Alvarez, LA, Exton, DA, Timmis, KN, Suggett, DJ & McGenity, TJ 2009, 'Characterization of marine isoprene‐degrading communities', Environmental Microbiology, vol. 11, no. 12, pp. 3280-3291.
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SummaryIsoprene is a volatile and climate‐altering hydrocarbon with an atmospheric concentration similar to that of methane. It is well established that marine algae produce isoprene; however, until now there was no specific information about marine isoprene sinks. Here we demonstrate isoprene consumption in samples from temperate and tropical marine and coastal environments, and furthermore show that the most rapid degradation of isoprene coincides with the highest rates of isoprene production in estuarine sediments. Isoprene‐degrading enrichment cultures, analysed by denaturing gradient gel electrophoresis and 454 pyrosequencing of the 16S rRNA gene and by culturing, were generally dominated by Actinobacteria, but included other groups such as Alphaproteobacteria and Bacteroidetes, previously not known to degrade isoprene. In contrast to specialist methane‐oxidizing bacteria, cultivated isoprene degraders were nutritionally versatile, and nearly all of them were able to use n‐alkanes as a source of carbon and energy. We therefore tested and showed that the ubiquitous marine hydrocarbon‐degrader, Alcanivorax borkumensis, could also degrade isoprene. A mixture of the isolates consumed isoprene emitted from algal cultures, confirming that isoprene can be metabolized at low, environmentally relevant concentrations, and suggesting that, in the absence of spilled petroleum hydrocarbons, algal production of isoprene could maintain viable populations of hydrocarbon‐degrading microbes. This discovery of a missing marine sink for isoprene is the first step in obtaining more robust predictions of its flux, and suggests that algal‐derived isoprene provides an additional source of carbon for diverse microbes in the oceans.
Arotsker, L, Siboni, N, Ben-Dov, E, Kramarsky-Winter, E, Loya, Y & Kushmaro, A 2009, 'Vibrio sp as a potentially important member of the Black Band Disease (BBD) consortium in Favia sp corals', FEMS MICROBIOLOGY ECOLOGY, vol. 70, no. 3, pp. 515-524.
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Baird, AH, Bhagooli, R, Ralph, PJ & Takahashi, S 2009, 'Coral bleaching: the role of the host', TRENDS IN ECOLOGY & EVOLUTION, vol. 24, no. 1, pp. 16-20.
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Coral bleaching caused by global warming is one of the major threats to coral reefs. Very recently, research has focused on the possibility of corals switching symbionts as a means of adjusting to accelerating increases in sea surface temperature. Although symbionts are clearly of fundamental importance, many aspects of coral bleaching cannot be readily explained by differences in symbionts among coral species. Here we outline several potential mechanisms by which the host might influence the bleaching response, and conclude that predicting the fate of corals in response to climate change requires both members of the symbiosis to be considered equally. © 2008 Elsevier Ltd. All rights reserved.
BARTLETT, CY, MANUA, C, CINNER, J, SUTTON, S, JIMMY, R, SOUTH, R, NILSSON, J & RAINA, J 2009, 'Comparison of Outcomes of Permanently Closed and Periodically Harvested Coral Reef Reserves', Conservation Biology, vol. 23, no. 6, pp. 1475-1484.
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Abstract: In many areas of the developing world, the establishment of permanent marine reserves is inhibited by cultural norms or socioeconomic pressures. Community conserved areas that are periodically harvested are increasingly being implemented as fisheries management tools, but few researchers have empirically compared them with permanently closed reserves. We used a hierarchal control‐impact experimental design to compare the abundance and biomass of reef fishes, invertebrates, and substrate composition in periodically harvested and permanent reserves and in openly fished (control sites) of the South Pacific island country of Vanuatu. Fished species had significantly higher biomass in periodically harvested reserves than in adjacent openly fished areas. We did not detect differences in substratum composition between permanent reserves and openly fished areas or between permanent reserves and periodically harvested reserves. Giant clams (tridacnids) and top shells (Trochus niloticus) were vulnerable to periodic harvest, and we suggest that for adequate management of these species, periodically harvested community conservation areas be used in conjunction with other management strategies. Periodic harvest within reserves is an example of adaptive and flexible management that may meet conservation goals and that is suited to the social, economic, and cultural contexts of many coastal communities in the developing world.
Bar-Zeev, E, Berman-Frank, I, Stambler, N, Vázquez Domínguez, E, Zohary, T, Capuzzo, E, Meeder, E, Suggett, DJ, Iluz, D, Dishon, G & Berman, T 2009, 'Transparent exopolymer particles (TEP) link phytoplankton and bacterial production in the Gulf of Aqaba', Aquatic Microbial Ecology, vol. 56, no. 2-3, pp. 217-225.
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Variations in transparent exopolymer particles (TEP), bacterial biomass production (BP) and primary productivity (PP) were followed over 52 h at a deep water station in the Gulf of Aqaba (Eilat, Israel) during the spring, in April 2008. About 20 h after the start of the study, there was a short (̃15 h) but intense storm event that probably caused a nutrient pulse and, subsequently, a brief outgrowth of diatoms in the euphotic layer. Concentrations of TEP and BP ranged from 23 to 228 μg gum xanthan equivalents l-1 and from 0.2 to 0.6 μg C l-1 h-1, respectively. Concentrations of TEP and BP were measured in unfiltered and in GF/C (1.2 μm)-prefiltered samples. Most of the TEP (59 ± 21% of total TEP, mean ± SD) were in the smaller (GF/C-filtered) size fraction (0.4-1.2 μm); however, after the crash of the diatom bloom, the majority of TEP were in the ≥1.2 μm size fraction. In the GF/Cfiltered fraction, BP averaged 59 ± 12% and 93 ± 5% of total BP in the upper water column and from 300 m, respectively. Significant correlations were observed between TEP and BP, suggesting that active heterotrophic bacteria may have been associated with these particles. During the 3 d of our study, PP and BP in the euphotic zone averaged 480 and 225 mg C m-2 d-1, respectively, suggesting that about half or more of the primary produced carbon was metabolized by heterotrophic bacteria in the upper water column. Coincident with strong mixing caused by the storm, TEP concentrations decreased in the surface water and increased at depth. We suggest that TEP acted to link carbon flux between the primary producers and heterotrophic bacteria, and that the downward movement of TEP from the upper water layers may be an important process in transferring organic carbon to deeper waters of the Gulf of Aquaba. Sinking TEP could provide not only organic carbon substrates for associated bacteria but also form 'hot spots' of elevated microbial metabolism and nutrient cycling throughout the wate...
Buxton, L, Badger, M & Ralph, P 2009, 'EFFECTS OF MODERATE HEAT STRESS AND DISSOLVED INORGANIC CARBON CONCENTRATION ON PHOTOSYNTHESIS AND RESPIRATION OF SYMBIODINIUM SP (DINOPHYCEAE) IN CULTURE AND IN SYMBIOSIS', JOURNAL OF PHYCOLOGY, vol. 45, no. 2, pp. 357-365.
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The influence of temperature and inorganic carbon (Ci) concentration on photosynthesis was examined in whole corals and samples of cultured symbiotic dinoflagellates (Symbiodinium sp.) using combined measurements from a membrane inlet mass spectrometer and chl a fluorometer. In whole corals, O2 production at 26°C was significantly limited at Ci concentrations below ambient seawater (∼2.2 mM). Further additions of Ci up to ∼10 mM caused no further stimulation of oxygenic photosynthesis. Following exposure to 30°C (2 d), net oxygen production decreased significantly in whole corals, as a result of reduced production of photosynthetically derived oxygen rather than increased host consumption. Whole corals maintained a rate of oxygen evolution around eight times lower than cultured Symbiodinium sp. at inorganic carbon concentrations <2 mM, but cultures displayed greater levels of photoinhibition following heat treatment (30°C, 2 d). Whole corals and cultured zooxanthellae differed considerably in their responses to Ci concentration and moderate heat stress, demonstrating that cultured Symbiodinium make an incongruous model for those in hospite. Reduced net oxygen evolution, in whole corals, under conditions of low Ci (<2 mM) has been interpreted in terms of possible sink limitation leading to increased nonphotochemical energy dissipation. The advantages of combined measurement of net gas exchange and fluorometry offered by this method are discussed. © 2009 Phycological Society of America.
Červený, J & Nedbal, L 2009, 'Metabolic Rhythms of the Cyanobacterium Cyanothece sp. ATCC 51142 Correlate with Modeled Dynamics of Circadian Clock', Journal of Biological Rhythms, vol. 24, no. 4, pp. 295-303.
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These experiments aim to reveal the dynamic features that occur during the metabolism of the unicellular, nitrogen fixing cyanobacterium Cyanothece sp. when exposed to diverse circadian forcing patterns (LD 16:8, LD 12:12, LD 8:16, LD 6:6). The chlorophyll concentration grew rapidly from subjective morning when first illuminated to around noon, then remained stable from later in the afternoon and throughout the night. The optical density measured at 735 nm was stable during the morning chlorophyll accumulation, then increased in the early afternoon toward a peak, followed at dusk by a rapid decline toward the late night steady state. The authors propose that these dynamics largely reflect accumulation and subsequent consumption of glycogen granules. This hypothesis is consistent with the sharp peak of respiration that coincides with the putative hydrocarbon catabolism. In the long-day regimen (LD 16:8), these events may mark the transition from the aerobic photosynthetic metabolism to microaerobic nitrogen metabolism that occurs at dusk, and thus cannot be triggered by the darkness that comes later. Rather, control is likely to originate in the circadian clock signaling an approaching night. To explore the dynamics of the link between respiration and circadian oscillations, the authors extrapolated an earlier model of the KaiABC oscillator from Synechococcus elongatus to Cyanothece sp. The measured peak of respiratory activity at dusk correlated strongly in its timing and time width with the modeled peak in accumulation of the KaiB4 complex, which marks the late afternoon phase of the circadian clock. The authors propose a hypothesis that high levels of KaiB4 (or of its Cyanothece sp. analog) trigger the glycogen catabolism that is reflected in the experiments in the respiratory peak. The degree of the correlation between the modeled KaiB4 dynamics and the dynamics of experimentally...
Červený, J, Šetlík, I, Trtílek, M & Nedbal, L 2009, 'Photobioreactor for cultivation and real‐time, in‐situ measurement of O2 and CO2 exchange rates, growth dynamics, and of chlorophyll fluorescence emission of photoautotrophic microorganisms', Engineering in Life Sciences, vol. 9, no. 3, pp. 247-253.
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AbstractA detailed knowledge about the dynamics of phytoplanktonic photosynthesis and respiration is crucial for the determination of primary productivity in open oceans as well as for biotechnological applications. The dynamics are best studied in photobioreactors that are able to simulate natural conditions in such, that light can be modulated not only diurnally but also mimicking effects of solar elevation angle from sunrise to sunset, variable cloudiness, light modulation in refractory sun flecks due to water waves, or light intermittence due to turbulent flow in dense suspensions. In addition, high performance photobioreactors ought to be able to monitor in real time photosynthetic and respiratory activities as well as culture growth. Here, we demonstrate performance of a newly designed bench‐top laboratory photobioreactor that meets these needs, with a study of green alga Scenedesmus quadricauda. The algal suspension was exposed to simulated daily variations of total photosynthetic active irradiance and spectral profile, with a larger proportion of red photons in the morning and evening hours. The instrument monitored automatically the culture growth by measuring the optical densities at 735 nm and 680 nm and by measuring steady state and maximal chlorophyll fluorescence emission yields. The photochemical yields were estimated from chlorophyll fluorescence data. These widely used but rather indirect yield estimates were confronted with direct measurements of oxygen evolution and consumption quantum yields. The CO2 fluxes in and out of the culture media as well as the dissolved CO2 in algal suspension were also recorded. The experiments demonstrated potential of the new photobioreactor to reveal minute modulations in gas exchange rates as well as to yield data for calculation of photon requirement of oxygen evolution in the suspension volume that i...
Cinner, JE, McClanahan, TR, Graham, NAJ, Pratchett, MS, Wilson, SK & Raina, J 2009, 'Gear‐based fisheries management as a potential adaptive response to climate change and coral mortality', Journal of Applied Ecology, vol. 46, no. 3, pp. 724-732.
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SummaryClimate change is emerging as one of the greatest threats to coral reef ecosystems. Climate‐induced warming events trigger coral bleaching and mortality, which can indirectly affect coral reef fishes. Managing fisheries across coral mortality events is expected to influence the persistence of species and reef recovery potential. The most common management recommendation has been to prohibit fishing using fisheries closures, but this response often has limited support from resource users.Here, we explore an alternative of managing fishing gear commonly used in artisanal coral reef fisheries. We examined fisheries landing data from 15 sites in Papua New Guinea and Kenya to explore whether or how specific gears select for: (i) species that depend on coral reefs for feeding or habitat and are likely to be susceptible to the loss of coral, and (ii) different functional groups of fishes.Only 6% of the fishes targeted by fishers were susceptible to the immediate effects of coral mortality; however, loss of habitat structure following coral mortality is expected to affect 56% of targeted species.Importantly, 25% of target species had feeding characteristics (i.e. reef scrapers/excavators and grazers) that contribute to the recovery of coral reef ecosystems, and gears differed considerably in catches of these species.Spear guns and traps target a high proportion of species likely to be affected by bleaching and key for the recovery of corals. These gears are strong candidates for management restrictions in reefs with high coral mortality. In contrast, line fishing catches the lowest proportion of susceptible and recovery‐enabling species and is preferential fo...
Collier, CJ, Lavery, PS, Ralph, PJ & Masini, RJ 2009, 'Shade-induced response and recovery of the seagrass Posidonia sinuosa', JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY, vol. 370, no. 1-2, pp. 89-103.
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The effect of shading on the seagrass Posidonia sinuosa Cambridge et Kuo was investigated to identify mechanisms that prolong its survival during periods of low light and permit its subsequent recovery. We also tested whether the responses were consistent in plants growing at different depths. Shade treatments were low (LS; 70 - 100% of ambient Photosynthetic Photon Flux Density), medium (MS; 12 - 39%) and heavy (HS; 5 - 4%) at the shallow (3 - 4 m) site, whilst the deep (7 - 8 m) site had no HS treatment. HS at the shallow and MS at the deep site were below minimum light requirements (MLR) for the long-term survival of P. sinuosa. Physiological, morphological and growth attributes were repeatedly measured during 198 d of shade treatments and a subsequent 384 d recovery period at ambient PPFD. Shoot density declined by 82% within 105 d under HS treatment, though 6% of shoots remained after 198 d. We estimate that complete shoot loss in HS would have taken 2 years. Rhizome sugar concentrations declined to 32 - 52% of the controls at the end of the most severe shading treatments but after shoot loss, sugar concentrations declined more slowly or increased, suggesting a return to positive carbon balance. In the treatments below MLR, shading induced changes in physiological, morphological and growth characteristics, including reduced leaf length and width, reduced δ13C and photosynthetic adaptation to low light (increased α, reduced Ek and ETRmax), though not consistently. After removal of shading, photosynthetic characteristics became more typical of high light adaptation, possibly induced by greater light penetration through the thinned canopy, including reversal of the changes in α, Ek and ETRmax and induction of non-photochemical quenching. Carbohydrate concentrations increased to ambient concentrations within 115 d at ambient PPFD. Recovery of shoot density was slow, remaining significantly reduced in the MS and HS treatments after 384 d recovery. Shoot...
Duxbury, Z, Schliep, M, Ritchie, RJ, Larkum, AWD & Chen, M 2009, 'Chromatic photoacclimation extends utilisable photosynthetically active radiation in the chlorophyll d-containing cyanobacterium, Acaryochloris marina', Photosynthesis Research, vol. 101, no. 1, pp. 69-75.
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Chromatic photoacclimation and photosynthesis were examined in two strains of Acaryochloris marina (MBIC11017 and CCMEE5410) and in Synechococcus PCC7942. Acaryochloris contains Chl d, which has an absorption peak at ca 710 nm in vivo. Cultures were grown in one of the three wavelengths (525 nm, 625 nm and 720 nm) of light from narrow-band photodiodes to determine the effects on pigment composition, growth rate and photosynthesis: no growth occurred in 525 nm light. Synechococcus did not grow in 720 nm light because Chl a does not absorb effectively at this long wavelength. Acaryochloris did grow in 720 nm light, although strain MBIC11017 showed a decrease in phycobilins over time. Both Synechococcus and Acaryochloris MBIC11017 showed a dramatic increase in phycobilin content when grown in 625 nm light. Acaryochloris CCMEE5410, which lacks phycobilins, would not grow satisfactorily under 625 nm light. The cells adjusted their pigment composition in response to the light spectral conditions under which they were grown. Photoacclimation and the Q (y) peak of Chl d could be understood in terms of the ecological niche of Acaryochloris, i.e. habitats enriched in near infrared radiation.
Fahnenstiel, G, Hong, Y, Millie, D, Doblin, M, Johengen, T & Reid, D 2009, 'Marine dinoflagellate cysts in the ballast tank sediments of ships entering the Laurentian Great Lakes', INTERNATIONAL ASSOCIATION OF THEORETICAL AND APPLIED LIMNOLOGY, VOL 30, PT. 7, PROCEEDINGS, vol. 30, no. 7, pp. 1035-1038.
Gribben, PE, Wright, JT, O'Connor, WA, Doblin, MA, Eyre, B & Steinberg, PD 2009, 'Reduced performance of native infauna following recruitment to a habitat-forming invasive marine alga', OECOLOGIA, vol. 158, no. 4, pp. 733-745.
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Despite well-documented negative impacts of invasive species on native biota, evidence for the facilitation of native organisms, particularly by habitat-forming invasive species, is increasing. However, most of these studies are conducted at the population or community level, and we know little about the individual fitness consequences of recruitment to habitat-forming invasive species and, consequently, whether recruitment to these habitats is adaptive. We determined the consequences of recruitment to the invasive green alga Caulerpa taxifolia on the native soft-sediment bivalve Anadara trapezia and nearby unvegetated sediment. Initially, we documented the growth and survivorship of A. trapezia following a natural recruitment event, to which recruitment to C. taxifolia was very high. After 12 months, few clams remained in either habitat, and those that remained showed little growth. Experimental manipulations of recruits demonstrated that all performance measures (survivorship, growth and condition) were significantly reduced in C. taxifolia sediments compared to unvegetated sediments. Exploration of potential mechanisms responsible for the reduced performance in C. taxifolia sediments showed that water flow and water column dissolved oxygen (DO) were significantly reduced under the canopy of C. taxifolia and that sediment anoxia was significantly higher and sediment sulphides greater in C. taxifolia sediments. However, phytoplankton abundance (an indicator of food supply) was significantly higher in C. taxifolia sediments than in unvegetated ones. Our results demonstrate that recruitment of native species to habitat-forming invasive species can reduce growth, condition and survivorship and that studies conducted at the community level may lead to erroneous conclusions about the impacts of invaders and should include studies on life-history traits, particularly juveniles.
Haapkylä, J, Seymour, AS, Barneah, O, Brickner, I, Hennige, S, Suggett, D & Smith, D 2009, 'Association of Waminoa sp. (Acoela) with corals in the Wakatobi Marine Park, South-East Sulawesi, Indonesia', Marine Biology, vol. 156, no. 5, pp. 1021-1027.
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This is the first quantitative study on the prevalence of epizoic Waminoa sp. acoel worms and their association with corals in the Wakatobi Marine National Park (WMNP), South-East Sulawesi, Indonesia. Three replicate transects were laid on the reef crest, flat and slope at six sites in 2006 and eight sites in 2007. Four of the sites were common in both years. In total 69 transects were surveyed in 2006, and 87 transects in 2007. A total of 4.8% of all observed hard corals were associated with acoel worms in 2006 and 2.6% of hard and soft corals in 2007. Acoels were present on 16 and 21 of the coral taxa studied in 2006 and 2007 respectively. The worms were strongly associated with the azooxanthellate coral Tubastrea spp. and were rare or absent on the most abundant coral genera Montipora and Porites. The mean number of corals having acoels was highest on reef slopes, whereas acoels were virtually absent on reef flats. Corals that had a high and a medium cover of worms were more common in 2007 than in 2006. No significant trend in the adaptation of the zooxanthellae of Waminoa sp. to different depths at different sites was revealed. The impact of the worm on the coral is unknown, but high numbers may have a shading effect and a negative impact on the coral's photophysiology. This acoel merits more study of its life cycle, its photophysiology, and its impact on its host corals. © 2009 Springer-Verlag.
Hennige, SJ, Suggett, DJ, Warner, ME, McDougall, KE & Smith, DJ 2009, 'Photobiology of Symbiodinium revisited: bio-physical and bio-optical signatures', Coral Reefs, vol. 28, no. 1, pp. 179-195.
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Light is often the most abundant resource within the nutrient-poor waters surrounding coral reefs. Consequently, zooxanthellae (Symbiodinium spp.) must continually photoacclimate to optimise productivity and ensure coral success. In situ coral photobiology is becoming dominated by routine assessments using state-of-the-art non-invasive bio-optical or chlorophyll a fluorescence (bio-physical) techniques. Multiple genetic types of Symbiodinium are now known to exist; however, little focus has been given as to how these types differ in terms of characteristics that are observable using these techniques. Therefore, this investigation aimed to revisit and expand upon a pivotal study by Iglesias-Prieto and Trench (1994) by comparing the photoacclimation characteristics of different Symbiodinium types based on their bio-physical (chlorophyll a fluorescence, reaction centre counts) and bio-optical (optical absorption, pigment concentrations) 'signatures'. Signatures described here are unique to Symbiodinium type and describe phenotypic responses to set conditions, and hence are not suitable to describe taxonomic structure of in hospite Symbiodinium communities. In this study, eight Symbiodinium types from clades and sub-clades (A-B, F) were grown under two PFDs (Photon Flux Density) and examined. The photoacclimation response by Symbiodinium was highly variable between algal types for all bio-physical and for many bio-optical measurements; however, a general preference to modifying reaction centre content over effective antennae-absorption was observed. Certain bio-optically derived patterns, such as light absorption, were independent of algal type and, when considered per photosystem, were matched by reaction centre stoichiometry. Only by better understanding genotypic and phenotypic variability between Symbiodinium types can future studies account for the relative taxonomic and physiological contribution by Symbiodinium to coral acclimation. © 2008 Springer-Verlag.
Hill, R, Ulstrup, KE & Ralph, PJ 2009, 'TEMPERATURE INDUCED CHANGES IN THYLAKOID MEMBRANE THERMOSTABILITY OF CULTURED, FRESHLY ISOLATED, AND EXPELLED ZOOXANTHELLAE FROM SCLERACTINIAN CORALS', BULLETIN OF MARINE SCIENCE, vol. 85, no. 3, pp. 223-244.
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Coral bleaching events are characterized by a dysfunction between the cnidarian coral host and the symbiotic dinoflagellate algae, known as zooxanthellae (genus Symbiodinium). Elevated temperature and intense light induce coral bleaching, where zooxanthellae are expelled from the host tissue. The primary cellular process in zooxanthellae which leads to coral bleaching is unresolved, and here, we investigated the sensitivity of the thylakoid membrane in a Symbiodinium culture and in genetically identified freshly isolated and expelled Symbiodinium cells. The fluorescence-temperature curve technique was used to measure the critical temperature (Tc) at which irreversible damage to the thylakoid membrane occurred. The accuracy of this technique was confirmed through the collection of scanning transmission electron micrographs which demonstrated the clear relationship between Tc and thylakoid membrane degradation. Analysis of 10 coral species with a diverse range of genetically distinct Symbiodinium communities showed a decline in Tc from summer to winter. A Symbiodinium culture and fragments of Pocillopora damicornis (Linnaeus, 1758) were exposed to a series of light and temperature treatments, where Tc increased from approximately 37 °C to 42 °C upon exposure to elevated temperature. Under bleaching conditions, the thermostability of the thylakoid membrane increased within 4 hrs by 5.1 °C, to a temperature far above bleaching thresholds, in both freshly isolated and photosynthetically competent zooxanthellae expelled from P. damicornis under these conditions. It is demonstrated that the thermostability of the thylakoid membrane increases in cultured, freshly isolated, and expelled zooxanthellae exposed to bleaching stress, suggesting it is not the primary site of impact during coral bleaching events.
Mark Moore, C, Mills, MM, Achterberg, EP, Geider, RJ, LaRoche, J, Lucas, MI, McDonagh, EL, Pan, X, Poulton, AJ, Rijkenberg, MJA, Suggett, DJ, Ussher, SJ & Woodward, EMS 2009, 'Large-scale distribution of Atlantic nitrogen fixation controlled by iron availability', Nature Geoscience, vol. 2, no. 12, pp. 867-871.
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Oceanic fixed-nitrogen concentrations are controlled by the balance between nitrogen fixation and denitrification. A number of factors, including iron limitation, can restrict nitrogen fixation, introducing the potential for decoupling of nitrogen inputs and losses. Such decoupling could significantly affect the oceanic fixed-nitrogen inventory and consequently the biological component of ocean carbon storage and hence air-sea partitioning of carbon dioxide. However, the extent to which nutrients limit nitrogen fixation in the global ocean is uncertain. Here, we examined rates of nitrogen fixation and nutrient concentrations in the surface waters of the Atlantic Ocean along a north-south 10,000 km transect during October and November 2005. We show that rates of nitrogen fixation were markedly higher in the North Atlantic compared with the South Atlantic Ocean. Across the two basins, nitrogen fixation was positively correlated with dissolved iron and negatively correlated with dissolved phosphorus concentrations. We conclude that inter-basin differences in nitrogen fixation are controlled by iron supply rather than phosphorus availability. Analysis of the nutrient content of deep waters suggests that the fixed nitrogen enters North Atlantic Deep Water. Our study thus supports the suggestion that iron significantly influences nitrogen fixation, and that subsequent interactions with ocean circulation patterns contribute to the decoupling of nitrogen fixation and loss. © 2009 Macmillan Publishers Limited. All rights reserved.
Pernice, M, Boucher, J, Boucher-Rodoni, R, Joannot, P & Bustamante, P 2009, 'Comparative bioaccumulation of trace elements between Nautilus pompilius and Nautilus macromphalus (Cephalopoda: Nautiloidea) from Vanuatu and New Caledonia', ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY, vol. 72, no. 2, pp. 365-371.
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The concentrations of 16 trace elements were investigated and compared for the first time in the digestive and excreting tissues of two Nautilus species (Cephalopoda: Nautiloidea) from two geologically contrasted areas: (1) N. macromphalus from New Caledonia, a region characterized by its richness in nickel ores and its lack of tectonic activities and (2) N. pompilius from the Vanuatu archipelago showing high volcanic and tectonic activities. In both Nautilus species, results clearly highlighted that the digestive gland played a key role in the bioaccumulation and storage of Ag, Cd, Ce, Co, Cu, Fe, La, Nd, V, and Zn whereas As, Cr, Mn, Ni, Pb, and Se were accumulated in a greater extent in the excreting tissues (i.e. pericardial and renal appendages). Despite contrasting environments, no significant difference (p<0.05) was found between the two Nautilus species in the concentrations of most of the essential and non-essential elements, including Ni and associated metals in Ni ores (i.e. Co and Mn). As nautilus lives on the outer shelf of barrier reefs, these results strongly support the hypothesis that the New Caledonian lagoon traps the major amount of the trace elements derived from natural erosion and the intense mining activities conducted on land. In contrast, the concentrations of the rare earth elements (Ce, La, and Nd) were significantly higher in N. pompilius than in N. macromphalus, probably as a result of the local enrichment of Vanuatu waters by specific environmental processes, such as volcanism or upwelling. © 2008 Elsevier Inc. All rights reserved.
Petrou, K, Doblin, M, Hassler, C & Ralph, P 2009, 'MULTIPLE STRESSORS ON ANTARCTIC MICROALGAE IMPACTS OF SEASONAL FREEZING AND MELTING OF SEA-ICE', PHYCOLOGIA, vol. 48, no. 4, pp. 106-106.
Quevrain, E, Domart-Coulon, I, Pernice, M & Bourguet-Kondracki, M-L 2009, 'Novel natural parabens produced by a Microbulbifer bacterium in its calcareous sponge host Leuconia nivea', ENVIRONMENTAL MICROBIOLOGY, vol. 11, no. 6, pp. 1527-1539.
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Raina, J-B, Tapiolas, D, Willis, BL & Bourne, DG 2009, 'Coral-Associated Bacteria and Their Role in the Biogeochemical Cycling of Sulfur', Applied and Environmental Microbiology, vol. 75, no. 11, pp. 3492-3501.
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ABSTRACTMarine bacteria play a central role in the degradation of dimethylsulfoniopropionate (DMSP) to dimethyl sulfide (DMS) and acrylic acid, DMS being critical to cloud formation and thereby cooling effects on the climate. High concentrations of DMSP and DMS have been reported in scleractinian coral tissues although, to date, there have been no investigations into the influence of these organic sulfur compounds on coral-associated bacteria. Two coral species,Montipora aequituberculataandAcropora millepora, were sampled and their bacterial communities were characterized by both culture-dependent and molecular techniques. Four genera,Roseobacter, Spongiobacter, Vibrio, andAlteromonas, which were isolated on media with either DMSP or DMS as the sole carbon source, comprised the majority of clones retrieved from coral mucus and tissue 16S rRNA gene clone libraries. Clones affiliated withRoseobactersp. constituted 28% of theM. aequituberculatatissue libraries, while 59% of the clones from theA. milleporalibraries were affiliated with sequences related to theSpongiobactergenus.Vibriospp. were commonly isolated from DMS and acrylic acid enrichments and were also present in 16S rRNA gene libraries from coral mucus, suggesting that under “normal” environmental conditions, they are a natural component of coral-associated communities. Genes homologous todddD, anddddL, previously implicated in DMSP degradation, were also characterized from isolated strains, confirming that bacteria associated with corals have the potential to metabolize this sulfur compound when present in coral tissues. Our results demonstrate that DMSP, DMS, and acrylic...
Rasoulouniriana, D, Siboni, N, Ben-Dov, E, Kramarsky-Winter, E, Loya, Y & Kushmaro, A 2009, 'Pseudoscillatoria coralii gen. nov., sp nov., a cyanobacterium associated with coral black band disease (BBD)', DISEASES OF AQUATIC ORGANISMS, vol. 87, no. 1-2, pp. 91-96.
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Seymour, JR, Ahmed, T & Stocker, R 2009, 'Bacterial chemotaxis towards the extracellular products of the toxic phytoplankton Heterosigma akashiwo', JOURNAL OF PLANKTON RESEARCH, vol. 31, no. 12, pp. 1557-1561.
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Marine bacteria exhibit positive chemotactic responses to the extracellular exudates of the toxic phytoplankton Heterosigma akashiwo. In the environment, this will support bacteriaalgae associations with potential implications for harmful algal bloom dynamics.
Seymour, JR, Marcos & Stocker, R 2009, 'Resource Patch Formation and Exploitation throughout the Marine Microbial Food Web', AMERICAN NATURALIST, vol. 173, no. 1, pp. E15-E29.
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Siboni, N, Martinez, S, Abelson, A, Sivan, A & Kushmaro, A 2009, 'Conditioning film and initial biofilm formation on electrochemical CaCO3 deposition on a metallic net in the marine environment', BIOFOULING, vol. 25, no. 7, pp. 675-683.
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Strom, D, Ralph, PJ & Stauber, JL 2009, 'Development of a Toxicity Identification Evaluation Protocol Using Chlorophyll-a Fluorescence in a Marine Microalga', ARCHIVES OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY, vol. 56, no. 1, pp. 30-38.
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Growth inhibition bioassays with the microalga Nitzschia closterium have recently been applied in marine Toxicity Identification Evaluation (TIE) testing. However, the 48-h test duration can result in substantial loss of toxicants over time, which might lead to an underestimation of the sample toxicity. Although shorter-term microalgal bioassays can minimize such losses, there are few bioassays available and none are adapted for marine TIE testing. The acute (5-min) chlorophyll-a fluorescence bioassay is one alternative; however, this bioassay was developed for detecting herbicides in freshwater aquatic systems and its suitability for marine TIE testing was not known. In this study, a chlorophyll-a fluorescence bioassay using the marine microalga Isochrysis galbana was able to detect contaminants other than herbicides at environmentally relevant concentrations and tolerated the physical and chemical manipulations needed for a Phase I TIE. Phase I TIE procedures were successfully developed using this chlorophyll-a fluorescence bioassay and used to identify all classes of contaminants present in a synthetic mixture of known chemical composition. In addition, TIEs with both the acute fluorescence bioassay and the standard growth inhibition bioassay identified the same classes of toxicants in a sample of an unknown complex effluent. Even though the acute chlorophyll-a fluorescence end point was less sensitive than the chronic cell division end point, TIEs with the chlorophyll-a fluorescence bioassay provided a rapid and attractive alternative to longer-duration bioassays. © 2008 Springer Science+Business Media, LLC.
Suggett, DJ, MacIntyre, HL, Kana, TM & Geider, RJ 2009, 'Comparing electron transport with gas exchange: parameterising exchange rates between alternative photosynthetic currencies for eukaryotic phytoplankton', Aquatic Microbial Ecology, vol. 56, no. 2-3, pp. 147-162.
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Estimates of aquatic primary productivity derived from in situ active chl a fluorescence have rapidly gained popularity over the past 2 decades. This trend has been driven primarily by the need to improve upon 'conventional' carbon (C) uptake- or oxygen (O2) evolution-based productivity estimates that require water samples to be incubated ex situ. Unlike the conventional approaches to measuring productivity, chlorophyll fluorescence measurements inherently describe only the activity of photosystem II (PSII) in the light reactions; thus, the photosynthetic 'currency' of the fluorescencebased approach is an electron turnover rate for PSII (ETRPSII). A photosynthetic currency of electrons has limited ecological relevance but can be converted to a currency of carbon if an 'exchange rate', i.e. a value or factor of equivalence for any single time point, is applied. We used fast repetition rate fluorometry (FRRf), mass inlet membrane spectrometry (MIMS) and 14C uptake to determine ETRPSII, gross and net O2 evolution and C fixation measured simultaneously for 6 microalgal species and for different steady-state growth conditions. Quantifying the PSII reaction centre (RCII) concentration and the spectral dependency of the effective absorption cross section yielded an FRRf approach that provided a robust estimate of the ETRPSII and gross O2 evolution for all species and conditions tested; however, the ETRPSII exceeded carbon dioxide (CO2) uptake by a factor of ̃5.4 to 11.6. At least 3 species exhibited substantial light-dependent O2 cycling to account for ̃40 to 60% of the difference between the ETRPSII and CO2 uptake. The highly variable nature of the ETRPSII:CO2 uptake 'exchange rate' observed here highlights the need for future studies that rely on active fluorescence to examine aquatic productivity to focus towards a systematic description of how electrons are coupled to C fixation in nature. © Inter-Research 2009.
Suggett, DJ, Moore, CM, Hickman, AE & Geider, RJ 2009, 'Interpretation of fast repetition rate (FRR) fluorescence: signatures of phytoplankton community structure versus physiological state', Marine Ecology Progress Series, vol. 376, pp. 1-19.
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Introduction of active chlorophyll a fluorescence protocols, in particular fast repetition rate (FRR) fluorometry, to oceanography and limnology 15 yr ago has enabled rapid assessment of photosynthetic physiology in situ. The FRR protocol generates simultaneous measurements of Photosystem II (PSII) effective absorption cross sections (termed σPSII) and photochemical efficiency (termed Fv/Fm). Both Fv/F m and σPSII measurements have been utilised to examine the effects of physiological stress on the photosynthetic apparatus of phytoplankton in an ever growing number of fluorescence-based studies. However, it is now becoming clearer that in situ values of Fv/Fm and σPSII also contain taxonomic information. Here, we present a synthesis of previously unpublished and published data, which show that F v/Fm and σPSII vary principally with broad-scale changes in community structure. These patterns observed in situ conform to trends observed in laboratory-grown cultures of a range of phytoplankton taxa. The magnitudes of variability in Fv/Fm and σPSII driven by changes in phytoplankton community structure often exceed that induced by nutrient limitation (as determined from controlled nutrient addition experiments). An exception to this general trend occurs in high-nutrient, low-chlorophyll a (HNLC) regions, where strong phenotypic changes in Fv/Fm and σPSII have been repeatedly demonstrated on relief of iron limitation. Overall, FRR fluorescence measurements of both Fv/Fm and σPSII in natural populations represent a combination of the taxonomic 'signature' (values of Fv/Fm and σPSII determined by the taxa present) within the phytoplankton community that is further modified according to the (photo-) physiological status. As such, fluorescence-based investigations of mixed populations must account for potential variations in phytoplankton community structure before interpretations of physiological status are made. © Inter-Research 2009.
Thompson, PA, Baird, ME, Ingleton, T & Doblin, MA 2009, 'Long-term changes in temperate Australian coastal waters: implications for phytoplankton', MARINE ECOLOGY PROGRESS SERIES, vol. 394, pp. 1-19.
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A ∼60 yr physical and chemical data set from 4 coastal stations around Australia plus remotely sensed SeaWiFS and phytoplankton taxonomic data were used to evaluate the temporal and spatial variation in phytoplankton ecology. The most consistent trend observed at all stations was a long-term increase in surface salinity of ∼0.003 ± 0.0008 psu yr-1. All stations showed positive trends in temperature, with the fastest surface warming (0.0202°C yr-1 over 60 yr) in the western Tasman Sea. Long-term trends in warming and stratification were more evident in some months and were not well characterized by annual averages. There was no general pattern of increasing stratification (0 to 50 m); only some stations and a few months showed significant changes. Long-term trends in surface nitrate and phosphate concentrations were either not significant (3 instances) or positive (5 instances) and were up to 6.1 nM phosphate yr-1. A pronounced decline in silicate was evident at the 3 east coast stations, with concentrations falling by as much as 58 nM yr-1 over the last ∼30 yr. The western Tasman Sea experienced a ∼50% decline in the growth rate and biomass of the spring bloom from 1997 to 2007, while other sites showed significant temporal variability in chlorophyll a that was associated with the Southern Oscillation Index (SOI). Diatoms tended to dominate the microplankton, especially during periods of low stratification. In conclusion, the physical, chemical and biological properties of Australian temperate waters have changed considerably over the last 60 yr in response to variation in the SOI and the strengthening East Australian Current. © Inter-Research 2009.
Hallegraeff, GM, Beardall, J, Brett, S, Doblin, MA, Hosja, W, de Salas, M & Thompson, P www.oceanclimatechange.org.au 2009, Marine climate change in Australia: Impacts and adaptation responses: Phytoplankton, pp. 1-10, Australia.
Salas, M, Cheal, A, Lough, J, McKinnon, D, Meekan, M, Sweatman, H, Coleman, M, Chambers, L, Dunlop, N, Church, J, Dowdney, J, Feng, M, Griffiths, S, Hobday, A, Matear, R, Poloczanska, E, Richardson, A, Ridgway, K, Risbey, J, Thompson, P, Thresher, R, Weller, E, Saintilan, N, Wilson, S, Lenanton, R, Hosja, W, Moore, P, Wernberg, T, Marshall, D, Connolly, R, Hill, K, Congdon, B, Devney, C, Fuentes, M, Graham, N, Hamann, M, Kingsford, M, Munday, P, Pratchett, M, Sheaves, M, Beardall, J, Brett, S, Waschka, M, Dann, P, Edgar, G, Swadling, K, Connell, S, Russell, B, Ward, T, Lukoschek, V, McGregor, S, Jenkins, G, Campbell, A, Steinberg, P, Anthony, K, Lovelock, C, Skilleter, G, Figueira, WF, Booth, DJ, Doblin, MA, Davidson, J, Holbrook, N, Howard, W, Kendrick, G & Smale, D NCCARF Publication 2009, Report Card of Marine Climate Change for Australia, pp. 1-2, Australia.
