Baghel, RS, Kumari, P, Bijo, AJ, Gupta, V, Reddy, CRK & Jha, B 2011, 'Genetic analysis and marker assisted identification of life phases of red alga Gracilaria corticata (J. Agardh)', Molecular Biology Reports, vol. 38, no. 6, pp. 4211-4218.
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Baird, ME, Suthers, IM, Griffin, DA, Hollings, B, Pattiaratchi, C, Everett, JD, Roughan, M, Oubelkheir, K & Doblin, M 2011, 'The effect of surface flooding on the physical-biogeochemical dynamics of a warm-core eddy off southeast Australia', DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY, vol. 58, no. 5, pp. 592-605.
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Warm core eddies (WCEs) formed from the East Australian Current (EAC) play an important role in the heat, mass and biogeochemical budgets of the western Tasman Sea. The development and separation of an EAC WCE during July-December 2008 was observed using remotely-sensed temperature, ocean colour and sea-level elevation, three Argo floats, a shipboard CTD, a shelf mooring array and a 15-day deployment of a Slocum glider.
Behrendt, L, Larkum, AWD, Norman, A, Qvortrup, K, Chen, M, Ralph, P, Sorensen, SJ, Trampe, E & Kuehl, M 2011, 'Endolithic chlorophyll d-containing phototrophs', ISME JOURNAL, vol. 5, no. 6, pp. 1072-1076.
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Cyanobacteria in the genus Acaryochloris are the only known oxyphototrophs that have exchanged chlorophyll a (Chl a) with Chl d as their primary photopigment, facilitating oxygenic photosynthesis with near infrared (NIR) light. Yet their ecology and natural habitats are largely unknown. We used hyperspectral and variable chlorophyll fluorescence imaging, scanning electron microscopy, photopigment analysis and DNA sequencing to show that Acaryochloris-like cyanobacteria thrive underneath crustose coralline algae in a widespread endolithic habitat on coral reefs. This finding suggests an important role of Chl d-containing cyanobacteria in a range of hitherto unexplored endolithic habitats, where NIR light-driven oxygenic photosynthesis may be significant. © 2011 International Society for Microbial Ecology. All rights reserved.
Ben-Dov, E, Siboni, N, Shapiro, OH, Arotsker, L & Kushmaro, A 2011, 'Substitution by Inosine at the 3 '-Ultimate and Penultimate Positions of 16S rRNA Gene Universal Primers', MICROBIAL ECOLOGY, vol. 61, no. 1, pp. 1-6.
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Brading, P, Warner, ME, Davey, P, Smith, DJ, Achterberg, EP & Suggett, DJ 2011, 'Differential effects of ocean acidification on growth and photosynthesis among phylotypes of Symbiodinium (Dinophyceae)', Limnology and Oceanography, vol. 56, no. 3, pp. 927-938.
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We investigated the effect of elevated partial pressure of CO2 (pCO2) on the photosynthesis and growth of four phylotypes (ITS2 types A1, A13, A2, and B1) from the genus Symbiodinium, a diverse dinoflagellate group that is important, both free‐living and in symbiosis, for the viability of cnidarians and is thus a potentially important model dinoflagellate group. The response of Symbiodinium to an elevated pCO2 was phylotype‐specific. Phylotypes A1 and B1 were largely unaffected by a doubling in pCO2; in contrast, the growth rate of A13 and the photosynthetic capacity of A2 both increased by ~ 60%. In no case was there an effect of ocean acidification (OA) upon respiration (dark‐ or light‐dependent) for any of the phylotypes examined. Our observations suggest that OA might preferentially select among free‐living populations of Symbiodinium, with implications for future symbioses that rely on algal acquisition from the environment (i.e., horizontal transmission). Furthermore, the carbon environment within the host could differentially affect the physiology of different Symbiodinium phylotypes. The range of responses we observed also highlights that the choice of species is an important consideration in OA research and that further investigation across phylogenetic diversity, for both the direction of effect and the underlying mechanism(s) involved, is warranted.
Chan, Y-W, Mohr, R, Millard, AD, Holmes, AB, Larkum, AW, Whitworth, AL, Mann, NH, Scanlan, DJ, Hess, WR & Clokie, MRJ 2011, 'Discovery of Cyanophage Genomes Which Contain Mitochondrial DNA Polymerase', Molecular Biology and Evolution, vol. 28, no. 8, pp. 2269-2274.
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Doblin, MA, Petrou, KL, Shelly, K, Westwood, K, van den Enden, R, Wright, S, Griffiths, B & Ralph, PJ 2011, 'Diel variation of chlorophyll-a fluorescence, phytoplankton pigments and productivity in the Sub-Antarctic and Polar Front Zones south of Tasmania, Australia', DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY, vol. 58, no. 21-22, pp. 2189-2199.
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Marine primary production is a fundamental measure of the ocean's capacity to convert carbon dioxide to particulate organic carbon for the marine foodweb, and as such is an essential variable used in ecosystem and biogeochemical models to assess trophic dynamics and carbon cycling. The Sub-Antarctic Zone (SAZ) is a major sink for atmospheric carbon and exhibits large gradients in ocean conditions on both temporal and spatial scales. In this dynamic system, an understanding of small-scale temporal changes is critical for modelling primary production at larger scales. Thus, we investigated diel effects on maximum quantum yield of PSII (FV/FM), photosynthetic pigment pools and primary productivity in the western (Diel 1) and eastern SAZ region (Diel 3) south of Tasmania, Australia, and compared this to a station at the polar front (Diel 2). Phytoplankton in the eastern SAZ had the greatest diel response, with cells showing decreased FV/FM and increased biosynthesis and transformation of xanthophyll and other photoprotective pigments during the day, but only in the surface waters (0 and 10m). Diel responses diminished by 30m. Cells in the western SAZ had similar responses across the depths sampled, increasing their FV/FM during the night and increasing their xanthophyll pigment content during the day. Phytoplankton at the polar front (Diel 2) showed intermediate diel-related variations in photophysiology, with xanthophyll conversion and increases in photoprotective pigments during the day but constant FV/FM. These diel changes at all sampling stations had little impact on carbon fixation rates, although cells sampled from the deep chlorophyll maximum at the polar front had significantly lower maximum carbon fixation and minimum saturating irradiance (Ek) compared to the other depths and stations. Considering the oceanographic context, cells at Diel 1 and 2 received less light and were more deeply mixed than cells at Diel 3, causing a dampening of the diel r...
Earp, A, Hanson, CE, Ralph, PJ, Brando, VE, Allen, S, Baird, M, Clementson, L, Daniel, P, Dekker, AG, Fearns, PRCS, Parslow, J, Strutton, PG, Thompson, PA, Underwood, M, Weeks, S & Doblin, MA 2011, 'Review of fluorescent standards for calibration of in situ fluorometers: Recommendations applied in coastal and ocean observing programs', OPTICS EXPRESS, vol. 19, no. 27, pp. 26768-26782.
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Fluorometers are widely used in ecosystem observing to monitor fluorescence signals from organic compounds, as well as to infer geophysical parameters such as chlorophyll or CDOM concentration, but measurements are susceptible to variation caused by biofouling, instrument design, sensor drift, operating environment, and calibration rigor. To collect high quality data, such sensors need frequent checking and regular calibration. In this study, a wide variety of both liquid and solid fluorescent materials were trialed to assess their suitability as reference standards for performance assessment of in situ fluorometers. Criteria used to evaluate the standards included the spectral excitation/emission responses of the materials relative to fluorescence sensors and to targeted ocean properties, the linearity of the fluorometer's optical response with increasing concentration, stability and consistency, availability and ease of use, as well as cost. Findings are summarized as a series of recommended reference standards for sensors deployed on stationary and mobile platforms, to suit a variety of in situ coastal to ocean sensor configurations. Repeated determinations of chlorophyll scale factor using the recommended liquid standard, Fluorescein, achieved an accuracy of 2.5%. Repeated measurements with the recommended solid standard, Plexiglas Satinice® plum 4H01 DC (polymethylmethacrylate), over an 18 day period varied from the mean value by 1.0% for chlorophyll sensors and 3.3% for CDOM sensors. © 2011 Optical Society of America.
Gupta, V, Baghel, RS, Kumar, M, Kumari, P, Mantri, VA, Reddy, CRK & Jha, B 2011, 'Growth and agarose characteristics of isomorphic gametophyte (male and female) and sporophyte of Gracilaria dura and their marker assisted selection', Aquaculture, vol. 318, no. 3-4, pp. 389-396.
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The characteristics of agarose and growth for three isomorphic life phases of G. dura with their bio-molecular marker assisted selection have been described in this study. The tetrasporophyte showed superior quality of agarose over gametophytes and recorded growth rate was highest for females. The genetic relatedness studied with ISSR markers showed quadratic line of correlation between these phases (R2=1). Their genetic diversity determinants as percentage of polymorphic loci (PPL), average heterozygosity (He) and Shannon's Weaver index (I) were 55.55%, 0.5±0.07 and 0.33 respectively. The cytological analysis for chromosome count revealed 8 chromosomes in haploid gametophytic thallus (N) and 16 for diploid tetrasporophyte (2N) together with genetic structure analysis confirmed to their sexual mating behaviour. Their marker assisted selection based on ISSR generated characteristic band of 430bp specific to male, 860bp for female and two bands of 800 and 1600bp for tetrasporophytic thallus from primer 'A'. Similarly ISSR primer 'E' also generated bands specific to male, female and tetrasporophytes while others gave bands specific to either of life phase. Interestingly, endogenic ABA content was significantly higher for haploid gametophytes (female more than male) than diploid tetrasporophyte while no significant difference was observed in IBA content. Thus the study described not only the features of three life phases of G. dura but also reliable biomarkers for differentiating such isomorphic life phases which could be beneficial for the selection of cultivar and in breeding programmes. © 2011 Elsevier B.V.
Gupta, V, Kumar, M, Brahmbhatt, H, Reddy, CRK, Seth, A & Jha, B 2011, 'Simultaneous determination of different endogenetic plant growth regulators in common green seaweeds using dispersive liquid–liquid microextraction method', Plant Physiology and Biochemistry, vol. 49, no. 11, pp. 1259-1263.
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A simple and rapid HPLC-based method was developed for simultaneous determination of major classes of plant growth regulators (PGRs) in Monostroma and different species of Ulva. The plant growth regulators determined included gibberellic acid (GA3), indole-3-acetic acid (IAA), abscisic acid (ABA), indole-3-butyric acid (IBA), salicylic acid and kinetin riboside (KR) and their respective elution time was 2.75, 3.3, 3.91, 4.95, 5.39 and 6.59min. The parameters optimized for distinct separation of PGRs were mobile phase (60:40 methanol and 0.6% acetic acid in water), column temperature (35°C) and flow rate (1ml/min). This method presented an excellent linearity (0.2-100μg/ml) with limit of detection (LOD) as 0.2μg/ml for ABA, 0.5μg/ml for KR and salicylic acid, and 1μg/ml for IAA, IBA and GA3. The precision and accuracy of the method was evaluated after inter and intra day analysis in triplicates. The effect of plant matrix was compensated after spiking and the resultant recoveries estimated were in the range of 80-120%. Each PGR thereby detected were further characterized by ESI-MS analysis. The method optimized in this study determined IBA along with IAA for the first time in the seaweed species investigated except Ulva linza where the former was not detected. In all the species studied, ABA level was detected to be the highest while kinetin riboside was the lowest. In comparison to earlier methods of PGR analysis, sample preparation and analysis time were substantially reduced while allowing determination of more classes of PGRs simultaneously. © 2011 Elsevier Masson SAS.
Gupta, V, Kumar, M, Kumari, P, Reddy, CRK & Jha, B 2011, 'Optimization of protoplast yields from the red algae Gracilaria dura (C. Agardh) J. Agardh and G. verrucosa (Huds.) Papenfuss', Journal of Applied Phycology, vol. 23, no. 2, pp. 209-218.
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This study reports on the optimization of protoplast yield from two important tropical agarophytes Gracilaria dura and Gracilaria verrucosa using different cell-wall-degrading enzymes obtained from commercial sources. The conditions for achieving the highest protoplast yield was investigated by optimizing key parameters such as enzyme combinations and their concentrations, duration of enzyme treatment, enzyme pH, mannitol concentration, and temperature. The significance of each key parameter was also further validated using the statistical central composite design. The enzyme composition with 4% cellulase Onozuka R-10, 2% macerozyme R-10, 0.5% pectolyase, and 100 U agarase, 0.4 M mannitol in seawater (30‰) adjusted to pH 7.5 produced the highest protoplast yields of 3.7±0.7 × 106 cells g-1 fresh wt for G. dura and 1.2±0.78×106 cells g-1 fresh wt for G. verrucosa when incubated at 25°C for 4-6 h duration. The young growing tips maximally released the protoplasts having a size of 7-15 μm in G. dura and 15-25 μm in G. verrucosa, mostly from epidermal and upper cortical regions. A few large-size protoplasts of 25-35 μm, presumably from cortical region, were also observed in G. verrucosa. © 2010 Springer Science+Business Media B.V.
Hassler, CS, Djajadikarta, JR, Doblin, MA, Everett, JD & Thompson, PA 2011, 'Characterisation of water masses and phytoplankton nutrient limitation in the East Australian Current separation zone during spring 2008', DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY, vol. 58, no. 5, pp. 664-677.
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This study focuses on the comparison of oceanic and coastal cold-core eddies with inner-shelf and East Australian Current (EAC) waters at the time of the spring bloom (October 2008).
Hill, R, Brown, CM, DeZeeuw, K, Campbell, DA & Ralph, PJ 2011, 'Increased rate of D1 repair in coral symbionts during bleaching is insufficient to counter accelerated photo-inactivation', LIMNOLOGY AND OCEANOGRAPHY, vol. 56, no. 1, pp. 139-146.
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We dissect the primary photo-inactivation and the counteracting metabolic repair rates in fragments of the scleractinian coral, Pocillopora damicornis, subjected to a combined stress of a shift to elevated temperature (from 26°C to 32°C) and increased light (from 200 μmol photons m-2 s-1 to 400 μmol photons m-2 s-1) to induce bleaching. During the bleaching treatment the dinoflagellate symbionts showed a 5.5-fold acceleration in their photosystem II (PSII) repair rate constant, demonstrating that they maintain strong metabolic capacity to clear and replace photo-damaged D1 protein at the elevated temperature and light conditions. Nevertheless, the symbionts concurrently suffered a seven-fold increase in the rate constant for PSII photo-inactivation. This rapid photo-inactivation exceeded the PSII repair capacity, therefore tipping the symbionts, and by implication the symbiosis, into net photo-inhibition. Increased photo-inactivation in hospite, rather than an inhibition of PSII repair, is the principle trigger for net photo-inhibition under bleaching conditions. © 2011, by the American Society of Limnology and Oceanography, Inc.
Hoeksema, BW & Matthews, JL 2011, 'Contrasting bleaching patterns in mushroom coral assemblages at Koh Tao, Gulf of Thailand', Coral Reefs, vol. 30, no. 1, pp. 95-95.
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Jeffries, TC, Seymour, JR, Gilbert, JA, Dinsdale, EA, Newton, K, Leterme, SSC, Roudnew, B, Smith, RJ, Seuront, L & Mitchell, JG 2011, 'Substrate Type Determines Metagenomic Profiles from Diverse Chemical Habitats', PLOS ONE, vol. 6, no. 9, pp. 1-9.
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Environmental parameters drive phenotypic and genotypic frequency variations in microbial communities and thus control the extent and structure of microbial diversity. We tested the extent to which microbial community composition changes are controlled by shifting physiochemical properties within a hypersaline lagoon. We sequenced four sediment metagenomes from the Coorong, South Australia from samples which varied in salinity by 99 Practical Salinity Units (PSU), an order of magnitude in ammonia concentration and two orders of magnitude in microbial abundance. Despite the marked divergence in environmental parameters observed between samples, hierarchical clustering of taxonomic and metabolic profiles of these metagenomes showed striking similarity between the samples (>89%). Comparison of these profiles to those derived from a wide variety of publically available datasets demonstrated that the Coorong sediment metagenomes were similar to other sediment, soil, biofilm and microbial mat samples regardless of salinity (>85% similarity). Overall, clustering of solid substrate and water metagenomes into discrete similarity groups based on functional potential indicated that the dichotomy between water and solid matrices is a fundamental determinant of community microbial metabolism that is not masked by salinity, nutrient concentration or microbial abundance.
Jimenez, IM, Kuhl, M, Larkum, AWD & Ralph, PJ 2011, 'Effects of flow and colony morphology on the thermal boundary layer of corals', JOURNAL OF THE ROYAL SOCIETY INTERFACE, vol. 8, no. 65, pp. 1785-1795.
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The thermal microenvironment of corals and the thermal effects of changing flow and radiation are critical to understanding heat-induced coral bleaching, a stress response resulting from the destruction of the symbiosis between corals and their photosynt
Kerrison, P, Hall-Spencer, JM, Suggett, DJ, Hepburn, LJ & Steinke, M 2011, 'Assessment of pH variability at a coastal CO2 vent for ocean acidification studies', Estuarine, Coastal and Shelf Science, vol. 94, no. 2, pp. 129-137.
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Marine environments with naturally high CO2 concentrations have become important research sites for studying the impacts of future ocean acidification on biological processes. We conducted high temporal resolution pH and temperature measurements in and around a shallow (2.5-3m) CO2 vent site off Ischia, Italy in May and June 2008. Loggers were deployed at five stations to monitor water at both the surface and benthos. Our reference station, 500m from the CO2 vent, had no noticeable vent influence. It had a naturally high and stable benthic pH (mean 8.16, inter-quartile range (IQ): 8.14-8.18) fluctuating with diel periodicity, presumably driven by community photosynthesis and respiration. A principal component analysis (PCA) revealed that the pH of this station was well constrained by meteorological parameters. In contrast, a station positioned within the vent zone, had a low and very variable benthic mean pH of 7.11 (IQ: 6.91-7.62) with large pH fluctuations not well constrained by a PCA. Any stations positioned within 20m of the main vent zone had lowered pH, but suffered from abnormally large pH fluctuations making them unsuitable representatives to predict future changes to a shallow coastal environment. Between these extremes, we identified a benthic area with a lower pH of 7.84 (IQ: 7.83-7.88) that retained many of the characteristics of the reference station such as a natural diel pH periodicity and low variability. Our results indicate that a range of pH environments maybe commonplace near CO2 vents due to their characteristic acidification of benthic water over a wide area. Such environments could become invaluable natural laboratories for ocean acidification research, closely mimicking future CO2 conditions in a natural setting. © 2011 Elsevier Ltd.
Khan, N-UH, Pandya, N, Maity, NC, Kumar, M, Patel, RM, Kureshy, RI, Abdi, SHR, Mishra, S, Das, S & Bajaj, HC 2011, 'Influence of chirality of V(V) Schiff base complexes on DNA, BSA binding and cleavage activity', European Journal of Medicinal Chemistry, vol. 46, no. 10, pp. 5074-5085.
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New chiral V(V) Schiff base complexes (S)-[VO(OMe)L] and (R)-[VO(OMe)L] were synthesized and characterized by microanalysis, infrared (IR), UV-Visible, Circular dichroism (CD) spectroscopy and single crystal X-ray studies. The interaction of these complexes with calf thymus (CT) DNA and bovine serum albumin (BSA) protein showed chiral expression DNA/protein binding strength. The influence of chirality was also observed in cytotoxicity assay of Hep 2 cells. (R)-[VO(OMe)L] enantiomer exhibited higher binding constant (5 ± 1 × 10 5 M -1) as compared to (S)-[VO(OMe)L] (8 ± 1 × 10 4 M -1). The fluorescence quenching, thermal melting and viscosity data suggest DNA surface and/or groove binding nature of the complexes and electrophoresis studies also showed greater activity for (R)-[VO(OMe)L] in cleaving DNA and protein as against (S)-[VO(OMe)L]. © 2011 Elsevier Masson SAS. All rights reserved.
Kumar, M, Gupta, V, Kumari, P, Reddy, CRK & Jha, B 2011, 'Assessment of nutrient composition and antioxidant potential of Caulerpaceae seaweeds', Journal of Food Composition and Analysis, vol. 24, no. 2, pp. 270-278.
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Abstract
The proximate nutrient composition, mineral contents, enzymatic and non-enzymatic antioxidant potential of three Caulerpa species were investigated. All three species were high in ash (24.20–33.70%) and carbohydrate content (37.23–48.95%) on dry weight basis (DW). The lipid content ranged between 2.64 and 3.06% DW. The mineral contents varied marginally among the species but were in the order of Na > K > Ca > Mg. The Na/K ratio among the species varied from 1.80 to 2.55 and was lowest in C. scalpelliformis. A 10 g DW of Caulerpa powder contains 11–21% Fe, 52–60% Ca and 35–43% Mg, which is higher than the recommended daily allowance (RDA), compared with non-seafood. The percentage sum of PUFAs (C18:2, C18:3, C20:4 and C20:5) in total fatty acids was highest in both C. scalpelliformis (39.25%) and C. veravelensis (36.73%) while it was the lowest in C. racemosa (24.50%). The n−6/n−3 ratio among the species varied from 1.44 to 7.72 and remained within the prescribed WHO standards (<10). Further, the higher enzymatic dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) and non-enzymatic antioxidant potential of Caulerpa species found in the present study confirm their usefulness in terms of nutrients and antioxidants.
Kumar, M, Gupta, V, Trivedi, N, Kumari, P, Bijo, AJ, Reddy, CRK & Jha, B 2011, 'Desiccation induced oxidative stress and its biochemical responses in intertidal red alga Gracilaria corticata (Gracilariales, Rhodophyta)', Environmental and Experimental Botany, vol. 72, no. 2, pp. 194-201.
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Intertidal alga Gracilaria corticata growing in natural environment experiences various abiotic stresses during the low tides. The aim of this study was to determine whether desiccation exposure would lead to oxidative stress and its effect varies with exposure periods. This study gives an account of various biochemical changes in G. corticata following the exposure to desiccation for a period of 0 (control), 1, 2, 3 and 4. h under controlled conditions. During desiccation, G. corticata thalli showed dramatic loss of water by almost 47% when desiccated for 4. h. The enhanced production of reactive oxygen species (ROS) and increased lipid peroxidation observed during the exposure of 3-4. h were chiefly contributed by higher lipoxygenase (LOX) activity with the induction of two new LOX isoforms (LOX-2, ~85. kDa; LOX-3, ~65. kDa). The chlorophyll, carotenoids and phycobiliproteins (phycoerythrin and phycocyanin) were increased during initial 2. h exposure compared to control and thereafter declined in the succeeding exposure. The antioxidative enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), glutathione peroxidase (GPX) and the regeneration rate of reduced ascorbate (AsA) and glutathione (GSH) increased during desiccation up to 2-3. h. Further, the isoforms of antioxidant enzymes Mn-SOD (~150. kDa), APX-4 (~110. kDa), APX-5 (~45. kDa), GPX-1 (~80. kDa) and GPX-2 (~65. kDa) responded specifically to the desiccation exposure. Compared to control, a relative higher content of both free and bound insoluble putrescine and spermine together with enhanced n-6 PUFAs namely C20:4(n-6) and C20:3(n-6) fatty acids found during 2. h exposure reveals their involvement in defence reactions against the desiccation induced oxidative stress. © 2011 Elsevier B.V.
Kumar, M, Kumari, P, Trivedi, N, Shukla, MK, Gupta, V, Reddy, CRK & Jha, B 2011, 'Minerals, PUFAs and antioxidant properties of some tropical seaweeds from Saurashtra coast of India', Journal of Applied Phycology, vol. 23, no. 5, pp. 797-810.
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Twenty-two tropical seaweeds from the Rhodophyta, Phaeophyta and Chlorophyta were examined for their possible use as nutritional supplements. All seaweeds contained balanced Na/K and C/N ratio and high amounts of macroelements (Na, K, Ca, and Mg) as compared to the terrestrial vegetables. Among the microelements, Fe was the highest followed by Zn, Mn, Cu and other trace elements. Fatty acid distribution showed high level of n-6 and n-3 polyunsaturated fatty acids (PUFAs), and their ratios were within the WHO prescribed limits. The higher ratios of PUFA/SFA (>0. 4) are in agreement with the recommendations of nutritional guidelines. Most of the species, especially the Chlorophyta and Phaeophyta, had permissible intake values of unsaturation, atherogenic and thrombogenic indexes comparable to milk-based products. Principal component analysis demonstrated a correlation between total phenolic content, total antioxidant activity, DPPH, and O2•- radical scavenging activity, suggesting polyphenols as the chief contributor to the antioxidant activity in seaweeds. These results indicate that these seaweeds could be a potential source of natural antioxidants, minerals and high-quality PUFAs and may be efficiently used as ingredients in functional foods. © 2010 Springer Science+Business Media B.V.
Kumar, M, Trivedi, N, Reddy, CRK & Jha, B 2011, 'Toxic Effects of Imidazolium Ionic Liquids on the Green Seaweed Ulva lactuca: Oxidative Stress and DNA Damage', Chemical Research in Toxicology, vol. 24, no. 11, pp. 1882-1890.
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The green credentials of ionic liquids (ILs) are being increasingly questioned due to the growing evidence of their toxicity to aquatic ecosystems, although the mechanisms of toxicity are unknown. This study provides insights into the mechanism of toxicity and biological effects of 1-alkyl-3- methylimidazolium bromide [C nmim]Br (n = 4 to 16) on the marine macroalga Ulva lactuca. The cell viability of this alga during IL exposure was found to be negatively correlated to the chain length of the alkyl group. The IL ([C 12mim]Br) exposure triggers the generation of reactive oxygen species (ROS viz. O 2•-, H 2O 2, and OH •), damage of the membrane and DNA, and inhibition of antioxidant systems in the alga. The enhanced production of ROS and lipid peroxidation in the alga subjected to LC 50 concentration for 4 days was largely attributed to lipoxygenase (LOX) activity coupled with the induction of two LOX isoforms (∼80 kDa and ∼55 kDa). Pretreatment of the algal thallus with enzyme inhibitors such as diphenylene iodonium, sodium azide, cantharidin, and oxadiazoloquinoxalin-1-one, prior to [C 12mim]Br exposure showed the regulation of ROS by the activation of membrane bound NADPH-oxidase and cytochrome oxidase. The IL exposure resulted in the accumulation of n-3 and n-6 fatty acids at 0.5 LC 50 concentration indicating the induction of desaturase enzymes. Furthermore, antioxidant enzyme activities such as superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR) were enhanced by 1.3-2.0-fold, while glutathione peroxidase (GSH-Px) diminished, together with a higher regeneration rate of reduced ascorbate and glutathione. The isoforms of antioxidant enzymes, namely, Mn-SOD (∼85 kDa), APX (∼125 and 45 kDa), and GR (∼135 kDa) regulated differentially to IL exposure. The comet assay performed for the first time for seaweeds revealed the significant induction of DNA damage (>50-70% increase in % tail DNA over control) in alga exposed to ...
Larkum, AWD, Salih, A & Kuehl, M 2011, 'Rapid Mass Movement of Chloroplasts during Segment Formation of the Calcifying Siphonalean Green Alga, Halimeda macroloba', PLOS ONE, vol. 6, no. 7, pp. 1-9.
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Background: The calcifying siphonalean green alga, Halimeda macroloba is abundant on coral reefs and is important in the production of calcium carbonate sediments. The process by which new green segments are formed over-night is revealed here for the first time. Methodology/Principal Findings: Growth of new segments was visualised by epifluorescence and confocal microscopy and by pulse amplitude modulation (PAM) fluorimetry. Apical colourless proto-segments were initiated on day 1, and formed a loose network of non-calcified, non-septate filaments, containing no chloroplasts. Rapid greening was initiated at dusk by i) the mass movement of chloroplasts into these filaments from the parent segment and ii) the growth of new filaments containing chloroplasts. Greening was usually complete in 3-5 h and certainly before dawn on day 2 when the first signs of calcification were apparent. Mass chloroplast movement took place at a rate of 0.65 mm/s. Photosynthetic yield and rate remained low for a period of 1 to several hours, indicating that the chloroplasts were made de novo. Use of the inhibitors colchicine and cytochalasin d indicated that the movement process is dependent on both microtubules and microfilaments. Significance: This unusual process involves the mass movement of chloroplasts at a high rate into new segments during the night and rapid calcification on the following day and may be an adaptation to minimise the impact of herbivorous activity.
Marcos, Seymour, JR, Luhar, M, Durham, WM, Mitchell, JG, Macke, A & Stocker, R 2011, 'Microbial alignment in flow changes ocean light climate', PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, vol. 108, no. 10, pp. 3860-3864.
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The growth of microbial cultures in the laboratory often is assessed informally with a quick flick of the wrist: dense suspensions of microorganisms produce translucent 'swirls' when agitated. Here, we rationalize the mechanism behind this phenomenon and show that the same process may affect the propagation of light through the upper ocean. Analogous to the shaken test tubes, the ocean can be characterized by intense fluid motion and abundant microorganisms. We demonstrate that the swirl patterns arise when elongated microorganisms align preferentially in the direction of fluid flow and alter light scattering. Using a combination of experiments and mathematical modeling, we find that this phenomenon can be recurrent under typical marine conditions. Moderate shear rates (0.1 s-1) can increase optical backscattering of natural microbial assemblages by more than 20%, and even small shear rates (0.001 s-1) can increase backscattering from blooms of large phytoplankton by more than 30%. These results imply that fluid flow, currently neglected in models of marine optics, may exert an important control on light propagation, influencing rates of global carbon fixation and how we estimate these rates via remote sensing.
Pernice, M, Dunn, SR, Miard, T, Dufour, S, Dove, S & Hoegh-Guldberg, O 2011, 'Regulation of Apoptotic Mediators Reveals Dynamic Responses to Thermal Stress in the Reef Building Coral Acropora millepora', PLoS ONE, vol. 6, no. 1, pp. e16095-e16095.
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Petrou, K & Ralph, PJ 2011, 'Photosynthesis and net primary productivity in three Antarctic diatoms: possible significance for their distribution in the Antarctic marine ecosystem', MARINE ECOLOGY PROGRESS SERIES, vol. 437, pp. 27-40.
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Photosynthesis and net primary productivity were measured in 3 Antarctic diatoms, Fragilariopsis cylindrus, Pseudo-nitzschia subcurvata and Chaetoceros sp., exposed to rapid changes in temperature and salinity representing a range of conditions found during a seasonal cycle. Measured differences in fluorescence-derived photosynthetic activity and oxygen evolution suggested that some alternative electron cycling activity was present under high irradiances. F. cylindrus displayed the highest rates of relative electron transport and net primary productivity under all salinity and temperature combinations and showed adaptive traits towards the sea-icelike environment. P. subcurvata displayed a preference for low saline conditions where production rates were greatest. However, there was evidence of photosynthetic sensitivity to the lowest temperatures and highest salinities, suggesting a lack of adaptation for dealing with sea-ice-like conditions. Chaetoceros sp. showed high plasticity, acclimating well to all conditions but performing best under pelagic conditions. The study shows species-specific sensitivities to environmental change, highlighting photosynthetic capacity as a potentially important mechanism in ecological niche adaptation. When these data were modelled over different seasons, integrated daily net primary production was greatest under summer pelagic conditions. The findings from this study support the general observations of light control and seasonal development of net primary productivity and species succession in the Antarctic marine ecosystem. © Inter-Research 2011.
Petrou, K, Doblin, MA & Ralph, PJ 2011, 'Heterogeneity in the photoprotective capacity of three Antarctic diatoms during short-term changes in salinity and temperature', MARINE BIOLOGY, vol. 158, no. 5, pp. 1029-1041.
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The Antarctic marine ecosystem changes seasonally, forming a temporal continuum of specialised niche habitats including open ocean, sea ice and meltwater environments. The ability for phytoplankton to acclimate rapidly to the changed conditions of these environments depends on the species' physiology and photosynthetic plasticity and may ultimately determine their long-term ecological niche adaptation. This study investigated the photophysiological plasticity and rapid acclimation response of three Antarctic diatoms-Fragilariopsis cylindrus, Pseudo-nitzschia subcurvata and Chaetoceros sp.-to a selected range of temperatures and salinities representative of the sea ice, meltwater and pelagic habitats in the Antarctic. Fragilariopsis cylindrus displayed physiological traits typical of adaptation to the sea ice environment. Equally, this species showed photosynthetic plasticity, acclimating to the range of environmental conditions, explaining the prevalence of this species in all Antarctic habitats. Pseudo-nitzschia subcurvata displayed a preference for the meltwater environment, but unlike F. cylindrus, photoprotective capacity was low and regulated via changes in PSII antenna size. Chaetoceros sp. had high plasticity in non-photochemical quenching, suggesting adaptation to variable light conditions experienced in the wind-mixed pelagic environment. While only capturing short-term responses, this study highlights the diversity in photoprotective capacity that exists amongst three dominant Antarctic diatom species and provides insight into links between ecological niche adaptation and species' distribution. © 2011 Springer-Verlag.
Petrou, K, Hassler, CS, Doblin, MA, Shelly, K, Schoemann, V, van den Enden, R, Wright, S & Ralph, PJ 2011, 'Iron-limitation and high light stress on phytoplankton populations from the Australian Sub-Antarctic Zone (SAZ)', DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY, vol. 58, no. 21-22, pp. 2200-2211.
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The high nutrient low chlorophyll (HNLC) surface waters of the Southern Ocean are characterised by high concentrations of nitrate and phosphate, low concentrations of dissolved iron and deep vertical mixing. Future climate scenarios predict increased surface temperatures and ocean stratification in the region. These changes to vertical mixing will result in a slowdown of nutrient supply to surface waters and an increase in the integrated irradiance in the upper mixed layer. To investigate the influence of iron-limitation and high irradiance on phytoplankton growth and physiology, a 6-day shipboard incubation experiment was conducted during the Sub-Antarctic Zone Sensitivity to Environmental Change (SAZ Sense) voyage using phytoplankton populations from the upper mixed layer in the north-eastern SAZ region. Iron-limitation was induced with an organic siderophore and was compared with a 1nM iron-enriched incubation and an unamended treatment (under silicate replete conditions). As expected, iron enrichment led to dominance by large diatoms and enhanced photosynthetic performance, while the iron-limited community showed a decline in total chl a and photochemical efficiency. Under the added stress of high light, the iron-limited community was able to cope with the shift from in situ (<150μmolphotonsm-2s-1) to incubation (mean=765μmolphotonsm-2s-1) irradiance by increasing the proportion of photoprotective pigments and diverting excess light energy via energy-dependent quenching (qE). The responses to iron-limitation under high light showed that the phytoplankton community was able to acclimate to these conditions, but exhibited an overall decline in photosynthetic activity. Data presented here suggest the community shifts, in particular the decrease in diatoms, and the decline in photosynthetic performance of phytoplankton under low iron-high irradiance conditions has the potential to impact future ocean productivity and biogeochemical cycling. © 2011 Elsevier Ltd.
Petrou, K, Hill, R, Doblin, MA, McMinn, A, Johnson, R, Wright, SW & Ralph, PJ 2011, 'PHOTOPROTECTION OF SEA-ICE MICROALGAL COMMUNITIES FROM THE EAST ANTARCTIC PACK ICE', JOURNAL OF PHYCOLOGY, vol. 47, no. 1, pp. 77-86.
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All photosynthetic organisms endeavor to balance energy supply with demand. For sea-ice diatoms, as with all marine photoautotrophs, light is the most important factor for determining growth and carbon-fixation rates. Light varies from extremely low to often relatively high irradiances within the sea-ice environment, meaning that sea-ice algae require moderate physiological plasticity that is necessary for rapid light acclimation and photoprotection. This study investigated photoprotective mechanisms employed by bottom Antarctic sea-ice algae in response to relatively high irradiances to understand how they acclimate to the environmental conditions presented during early spring, as the light climate begins to intensify and snow and sea-ice thinning commences. The sea-ice microalgae displayed high photosynthetic plasticity to increased irradiance, with a rapid decline in photochemical efficiency that was completely reversible when placed under low light. Similarly, the photoprotective xanthophyll pigment diatoxanthin (Dt) was immediately activated but reversed during recovery under low light. The xanthophyll inhibitor dithiothreitol (DTT) and state transition inhibitor sodium fluoride (NaF) were used in under-ice in situ incubations and revealed that nonphotochemical quenching (NPQ) via xanthophyll-cycle activation was the preferred method for light acclimation and photoprotection by bottom sea-ice algae. This study showed that bottom sea-ice algae from the east Antarctic possess a high level of plasticity in their light-acclimation capabilities and identified the xanthophyll cycle as a critical mechanism in photoprotection and the preferred means by which sea-ice diatoms regulate energy flow to PSII. © 2011 Phycological Society of America.
Ponton, F, Chapuis, M-P, Pernice, M, Sword, GA & Simpson, SJ 2011, 'Evaluation of potential reference genes for reverse transcription-qPCR studies of physiological responses in Drosophila melanogaster', Journal of Insect Physiology, vol. 57, no. 6, pp. 840-850.
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Drosophila melanogaster is one of the most important genetic models and techniques such as reverse transcription quantitative real-time PCR (RT-qPCR) are being employed extensively for deciphering the genetics basis of physiological functions. In RT-qPCR, the expression levels of target genes are estimated on the basis of endogenous controls. The purpose of these reference genes is to control for variations in RNA quantity and quality. Although determination of suitable reference genes is essential to RT-qPCR studies, reports on the evaluation of reference genes in D. melanogaster studies are lacking. We analyzed the expression levels of seven candidate reference genes (Actin, EF1, Mnf, Rps20, Rpl32, Tubulin and 18S) in flies that were injured, heat-stressed, or fed different diets. Statistical analyses of variation were determined using three established software programs for reference gene selection, geNorm, NormFinder and BestKeeper. Best-ranked references genes differed across the treatments. Normalization candidacy of the selected candidate reference genes was supported by an analysis of gene expression values obtained from microarray datasets available online. The differences between the experimental treatments suggest that assessing the stability of reference gene expression patterns, determining candidates and testing their suitability is required for each experimental investigation. © 2011.
Raghu, AV, Unnikrishnan, K, Geetha, SP, Martin, G & Balachandran, I 2011, 'Plant regeneration and production of embelin from organogenic and embryogenic callus cultures of Embelia ribes Burm. f.-a vulnerable medicinal plant', IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY-PLANT, vol. 47, no. 4, pp. 506-515.
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Rosic, NN, Pernice, M, Dove, S, Dunn, S & Hoegh-Guldberg, O 2011, 'Gene expression profiles of cytosolic heat shock proteins Hsp70 and Hsp90 from symbiotic dinoflagellates in response to thermal stress: possible implications for coral bleaching', CELL STRESS & CHAPERONES, vol. 16, no. 1, pp. 69-80.
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Unicellular photosynthetic dinoflagellates of the genus Symbiodinium are the most common endosymbionts of reef-building scleractinian corals, living in a symbiotic partnership known to be highly susceptible to environmental changes such as hyperthermic stress. In this study, we identified members of two major heat shock proteins (HSPs) families, Hsp70 and Hsp90, in Symbiodinium sp. (clade C) with full-length sequences that showed the highest similarity and evolutionary relationship with other known HSPs from dinoflagellate protists. Regulation of HSPs gene expression was examined in samples of the scleractinian coral Acropora millepora subjected to elevated temperatures progressively over 18 h (fast) and 120 h (gradual thermal stress). Moderate to severe heat stress at 26°C and 29°C (+3°C and +6°C above average sea temperature) resulted in an increase in algal Hsp70 gene expression from 39% to 57%, while extreme heat stress (+9°C) reduced Hsp70 transcript abundance by 60% (after 18 h) and 70% (after 120 h). Elevated temperatures decreased an Hsp90 expression under both rapid and gradual heat stress scenarios. Comparable Hsp70 and Hsp90 gene expression patterns were observed in Symbiodinium cultures and in hospite, indicating their independent regulation from the host. Differential gene expression profiles observed for Hsp70 and Hsp90 suggests diverse roles of these molecular chaperones during heat stress response. Reduced expression of the Hsp90 gene under heat stress can indicate a reduced role in inhibiting the heat shock transcription factor which may lead to activation of heat-inducible genes and heat acclimation. © Cell Stress Society International 2010.
Rosic, NN, Pernice, M, Rodriguez-Lanetty, M & Hoegh-Guldberg, O 2011, 'Validation of Housekeeping Genes for Gene Expression Studies in Symbiodinium Exposed to Thermal and Light Stress', Marine Biotechnology, vol. 13, no. 3, pp. 355-365.
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Šafránek, D, Červený, J, Klement, M, Pospíšilová, J, Brim, L, Lazár, D & Nedbal, L 2011, 'E-photosynthesis: Web-based platform for modeling of complex photosynthetic processes', Biosystems, vol. 103, no. 2, pp. 115-124.
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Shukla, MK, Kumar, M, Prasad, K, Reddy, CRK & Jha, B 2011, 'Partial characterization of sulfohydrolase from Gracilaria dura and evaluation of its potential application in improvement of the agar quality', Carbohydrate Polymers, vol. 85, no. 1, pp. 157-163.
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Sulfohydrolase extracted from Gracilaria dura was purified to homogeneity and investigated for improving the quality of commercial agar. The purified enzyme (50 kDa) showed optimum activity at pH 8.0 and temperature 35 °C. The agar treated with ∼50 U of purified enzyme exhibited 1.66-fold increase in 3,6-AG content with 60% sulfate removal and also resulted an increase of ≥2-fold in viscosity and gel strength with a recovery of 90% agar. Further, the gelling and melting temperatures were markedly decreased to 31 °C and 82 °C respectively over the control values of 39 °C and 90 °C. The scanning electron microscopy revealed higher cross-linking and rigidity in the treated agar while FT-IR spectral analysis confirmed the increased 3,6-AG content with decreased sulfate. Therefore, the possibility for cloning of sulfohydrolase encoding gene(s) for its commercial production and exploitation in desulfation of agar could be an eco-friendly and alternative method to alkali treatment. © 2011 Elsevier Ltd. All rights reserved.
Singh, RP, Gupta, V, Kumari, P, Kumar, M, Reddy, CRK, Prasad, K & Jha, B 2011, 'Purification and partial characterization of an extracellular alginate lyase from Aspergillus oryzae isolated from brown seaweed', Journal of Applied Phycology, vol. 23, no. 4, pp. 755-762.
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The extracellular enzyme alginate lyase produced from marine fungus Aspergillus oryzae isolated from brown alga Dictyota dichotoma was purified, partially characterized, and evaluated for its sodium alginate depolymerization abilities. The enzyme characterization studies have revealed that alginate lyase consisted of two polypeptides with about 45 and 50 kDa each on 10% sodium dodecyl sulfate polyacrylamide gel electrophoresis and showed 140-fold higher activity than crude enzyme under optimized pH (6.5) and temperature (35°C) conditions. Zn2+, Mn2+, Cu2+, Mg2+, Co2+ and NaCl were found to enhance the enzyme activity while (Ca2+, Cd2+, Fe2+, Hg2+, Sr2+, Ni2+), glutathione, and metal chelators (ethylenediaminetetraacetic acid and ethylene glycol tetraacetic acid) suppressed the activity. Fourier transform infrared and thin-layer chromatography analysis of depolymerized sodium alginate indicated the enzyme specificity for cleaving at the β-1,4 glycosidic bond between polyM and polyG blocks of sodium alginate and therefore resulted in estimation of relatively higher polyM content than polyG. Comparison of chemical shifts in 13C nuclear magnetic resonance spectra of both polyM and polyG from that of sodium alginate also showed further evidence for enzymatic depolymerization of sodium alginate. © 2010 Springer Science+Business Media B.V.
Sinutok, S, Hill, R, Doblin, MA, Wuhrer, R & Ralph, PJ 2011, 'Warmer more acidic conditions cause decreased productivity and calcification in subtropical coral reef sediment-dwelling calcifiers', LIMNOLOGY AND OCEANOGRAPHY, vol. 56, no. 4, pp. 1200-1212.
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The effects of elevated CO(2) and temperature on photosynthesis and calcification in the calcifying algae Halimeda macroloba and Halimeda cylindracea and the symbiont-bearing benthic foraminifera Marginopora vertebralis were investigated through exposure to a combination of four temperatures (28 degrees C, 30 degrees C, 32 degrees C, and 34 degrees C) and four CO(2) levels (39, 61, 101, and 203 Pa; pH 8.1, 7.9, 7.7, and 7.4, respectively). Elevated CO(2) caused a profound decline in photosynthetic efficiency (F(V) : F(M)), calcification, and growth in all species. After five weeks at 34 degrees C under all CO(2) levels, all species died. Chlorophyll (Chl) a and b concentration in Halimeda spp. significantly decreased in 203 Pa, 32 degrees C and 34 degrees C treatments, but Chl a and Chl c(2) concentration in M. vertebralis was not affected by temperature alone, with significant declines in the 61, 101, and 203 Pa treatments at 28 degrees C. Significant decreases in F(V) : F(M) in all species were found after 5 weeks of exposure to elevated CO(2) (203 Pa in all temperature treatments) and temperature (32 degrees C and 34 degrees C in all pH treatments). The rate of oxygen production declined at 61, 101, and 203 Pa in all temperature treatments for all species. The elevated CO(2) and temperature treatments greatly reduced calcification (growth and crystal size) in M. vertebralis and, to a lesser extent, in Halimeda spp. These findings indicate that 32 degrees C and 101 Pa CO(2), are the upper limits for survival of these species on Heron Island reef, and we conclude that these species will be highly vulnerable to the predicted future climate change scenarios of elevated temperature and ocean acidification.
Steinke, M, Brading, P, Kerrison, P, Warner, ME & Suggett, DJ 2011, 'CONCENTRATIONS OF DIMETHYLSULFONIOPROPIONATE AND DIMETHYL SULFIDE ARE STRAIN-SPECIFIC IN SYMBIOTIC DINOFLAGELLATES (SYMBIODINIUM SP., DINOPHYCEAE)1', Journal of Phycology, vol. 47, no. 4, pp. 775-783.
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Dimethyl sulfide (DMS) and dimethylsulfoniopropionate (DMSP) are sulfur compounds that may function as antioxidants in algae. Symbiotic dinoflagellates of the genus Symbiodinium show strain-specific differences in their susceptibility to temperature-induced oxidative stress and have been shown to contain high concentrations of DMSP. We investigated continuous cultures of four strains from distinct phylotypes (A1, A13, A2, and B1) that can be characterized by differential thermal tolerances. We hypothesized that strains with high thermal tolerance have higher concentrations of DMSP and DMS in comparison to strains with low thermal tolerance. DMSP concentrations were strain-specific with highest concentrations occurring in A1 (225±3.5mmol·L-1 cell volume [CV]) and lowest in A2 (158±3.8mmol· L-1CV). Both strains have high thermal tolerance. Strains with low thermal tolerance (A13 and B1) showed DMSP concentrations in between these extremes (194±19.0 and 160±6.1mmol·L-1 CV, respectively). DMS data further confirmed this general pattern with high DMS concentrations in A1 and A13 (4.1±1.22 and 2.1±0.37mmol·L-1CV, respectively) and low DMS concentrations in A2 and B1 (0.3±0.06 and 0.5±0.22mmol·L-1 CV, respectively). Hence, the strain-specific differences in DMSP and DMS concentrations did not match the different abilities of the four phylotypes to withstand thermal stress. Future work should quantify the possible dynamics in DMSP and DMS concentrations during periods of high oxidative stress in Symbiodinium sp. and address the role of these antioxidants in zooxanthellate cnidarians. © 2011 Phycological Society of America.
SUGGETT, DJ & SMITH, DJ 2011, 'Interpreting the sign of coral bleaching as friend vs. foe', Global Change Biology, vol. 17, no. 1, pp. 45-55.
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Coral bleaching is a major concern to researchers, conservationists and the general public worldwide. To date, much of the high profile attention for bleaching has coincided with major environmental impacts and for many the term coral bleaching is synonymously associated with coral mortality (so-called 'lethal' bleaching episodes). While this synonymous association has undoubtedly been key in raising public support, it carries unfair representation: nonlethal bleaching is, and always has been, a phenomenon that effectively occurs regularly in nature as corals acclimatize to regular periodic changes in growth environment (days, seasons etc). In addition, corals can exhibit sublethal bleaching during extreme environmental conditions whereby mortality does not occur and corals can potentially subsequently recover once ambient environmental conditions return. Perhaps not surprisingly it is the frequency and extent of these non and sublethal processes that yield key evidence as to how coral species and reef systems will likely withstand environmental and thus climatic change. Observations of non and sublethal bleaching (and subsequent recovery) are arguably not as readily reported as those of lethal bleaching since (1) the convenient tools used to quantify bleaching yield major ambiguity (and hence high potential for misidentification) as to the severity of bleaching; and (2) lethal bleaching events inevitably receive higher profile (media) attention and so are more readily reported. Under-representation of non and sublethal bleaching signs may over-classify the severity of bleaching, under-estimate the potential resilience of reefs against environmental change, and thus ultimately limit (if not depreciate) the validity and effectiveness of reef management policies and practices. While bleaching induced coral mortality must remain our key concern it must be better placed within the context of bleaching signs that do not result in a long-term loss of reef via...
Thompson, PA, Bonham, P, Waite, AM, Clementson, LA, Cherukuru, N, Hassler, C & Doblin, MA 2011, 'Contrasting oceanographic conditions and phytoplankton communities on the east and west coasts of Australia', DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY, vol. 58, no. 5, pp. 645-663.
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The composition and dynamics of the phytoplankton communities and hydrographic factors that control them are described for eastern and western Australia with a focus on the Eastern Australian Current (EAC) and Leeuwin Current (LC) between 27.5 degrees and 34.51S latitude.
Trivedi, N, Gupta, V, Kumar, M, Kumari, P, C.R.K.Reddy & Jha, B 2011, 'An alkali-halotolerant cellulase from Bacillus flexus isolated from green seaweed Ulva lactuca', Carbohydrate Polymers, vol. 83, no. 2, pp. 891-897.
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An extracellular alkali-halotolerant cellulase from the strain Bacillus flexus NT isolated from Ulva lactuca was purified to homogeneity with a recovery of 25.03% and purity fold of 22.31. The molecular weight of the enzyme was about 97 kDa and the Vmax and Km was 370.17 U/ml/min and 6.18 mg/ml respectively. The optimum pH and temperature for enzyme activity was 10 and 45 °C respectively. The enzymatic hydrolysis of the CMC was confirmed with GPC and GC-MS analysis. The stabilized activity of the enzyme even at high pH of 9.0-12.0 and residual activity of about 70% at salt concentration (NaCl 15%) revealed for its alkali-halotolerance nature. The metal ions Cd 2+ and Li1+ were found as inducers while Cr2+, Co2+, Zn2+ and metal chelator EDTA have significantly inhibited the enzyme activity. Enzyme activity was insensitive to ethanol and isopropanol while partially inhibited by acetone, cyclohexane and benzene. © 2010 Elsevier Ltd. All rights reserved.
Trivedi, N, Gupta, V, Kumar, M, Kumari, P, Reddy, CRK & Jha, B 2011, 'Solvent tolerant marine bacterium Bacillus aquimaris secreting organic solvent stable alkaline cellulase', Chemosphere, vol. 83, no. 5, pp. 706-712.
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The organic solvent tolerant bacteria with their physiological abilities to decontaminate the organic pollutants have potentials to secrete extracellular enzymes of commercial importance. Of the 19 marine bacterial isolates examined for their solvent tolerance at 10vol.% concentration, one had the significant tolerance and showed a relative growth yield of 86% for acetone, 71% for methanol, 52% for benzene, 35% for heptane, 24% for toluene and 19% for ethylacetate. The phylogenetic analysis of this strain using 16S rDNA sequence revealed 99% homology with Bacillus aquimaris. The cellulase enzyme secreted by this strain under normal conditions showed an optimum activity at pH 11 and 45°C. The enzyme did show functional stability even at higher pH (12) and temperature (75°C) with residual activity of 85% and 95% respectively. The enzyme activity in the presence of different additives were in the following order: Co+2>Fe+2>NaOCl2>CuSO4>KCl>NaCl. The enzyme stability in the presence of solvents at 20vol.% concentration was highest in benzene with 122% followed by methanol (85%), acetone (75%), toluene (73%) and heptane (42%). The pre-incubation of enzyme in ionic liquids such as 1-ethyl-3-methylimidazolium methanesulfonate and 1-ethyl-3-methylimidazolium bromide increased its activity to 150% and 155% respectively. The change in fatty acid profile with different solvents further elucidated the physiological adaptations of the strain to tolerate such extreme conditions. © 2011 Elsevier Ltd.
Ulstrup, KE, Kuhl, M, van Oppen, MJH, Cooper, TF & Ralph, PJ 2011, 'Variation in photosynthesis and respiration in geographically distinct populations of two reef-building coral species', AQUATIC BIOLOGY, vol. 12, no. 3, pp. 241-248.
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Studies of the regulation and importance of physiological processes such as coral photosynthesis and respiration on coral reefs require knowledge of spatio-temporal patterns of variability at different scales. Oxygen microelectrodes were used to measure photosynthesis and dark respiration of 2 corals, Pocillopora damicornis and Turbinaria reniformis, in the northern (Lizard Island) and central (Davies and Broadhurst Reefs) regions of the Great Barrier Reef (GBR) in winter and summer. Genetic characterisation of Symbiodinium revealed that P. damicornis hosted a single symbiont type (Symbiodinium C1) in both regions, whereas T. reniformis harboured 2 types, dependent on location. Colonies at Lizard Island harboured Symbiodinium D, whereas colonies at Davies Reef harboured Symbiodinium C2. Rates of gross photosynthesis were greater in the central than in the northern GBR in summer. A similar pattern was detected for dark respiration rates in T. reniformis. No seasonal change in either photosynthesis or dark respiration was evident in the northern GBR, possibly due to less annual variability in light conditions, and for T. reniformis, additionally the presence of Symbiodinium D. These results highlight that environmental conditions coupled with regional-scale distribution of Symbiodinium are likely to exert important influences on respiration and photosynthetic performance of reef-building corals. & copy Inter-Research 2011.
Van Dongen-Vogels, V, Seymour, JR, Middleton, JF, Mitchell, JG & Seuront, L 2011, 'Influence of local physical events on picophytoplankton spatial and temporal dynamics in South Australian continental shelf waters', JOURNAL OF PLANKTON RESEARCH, vol. 33, no. 12, pp. 1825-1841.
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We investigated the space-time dynamics of picophytoplankton in South Australian continental shelf waters from February 2008 to January 2009, focusing on localized physical events. We discriminated six picophytoplankton populations by flow cytometry, including Synechococcus (SYN1, SYN2), Prochlorococcus (PROC1, PROC2) and small and large picoeukaryotes (EUKS, EUKL). Local physical events observed included downwelling and dense waters outflowing from a nearby gulf in winter-early spring 2008, upwelling in summer and early spring 2008 and eddy formation in January 2009. Each population responded differently to these events, which resulted in up to four orders of magnitude changes in their abundances. Population-specific hotspots reflected a succession of distinct dominant communities associated with the strength of upwelling events, changes in fluorescence maximum depths and local downwelling and mixing processes. The unexpected high abundances and local dominance of Prochlorococcus in summer reflected the possible influence of eastward and westward current transports and the presence of a High-Light (PROC1)-and Low-Light (PROC2)-adapted ecotypes. This study highlights the role of localized physical events in the dominance of all three picophytoplankton groups that may be critical for the high productivity of the study region, and suggests the importance of hydroclimatic forcing for inter-annual changes in picophytoplankton communities.
