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1. Kinetic Isotope Effects During Reduction of Fe(III) to Fe(II): Large Normal and Inverse Isotope Effects for Abiotic Reduction and Smaller Fractionations by Phytoplankton in Culture.

Author

John, S. G., Boyle, E. A., Cunningham, B. R., Fu, F.‐X., Greene, S., Hodierne, C., Hutchins, D. A., Kavner, A., King, A. L., Rosenberg, A. D., Saito, M. A., and Wasson, A.

Subjects
KINETIC isotope effects, IRON isotopes, ETHYLENEDIAMINETETRAACETIC acid, ISOTOPES, ISOTOPIC fractionation, CHEMICAL testing
Abstract

Iron stable isotopes (δ56Fe) are a useful tool for studying Earth processes, many of which involve redox transformations between Fe(III) and Fe(II). Here, we present two related experimental efforts, a study of the kinetic isotope effects (KIEs) associated with the reduction of Fe(III)‐ethylenediaminetetraacetic acid (EDTA) to Fe(II), and measurements of the biological fractionation of Fe isotopes by phytoplankton in culture. Reductants tested were ascorbate, hydroxylamine, Mn(II), dithionite, and photoreduction at pH between 5 and 9 and temperatures from 0 to 100°C. Isotope fractionations were very large, and included both normal and inverse KIEs, ranging from −4‰ to +5‰. Experiments were reproducible, yielding similar results for triplicate experiments run concurrently and for experiments run weeks apart. However, fractionations were not predictable, without a clear relationship to reaction rate, temperature, pH, or the reductant used. Acquisition of Fe by eukaryotic phytoplankton also often involves the reduction of Fe(III) to Fe(II). Several species of diatoms and a coccolithophore were tested for Fe isotope fractionation in culture using EDTA, NTA, and DFB as Fe(III) chelating ligands, yielding fractionations from −1.3‰ to +0.6‰. Biological isotope effects were also unpredictable, showing no clear relationship to species, growth rate, or Fe concentration. Variability in Fe isotope fractionation observed in culture may be explained in part by the sensitivity of KIEs. This work has implications for the industrial purification of isotopes, interpretation of natural δ56Fe, and the use of Fe isotopes as a tracer Fe source and biological processes in the ocean and other natural systems. Plain Language Summary: The stable isotopes of iron react at slightly different rates during natural processes, giving rise to variations in Fe stable isotope ratios (δ56Fe) on Earth's surface. We therefore designed two kinds of experiments with the goal of better understanding variations in δ56Fe on Earth. First, Fe(III) bound to the organic molecule ethylenediaminetetraacetic acid was reduced to Fe(II). It was found that under some conditions the lighter isotopes reacted more quickly and under some conditions heavier isotopes reacted more quickly, however there were no clear patterns which allowed us to predict these isotope fractionations. Second, phytoplankton were grown in the laboratory, and their Fe isotope ratios were measured and compared to the media in which they were grown. In these experiments too, a range of fractionations was observed but there were no clear patterns in the results. Though our experiments did not lead to easily predictable results, they contribute to our understanding of how Fe isotopes behave; for example, the large isotope fractionations observed here might have industrial applications for isotope purification, and our work suggests that determining the magnitude of biological Fe isotope fractionation might be better accomplished by in situ observation rather than additional laboratory experiments. Key Points: Iron isotope fractionation was tested during chemical reduction of Fe(III)‐ethylenediaminetetraacetic acid to Fe(II)‐(ferrozine)3Biological fractionation of Fe isotopes was tested for eukaryotic phytoplankton in cultureResults are not easily interpreted but have implications for understanding redox kinetic isotope effects in the laboratory and in nature [ABSTRACT FROM AUTHOR]

Published
2024
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2. Temperature variability interacts with mean temperature to influence the predictability of microbial phenotypes.

Author

Fu, F-X, Tschitschko, B, Hutchins, DA, Larsson, ME, Baker, KG, McInnes, A, Kahlke, T, Verma, A, Murray, SA, Doblin, MA, Fu, F-X, Tschitschko, B, Hutchins, DA, Larsson, ME, Baker, KG, McInnes, A, Kahlke, T, Verma, A, Murray, SA, and Doblin, MA

Abstract

Despite their relatively high thermal optima (Topt ), tropical taxa may be particularly vulnerable to a rising baseline and increased temperature variation because they live in relatively stable temperatures closer to their Topt . We examined how microbial eukaryotes with differing thermal histories responded to temperature fluctuations of different amplitudes (0 control, ±2, ±4°C) around mean temperatures below or above their Topt . Cosmopolitan dinoflagellates were selected based on their distinct thermal traits and included two species of the same genus (tropical and temperate Coolia spp.), and two strains of the same species maintained at different temperatures for >500 generations (tropical Amphidinium massartii control temperature and high temperature, CT and HT, respectively). There was a universal decline in population growth rate under temperature fluctuations, but strains with narrower thermal niche breadth (temperate Coolia and HT) showed ~10% greater reduction in growth. At suboptimal mean temperatures, cells in the cool phase of the fluctuation stopped dividing, fixed less carbon (C) and had enlarged cell volumes that scaled positively with elemental C, N, and P and C:Chlorophyll-a. However, at a supra-optimal mean temperature, fixed C was directed away from cell division and novel trait combinations developed, leading to greater phenotypic diversity. At the molecular level, heat-shock proteins, and chaperones, in addition to transcripts involving genome rearrangements, were upregulated in CT and HT during the warm phase of the supra-optimal fluctuation (30 ± 4°C), a stress response indicating protection. In contrast, the tropical Coolia species upregulated major energy pathways in the warm phase of its supra-optimal fluctuation (25 ± 4°C), indicating a broadscale shift in metabolism. Our results demonstrate divergent effects between taxa and that temporal variability in environmental conditions interacts with changes in the thermal mean to mediate micr

Published
2022

3. Global surveillance of trends in cancer survival 2000–14 (CONCORD-3): analysis of individual records for 37 513 025 patients diagnosed with one of 18 cancers from 322 population-based registries in 71 countries

Author

Allemani, Claudia, primary, Matsuda, Tomohiro, additional, Di Carlo, Veronica, additional, Harewood, Rhea, additional, Matz, Melissa, additional, Nikšić, Maja, additional, Bonaventure, Audrey, additional, Valkov, Mikhail, additional, Johnson, Christopher J, additional, Estève, Jacques, additional, Ogunbiyi, Olufemi J, additional, Azevedo e Silva, Gulnar, additional, Chen, Wan-Qing, additional, Eser, Sultan, additional, Engholm, Gerda, additional, Stiller, Charles A, additional, Monnereau, Alain, additional, Woods, Ryan R, additional, Visser, Otto, additional, Lim, Gek Hsiang, additional, Aitken, Joanne, additional, Weir, Hannah K, additional, Coleman, Michel P, additional, Bouzbid, S, additional, Hamdi-Chérif, M, additional, Zaidi, Z, additional, Meguenni, K, additional, Regagba, D, additional, Bayo, S, additional, Cheick Bougadari, T, additional, Manraj, S S, additional, Bendahhou, K, additional, Fabowale, A, additional, Bradshaw, D, additional, Somdyala, N I M, additional, Kumcher, I, additional, Moreno, F, additional, Calabrano, G H, additional, Espinola, S B, additional, Carballo Quintero, B, additional, Fita, R, additional, Diumenjo, M C, additional, Laspada, W D, additional, Ibañez, S G, additional, Lima, C A, additional, De Souza, P C F, additional, Del Pino, K, additional, Laporte, C, additional, Curado, M P, additional, de Oliveira, J C, additional, Veneziano, C L A, additional, Veneziano, D B, additional, Latorre, M R D O, additional, Tanaka, L F, additional, Rebelo, M S, additional, Santos, M O, additional, Galaz, J C, additional, Aparicio Aravena, M, additional, Sanhueza Monsalve, J, additional, Herrmann, D A, additional, Vargas, S, additional, Herrera, V M, additional, Uribe, C J, additional, Bravo, L E, additional, Garcia, L S, additional, Arias-Ortiz, N E, additional, Morantes, D, additional, Jurado, D M, additional, Yépez Chamorro, M C, additional, Delgado, S, additional, Ramirez, M, additional, Galán Alvarez, Y H, additional, Torres, P, additional, Martínez-Reyes, F, additional, Jaramillo, L, additional, Quinto, R, additional, Castillo, J, additional, Mendoza, M, additional, Cueva, P, additional, Yépez, J G, additional, Bhakkan, B, additional, Deloumeaux, J, additional, Joachim, C, additional, Macni, J, additional, Carrillo, R, additional, Shalkow Klincovstein, J, additional, Rivera Gomez, R, additional, Poquioma, E, additional, Tortolero-Luna, G, additional, Zavala, D, additional, Alonso, R, additional, Barrios, E, additional, Eckstrand, A, additional, Nikiforuk, C, additional, Noonan, G, additional, Turner, D, additional, Kumar, E, additional, Zhang, B, additional, McCrate, F R, additional, Ryan, S, additional, MacIntyre, M, additional, Saint-Jacques, N, additional, Nishri, D E, additional, McClure, C A, additional, Vriends, K A, additional, Kozie, S, additional, Stuart-Panko, H, additional, Freeman, T, additional, George, J T, additional, Brockhouse, J T, additional, O'Brien, D K, additional, Holt, A, additional, Almon, L, additional, Kwong, S, additional, Morris, C, additional, Rycroft, R, additional, Mueller, L, additional, Phillips, C E, additional, Brown, H, additional, Cromartie, B, additional, Schwartz, A G, additional, Vigneau, F, additional, Levin, G M, additional, Wohler, B, additional, Bayakly, R, additional, Ward, K C, additional, Gomez, S L, additional, McKinley, M, additional, Cress, R, additional, Green, M D, additional, Miyagi, K, additional, Ruppert, L P, additional, Lynch, C F, additional, Huang, B, additional, Tucker, T C, additional, Deapen, D, additional, Liu, L, additional, Hsieh, M C, additional, Wu, X C, additional, Schwenn, M, additional, Gershman, S T, additional, Knowlton, R C, additional, Alverson, G, additional, Copeland, G E, additional, Bushhouse, S, additional, Rogers, D B, additional, Jackson-Thompson, J, additional, Lemons, D, additional, Zimmerman, H J, additional, Hood, M, additional, Roberts-Johnson, J, additional, Rees, J R, additional, Riddle, B, additional, Pawlish, K S, additional, Stroup, A, additional, Key, C, additional, Wiggins, C, additional, Kahn, A R, additional, Schymura, M J, additional, Radhakrishnan, S, additional, Rao, C, additional, Giljahn, L K, additional, Slocumb, R M, additional, Espinoza, R E, additional, Khan, F, additional, Aird, K G, additional, Beran, T, additional, Rubertone, J J, additional, Slack, S J, additional, Garcia, L, additional, Rousseau, D L, additional, Janes, T A, additional, Schwartz, S M, additional, Bolick, S W, additional, Hurley, D M, additional, Whiteside, M A, additional, Miller-Gianturco, P, additional, Williams, M A, additional, Herget, K, additional, Sweeney, C, additional, Johnson, A T, additional, Keitheri Cheteri, M B, additional, Migliore Santiago, P, additional, Blankenship, S E, additional, Farley, S, additional, Borchers, R, additional, Malicki, R, additional, Espinoza, J R, additional, Grandpre, J, additional, Wilson, R, additional, Edwards, B K, additional, Mariotto, A, additional, Lei, Y, additional, Wang, N, additional, Chen, J S, additional, Zhou, Y, additional, He, Y T, additional, Song, G H, additional, Gu, X P, additional, Mei, D, additional, Mu, H J, additional, Ge, H M, additional, Wu, T H, additional, Li, Y Y, additional, Zhao, D L, additional, Jin, F, additional, Zhang, J H, additional, Zhu, F D, additional, Junhua, Q, additional, Yang, Y L, additional, Jiang, C X, additional, Biao, W, additional, Wang, J, additional, Li, Q L, additional, Yi, H, additional, Zhou, X, additional, Dong, J, additional, Li, W, additional, Fu, F X, additional, Liu, S Z, additional, Chen, J G, additional, Zhu, J, additional, Li, Y H, additional, Lu, Y Q, additional, Fan, M, additional, Huang, S Q, additional, Guo, G P, additional, Zhaolai, H, additional, Wei, K, additional, Zeng, H, additional, Demetriou, A V, additional, Mang, W K, additional, Ngan, K C, additional, Kataki, A C, additional, Krishnatreya, M, additional, Jayalekshmi, P A, additional, Sebastian, P, additional, Nandakumar, A, additional, Malekzadeh, R, additional, Roshandel, G, additional, Keinan-Boker, L, additional, Silverman, B G, additional, Ito, H, additional, Nakagawa, H, additional, Sato, M, additional, Tobori, F, additional, Nakata, I, additional, Teramoto, N, additional, Hattori, M, additional, Kaizaki, Y, additional, Moki, F, additional, Sugiyama, H, additional, Utada, M, additional, Nishimura, M, additional, Yoshida, K, additional, Kurosawa, K, additional, Nemoto, Y, additional, Narimatsu, H, additional, Sakaguchi, M, additional, Kanemura, S, additional, Naito, M, additional, Narisawa, R, additional, Miyashiro, I, additional, Nakata, K, additional, Sato, S, additional, Yoshii, M, additional, Oki, I, additional, Fukushima, N, additional, Shibata, A, additional, Iwasa, K, additional, Ono, C, additional, Nimri, O, additional, Jung, K W, additional, Won, Y J, additional, Alawadhi, E, additional, Elbasmi, A, additional, Ab Manan, A, additional, Adam, F, additional, Sanjaajmats, E, additional, Tudev, U, additional, Ochir, C, additional, Al Khater, A M, additional, El Mistiri, M M, additional, Teo, Y Y, additional, Chiang, C J, additional, Lee, W C, additional, Buasom, R, additional, Sangrajrang, S, additional, Kamsa-ard, S, additional, Wiangnon, S, additional, Daoprasert, K, additional, Pongnikorn, D, additional, Leklob, A, additional, Sangkitipaiboon, S, additional, Geater, S L, additional, Sriplung, H, additional, Ceylan, O, additional, Kög, I, additional, Dirican, O, additional, Köse, T, additional, Gurbuz, T, additional, Karaşahin, F E, additional, Turhan, D, additional, Aktaş, U, additional, Halat, Y, additional, Yakut, C I, additional, Altinisik, M, additional, Cavusoglu, Y, additional, Türkköylü, A, additional, Üçüncü, N, additional, Hackl, M, additional, Zborovskaya, A A, additional, Aleinikova, O V, additional, Henau, K, additional, Van Eycken, L, additional, Valerianova, Z, additional, Yordanova, M R, additional, Šekerija, M, additional, Dušek, L, additional, Zvolský, M, additional, Storm, H, additional, Innos, K, additional, Mägi, M, additional, Malila, N, additional, Seppä, K, additional, Jégu, J, additional, Velten, M, additional, Cornet, E, additional, Troussard, X, additional, Bouvier, A M, additional, Guizard, A V, additional, Bouvier, V, additional, Launoy, G, additional, Arveux, P, additional, Maynadié, M, additional, Mounier, M, additional, Woronoff, A S, additional, Daoulas, M, additional, Robaszkiewicz, M, additional, Clavel, J, additional, Goujon, S, additional, Lacour, B, additional, Baldi, I, additional, Pouchieu, C, additional, Amadeo, B, additional, Coureau, G, additional, Orazio, S, additional, Preux, P M, additional, Rharbaoui, F, additional, Marrer, E, additional, Trétarre, B, additional, Colonna, M, additional, Delafosse, P, additional, Ligier, K, additional, Plouvier, S, additional, Cowppli-Bony, A, additional, Molinié, F, additional, Bara, S, additional, Ganry, O, additional, Lapôtre-Ledoux, B, additional, Grosclaude, P, additional, Bossard, N, additional, Uhry, Z, additional, Bray, F, additional, Piñeros, M, additional, Stabenow, R, additional, Wilsdorf-Köhler, H, additional, Eberle, A, additional, Luttmann, S, additional, Löhden, I, additional, Nennecke, A L, additional, Kieschke, J, additional, Sirri, E, additional, Emrich, K, additional, Zeissig, S R, additional, Holleczek, B, additional, Eisemann, N, additional, Katalinic, A, additional, Asquez, R A, additional, Kumar, V, additional, Petridou, E, additional, Ólafsdóttir, E J, additional, Tryggvadóttir, L, additional, Clough-Gorr, K, additional, Walsh, P M, additional, Sundseth, H, additional, Mazzoleni, G, additional, Vittadello, F, additional, Coviello, E, additional, Cuccaro, F, additional, Galasso, R, additional, Sampietro, G, additional, Giacomin, A, additional, Magoni, M, additional, Ardizzone, A, additional, D'Argenzio, A, additional, Castaing, M, additional, Grosso, G, additional, Lavecchia, A M, additional, Sutera Sardo, A, additional, Gola, G, additional, Gatti, L, additional, Ricci, P, additional, Ferretti, S, additional, Serraino, D, additional, Zucchetto, A, additional, Celesia, M V, additional, Filiberti, R A, additional, Pannozzo, F, additional, Melcarne, A, additional, Quarta, F, additional, Russo, A G, additional, Carrozzi, G, additional, Cirilli, C, additional, Cavalieri d'Oro, L, additional, Rognoni, M, additional, Fusco, M, additional, Vitale, M F, additional, Usala, M, additional, Cusimano, R, additional, Mazzucco, W, additional, Michiara, M, additional, Sgargi, P, additional, Boschetti, L, additional, Borciani, E, additional, Seghini, P, additional, Maule, M M, additional, Merletti, F, additional, Tumino, R, additional, Mancuso, P, additional, Vicentini, M, additional, Cassetti, T, additional, Sassatelli, R, additional, Falcini, F, additional, Giorgetti, S, additional, Caiazzo, A L, additional, Cavallo, R, additional, Cesaraccio, R, additional, Pirino, D R, additional, Contrino, M L, additional, Tisano, F, additional, Fanetti, A C, additional, Maspero, S, additional, Carone, S, additional, Mincuzzi, A, additional, Candela, G, additional, Scuderi, T, additional, Gentilini, M A, additional, Piffer, S, additional, Rosso, S, additional, Barchielli, A, additional, Caldarella, A, additional, Bianconi, F, additional, Stracci, F, additional, Contiero, P, additional, Tagliabue, G, additional, Rugge, M, additional, Zorzi, M, additional, Beggiato, S, additional, Brustolin, A, additional, Berrino, F, additional, Gatta, G, additional, Sant, M, additional, Buzzoni, C, additional, Mangone, L, additional, Capocaccia, R, additional, De Angelis, R, additional, Zanetti, R, additional, Maurina, A, additional, Pildava, S, additional, Lipunova, N, additional, Vincerževskiené, I, additional, Agius, D, additional, Calleja, N, additional, Siesling, S, additional, Larønningen, S, additional, Møller, B, additional, Dyzmann-Sroka, A, additional, Trojanowski, M, additional, Góźdź, S, additional, Mężyk, R, additional, Mierzwa, T, additional, Molong, L, additional, Rachtan, J, additional, Szewczyk, S, additional, Błaszczyk, J, additional, Kępska, K, additional, Kościańska, B, additional, Tarocińska, K, additional, Zwierko, M, additional, Drosik, K, additional, Maksimowicz, K M, additional, Purwin-Porowska, E, additional, Reca, E, additional, Wójcik-Tomaszewska, J, additional, Tukiendorf, A, additional, Grądalska-Lampart, M, additional, Radziszewska, A U, additional, Gos, A, additional, Talerczyk, M, additional, Wyborska, M, additional, Didkowska, J A, additional, Wojciechowska, U, additional, Bielska-Lasota, M, additional, Forjaz de Lacerda, G, additional, Rego, R A, additional, Bastos, J, additional, Silva, M A, additional, Antunes, L, additional, Laranja Pontes, J, additional, Mayer-da-Silva, A, additional, Miranda, A, additional, Blaga, L M, additional, Coza, D, additional, Gusenkova, L, additional, Lazarevich, O, additional, Prudnikova, O, additional, Vjushkov, D M, additional, Egorova, A G, additional, Orlov, A E, additional, Kudyakov, L A, additional, Pikalova, L V, additional, Adamcik, J, additional, Safaei Diba, C, additional, Primic-Žakelj, M, additional, Zadnik, V, additional, Larrañaga, N, additional, Lopez de Munain, A, additional, Herrera, A A, additional, Redondas, R, additional, Marcos-Gragera, R, additional, Vilardell Gil, M L, additional, Molina, E, additional, Sánchez Perez, M J, additional, Franch Sureda, P, additional, Ramos Montserrat, M, additional, Chirlaque, M D, additional, Navarro, C, additional, Ardanaz, E E, additional, Guevara, M M, additional, Fernández-Delgado, R, additional, Peris-Bonet, R, additional, Carulla, M, additional, Galceran, J, additional, Alberich, C, additional, Vicente-Raneda, M, additional, Khan, S, additional, Pettersson, D, additional, Dickman, P, additional, Avelina, I, additional, Staehelin, K, additional, Camey, B, additional, Bouchardy, C, additional, Schaffar, R, additional, Frick, H, additional, Herrmann, C, additional, Bulliard, J L, additional, Maspoli-Conconi, M, additional, Kuehni, C E, additional, Redmond, S M, additional, Bordoni, A, additional, Ortelli, L, additional, Chiolero, A, additional, Konzelmann, I, additional, Matthes, K L, additional, Rohrmann, S, additional, Broggio, J, additional, Rashbass, J, additional, Fitzpatrick, D, additional, Gavin, A, additional, Clark, D I, additional, Deas, A J, additional, Huws, D W, additional, White, C, additional, Montel, L, additional, Rachet, B, additional, Turculet, A D, additional, Stephens, R, additional, Chalker, E, additional, Phung, H, additional, Walton, R, additional, You, H, additional, Guthridge, S, additional, Johnson, F, additional, Gordon, P, additional, D'Onise, K, additional, Priest, K, additional, Stokes, B C, additional, Venn, A, additional, Farrugia, H, additional, Thursfield, V, additional, Dowling, J, additional, Currow, D, additional, Hendrix, J, additional, and Lewis, C, additional

Published
2018
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4. Interactions between changing pCO2, N2 fixation, and Fe limitation in the marine unicellular cyanobacterium Crocosphaera

Author

Fu, F.-X., Mulholland, M. R., Garcia, N. S., Beck, Aaron J., Bernhardt, P. W., Warner, M. E., Sañudo-Wilhelmy, S. A., Hutchins, D. A., Fu, F.-X., Mulholland, M. R., Garcia, N. S., Beck, Aaron J., Bernhardt, P. W., Warner, M. E., Sañudo-Wilhelmy, S. A., and Hutchins, D. A.

Abstract

We examined the physiological responses of steady-state iron (Fe)-replete and Fe-limited cultures of the biogeochemically critical marine unicellular diazotrophic cyanobacterium Crocosphaera at glacial (19 Pa; 190 ppm), current (39 Pa; 380 ppm), and projected year 2100 (76 Pa; 750 ppm) CO2 levels. Rates of N2 and CO2 fixation and growth increased in step with increasing partial pressure of CO2 (pCO2), but only under Fe-replete conditions. N2 and carbon fixation rates at 75 Pa CO2 were 1.4-1.8-fold and 1.2-2.0-fold higher, respectively, relative to those at present day and glacial pCO2 levels. In Fe-replete cultures, cellular Fe and molybdenum quotas varied threefold and were linearly related to N2 fixation rates and to external pCO2. However, N2 fixation and trace metal quotas were decoupled from pCO2 in Fe-limited Crocosphaera. Higher CO2 and Fe concentrations both resulted in increased cellular pigment contents and affected photosynthesis vs. irradiance parameters. If these results also apply to natural Crocosphaera populations, anthropogenic CO2 enrichment could substantially increase global oceanic N2 and CO2 fixation, but this effect may be tempered by Fe availability. Possible biogeochemical consequences may include elevated inputs of new nitrogen to the ocean and increased potential for Fe and/or phosphorus limitation in the future high-CO2 ocean, and feedbacks to atmospheric pCO2 in both the near future and over glacial to interglacial timescales.

Published
2008
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6. CO2 control of Trichodesmium N2 fixation, photosynthesis, growth rates, and elemental ratios: Implications for past, present, and future ocean biogeochemistry.

Author

Hutchins, D. A., Fu, F.-X., Zhang, Y., Warner, M. E., Feng, Y., Portune, K., Bernhardt, P. W., and Mulholland, M. R.

Subjects
*CYANOBACTERIA, *PROKARYOTES, *TRICHODESMIUM, *CARBON dioxide, *NITROGEN, *PHOSPHORUS
Abstract

Diazotrophic marine cyanobacteria in the genus Trichodesmium contribute a large fraction of the new nitrogen entering the oligotrophic oceans, but little is known about how they respond to shifts in global change variables such as carbon dioxide (CO²) and temperature. We compared Trichodesmium dinitrogen (N²) and CO² fixation rates during steady-state growth under past, current, and future CO² scenarios, and at two relevant temperatures. At projected CO² levels of year 2100 (76 Pa, 750 ppm), N² fixation rates of Pacific and Atlantic isolates increased 35-100%, and CO2 fixation rates increased 15-128% relative to present day CO² conditions (39 Pa, 380 ppm). CO²-mediated rate increases were of similar relative magnitude in both phosphorus (P)-replete and P-limited cultures, suggesting that this effect may be independent of resource limitation. Neither isolate could grow at 15 Pa (150 ppm) CO², but N² and CO² fixation rates, growth rates, and nitrogen : phosophorus (N : P) ratios all increased significantly between 39 Pa and 152 Pa (1500 ppm). In contrast, these parameters were affected only minimally or not at all by a 4°C temperature change. Photosynthesis versus irradiance parameters, however, responded to both CO² and temperature but in different ways for each isolate. These results suggest that by the end of this century, elevated CO² could substantially increase global Trichodesmium N² and CO² fixation, fundamentally altering the current marine N and C cycles and potentially driving some oceanic regimes towards P limitation. CO² limitation of Trichodesmium diazotrophy during past glacial periods could also have contributed to setting minimum atmospheric CO² levels through downregulation of the biological pump. The relationship between marine N² fixation and atmospheric CO² concentration appears to be more complex than previously realized and needs to be considered in the context of the rapidly changing oligotrophic oceans [ABSTRACT FROM AUTHOR]

Published
2007
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