Chaloub, RM, Reinert, F, Nassar, CAG, Fleury, BG, Mantuano, DG & Larkum, AWD 2010, 'Photosynthetic properties of three Brazilian seaweeds', Revista Brasileira de Botânica, vol. 33, no. 2, pp. 371-374.
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Photosynthetic performance of distinct marine macroalgae, Ulva fasciata Delile (green alga), Lobophora variegata (J. V. Lamouroux) Womersley ex E. C. Oliveira (brown alga), and Plocamium brasiliensis (Greville) M. A. Howe & W. R. Taylor (red alga), were compared using a pulse amplitude-modulated fluorometer. The maximum quantum yield (Fv/Fm) ranged from 0.80 to 0.51, and the lowest value was found in P. brasiliensis. Under 400 μmol photons m-2 s-1 irradiance, the highest value of photochemical quenching (qP = 0.92 ± 0.13) was observed for U. fasciata. The red alga P. brasiliensis dissipated high amounts of excitation energy (qN = 0.56 ± 0.09), resulting in relatively low values for the effective quantum yield of PS-II (0.23 ± 0.04), as well as for the relative electron transport rate (3.3 ± 0.7). The high photosynthetic potential found for U. fasciata partially explains the species ability for rapid growth and high productivity.
Csaszar, NBM, Ralph, PJ, Frankham, R, Berkelmans, R & van Oppen, MJH 2010, 'Estimating the Potential for Adaptation of Corals to Climate Warming', PLOS ONE, vol. 5, no. 3, pp. 1-8.
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The persistence of tropical coral reefs is threatened by rapidly increasing climate warming, causing a functional breakdown of the obligate symbiosis between corals and their algal photosymbionts (Symbiodinium) through a process known as coral bleaching. Yet the potential of the coral-algal symbiosis to genetically adapt in an evolutionary sense to warming oceans is unknown. Using a quantitative genetics approach, we estimated the proportion of the variance in thermal tolerance traits that has a genetic basis (i.e. heritability) as a proxy for their adaptive potential in the widespread Indo-Pacific reef-building coral Acropora millepora. We chose two physiologically different populations that associate respectively with one thermotolerant (Symbiodinium clade D) and one less tolerant symbiont type (Symbiodinium C2). In both symbiont types, pulse amplitude modulated (PAM) fluorometry and high performance liquid chromatography (HPLC) analysis revealed significant heritabilities for traits related to both photosynthesis and photoprotective pigment profile. However, quantitative real-time polymerase chain reaction (qRT-PCR) assays showed a lack of heritability in both coral host populations for their own expression of fundamental stress genes. Coral colony growth, contributed to by both symbiotic partners, displayed heritability. High heritabilities for functional key traits of algal symbionts, along with their short clonal generation time and high population sizes allow for their rapid thermal adaptation. However, the low overall heritability of coral host traits, along with the corals' long generation time, raise concern about the timely adaptation of the coral-algal symbiosis in the face of continued rapid climate warming. © 2010 Császár et al.
Doblin, MA, Murphy, KR & Ruiz, GM 2010, 'Thresholds for tracing ships' ballast water: an Australian case study', MARINE ECOLOGY PROGRESS SERIES, vol. 408, pp. 19-32.
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To limit the spread of non-indigenous marine species, ships can be legally required to conduct ballast water exchange (BWE) prior to discharging ballast water. It has been proposed to verify BWE by measuring concentrations of coastal tracers in ballast tanks, which should track their removal. Using 3 Australian ports as case studies (Port Botany, Port Curtis and Port Phillip Bay), each representing a different BWE verification difficulty level, the spatial and temporal variability of chromophoric dissolved organic matter (CDOM) and 3 trace elements (manganese [Mn], barium [Ba] and phosphorus [P]), were measured to assess their utility as tracers of coastal (unexchanged) ballast water. CDOM fluorescence at λex/λem = 320/414 nm (C2*) and 370/494 nm (C3*) and Mn concentrations were significantly higher in ports than in the adjacent Tasman Sea, except near port entrances and at a few sites in Port Botany. Ba concentrations demonstrated the least power to discriminate coastal sources, but P easily discriminated water from mesotrophic Port Phillip Bay. In general, tracers showed greater variation between and within ports, rather than between seasons. Conservative BWE thresholds were calculated to be 1.6 quinine sulphate equivalents for C2*, 0.9 quinine sulphate equivalents for C3*, 1.4 μg lâ1 for Mn and 6.9 μg lâ1 for Ba. Overall, these thresholds would allow water sourced from eastern Australian ports to be identified as coastal at 92%, 69% and 74% of sites examined using C3*, Mn and Ba, respectively, requiring 71 ± 26%, 54 ± 40% and 59 ± 38% replacement with mid-ocean water to be within ocean baseline concentration ranges.
Exton, DA, Smith, DJ, McGenity, TJ, Steinke, M, Hills, AJ & Suggett, DJ 2010, 'Application of a Fast Isoprene Sensor (FIS) for measuring isoprene production from marine samples', Limnology and Oceanography: Methods, vol. 8, no. 5, pp. 185-195.
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Research into isoprene production from marine sources traditionally relies on gas chromatography techniques which are labor intensive, provide a slow sample turnover, and require significant method training. An alternative method is the use of a Fast Isoprene Sensor (FIS), a chemiluminescence‐based approach that provides real time isoprene analysis, but is relatively simple to run and also portable. Until now, the FIS has been used in terrestrial but not aquatic isoprene studies. Due to the added difficulties with marine compared with terrestrial sampling, particularly potential interference from dimethyl sulfide (DMS), we have developed a new protocol that allows accurate and reliable data to be obtained from FIS analysis. The detection limit of our modified system to standard gas was 0.02 nM (0.5 ppbv), while minimum isoprene production detected by the FIS was 0.59 nmol h−1 (for Thalassiosira weissflogii). We also compared our FIS‐based approach with GC analysis of isoprene emission from marine samples of micro‐ and macro‐algae, and demonstrated a strong similarity (r2 = 0.910, slope = 1.003). The ability to use FIS analysis with marine samples will significantly broaden the scope of isoprene research in marine environments, permitting remote field work, and allow previously unanswered questions to be addressed.
Hennige, SJ, Smith, DJ, Walsh, S-J, McGinley, MP, Warner, ME & Suggett, DJ 2010, 'Acclimation and adaptation of scleractinian coral communities along environmental gradients within an Indonesian reef system', Journal of Experimental Marine Biology and Ecology, vol. 391, no. 1-2, pp. 143-152.
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In 2007 and 2008, multiple sites were identified in the Wakatobi Marine National Park, South East Sulawesi, Indonesia, which each represented a point along a gradient of light quality, temperature and turbidity. This gradient included 'optimal', intermediate and marginal sites, where conditions were close to the survival threshold limit for corals. Coral communities changed across this gradient from diverse, mixed growth form assemblages to specialised, massive growth form dominated communities. The massive coral Goniastrea aspera was the only species identified at the most marginal and optimal sites. Branching species Acropora formosa and Porites cylindrica were only identified at optimal sites. The in hospite Symbiodinium community also changed across the environmental gradient from members of the Symbiodinium clade C on optimal reefs (in branching and massive species) to clade D on marginal reefs (in massive species). Substantial variability in respiration and photosynthesis was observed in massive coral species under different environmental conditions, which suggests that all corals cannot be considered equal across environments. Studying present-day marginal environments is crucial to further understanding of future reef bio-diversity, functioning and accretion, and from work presented here, it is likely that as future climate change extends marginal reef range, branching coral diversity may decrease relative to massive, more resilient corals. © 2010 Elsevier B.V.
Herrera-Silveira, JA, Cebrian, J, Hauxwell, J, Ramirez-Ramirez, J & Ralph, P 2010, 'Evidence of negative impacts of ecological tourism on turtlegrass (Thalassia testudinum) beds in a marine protected area of the Mexican Caribbean', AQUATIC ECOLOGY, vol. 44, no. 1, pp. 23-31.
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Many marine protected areas (MPAs) have been established in recent years. Some MPAs are open to tourists to foster environmental education and generate revenue for the MPA. This has been coined âecological tourismâ. Here, we examine the impact of ecological tourism on turtlegrass (Thalassia testudinum) health in one area of the âCosta Occidental de Isla Mujeres, Punta Cancún y Punta Nizucâ MPA in the Mexican Caribbean. A heavily visited location was compared with an unvisited location. Turtlegrass leaves at the visited location were sparser, shorter, grew more slowly, and had more epiphytes than at the unvisited location. Vertical and horizontal rhizomes of turtlegrass also grew more slowly at the visited than at the unvisited location. There is reasonable evidence to suggest that the observed differences are likely due to the deleterious impacts of novice and careless snorkelers. If continuing, these impacts could cause severe degradation of the visited areas in this MPA and, thus, changes in management policies seem in order.
Khan, N-UH, Pandya, N, Kumar, M, Bera, PK, Kureshy, RI, Abdi, SHR & Bajaj, HC 2010, 'Influence of chirality using Mn(iii) salen complexes on DNA binding and antioxidant activity', Organic & Biomolecular Chemistry, vol. 8, no. 19, pp. 4297-4297.
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Korecko, J, Jirka, V, Sourek, B & Cerveny, J 2010, 'Module greenhouse with high efficiency of transformation of solar energy, utilizing active and passive glass optical rasters', Solar Energy, vol. 84, no. 10, pp. 1794-1808.
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Kumar, M, Kumari, P, Gupta, V, Anisha, PA, Reddy, CRK & Jha, B 2010, 'Differential responses to cadmium induced oxidative stress in marine macroalga Ulva lactuca (Ulvales, Chlorophyta)', BioMetals, vol. 23, no. 2, pp. 315-325.
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Kumar, M, Kumari, P, Gupta, V, Reddy, CRK & Jha, B 2010, 'Biochemical responses of red alga Gracilaria corticata (Gracilariales, Rhodophyta) to salinity induced oxidative stress', Journal of Experimental Marine Biology and Ecology, vol. 391, no. 1-2, pp. 27-34.
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Kumari, P, Kumar, M, Gupta, V, Reddy, CRK & Jha, B 2010, 'Tropical marine macroalgae as potential sources of nutritionally important PUFAs', Food Chemistry, vol. 120, no. 3, pp. 749-757.
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Larkum, AWD 2010, 'Limitations and prospects of natural photosynthesis for bioenergy production', CURRENT OPINION IN BIOTECHNOLOGY, vol. 21, no. 3, pp. 271-276.
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Solar energy is clearly a major future source of energy for humans. While solar photovoltaic and thermal harvesting are attractive there will be a need for biofuels to replace fossil fuels. Natural photosynthesis offers a means to do this, but photosynthesis is inherently inefficient. Terrestrial plants have already been used as a source of biofuels and this use will increase in the future, despite a number of attendant problems. Microalgae as a source of biofuels have to be technically proven and artificial photosynthesis/biohydrogen production lies further into the future. Consideration of these approaches must be weighed against (i) crop production in a hungry, as well as a fuel-hungry, world and (ii) the need to sustain biodiversity. © 2010 Elsevier Ltd.
Lavery, TJ, Roudnew, B, Gill, P, Seymour, J, Seuront, L, Johnson, G, Mitchell, JG & Smetacek, V 2010, 'Iron defecation by sperm whales stimulates carbon export in the Southern Ocean', Proceedings of the Royal Society B: Biological Sciences, vol. 277, no. 1699, pp. 3527-3531.
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The iron-limited Southern Ocean plays an important role in regulating atmospheric CO 2 levels. Marine mammal respiration has been proposed to decrease the efficiency of the Southern Ocean biological pump by returning photosynthetically fixed carbon to the atmosphere. Here, we show that by consuming prey at depth and defecating iron-rich liquid faeces into the photic zone, sperm whales ( Physeter macrocephalus ) instead stimulate new primary production and carbon export to the deep ocean. We estimate that Southern Ocean sperm whales defecate 50 tonnes of iron into the photic zone each year. Molar ratios of C export ∶Fe added determined during natural ocean fertilization events are used to estimate the amount of carbon exported to the deep ocean in response to the iron defecated by sperm whales. We find that Southern Ocean sperm whales stimulate the export of 4 × 10 5 tonnes of carbon per year to the deep ocean and respire only 2 × 10 5 tonnes of carbon per year. By enhancing new primary production, the populations of 12 000 sperm whales in the Southern Ocean act as a carbon sink, removing 2 × 10 5 tonnes more carbon from the atmosphere than they add during respiration. The ability of the Southern Ocean to act as a carbon sink may have been diminished by large-scale removal of sperm whales during industrial whaling.
Lilley, RM, Ralph, PJ & Larkum, AWD 2010, 'The determination of activity of the enzyme Rubisco in cell extracts of the dinoflagellate alga Symbiodinium sp by manganese chemiluminescence and its response to short-term thermal stress of the alga', PLANT CELL AND ENVIRONMENT, vol. 33, no. 6, pp. 995-1004.
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The dinoflagellate alga Symbiodinium sp., living in symbiosis with corals, clams and other invertebrates, is a primary producer in coral reefs and other marine ecosystems. The function of the carbon-fixing enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) in dinoflagellates is difficult to study because its activity is rapidly lost after extraction from the cell. We report procedures for the extraction of Rubisco from Symbiodinium cells and for stable storage. We describe a continuous assay for Rubisco activity in these crude cell extracts using the Mn2+ chemiluminescence of Rubisco oxygenase. Chemiluminescence time courses exhibited initial transients resembling bacterial Form II Rubisco, followed by several minutes of linearly decreasing activity. The initial activity was determined from extrapolation of this linear section of the time course. The activity of fast-frozen cell extracts was stable at -80 °C and, after thawing and storage on ice, remained stable for up to 1 h before declining non-linearly. Crude cell extracts bound [14C] 2-carboxy-D-arabitinol 1,5-bisphosphate to a high molecular mass fraction separable by gel filtration chromatography. After pre-treatment of Symbiodinium cell cultures in darkness at temperatures above 30 °C, the extracted Rubisco activities decreased, with almost complete loss of activity above 36 °C. The implications for the sensitivity to elevated temperature of Symbiodinium photosynthesis are assessed. © 2010 Blackwell Publishing Ltd.
McMinn, A, Pankowskii, A, Ashworth, C, Bhagooli, R, Ralph, P & Ryan, K 2010, 'In situ net primary productivity and photosynthesis of Antarctic sea ice algal, phytoplankton and benthic algal communities', MARINE BIOLOGY, vol. 157, no. 6, pp. 1345-1356.
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Primary production at Antarctic coastal sites is contributed from sea ice algae, phytoplankton and benthic algae. Oxygen microelectrodes were used to estimate sea ice and benthic primary production at several sites around Casey, a coastal area in eastern Antarctica. Maximum oxygen export from sea ice was 0. 95 mmol O2 m-2 h-1 (~11. 7 mg C m-2 h-1) while from the sediment it was 6. 08 mmol O2 m-2 h-1 (~70. 8 mg C m-2 h-1). When the ice was present O2 export from the benthos was either low or negative. Sea ice algae assimilation rates were up to 3. 77 mg C (mg Chl-a)-1 h-1 while those from the benthos were up to 1. 53 mg C (mg Chl-a)-1 h-1. The contribution of the major components of primary productivity was assessed using fluorometric techniques. When the ice was present approximately 55-65% of total daily primary production occurred in the sea ice with the remainder unequally partitioned between the sediment and the water column. When the ice was absent, the benthos contributed nearly 90% of the primary production. © 2010 Springer-Verlag.
Mohr, R, Voß, B, Schliep, M, Kurz, T, Maldener, I, Adams, DG, Larkum, ADW, Chen, M & Hess, WR 2010, 'A new chlorophyll d-containing cyanobacterium: evidence for niche adaptation in the genus Acaryochloris', The ISME Journal, vol. 4, no. 11, pp. 1456-1469.
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Abstract Chlorophyll d is a photosynthetic pigment that, based on chemical analyses, has only recently been recognized to be widespread in oceanic and lacustrine environments. However, the diversity of organisms harbouring this pigment is not known. Until now, the unicellular cyanobacterium Acaryochloris marina is the only characterized organism that uses chlorophyll d as a major photopigment. In this study we describe a new cyanobacterium possessing a high amount of chlorophyll d, which was isolated from waters around Heron Island, Great Barrier Reef (23° 26′ 31.2″ S, 151° 54′ 50.4″ E). The 16S ribosomal RNA is 2% divergent from the two previously described isolates of A. marina, which were isolated from waters around the Palau islands (Pacific Ocean) and the Salton Sea lake (California), suggesting that it belongs to a different clade within the genus Acaryochloris. An overview sequence analysis of its genome based on Illumina technology yielded 871 contigs with an accumulated length of 8 371 965 nt. Their analysis revealed typical features associated with Acaryochloris, such as an extended gene family for chlorophyll-binding proteins. However, compared with A. marina MBIC11017, distinct genetic, morphological and physiological differences were observed. Light saturation is reached at lower light intensities, Chl d/a ratios are less variable with light intensity and the phycobiliprotein phycocyanin is lacking, suggesting that cyanobacteria of the genus Acaryochloris occur in distinct ecotypes. These data characterize Acaryochloris as a niche-adapted cyanobacterium and show that more rigorous attempts are worthwhile to isolate, cultivate and analyse chlorophyll d-containing cyanobacteria for understanding the ecophysiology of these organisms.
Nedbal, L, Červený, J, Keren, N & Kaplan, A 2010, 'Experimental validation of a nonequilibrium model of CO2 fluxes between gas, liquid medium, and algae in a flat-panel photobioreactor', Journal of Industrial Microbiology & Biotechnology, vol. 37, no. 12, pp. 1319-1326.
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Perinchery, SM, Kuzhiumparambil, U, Vemulpad, S & Goldys, EM 2010, 'The influence of indoxyl sulfate and ammonium on the autofluorescence of human urine', TALANTA, vol. 80, no. 3, pp. 1269-1276.
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Perinchery, SM, Kuzhiumparambil, U, Vemulpad, S & Goldys, EM 2010, 'The potential of autofluorescence spectroscopy to detect human urinary tract infection', TALANTA, vol. 82, no. 3, pp. 912-917.
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Petrou, K, Hill, R, Brown, CM, Campbell, DA, Doblin, MA & Ralph, PJ 2010, 'Rapid photoprotection in sea-ice diatoms from the East Antarctic pack ice', LIMNOLOGY AND OCEANOGRAPHY, vol. 55, no. 3, pp. 1400-1407.
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Photoinhibition and D1 protein re-synthesis were investigated in bottom-dwelling sea-ice microalgal communities from the East Antarctic pack ice during early spring. Bottom-dwelling sea-ice microalgal communities were dominated by diatoms that exhibited rapid photoprotection when exposed to a range of different light levels (10 μmol photons m-2 s -1, 50 μmol photons m-2 s-1, 100 μmol photons m-2 s-1, and 200 μmol photons m-2 s-1). Photosynthetic capacity of photosystem II (PSII) dropped significantly over 3 h under 200 μmol photons m-2 s-1, but largely recovered when placed in a low-light environment (10 μmol photons m-2 s-1) for an additional 3 h. PSII repair rates increased with increasing irradiance, and the D1-protein pool remained steady even under high light (200 μmol photons m-2 s-1). Sea-ice diatoms showed a low intrinsic susceptibility to photoinactivation of PSII across all the light treatments, and a strong and irradiance-dependent induction of nonphotochemical quenching, which did not depend upon chloroplast protein synthesis, was also seen. These highly plastic organisms, once thought to be adapted to shade, are in fact well equipped to withstand rapid and relatively large changes in light at low temperatures with minimal long-term effect on their photosynthetic machinery. © 2010, by the American Society of Limnology and Oceanography, Inc.
Ragni, M, Airs, RL, Hennige, SJ, Suggett, DJ, Warner, ME & Geider, RJ 2010, 'PSII photoinhibition and photorepair in Symbiodinium (Pyrrhophyta) differs between thermally tolerant and sensitive phylotypes', Marine Ecology Progress Series, vol. 406, pp. 57-70.
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Cnidarians containing symbiotic microalgae often inhabit highly variable light environments where successful growth requires that, during transient (potentially stressful) periods of high light (HL), the microalgal cells invest energy in photoprotection to minimise photodamage, or allow for photodamage to occur and invest in photorepair; however, the relative contribution of photoprotection and photorepair remains uncharacterised. Here we determined the light dependence of Photosystem II (PSII) photoinhibition and photorepair in 2 phylotypes of Symbiodinium displaying different susceptibilities to thermal stress. Upon exposure to photon flux densities (PFDs) >500 μmol photons m-2 s-1 the thermally 'sensitive' Strain A1.1 displayed higher net photoinhibition, measured as a decrease in maximum PSII efficiency (Fv/Fm), than the thermally 'tolerant' Strain A1. In contrast, gross photoinhibition, assessed as the decline of Fv/F m in the presence of an inhibitor of D1 protein synthesis, was similar in the 2 strains. Therefore, photorepair was considered to be the key mechanism minimising net photoinhibition in Strain A1. Consistent with this conclusion, the 2 strains displayed similar capacities for other mechanisms of avoiding photodamage, specifically, photochemical (qP) and non-photochemical (NPQ) excitation energy quenching. Measurements on Strain A1 grown under 2 PFDs (100 and 650 μmol photons m-2 s-1) revealed that photoacclimation to HL involved the upregulation of qP, which minimised gross photoinhibition by maintaining PSII in a more oxidised state. We conclude that both interspecific (e.g. phylotype diversity) and intraspecific (e.g. photoacclimation state) factors affect the susceptibility of Symbiodinium to light stress. © Inter-Research 2010.
Raina, J-B, Dinsdale, EA, Willis, BL & Bourne, DG 2010, 'Do the organic sulfur compounds DMSP and DMS drive coral microbial associations?', Trends in Microbiology, vol. 18, no. 3, pp. 101-108.
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Dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) are key compounds in the global sulfur cycle. Moreover, DMS is particularly important in climate regulation owing to its role in cloud formation. Reef building corals are major contributors to the production of these two compounds and also form diverse and complex associations with bacteria, which are known to play a crucial role in the degradation of DMSP and DMS. Here, we highlight an extensive overlap between bacterial species implicated in DMSP/DMS degradation and those associated with corals, leading to the hypothesis that these two compounds play a major role in structuring coral-associated bacterial communities, with important consequences for coral health and the resilience of coral reefs. We also explore the publically available metagenome databases and show that genes implicated in DMSP metabolism are abundant in the viral component of coral-reef-derived metagenomes, indicating that viruses can act as a reservoir for such genes.
Rosic, NN, Pernice, M, Dunn, S, Dove, S & Hoegh-Guldberg, O 2010, 'Differential Regulation by Heat Stress of Novel Cytochrome P450 Genes from the Dinoflagellate Symbionts of Reef-Building Corals', APPLIED AND ENVIRONMENTAL MICROBIOLOGY, vol. 76, no. 9, pp. 2823-2829.
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Exposure to heat stress has been recognized as one of the major factors leading to the breakdown of the coral-alga symbiosis and coral bleaching. Here, we describe the presence of three new cytochrome P450 (CYP) genes from the reef-building coral endosymbiont Symbiodinium (type C3) and changes in their expression during exposure to severe and moderate heat stress conditions. Sequence analysis of the CYP C-terminal region and two conserved domains, the 'PERF' and 'heme-binding' domains, confirmed the separate identities of the CYP genes analyzed. In order to explore the effects of different heat stress scenarios, samples of the scleractinian coral Acropora millepora were exposed to elevated temperatures incrementally over an 18-h period (rapid thermal stress) and over a 120-h period (gradual thermal stress). After 18 h of gradual heating and incubation at 26°C, the Symbiodinium CYP mRNA pool was approximately 30% larger, while a further 6°C increase to a temperature above the average sea temperature (29°C after 72 h) resulted in a 2- to 4-fold increase in CYP expression. Both rapid heat stress and gradual heat stress at 32°C resulted in 50% to 90% decreases in CYP gene transcript abundance. Consequently, the initial upregulation of expression of CYP genes at moderately elevated temperatures (26°C and 29°C) was followed by a decrease in expression under the greater thermal stress conditions at 32°C. These findings indicate that in the coral-alga symbiosis under heat stress conditions there is production of chemical stressors and/or transcriptional factors that regulate the expression of genes, such as the genes encoding cytochrome P450 monooxygenases, that are involved in the first line of an organism's chemical defense. Copyright © 2010, American Society for Microbiology. All Rights Reserved.
Seery, CR & Ralph, PJ 2010, 'Ecological relevance of a chlorophyllafluorescence ecotoxicological endpoint', Toxicological & Environmental Chemistry, vol. 92, no. 8, pp. 1529-1540.
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With the increasing use of new techniques to assess toxic stress and the effects of pollution, it is important to ensure that any 'new' endpoint employed is able to demonstrate a level of eco-relevance. Though recent application of chlorophyll a fluorescence parameters to macroalgal bioassays has been successful, a level of eco-relevance for such use has not been experimentally shown. As such, this article presents a series of experiments designed to establish a link between fluorescence parameters and higher-level effects (supra-individual level). The results show that fluorescence parameters are capable of predicting germination success of macroalgal gametes and can do so much sooner than the actual event of germination. Furthermore, a decline in ΔF/F′m is shown to be strongly associated with a reduced germination success. Thus, a level of eco-relevance has been established for the fluorescence endpoint that is at least equal to that of the widely accepted germination-based macroalgal bioassays. © Taylor & Francis.
Seuront, L, Leterme, SC, Seymour, JR, Mitchell, JG, Ashcroft, D, Noble, W, Thomson, PG, Davidson, AT, van den Enden, R, Scott, FJ, Wright, SW, Schapira, M, Chapperon, C & Cribb, N 2010, 'Role of microbial and phytoplanktonic communities in the control of seawater viscosity off East Antarctica (30-80 degrees E)', DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY, vol. 57, no. 9-10, pp. 877-886.
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Despite the long-standing belief that seawater viscosity is driven by temperature and salinity, biologically increased seawater viscosity has repeatedly been reported in relation to phytoplankton exudates in shallow, productive coastal waters. Here, seawater viscosity was investigated in relation to microbial and phytoplanktonic communities off the coast of East Antarctica along latitudinal transects located between 30°E and 80°E in sub-surface waters and at the deep chlorophyll maximum (DCM). The physical component of seawater viscosity observed along each transects ranged from 1.80 to 1.95 cP, while the actual seawater viscosity ranged from 1.85 to 3.69 cP. This resulted in biologically increased seawater viscosity reaching up to 84.9% in sub-surface waters and 77.6% at the DCM. Significant positive correlations were found between elevated seawater viscosity and (i) bacterial abundance in sub-surface waters and (ii) chlorophyll a concentration and the abundance of flow cytometrically-defined auto- and heterotrophic protists at the DCM. Among the 12 groups and 108 species of protists identified under light microscopy, dinoflagellates and more specifically Alexandrium tamarense and Prorocentrum sp. were the main contributors to the patterns observed for elevated seawater viscosity. Our observations, which generalised the link previously identified between seawater viscosity and phytoplankton composition and standing stock to the Southern Ocean, are the first demonstration of increases in seawater viscosity linked to marine bacterial communities, and suggest that the microbially-increased viscosity might quantitatively be at least as important as the one related to phytoplankton secretion. © 2009 Elsevier Ltd.
Seymour, JR, Ahmed, T, Durham, WM & Stocker, R 2010, 'Chemotactic response of marine bacteria to the extracellular products of Synechococcus and Prochlorococcus', AQUATIC MICROBIAL ECOLOGY, vol. 59, no. 2, pp. 161-168.
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The cyanobacterial genera Prochlorococcus and Synechococcus are key phototrophic organisms in the open ocean, and ecological interactions between these groups and heterotrophic bacteria have fundamental importance for marine carbon and nutrient cycling.
Seymour, JR, Simo, R, Ahmed, T & Stocker, R 2010, 'Chemoattraction to Dimethylsulfoniopropionate Throughout the Marine Microbial Food Web', SCIENCE, vol. 329, no. 5989, pp. 342-345.
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Phytoplankton-produced dimethylsulfoniopropionate (DMSP) provides underwater and atmospheric foraging cues for several species of marine invertebrates, fish, birds, and mammals. However, its role in the chemical ecology of marine planktonic microbes is Largely unknown, and there is evidence for contradictory functions. By using microfluidics and image analysis of swimming behavior, we observed attraction toward microscale pulses of DMSP and related compounds among several motile strains of phytoplankton, heterotrophic bacteria, and bacterivore and herbivore microzooplankton. Because microbial DMSP cycling is the main natural source of cloud-forming sulfur aerosols, our results highlight how adaptations to microscale chemical seascapes shape planktonic food webs, while potentially influencing climate at the global scale.
Siboni, N, Rasoulouniriana, D, Ben-Dov, E, Kramarsky-Winter, E, Sivan, A, Loya, Y, Hoegh-Guldberg, O & Kushmaro, A 2010, 'Stramenopile Microorganisms Associated with the Massive Coral Favia sp.', JOURNAL OF EUKARYOTIC MICROBIOLOGY, vol. 57, no. 3, pp. 236-244.
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Wright, JT, Byers, JE, Koukoumaftsis, LP, Ralph, PJ & Gribben, PE 2010, 'Native species behaviour mitigates the impact of habitat-forming invasive seaweed', OECOLOGIA, vol. 163, no. 2, pp. 527-534.
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Habitat-forming invasive species cause large, novel changes to the abiotic environment. These changes may elicit important behavioural responses in native fauna, yet little is known about mechanisms driving this behaviour and how such trait-mediated responses influence the fitness of native species. Low dissolved oxygen is a key abiotic change created by the habitat-forming invasive seaweed, Caulerpa taxifolia, which influences an important behavioural response (burrowing depth) in the native infaunal bivalve Anadara trapezia. In Caulerpa-colonised areas, Anadara often emerged completely from the sediment, and we experimentally demonstrate that water column hypoxia beneath the Caulerpa canopy is the mechanism instigating this 'pop-up' behaviour. Importantly, pop-up in Caulerpa allowed similar survivorship to that in unvegetated sediment; however, when we prevented Anadara from popping-up, they suffered >50% mortality in just 1 month. Our findings not only highlight the substantial environmental alteration by Caulerpa, but also an important role for the behaviour of native species in mitigating the effects of habitat-forming invasive species. © 2010 Springer-Verlag.
