The Experts below are selected from a list of 591 Experts worldwide ranked by ideXlab platform
Paul E. Hargraves - One of the best experts on this subject based on the ideXlab platform.
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UV resonance Raman detection and quantitation of domoic acid in phytoplankton.
Analytical chemistry, 2000Co-Authors: Wu Q, Paul E. Hargraves, W. H. Nelson, Marek Kirs, Michael S. Feld, Desari R, Ramasamy Manoharan, Eugene B. HanlonAbstract:Cultures of the phytoplankton diatom, Pseudonitzschia multiseries, have been harvested under controlled growth conditions ranging from late logarithmic to late stationary phase (17-58 days). The amount of domoic acid (DA) present in the growth media and in the homogenized cells has been determined by HPLC. Defined samples of media, homogenized cells, whole cells, and whole cells in media have been laser excited at 251 nm for the purpose of selectively exciting intense UV resonance Raman spectra from DA in the samples. Neither media nor cell component spectra from algae seriously interfere with DA spectra. The spectral cross sections for the dominant 1652-cm-1 mode of DA have been determined for 242-, 251-, and 257-nm excitation. Maximum sensitivities are achieved with 251-nm excitation because cross sections for DA are a maximum, and interference from other algal components becomes very small. DA concentrations that have been determined with 251-nm excitation by resonance Raman methods correlate closely with values determined independently with HPLC, especially at higher DA concentrations. The UV resonance Raman analysis of DA in phytoplankton algae is shown to be very sensitive and quantitative as well as rapid and nonintrusive.
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Growth characteristics of the diatoms Pseudonitzschia pungens and P. fraudulenta exposed to ultraviolet radiation
Hydrobiologia, 1993Co-Authors: Paul E. Hargraves, R. Wang, J Zhang, Y ShimizuAbstract:Interest in the biology of planktonic, chain-forming Pseudonitzschia species has grown recently after the discovery of toxin production in Pseudonitzschia pungens and related taxa, following the outbreak of shellfish toxicity in Canada in 1987 . As part of a broader study on the effects of enhanced ultraviolet light on the growth of bloom-forming phytoplankton, we have examined the growth rates and production of the toxin domoic acid and two additional chemicals [bacillariolides I and II] by Pseudonitzschia pungens varieties and Pseudonitzschia fraudulenta from Narragansett Bay, Rhode Island . Growth of P. fraudulenta is significantly inhibited by enhanced UV, P. pungens var. pungens shows slight inhibition, and P. pungens var. multiseries is unaffected. Production of bacillariolides I and II by P. pungens var. multiseries is similar in enhanced and deleted UV light . Tolerance of UV light by P. pungens var. multiseries appears to be acquired, and persistent . If ambient UV light continues to increase as a result of global ozone depletion, one may expect UV-resistant taxa such as P. pungens var. multiseries to become more prominent in coastal phytoplankton communities .
Y Shimizu - One of the best experts on this subject based on the ideXlab platform.
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Growth characteristics of the diatoms Pseudonitzschia pungens and P. fraudulenta exposed to ultraviolet radiation
Hydrobiologia, 1993Co-Authors: Paul E. Hargraves, R. Wang, J Zhang, Y ShimizuAbstract:Interest in the biology of planktonic, chain-forming Pseudonitzschia species has grown recently after the discovery of toxin production in Pseudonitzschia pungens and related taxa, following the outbreak of shellfish toxicity in Canada in 1987 . As part of a broader study on the effects of enhanced ultraviolet light on the growth of bloom-forming phytoplankton, we have examined the growth rates and production of the toxin domoic acid and two additional chemicals [bacillariolides I and II] by Pseudonitzschia pungens varieties and Pseudonitzschia fraudulenta from Narragansett Bay, Rhode Island . Growth of P. fraudulenta is significantly inhibited by enhanced UV, P. pungens var. pungens shows slight inhibition, and P. pungens var. multiseries is unaffected. Production of bacillariolides I and II by P. pungens var. multiseries is similar in enhanced and deleted UV light . Tolerance of UV light by P. pungens var. multiseries appears to be acquired, and persistent . If ambient UV light continues to increase as a result of global ozone depletion, one may expect UV-resistant taxa such as P. pungens var. multiseries to become more prominent in coastal phytoplankton communities .
E. Timmins-schiffman - One of the best experts on this subject based on the ideXlab platform.
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Physiological responses of a Southern Ocean diatom to complex future ocean conditions
Nature Climate Change, 2016Co-Authors: P. w. Boyd, P. w. Dillingham, C. m. Mcgraw, E. a. Armstrong, C. e. Cornwall, Y.-y. Feng, C. l. Hurd, M. Gault-ringold, M. y. Roleda, E. Timmins-schiffmanAbstract:Investigation of multiple stressors on a subantarctic diatom reveals the importance of considering individual and interactive effects. Experiments show that temperature and iron enrichment enhance growth and help overcome nutrient depletion. A changing climate is altering many ocean properties that consequently will modify marine productivity. Previous phytoplankton manipulation studies have focused on individual or subsets of these properties. Here, we investigate the cumulative effects of multi-faceted change on a subantarctic diatom Pseudonitzschia multiseries by concurrently manipulating five stressors (light/nutrients/CO_2/temperature/iron) that primarily control its physiology, and explore underlying reasons for altered physiological performance. Climate change enhances diatom growth mainly owing to warming and iron enrichment, and both properties decrease cellular nutrient quotas, partially offsetting any effects of decreased nutrient supply by 2100. Physiological diagnostics and comparative proteomics demonstrate the joint importance of individual and interactive effects of temperature and iron, and reveal biased future predictions from experimental outcomes when only a subset of multi-stressors is considered. Our findings for subantarctic waters illustrate how composite regional studies are needed to provide accurate global projections of future shifts in productivity and distinguish underlying species-specific physiological mechanisms.
Ralph E. H. Smith - One of the best experts on this subject based on the ideXlab platform.
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Influence of ultraviolet radiation on growth and photosynthesis of two cold ocean diatoms
Journal of Phycology, 1997Co-Authors: Jusri Nilawati, Bruce M. Greenberg, Ralph E. H. SmithAbstract:The influence of chronic exposure to UV-B and UV-A radiation on growth and photosynthesis of two polar marine diatoms (Pseudonitzschia seriata and Nitzschia sp.) was investigated in cultures exposed to moderate photon fluences for 3-7 days. Population growth rates were diminished 50% by UV-B. Fluorescence induction kinetics of photosystem II (PSII) revealed that UV-B caused lower F-v/F-m ratios and half-rise times, indicating damage to the reaction center of PSII and to related elements of the photosynthetic electron transport chain. Carbon assimilation rates Per cell and 'Per chlorophyll a were nonetheless highest for UV-B-exposed populations, which also had the highest chlorophyll a content per cell. The UV-B-exposed cells were, however, more vulnerable to visible light-induced photoinhibition. Exposure to UV-A in the absence of UV-B had little effect on growth, fluorescence induction of PSII, or chlorophyll a contents but did have some inhibitory effects on carbon assimilation per chlorophyll a and per cell. The increased photosynthetic capacity of UV-B-exposed cells suggested some ability to compensate for damage to the photosynthetic apparatus.
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The interactive effects of temperature and silicon limitation on the psychrophilic ice diatomPseudonitszchia seriata
Polar Biology, 1996Co-Authors: Lynn S. Stapleford, Ralph E. H. SmithAbstract:Pseudonitzschia seriata , isolated from sea ice in the Canadian Arctic, was grown in silicon-limited batch and semi-continuous culture to determine the effects of temperature on its nutrient utilization. Resource-saturated growth rate (μ_max) increased significantly with temperature from -1.5 to 6°C with a Q_10 of 1.63. The efficiency of the algae in using exogenous silicic acid for growth had no significant monotonic relationship with temperature but was significantly ( P 0°C than in those at lower temperatures. Silicic acid uptake kinetics did not differ between high and low temperatures. Silicon cell quotas were significantly higher at temperatures
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The interactive effects of temperature and silicon limitation on the psychrophilic ice diatom Pseudonitszchia seriata
Polar Biology, 1996Co-Authors: Lynn S. Stapleford, Ralph E. H. SmithAbstract:Pseudonitzschia seriata, isolated from sea ice in the Canadian Arctic, was grown in silicon-limited batch and semi-continuous culture to determine the effects of temperature on its nutrient utilization. Resource-saturated growth rate (μmax) increased significantly with temperature from -1.5 to 6°C with a Q10 of 1.63. The efficiency of the algae in using exogenous silicic acid for growth had no significant monotonic relationship with temperature but was significantly (P 0°C than in those at lower temperatures. Silicic acid uptake kinetics did not differ between high and low temperatures. Silicon cell quotas were significantly higher at temperatures
J Zhang - One of the best experts on this subject based on the ideXlab platform.
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Growth characteristics of the diatoms Pseudonitzschia pungens and P. fraudulenta exposed to ultraviolet radiation
Hydrobiologia, 1993Co-Authors: Paul E. Hargraves, R. Wang, J Zhang, Y ShimizuAbstract:Interest in the biology of planktonic, chain-forming Pseudonitzschia species has grown recently after the discovery of toxin production in Pseudonitzschia pungens and related taxa, following the outbreak of shellfish toxicity in Canada in 1987 . As part of a broader study on the effects of enhanced ultraviolet light on the growth of bloom-forming phytoplankton, we have examined the growth rates and production of the toxin domoic acid and two additional chemicals [bacillariolides I and II] by Pseudonitzschia pungens varieties and Pseudonitzschia fraudulenta from Narragansett Bay, Rhode Island . Growth of P. fraudulenta is significantly inhibited by enhanced UV, P. pungens var. pungens shows slight inhibition, and P. pungens var. multiseries is unaffected. Production of bacillariolides I and II by P. pungens var. multiseries is similar in enhanced and deleted UV light . Tolerance of UV light by P. pungens var. multiseries appears to be acquired, and persistent . If ambient UV light continues to increase as a result of global ozone depletion, one may expect UV-resistant taxa such as P. pungens var. multiseries to become more prominent in coastal phytoplankton communities .
