The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Jef Huisman - One of the best experts on this subject based on the ideXlab platform.
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Competition and facilitation between unicellular Nitrogen-Fixing Cyanobacteria and non—Nitrogen-Fixing phytoplankton species
Limnology and Oceanography, 2020Co-Authors: Nona S.r. Agawin, Sophie Rabouille, Lidewij Servatius, Marcel J.w. Veldhuis, Harriët M. J. Van Overzee, Jef HuismanAbstract:Recent discoveries show that small unicellular Nitrogen-Fixing Cyanobacteria are more widespread than previously thought and can make major contributions to the nitrogen budget of the oceans. We combined theory and experiments to investigate competition for nitrogen and light between these small unicellular diazotrophs and other phytoplankton species. We developed a competition model that incorporates several physiological processes, including the light dependence of nitrogen fixation, the switch between nitrate assimilation and nitrogen fixation, and the release of fixed nitrogen. Model predictions were tested in nitrogen-limited and lightlimited chemostat experiments using the unicellular Nitrogen-Fixing cyanobacterium Cyanothece sp. Miami BG 043511, the picocyanobacterium Synechococcus bacillaris CCMP 1333, and the small green alga Chlorella_cf sp. CCMP 1227. Parameter values of the species were estimated by calibration of the model in monoculture experiments. The model predictions were subsequently tested in a series of competition experiments at different nitrate levels. The model predictions were generally in good agreement with observed population dynamics. As predicted, in experiments with high nitrate input concentrations, the species with lowest critical light intensity (S. bacillaris) competitively excluded the other species. At low nitrate input concentration, nitrogen release by Cyanothece enabled stable coexistence of Cyanothece and S. bacillaris. More specifically, model simulations predicted that fixed nitrogen release by Cyanothece enabled S. bacillaris to become four times more abundant in the species mixture than it would have been in monoculture. This intricate interplay between competition and facilitation is likely to be a major determinant of the relative abundances of unicellular Nitrogen-Fixing Cyanobacteria and non–Nitrogen-Fixing phytoplankton species in the oligotrophic ocean.
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Competition and facilitation between unicellular Nitrogen-Fixing Cyanobacteria and non-Nitrogen-Fixing phytoplankton species
Limnology and Oceanography, 2007Co-Authors: Nona S.r. Agawin, Sophie Rabouille, Lidewij Servatius, Harriët M.j. Van Overzee, Suzanne Hol, Marcel J.w. Veldhuis, Jef HuismanAbstract:Recent discoveries show that small unicellular Nitrogen-Fixing Cyanobacteria are more widespread than previously thought and can make major contributions to the nitrogen budget of the oceans. We combined theory and experiments to investigate competition for nitrogen and light between these small unicellular diazotrophs and other phytoplankton species. We developed a competition model that incorporates several physiological processes, including the light dependence of nitrogen fixation, the switch between nitrate assimilation and nitrogen fixation, and the release of fixed nitrogen. Model predictions were tested in nitrogen-limited and light- limited chemostat experiments using the unicellular Nitrogen-Fixing cyanobacterium Cyanothece sp. Miami BG 043511, the picocyanobacterium Synechococcus bacillaris CCMP 1333, and the small green alga Chlorellacf sp. CCMP 1227. Parameter values of the species were estimated by calibration of the model in monoculture experiments. The model predictions were subsequently tested in a series of competition experiments at different nitrate levels. The model predictions were generally in good agreement with observed population dynamics. As predicted, in experiments with high nitrate input concentrations, the species with lowest critical light intensity (S. bacillaris) competitively excluded the other species. At low nitrate input concentration, nitrogen release by Cyanothece enabled stable coexistence of Cyanothece and S. bacillaris. More specifically, model simulations predicted that fixed nitrogen release by Cyanothece enabled S. bacillaris to become four times more abundant in the species mixture than it would have been in monoculture. This intricate interplay between competition and facilitation is likely to be a major determinant of the relative abundances of unicellular Nitrogen-Fixing Cyanobacteria and nonNitrogen-Fixing phytoplankton species in the oligotrophic ocean.
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Competition for phosphorus between the nitrogen‐fixing Cyanobacteria Anabaena and Aphanizomenon
FEMS Microbiology Ecology, 2006Co-Authors: W. T. De Nobel, Jef Huisman, Jacky L. SnoepAbstract:The influence of N2 fixation on the P-limited growth of two strains of Anabaena and Aphanizomenon was investigated using continuous cultures. Under N2-fixing conditions Anabaena had a higher maximum growth rate, a greater affinity for P, a higher yield on P and a higher N2 fixation activity than Aphanizomenon. In contrast to Anabaena, Aphanizomenon did not adjust its specific N2 fixation activity and its cells became N depleted at high growth rates. Metabolic control analysis revealed that the growth rate of Aphanizomenon was controlled to a lesser extent by P than Anabaena's growth rate. As predicted on the basis of these monoculture measurements, Anabaena was the superior competitor for P in competition experiments. The results might help to distinguish the niches of these two closely related species.
Takuji Ohyam - One of the best experts on this subject based on the ideXlab platform.
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Nitrogen Fixing Cyanobacteria: Future Prospect
Advances in Biology and Ecology of Nitrogen Fixation, 2014Co-Authors: Mohamed Hemida, Takuji OhyamAbstract:273 pages | With TOC In this book there are 11 chapters related to biological nitrogen fixation, regulation of legume-rhizobium symbiosis, and agriculture and ecology of biological nitrogen fixation, including new models for autoregulation of nodulation in legumes, endophytic nitrogen fixation in sugarcane or forest trees, etc. The book will contribute to biological, ecological, and agricultural sciences. Biological nitrogen fixation has essential role in N cycle in global ecosystem. Several types of nitrogen fixing bacteria are recognized: the free-living bacteria in soil or water; symbiotic bacteria making root nodules in legumes or non-legumes; associative nitrogen fixing bacteria that resides outside the plant roots and provides fixed nitrogen to the plants; endophytic nitrogen fixing bacteria living in the roots, stems and leaves of plants. ______________________________________ Table Of Contents: Preface 1 Nitrogen Fixation Outside and Inside Plant Tissues 2 Nitrogen Fixing Cyanobacteria: Future Prospect 3 Nitrogen Fixation in Sugarcane 4 Autoregulation of Nodulation in Soybean Plants
L.a. Sherman - One of the best experts on this subject based on the ideXlab platform.
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Unicellular, aerobic Nitrogen-Fixing Cyanobacteria of the genus Cyanothece
Journal of Bacteriology, 1993Co-Authors: K.j. Reddy, J. B. Haskell, D. M. Sherman, L.a. ShermanAbstract:Two marine, unicellular aerobic Nitrogen-Fixing Cyanobacteria, Cyanothece strain BH63 and Cyanothece strain BH68, were isolated from the intertidal sands of the Texas Gulf coast in enrichment conditions designed to favor rapid growth. By cell morphology, ultrastructure, a GC content of 40%, and aerobic nitrogen fixation ability, these strains were assigned to the genus Cyanothece. These strains can use molecular nitrogen as the sole nitrogen source and are capable of photoheterotrophic growth in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea and glycerol. The strains demonstrated a doubling time of 10 to 14 h in the presence of nitrate and 16 to 20 h under Nitrogen-Fixing conditions. Rapid growth of Nitrogen-Fixing cultures can be obtained in continuous light even when the cultures are continuously shaken or bubbled with air. Under 12-h alternating light and dark cycles, the aerobic nitrogenase activity was confined to the dark phase. The typical rates of aerobic nitrogenase activity in Cyanothece strains BH63 and BH68 were 1,140 and 1,097 nmol of C2H2 reduced per mg (dry weight) per h, respectively, and nitrogenase activity was stimulated twofold by light. Ultrastructural observations revealed that numerous inclusion granules formed between the photosynthetic membranes in cells grown under Nitrogen-Fixing conditions. These Cyanothece strains posses many characteristics that make them particularly attractive for a detailed analysis of the interaction of nitrogen fixation and photosynthesis in an aerobic diazotroph.
Norbert Wasmund - One of the best experts on this subject based on the ideXlab platform.
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Internal ecosystem feedbacks enhance Nitrogen-Fixing Cyanobacteria blooms and complicate management in the Baltic Sea.
Ambio, 2020Co-Authors: Emil Vahtera, Daniel J. Conley, Bo G. Gustafsson, Harri Kuosa, Heikki Pitkänen, Oleg P. Savchuk, Timo Tamminen, Markku Viitasalo, Maren Voss, Norbert WasmundAbstract:Eutrophication of the Baltic Sea has potentially increased the frequency and magnitude of Cyanobacteria blooms. Eutrophication leads to increased sedimentation of organic material, increasing the extent of anoxic bottoms and subsequently increasing the internal phosphorus loading. In addition, the hypoxic water volume displays a negative relationship with the total dissolved inorganic nitrogen pool, suggesting greater overall nitrogen removal with increased hypoxia. Enhanced internal loading of phosphorus and the removal of dissolved inorganic nitrogen leads to lower nitrogen to phosphorus ratios, which are one of the main factors promoting nitrogenfixing Cyanobacteria blooms. Because Cyanobacteria blooms in the open waters of the Baltic Sea seem to be strongly regulated by internal processes, the effects of external nutrient reductions are scale-dependent. During longer time scales, reductions in external phosphorus load may reduce Cyanobacteria blooms; however, on shorter time scales the internal phosphorus loading can counteract external phosphorus reductions. The coupled processes inducing internal loading, nitrogen removal, and the prevalence of Nitrogen-Fixing Cyanobacteria can qualitatively be described as a potentially self-sustaining "vicious circle." To effectively reduce Cyanobacteria blooms and overall signs of eutrophication, reductions in both nitrogen and phosphorus external loads appear essential.
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Internal Ecosystem Feedbacks Enhance Nitrogen-Fixing Cyanobacteria Blooms and Complicate Management in the Baltic Sea
AMBIO: A Journal of the Human Environment, 2007Co-Authors: Emil Vahtera, Daniel J. Conley, Bo G. Gustafsson, Harri Kuosa, Heikki Pitkänen, Oleg P. Savchuk, Timo Tamminen, Markku Viitasalo, Maren Voss, Norbert WasmundAbstract:Abstract Eutrophication of the Baltic Sea has potentially increased the frequency and magnitude of Cyanobacteria blooms. Eutrophication leads to increased sedimentation of organic material, increasing the extent of anoxic bottoms and subsequently increasing the internal phosphorus loading. In addition, the hypoxic water volume displays a negative relationship with the total dissolved inorganic nitrogen pool, suggesting greater overall nitrogen removal with increased hypoxia. Enhanced internal loading of phosphorus and the removal of dissolved inorganic nitrogen leads to lower nitrogen to phosphorus ratios, which are one of the main factors promoting Nitrogen-Fixing Cyanobacteria blooms. Because Cyanobacteria blooms in the open waters of the Baltic Sea seem to be strongly regulated by internal processes, the effects of external nutrient reductions are scale-dependent. During longer time scales, reductions in external phosphorus load may reduce Cyanobacteria blooms; however, on shorter time scales the inter...
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Phytoplankton Periodicity in a Eutrophic Coastal Water of the Baltic Sea
International Review of Hydrobiology, 1994Co-Authors: Norbert WasmundAbstract:The phytoplankton periodicity in the Darss-Zingst bodden chain, an estuary-like coastal water of the southern Baltic Sea, was investigated from 1984 to 1990. The following functional groups were established: 1.) Nitrogen-Fixing Cyanobacteria plus Oscillatoria limnetica, 2.) coccoid Chlorophyceae, Gomphosphaeria pusilla, Lyngbya contorta and Stephanodiscus hantzschii, 3.) coccoid Cyanobacteria except Gomphosphaeria, 4.) diatoms except Stephanodiscus, 5.) Cryptophyceae and some other flagellates. A general seasonal pattern was observable: in cold winters group 5 dominates; in spring a diatom bloom (= group 4) occurred, which was followed by the development of group 2; steep temperature increases caused a summer bloom of Nitrogen-Fixing Cyanobacteria (= group 1), which was followed by groups 2 and 3 in autumn; in bland winters group 2 lasts until spring. Grazing was shown to be of minor importance for the phytoplankton periodicity.
Nona S.r. Agawin - One of the best experts on this subject based on the ideXlab platform.
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Competition and facilitation between unicellular Nitrogen-Fixing Cyanobacteria and non—Nitrogen-Fixing phytoplankton species
Limnology and Oceanography, 2020Co-Authors: Nona S.r. Agawin, Sophie Rabouille, Lidewij Servatius, Marcel J.w. Veldhuis, Harriët M. J. Van Overzee, Jef HuismanAbstract:Recent discoveries show that small unicellular Nitrogen-Fixing Cyanobacteria are more widespread than previously thought and can make major contributions to the nitrogen budget of the oceans. We combined theory and experiments to investigate competition for nitrogen and light between these small unicellular diazotrophs and other phytoplankton species. We developed a competition model that incorporates several physiological processes, including the light dependence of nitrogen fixation, the switch between nitrate assimilation and nitrogen fixation, and the release of fixed nitrogen. Model predictions were tested in nitrogen-limited and lightlimited chemostat experiments using the unicellular Nitrogen-Fixing cyanobacterium Cyanothece sp. Miami BG 043511, the picocyanobacterium Synechococcus bacillaris CCMP 1333, and the small green alga Chlorella_cf sp. CCMP 1227. Parameter values of the species were estimated by calibration of the model in monoculture experiments. The model predictions were subsequently tested in a series of competition experiments at different nitrate levels. The model predictions were generally in good agreement with observed population dynamics. As predicted, in experiments with high nitrate input concentrations, the species with lowest critical light intensity (S. bacillaris) competitively excluded the other species. At low nitrate input concentration, nitrogen release by Cyanothece enabled stable coexistence of Cyanothece and S. bacillaris. More specifically, model simulations predicted that fixed nitrogen release by Cyanothece enabled S. bacillaris to become four times more abundant in the species mixture than it would have been in monoculture. This intricate interplay between competition and facilitation is likely to be a major determinant of the relative abundances of unicellular Nitrogen-Fixing Cyanobacteria and non–Nitrogen-Fixing phytoplankton species in the oligotrophic ocean.
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Competition and facilitation between unicellular Nitrogen-Fixing Cyanobacteria and non-Nitrogen-Fixing phytoplankton species
Limnology and Oceanography, 2007Co-Authors: Nona S.r. Agawin, Sophie Rabouille, Lidewij Servatius, Harriët M.j. Van Overzee, Suzanne Hol, Marcel J.w. Veldhuis, Jef HuismanAbstract:Recent discoveries show that small unicellular Nitrogen-Fixing Cyanobacteria are more widespread than previously thought and can make major contributions to the nitrogen budget of the oceans. We combined theory and experiments to investigate competition for nitrogen and light between these small unicellular diazotrophs and other phytoplankton species. We developed a competition model that incorporates several physiological processes, including the light dependence of nitrogen fixation, the switch between nitrate assimilation and nitrogen fixation, and the release of fixed nitrogen. Model predictions were tested in nitrogen-limited and light- limited chemostat experiments using the unicellular Nitrogen-Fixing cyanobacterium Cyanothece sp. Miami BG 043511, the picocyanobacterium Synechococcus bacillaris CCMP 1333, and the small green alga Chlorellacf sp. CCMP 1227. Parameter values of the species were estimated by calibration of the model in monoculture experiments. The model predictions were subsequently tested in a series of competition experiments at different nitrate levels. The model predictions were generally in good agreement with observed population dynamics. As predicted, in experiments with high nitrate input concentrations, the species with lowest critical light intensity (S. bacillaris) competitively excluded the other species. At low nitrate input concentration, nitrogen release by Cyanothece enabled stable coexistence of Cyanothece and S. bacillaris. More specifically, model simulations predicted that fixed nitrogen release by Cyanothece enabled S. bacillaris to become four times more abundant in the species mixture than it would have been in monoculture. This intricate interplay between competition and facilitation is likely to be a major determinant of the relative abundances of unicellular Nitrogen-Fixing Cyanobacteria and nonNitrogen-Fixing phytoplankton species in the oligotrophic ocean.