppen, MJH 2012, 'Allorecognition maturation in the broadcast-spawning coral Acropora millepora', Coral Reefs, vol. 31, no. 4, pp. 1019-1028.
View/Download from: Publisher's site
View description>>
Many sessile marine invertebrates discriminate self from non-self with great precision, but maturation of allorecognition generally takes months to develop in juveniles. Here, we compare the development of allorecognition in full-sibling, half-sibling and non-sibling contact reactions between newly settled juveniles of the broadcast-spawning coral Acropora millepora on the Great Barrier Reef (Australia). Absence of a rejection response showed that A. millepora lacks a mature allorecognition system in the first 2 months post-settlement. From thereon, incompatibilities were observed between juveniles, their level of relatedness (i.e. full-, half- and non-sibling status) governing the rate of allorecognition maturation. All contact reactions between non-siblings resulted in rejections by 3 months post-settlement, whereas the expression of allorecognition took at least 5 months between half-siblings and longer than 13 months for some full-siblings. Approximately 74 % of fused full-siblings ( n = 19) persisted as chimeras at 11 months, thus maturation of allorecognition in this spawning coral appeared to be slower (>13 months) than in brooding corals (~4 months). We hypothesize that late maturation of allorecognition may contribute to flexibility in Symbiodinium uptake in corals with horizontal transmission, and could allow fusions and chimera formation in early ontogeny, which potentially enable rapid size increase through fusion
Ritchie, RJ & Larkum, AWD 2012, 'Modelling photosynthesis in shallow algal production ponds', PHOTOSYNTHETICA, vol. 50, no. 4, pp. 481-500.
View/Download from: Publisher's site
View description>>
Shallow ponds with rapidly photosynthesising cyanobacteria or eukaryotic algae are used for growing biotechnology feedstock and have been proposed for biofuel production but a credible model to predict the productivity of a column of phytoplankton in suc
Roudnew, B, Seymour, JR, Jeffries, TC, Lavery, TJ, Smith, RJ & Mitchell, JG 2012, 'Bacterial and Virus-Like Particle Abundances in Purged and Unpurged Groundwater Depth Profiles', GROUND WATER MONITORING AND REMEDIATION, vol. 32, no. 4, pp. 72-77.
View/Download from: Publisher's site
View description>>
Bacteria and viruses are ubiquitous in subterranean aquatic habitats. Bacterial abundance is known to vary with depth in aquifers; however, whether viral abundance varies with depth is less well known. Here we use flow cytometry (FCM) to enumerate bacteria and virus-like particles (VLP) from groundwater depth profiles. Groundwater samples were obtained from a set of nested piezometers from depths of 15, 30, 45, 60, 80, and 90?m and bacteria and VLP abundances were determined in purged aquifer water and unpurged water at each slot depth. Mean bacterial abundance (cells?/?mL) was not significantly different in unpurged water (3.2?×?105) compared to purged water (1.4?×?105); however, mean VLP abundance (particles?/?mL) was significantly greater in unpurged water (4.4?×?105) compared to purged water (2.3?×?105). Purged water was used to investigate the aquifer depth profile and bacterial and VLP abundances were observed to vary significantly between depths. The virus-bacteria ratio was determined and was observed to steadily increase with depth. Overall, our data indicate the dynamic nature of bacterial and viral abundances in subsurface environments which should be considered when designing groundwater microbial sampling methodologies.
Seymour, JR, Doblin, MA, Jeffries, TC, Brown, MV, Newton, K, Ralph, PJ, Baird, M & Mitchell, JG 2012, 'Contrasting microbial assemblages in adjacent water masses associated with the East Australian Current', ENVIRONMENTAL MICROBIOLOGY REPORTS, vol. 4, no. 5, pp. 548-555.
View/Download from: Publisher's site
View description>>
Different oceanographic provinces host discrete microbial assemblages that are adapted to local physicochemical conditions. We sequenced and compared the metagenomes of two microbial communities inhabiting adjacent water masses in the Tasman Sea, where the recent strengthening of the East Australian Current (EAC) has altered the ecology of coastal environments. Despite the comparable latitude of the samples, significant phylogenetic differences were apparent, including shifts in the relative frequency of matches to Cyanobacteria, Crenarchaeota and Euryarchaeota. Fine-scale variability in the structure of SAR11, Prochlorococcus and Synechococcus populations, with more matches to 'warm-water' ecotypes observed in the EAC, indicates the EAC may drive an intrusion of tropical microbes into temperate regions of the Tasman Sea. Furthermore, significant shifts in the relative importance of 17 metabolic categories indicate that the EAC prokaryotic community has different physiological properties than surrounding waters. © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd.
Siboni, N, Abrego, D, Seneca, F, Motti, CA, Andreakis, N, Tebben, J, Blackall, LL & Harder, T 2012, 'Using Bacterial Extract along with Differential Gene Expression in Acropora millepora Larvae to Decouple the Processes of Attachment and Metamorphosis', PLOS ONE, vol. 7, no. 5.
View/Download from: Publisher's site
Siboni, N, Ben-Dov, E, Sivan, A & Kushmaro, A 2012, 'Geographic Specific Coral-Associated Ammonia-Oxidizing Archaea in the Northern Gulf of Eilat (Red Sea)', MICROBIAL ECOLOGY, vol. 64, no. 1, pp. 18-24.
View/Download from: Publisher's site
Sinetova, MA, Červený, J, Zavřel, T & Nedbal, L 2012, 'On the dynamics and constraints of batch culture growth of the cyanobacterium Cyanothece sp. ATCC 51142', Journal of Biotechnology, vol. 162, no. 1, pp. 148-155.
View/Download from: Publisher's site
Sinutok, S, Hill, R, Doblin, MA, Kuhl, M & Ralph, PJ 2012, 'Microenvironmental changes support evidence of photosynthesis and calcification inhibition in Halimeda under ocean acidification and warming', CORAL REEFS, vol. 31, no. 4, pp. 1201-1213.
View/Download from: Publisher's site
View description>>
The effects of elevated CO 2 and temperature on photosynthesis and calcification of two important calcifying reef algae (Halimedamacroloba and Halimeda cylindracea) were investigated with O 2 microsensors and chlorophyll a fluorometry through a combination of two pCO 2 (400 and 1,200 µatm) and two temperature treatments (28 and 32 °C) equivalent to the present and predicted conditions during the 2100 austral summer. Combined exposure to pCO 2 and elevated temperature impaired calcification and photosynthesis in the two Halimeda species due to changes in the microenvironment around the algal segments and a reduction in physiological performance. There were no significant changes in controls over the 5-week experiment, but there was a 50-70 % decrease in photochemical efficiency (maximum quantum yield), a 70-80 % decrease in O 2 production and a threefold reduction in calcification rate in the elevated CO 2 and high temperature treatment. Calcification in these species is closely coupled with photosynthesis, such that a decrease in photosynthetic efficiency leads to a decrease in calcification. Although pH seems to be the main factor affecting Halimeda species, heat stress also has an impact on their photosystem II photochemical efficiency. There was a strong combined effect of elevated CO 2 and temperature in both species, where exposure to elevated CO 2 or temperature alone decreased photosynthesis and calcification, but exposure to both elevated CO 2 and temperature caused a greater decline in photosynthesis and calcification than in each stress individually. Our study shows that ocean acidification and ocean warming are drivers of calcification and photosynthesis inhibition in Halimeda. Predicted climate change scenarios for 2100 would therefore severely affect the fitness of Halimeda, which can result in a strongly reduced production of carbonate sediments on coral reefs under such changed climate conditions.
Smale, DA, Barnes, DKA, Barnes, RSK, Smith, DJ & Suggett, DJ 2012, 'Spatial variability in the structure of intertidal crab and gastropod assemblages within the Seychelles Archipelago (Indian Ocean)', Journal of Sea Research, vol. 69, pp. 8-15.
View/Download from: Publisher's site
View description>>
Tropical nearshore ecosystems represent global hotspots of marine biodiversity and endemism but are often poorly understood and impacted by human activities. The Seychelles Archipelago (Western Indian Ocean) sustains a wealth of marine life, much of which is threatened by rapid development associated with tourism and climate change. Six marine parks exist within the Archipelago, but their biodiversity value and ecological health are poorly known, especially with regards to non-fish and coral species. Here we investigate spatial patterns of littoral biodiversity on 6 islands, 5 of which were granitic and within marine parks, including the first surveys of Curieuse and Ile Cocos. Our surveys formed a nested sampling design, to facilitate an examination of variability in species richness, faunal abundance, taxonomic distinctness and assemblage composition at multiple spatial scales, from islands (>. 100. s. km) to quadrats (metres). We identified (mostly to species) and enumerated two target taxa, brachyuran decapod crustaceans and gastropod molluscs, and recorded over 8300 individuals belonging to over 150 species. Crabs and gastropods exhibited different patterns of spatial variability, as crab assemblages were generally more distinct between islands, while gastropod assemblages were markedly variable at the smallest spatial scales of 'patch' and 'quadrat'. Intertidal biodiversity was greatest on Curieuse Island and least at Desroches, the latter was being the only coral atoll we surveyed and thereby differing in its geological and ecological context. We discuss likely drivers of these biodiversity patterns and highlight urgently-needed research directions. Our assessment of the status of poorly-known invertebrate assemblages across the Seychelles will complement more extensive surveys of coral and fish assemblages and, in doing so, provide a useful baseline for monitoring the effects of key stressors in the region, such as coastal development and climat...
Smith, RJ, Jeffries, TC, Roudnew, B, Fitch, AJ, Seymour, JR, Delpin, MW, Newton, K, Brown, MH & Mitchell, JG 2012, 'Metagenomic comparison of microbial communities inhabiting confined and unconfined aquifer ecosystems', ENVIRONMENTAL MICROBIOLOGY, vol. 14, no. 1, pp. 240-253.
View/Download from: Publisher's site
View description>>
A metagenomic analysis of two aquifer systems located under a dairy farming region was performed to examine to what extent the composition and function of microbial communities varies between confined and surface-influenced unconfined groundwater ecosystems. A fundamental shift in taxa was seen with an overrepresentation of Rhodospirillales, Rhodocyclales, Chlorobia and Circovirus in the unconfined aquifer, while Deltaproteobacteria and Clostridiales were overrepresented in the confined aquifer. A relative overrepresentation of metabolic processes including antibiotic resistance (beta-lactamase genes), lactose and glucose utilization and DNA replication were observed in the unconfined aquifer, while flagella production, phosphate metabolism and starch uptake pathways were all overrepresented in the confined aquifer. These differences were likely driven by differences in the nutrient status and extent of exposure to contaminants of the two groundwater systems. However, when compared with freshwater, ocean, sediment and animal gut metagenomes, the unconfined and confined aquifers were taxonomically and metabolically more similar to each other than to any other environment. This suggests that intrinsic features of groundwater ecosystems, including low oxygen levels and a lack of sunlight, have provided specific niches for evolution to create unique microbial communities. Obtaining a broader understanding of the structure and function of microbial communities inhabiting different groundwater systems is particularly important given the increased need for managing groundwater reserves of potable water.
Stocker, R & Seymour, JR 2012, 'Ecology and Physics of Bacterial Chemotaxis in the Ocean', MICROBIOLOGY AND MOLECULAR BIOLOGY REVIEWS, vol. 76, no. 4, pp. 792-812.
View/Download from: Publisher's site
View description>>
Summary: Intuitively, it may seem that from the perspective of an individual bacterium the ocean is a vast, dilute, and largely homogeneous environment. Microbial oceanographers have typically considered the ocean from this point of view. In reality, marine bacteria inhabit a chemical seascape that is highly heterogeneous down to the microscale, owing to ubiquitous nutrient patches, plumes, and gradients. Exudation and excretion of dissolved matter by larger organisms, lysis events, particles, animal surfaces, and fluxes from the sediment-water interface all contribute to create strong and pervasive heterogeneity, where chemotaxis may provide a significant fitness advantage to bacteria. The dynamic nature of the ocean imposes strong selective pressures on bacterial foraging strategies, and many marine bacteria indeed display adaptations that characterize their chemotactic motility as high performance compared to that of enteric model organisms. Fast swimming speeds, strongly directional responses, and effective turning and steering strategies ensure that marine bacteria can successfully use chemotaxis to very rapidly respond to chemical gradients in the ocean.
Suggett, DJ, Hall‐Spencer, JM, Rodolfo‐Metalpa, R, Boatman, TG, Payton, R, Tye Pettay, D, Johnson, VR, Warner, ME & Lawson, T 2012, 'Sea anemones may thrive in a high CO2 world', Global Change Biology, vol. 18, no. 10, pp. 3015-3025.
View/Download from: Publisher's site
View description>>
AbstractIncreased seawater pCO2, and in turn ‘ocean acidification’ (OA), is predicted to profoundly impact marine ecosystem diversity and function this century. Much research has already focussed on calcifying reef‐forming corals (Class: Anthozoa) that appear particularly susceptible to OA via reduced net calcification. However, here we show that OA‐like conditions can simultaneously enhance the ecological success of non‐calcifying anthozoans, which not only play key ecological and biogeochemical roles in present day benthic ecosystems but also represent a model organism should calcifying anthozoans exist as less calcified (soft‐bodied) forms in future oceans. Increased growth (abundance and size) of the sea anemone (Anemonia viridis) population was observed along a natural CO2 gradient at Vulcano, Italy. Both gross photosynthesis (PG) and respiration (R) increased with pCO2 indicating that the increased growth was, at least in part, fuelled by bottom up (CO2 stimulation) of metabolism. The increase of PG outweighed that of R and the genetic identity of the symbiotic microalgae (Symbiodinium spp.) remained unchanged (type A19) suggesting proximity to the vent site relieved CO2 limitation of the anemones' symbiotic microalgal population. Our observations of enhanced productivity with pCO2, which are consistent with previous reports for some calcifying corals, convey an increase in fitness that may enable non‐calcifying anthozoans to thrive in future environments, i.e. higher seawater pCO2. Understanding how CO2
Suggett, DJ, Kikuchi, RKP, Oliveira, MDM, Spanó, S, Carvalho, R & Smith, DJ 2012, 'Photobiology of corals from Brazil’s near-shore marginal reefs of Abrolhos', Marine Biology, vol. 159, no. 7, pp. 1461-1473.
View/Download from: Publisher's site
View description>>
Coral communities were examined from highly turbid near-shore marginal reefs of Abrolhos (Brazil) to test a paradigm previously developed from observations in clear water reefs; specifically, that coral photobiological properties follow a highly conserved linear relationship with optical depth (ζ) via preferential 'non-photochemical' over 'photochemical' dissipation of absorbed light energy. PAM flourometry in situ was used to examine the photobiology of the most dominant coral species throughout the platform surfaces and bases of Abrolhos' characteristic 'chapeirões' reef framework; however, none of the species consistently adhered to the 'clear water paradigm'. PAM measurements further demonstrated that species conformed to two different strategies of non-photochemical energy dissipation: transient but relatively rapid for the two closely related endemic species (Mussismilia braziliensis and Mussismilia harttii) as opposed to more persistent for Montastrea cavernosa, Porites astreoides and Siderastrea stellata. Further experiments demonstrated that tolerance to anomalous stress amongst species did not correspond with the non-photochemical energy dissipation strategy present but was consistent with the relative dominance of species within the chapeirões coral communities. © 2012 Springer-Verlag.
van Dongen-Vogels, V, Seymour, JR, Middleton, JF, Mitchell, JG & Seuront, L 2012, 'Shifts in picophytoplankton community structure influenced by changing upwelling conditions', ESTUARINE COASTAL AND SHELF SCIENCE, vol. 109, pp. 81-90.
View/Download from: Publisher's site
View description>>
The influence of upwelling events on the structure of picophytoplankton communities was assessed at the annual scale from a station within the South Australian shelf region. In this region, local (wind) and global (La Niña/El NiñoSouthern Oscillation) hydroclimatic conditions affect the development of upwelling over the austral summer. Using flow cytometry, changes in picophytoplankton community structure were investigated in relation to the properties of the water column when the nature and strength of upwelling event differed for the upwelling seasons of 2008, 2009, and 2010. In 2008, strong upwelling favorable southeasterlies were responsible for extensive upwelling and the dominance of picoeukaryotes. Alternatively, in 2009, the observed dominance of Prochlorococcus reflected the presence of oligotrophic conditions whilst southeasterlies were replaced by downwelling favorable north-westerlies that likely prohibited the full development of upwelling. In 2010, whilst southeasterlies remained relatively weak, particularly cold and low saline upwelled waters indicated enhanced upwelling events. This weak local wind field together with the occurrence of El Niño explained the observation of shallow upwelled waters below the warm surface layer and subsequent enhanced stratification. These conditions led to the dominance of Synechococcus in surface and fluorescence maximum depths, but of Prochlorococcus in bottom upwelled waters. The tight association between upwelling and stratification, i.e. whether upwelled waters reach shallower depths and/or mix with those of the surface as a result of variable climatic conditions, was suggested as the process driving the vertical heterogeneity of picophytoplankton populations. This study brings valuable information for changing picophytoplankton community structure with potential future changing hydroclimatic forcing.
Verhoeven, MPC, Kelaher, BP, Bishop, MJ & Ralph, PJ 2012, 'Epiphyte grazing enhances productivity of remnant seagrass patches', AUSTRAL ECOLOGY, vol. 37, no. 8, pp. 885-892.
View/Download from: Publisher's site
View description>>
Anthropogenic nutrient enrichment is increasingly modifying community structure and ecosystem functioning in terrestrial and aquatic ecosystems. In marine ecosystems, the paradigm is that nutrient enrichment leads to a decline of seagrasses by stimulatin
Wangpraseurt, D, Larkum, AWD, Ralph, PJ & Kuehl, M 2012, 'Light gradients and optical microniches in coral tissues', FRONTIERS IN MICROBIOLOGY, vol. 3, no. 316, pp. 1-9.
View/Download from: Publisher's site
View description>>
Light quantity and quality are among the most important factors determining the physiology and stress response of zooxanthellate corals. Yet, almost nothing is known about the light ?eld that Symbiodinium experiences within their coral host, and the basic optical properties of coral tissue are unknown. We used scalar irradiance microprobes to characterize vertical and lateral light gradients within and across tissues of several coral species. Our results revealed the presence of steep light gradients with photosynthetically available radiation decreasing by about one order of magnitude from the tissue surface to the coral skeleton. Surface scalar irradiance was consistently higher over polyp tissue than over coenosarc tissue in faviid corals. Coral bleaching increased surface scalar irradiance by ~150% (between 500 and 700 nm) relative to a healthy coral. Photosynthesis peaked around 300 µm within the tissue, which corresponded to a zone exhibiting strongest depletion of scalar irradiance. Deeper coral tissue layers, e.g., ~1000 µm into aboral polyp tissues, harbor optical microniches, where only ~10% of the incident irradiance remains. We conclude that the optical microenvironment of corals exhibits strong lateral and vertical gradients of scalar irradiance, which are affected by both tissue and skeleton optical properties. Our results imply that zooxanthellae populations inhabit a strongly heterogeneous light environment and highlight the presence of different optical microniches in corals; an important ?nding for understanding the photobiology, stress response, as well as the phenotypic and genotypic plasticity of coral symbionts.
Wilson, KG & Ralph, PJ 2012, 'Laboratory testing protocol for the impact of dispersed petrochemicals on seagrass', MARINE POLLUTION BULLETIN, vol. 64, no. 11, pp. 2421-2427.
View/Download from: Publisher's site
View description>>
To improve the effectiveness of oil spill mitigation, we developed a rapid, logistically simple protocol to detect petrochemical stress on seagrass. Sections of leaf blades from Zostera muelleri subsp. capricorni were exposed to the water accommodated fraction (WAF) of non-dispersed and dispersed Tapis crude oil and fuel oil (IFO-380) for 5. h. Photosynthetic health was monitored by assessing changes in effective quantum yield of photosystem II (ΔF/Fm') and chlorophyll a pigment concentrations. Loss of total petroleum hydrocarbons (TPH) was measured using an oil-in-water fluorometer, whilst GC-MS analyses quantified the hydrocarbon components within each treatment. Few significant differences were detected in the chlorophyll a pigment analyses; however, ΔF/Fm' appeared sensitive to petrochemical exposure. Dispersing both types of oil resulted in a substantial increase in the TPH of the WAF and was generally correlated with a greater physiological impact to the seagrass health, compared with the oil alone. © 2012 Elsevier Ltd.
