The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
Eve Toulza - One of the best experts on this subject based on the ideXlab platform.
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Thermal Regime and host clade, rather than geography, drive Symbiodinium and bacterial assemblages in the scleractinian coral Pocillopora damicornis sensu lato
Microbiome, 2018Co-Authors: Kelly Brener-raffalli, Jérémie Vidal-dupiol, Guillaume Mitta, Mehdi Adjeroud, Marine Pratlong, Didier Aurelle, François Bonhomme, Camille Clerissi, Eve ToulzaAbstract:BackgroundAlthough the term holobiont has been popularized in corals with the advent of the hologenome theory of evolution, the underlying concepts are still a matter of debate. Indeed, the relative contribution of host and environment and especially Thermal Regime in shaping the microbial communities should be examined carefully to evaluate the potential role of symbionts for holobiont adaptation in the context of global changes. We used the sessile, long-lived, symbiotic and environmentally sensitive reef-building coral Pocillopora damicornis to address these issues.ResultsWe sampled Pocillopora damicornis colonies corresponding to two different mitochondrial lineages in different geographic areas displaying different Thermal Regimes: Djibouti, French Polynesia, New Caledonia, and Taiwan. The community composition of bacteria and the algal endosymbiont Symbiodinium were characterized using high-throughput sequencing of 16S rRNA gene and internal transcribed spacer, ITS2, respectively. Bacterial microbiota was very diverse with high prevalence of Endozoicomonas, Arcobacter, and Acinetobacter in all samples. While Symbiodinium sub-clade C1 was dominant in Taiwan and New Caledonia, D1 was dominant in Djibouti and French Polynesia. Moreover, we also identified a high background diversity (i.e., with proportions
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Thermal Regime and host clade rather than geography drive symbiodinium and bacterial assemblages in the scleractinian coral pocillopora damicornis sensu lato
Microbiome, 2018Co-Authors: Kelly Brenerraffalli, Guillaume Mitta, Mehdi Adjeroud, Marine Pratlong, Didier Aurelle, François Bonhomme, Camille Clerissi, Jeremie Vidaldupiol, Eve ToulzaAbstract:Although the term holobiont has been popularized in corals with the advent of the hologenome theory of evolution, the underlying concepts are still a matter of debate. Indeed, the relative contribution of host and environment and especially Thermal Regime in shaping the microbial communities should be examined carefully to evaluate the potential role of symbionts for holobiont adaptation in the context of global changes. We used the sessile, long-lived, symbiotic and environmentally sensitive reef-building coral Pocillopora damicornis to address these issues. We sampled Pocillopora damicornis colonies corresponding to two different mitochondrial lineages in different geographic areas displaying different Thermal Regimes: Djibouti, French Polynesia, New Caledonia, and Taiwan. The community composition of bacteria and the algal endosymbiont Symbiodinium were characterized using high-throughput sequencing of 16S rRNA gene and internal transcribed spacer, ITS2, respectively. Bacterial microbiota was very diverse with high prevalence of Endozoicomonas, Arcobacter, and Acinetobacter in all samples. While Symbiodinium sub-clade C1 was dominant in Taiwan and New Caledonia, D1 was dominant in Djibouti and French Polynesia. Moreover, we also identified a high background diversity (i.e., with proportions < 1%) of A1, C3, C15, and G Symbiodinum sub-clades. Using redundancy analyses, we found that the effect of geography was very low for both communities and that host genotypes and temperatures differently influenced Symbiodinium and bacterial microbiota. Indeed, while the constraint of host haplotype was higher than temperatures on bacterial composition, we showed for the first time a strong relationship between the composition of Symbiodinium communities and minimal sea surface temperatures. Because Symbiodinium assemblages are more constrained by the Thermal Regime than bacterial communities, we propose that their contribution to adaptive capacities of the holobiont to temperature changes might be higher than the influence of bacterial microbiota. Moreover, the link between Symbiodinium community composition and minimal temperatures suggests low relative fitness of clade D at lower temperatures. This observation is particularly relevant in the context of climate change, since corals will face increasing temperatures as well as much frequent abnormal cold episodes in some areas of the world.
Frederick E Nelson - One of the best experts on this subject based on the ideXlab platform.
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changes in the 1963 2013 shallow ground Thermal Regime in russian permafrost regions
Environmental Research Letters, 2015Co-Authors: Dmitry Streletskiy, Artem B Sherstiukov, Oliver W Frauenfeld, Frederick E NelsonAbstract:Spatial variability and temporal trends of the shallow ground Thermal Regime and permafrost active-layer thickness (ALT) were estimated over 1963–2013 using daily soil temperature data available from stations of the Russian Hydrometeorological Service. Correlation analysis was used to evaluate the role of changing climatic conditions on the ground Thermal Regime. ALT data collected by the Circumpolar Active Layer Monitoring program in Russia were used to expand the geography of ALT observations over 1999–2013, and to identify 'hot spots' of soil temperature and ALT change. Results indicate that a substantially higher rate of change in the Thermal Regime of permafrost-affected soils prevailed during 1999–2013, relative to the last fifty years. Results indicate that the Thermal Regime of the upper permafrost in western Russia is strongly associated with air temperature, with much weaker relationships in central and eastern Russia. The Thermal Regime of permafrost-affected soils shows stronger dependence on climatic conditions over the last fifteen years relative to the historical 50-year period. Geostatistical analysis revealed that the cities of Norilsk and Susuman are hot spots of permafrost degradation. Of six settlements selected for detailed analysis in various parts of the permafrost regions, all but one (Chukotka), show substantial changes in the shallow ground Thermal Regime. Northern locations in the continuous permafrost region show thickening of the active layer, while those farther south experienced development of residual thaw layers above the permafrost and decreases in the duration of the freezing period.
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Changes in the 1963–2013 shallow ground Thermal Regime in Russian permafrost regions
Environmental Research Letters, 2015Co-Authors: Dmitry Streletskiy, Artem B Sherstiukov, Oliver W Frauenfeld, Frederick E NelsonAbstract:Spatial variability and temporal trends of the shallow ground Thermal Regime and permafrost active-layer thickness (ALT) were estimated over 1963–2013 using daily soil temperature data available from stations of the Russian Hydrometeorological Service. Correlation analysis was used to evaluate the role of changing climatic conditions on the ground Thermal Regime. ALT data collected by the Circumpolar Active Layer Monitoring program in Russia were used to expand the geography of ALT observations over 1999–2013, and to identify 'hot spots' of soil temperature and ALT change. Results indicate that a substantially higher rate of change in the Thermal Regime of permafrost-affected soils prevailed during 1999–2013, relative to the last fifty years. Results indicate that the Thermal Regime of the upper permafrost in western Russia is strongly associated with air temperature, with much weaker relationships in central and eastern Russia. The Thermal Regime of permafrost-affected soils shows stronger dependence on climatic conditions over the last fifteen years relative to the historical 50-year period. Geostatistical analysis revealed that the cities of Norilsk and Susuman are hot spots of permafrost degradation. Of six settlements selected for detailed analysis in various parts of the permafrost regions, all but one (Chukotka), show substantial changes in the shallow ground Thermal Regime. Northern locations in the continuous permafrost region show thickening of the active layer, while those farther south experienced development of residual thaw layers above the permafrost and decreases in the duration of the freezing period.
Dmitry Streletskiy - One of the best experts on this subject based on the ideXlab platform.
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changes in the 1963 2013 shallow ground Thermal Regime in russian permafrost regions
Environmental Research Letters, 2015Co-Authors: Dmitry Streletskiy, Artem B Sherstiukov, Oliver W Frauenfeld, Frederick E NelsonAbstract:Spatial variability and temporal trends of the shallow ground Thermal Regime and permafrost active-layer thickness (ALT) were estimated over 1963–2013 using daily soil temperature data available from stations of the Russian Hydrometeorological Service. Correlation analysis was used to evaluate the role of changing climatic conditions on the ground Thermal Regime. ALT data collected by the Circumpolar Active Layer Monitoring program in Russia were used to expand the geography of ALT observations over 1999–2013, and to identify 'hot spots' of soil temperature and ALT change. Results indicate that a substantially higher rate of change in the Thermal Regime of permafrost-affected soils prevailed during 1999–2013, relative to the last fifty years. Results indicate that the Thermal Regime of the upper permafrost in western Russia is strongly associated with air temperature, with much weaker relationships in central and eastern Russia. The Thermal Regime of permafrost-affected soils shows stronger dependence on climatic conditions over the last fifteen years relative to the historical 50-year period. Geostatistical analysis revealed that the cities of Norilsk and Susuman are hot spots of permafrost degradation. Of six settlements selected for detailed analysis in various parts of the permafrost regions, all but one (Chukotka), show substantial changes in the shallow ground Thermal Regime. Northern locations in the continuous permafrost region show thickening of the active layer, while those farther south experienced development of residual thaw layers above the permafrost and decreases in the duration of the freezing period.
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Changes in the 1963–2013 shallow ground Thermal Regime in Russian permafrost regions
Environmental Research Letters, 2015Co-Authors: Dmitry Streletskiy, Artem B Sherstiukov, Oliver W Frauenfeld, Frederick E NelsonAbstract:Spatial variability and temporal trends of the shallow ground Thermal Regime and permafrost active-layer thickness (ALT) were estimated over 1963–2013 using daily soil temperature data available from stations of the Russian Hydrometeorological Service. Correlation analysis was used to evaluate the role of changing climatic conditions on the ground Thermal Regime. ALT data collected by the Circumpolar Active Layer Monitoring program in Russia were used to expand the geography of ALT observations over 1999–2013, and to identify 'hot spots' of soil temperature and ALT change. Results indicate that a substantially higher rate of change in the Thermal Regime of permafrost-affected soils prevailed during 1999–2013, relative to the last fifty years. Results indicate that the Thermal Regime of the upper permafrost in western Russia is strongly associated with air temperature, with much weaker relationships in central and eastern Russia. The Thermal Regime of permafrost-affected soils shows stronger dependence on climatic conditions over the last fifteen years relative to the historical 50-year period. Geostatistical analysis revealed that the cities of Norilsk and Susuman are hot spots of permafrost degradation. Of six settlements selected for detailed analysis in various parts of the permafrost regions, all but one (Chukotka), show substantial changes in the shallow ground Thermal Regime. Northern locations in the continuous permafrost region show thickening of the active layer, while those farther south experienced development of residual thaw layers above the permafrost and decreases in the duration of the freezing period.
Tingjun Zhang - One of the best experts on this subject based on the ideXlab platform.
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influence of the seasonal snow cover on the ground Thermal Regime an overview
Reviews of Geophysics, 2005Co-Authors: Tingjun ZhangAbstract:[1] The presence of seasonal snow cover during the cold season of the annual air temperature cycle has significant influence on the ground Thermal Regime in cold regions. Snow has high albedo and emissivity that cool the snow surface, high absorptivity that tends to warm the snow surface, low Thermal conductivity so that a snow layer acts as an insulator, and high latent heat due to snowmelt that is a heat sink. The overall impact of snow cover on the ground Thermal Regime depends on the timing, duration, accumulation, and melting processes of seasonal snow cover; density, structure, and thickness of seasonal snow cover; and interactions of snow cover with micrometeorological conditions, local microrelief, vegetation, and the geographical locations. Over different timescales either the cooling or warming impact of seasonal snow cover may dominate. In the continuous permafrost regions, impact of seasonal snow cover can result in an increase of the mean annual ground and permafrost surface temperature by several degrees, whereas in discontinuous and sporadic permafrost regions the absence of seasonal snow cover may be a key factor for permafrost development. In seasonally frozen ground regions, snow cover can substantially reduce the seasonal freezing depth. However, the influence of seasonal snow cover on seasonally frozen ground has received relatively little attention, and further study is needed. Ground surface temperatures, reconstructed from deep borehole temperature gradients, have increased by up to 4°C in the past centuries and have been widely used as evidence of paleoclimate change. However, changes in air temperature alone cannot account for the changes in ground temperatures. Changes in seasonal snow conditions might have significantly contributed to the ground surface temperature increase. The influence of seasonal snow cover on soil temperature, soil freezing and thawing processes, and permafrost has considerable impact on carbon exchange between the atmosphere and the ground and on the hydrological cycle in cold regions/cold seasons.
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a numerical model for surface energy balance and Thermal Regime of the active layer and permafrost containing unfrozen water
Cold Regions Science and Technology, 2004Co-Authors: Feng Ling, Tingjun ZhangAbstract:Abstract This paper describes a surface energy balance approach-based one-dimensional heat transfer model for estimating surface energy balance components and the Thermal Regime of soil. The surface energy balance equation was used to estimate the upper boundary temperature conditions for Thermal conduction calculations and to calculate surface heat fluxes. The influence of unfrozen water on the Thermal properties of soils was accounted for in the heat transfer model. The effect of snow was included in the model by extending the heat conduction solution into the snow layer and computing the surface heat balance components and the snow surface temperature. The model was driven by meteorological data collected at Barrow, AK, and was validated against the observed ground temperatures at Barrow. The results show good agreement between the simulated and the measured soil temperatures at depths of 0.01, 0.29, 0.50, and 1.0 m. When snow cover was present, snow surface temperatures were colder than ground surface temperatures and air temperatures, with mean temperature differences of −5.36 and −1.55 °C, respectively. We conclude that the model presented in this study can be used to calculate the surface energy balance components, simulate the ground temperatures, and investigate the impact of seasonal snow cover on the Thermal Regime of the active layer and permafrost containing unfrozen water with a quite reasonable accuracy. Snow density, which determines the snow Thermal conductivity, volumetric heat capacity, and albedo in this model, can strongly affect the performance of this model.
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numerical simulation of permafrost Thermal Regime and talik development under shallow thaw lakes on the alaskan arctic coastal plain
Journal of Geophysical Research, 2003Co-Authors: Feng Ling, Tingjun ZhangAbstract:[1] Thaw lakes are one of the most obvious manifestations of the hydrological system at work in the tundra regions of the Alaskan Arctic Coastal Plain, but the extent of the role of thaw lakes in Arctic land-atmosphere interactions and feedback has yet to be fully understood. This study uses a two-dimensional heat transfer model with phase change under a cylindrical coordinate system to simulate the long-term influence of shallow thaw lakes on the Thermal Regime of permafrost and talik development on the Alaskan Arctic Coastal Plain. On the basis of previous studies of permafrost and thaw lakes at Barrow, Alaska, a series of simulation cases was conducted using different combinations of long-term mean lake bottom temperature and lake depth. The simulated results indicate that shallow thaw lakes are a significant heat source to permafrost and talik. For a thaw lake with a long-term mean lake bottom temperature of greater than 0.0°C a talik forms under the thaw lake. The maximum talik thicknesses (vertical distance from the ground surface to the permafrost surface) are 28.0, 43.0, and 53.2 m 3000 years after the formation of a shallow thaw lake with long-term mean lake bottom temperatures of 1.0°, 2.0°, and 3.0°C, respectively. Talik development rate is very high in the first several years after a thaw lake formation and decreases gradually with time. No talik forms below a thaw lake with a long-term mean lake bottom temperature equal to or lower than 0.0°C, but the temperature of permafrost below the thaw lake increases with time. Three thousand years after the formation of a thaw lake with a long-term mean lake bottom temperature of greater than or equal to −2.0°C, ground temperature increases of more than 0.5°C occur as far as 300 m from the lake shore and as deep as about 400 m below the ground surface. It is concluded that variation of long-term mean lake bottom temperature has a significant influence on permafrost Thermal Regime and talik development. Continued monitoring for thaw lake bottom temperature and ground temperature under shallow thaw lakes is needed to further improve the simulation.
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influence of the depth hoar layer of the seasonal snow cover on the ground Thermal Regime
Water Resources Research, 1996Co-Authors: Tingjun Zhang, T E Osterkamp, Knut StamnesAbstract:Snow cover is a good insulator since it has low Thermal conductivity. The structure of the seasonal snow cover usually consists of higher-density layers at the top with coarse, lower-density depth hoar layers at the base. Because of its much smaller Thermal conductivity, changes in depth hoar fraction can have a significant impact on the insulating effect of the seasonal snow cover. A one-dimensional finite difference conductive heat transfer model with phase change was applied to investigate the effect of variations in the depth hoar fraction of the seasonal snow cover on the ground Thermal Regime. The snow cover was treated as a single layer with the effective Thermal properties determined with considerations of the effect of the wind slab and depth hoar layer. The model was applied to investigate the Thermal Regime of the active layer and permafrost from October 5, 1986, through July 13, 1991, at West Dock near Prudhoe Bay, Alaska. Results indicate that the calculated temperatures on the ground surface, in the active layer, and in deep permafrost are in excellent agreement with the measured temperatures. A sensitivity study shows that in permafrost regions, variations in the depth hoar fraction from 0.0 to 0.6 can increase the daily ground surface temperature 12.8°C and the mean annual ground surface temperature by 5.5°C and delay the active layer freeze-up by several months. In nonpermafrost regions an increase in the depth hoar fraction from 0.0 to 0.6 can increase the daily ground surface temperature by 8.4°C and the mean annual ground surface temperature by up to 2.4°C and reduce the seasonal freezing depth by up to 80%.
François Bonhomme - One of the best experts on this subject based on the ideXlab platform.
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Thermal Regime and host clade, rather than geography, drive Symbiodinium and bacterial assemblages in the scleractinian coral Pocillopora damicornis sensu lato
Microbiome, 2018Co-Authors: Kelly Brener-raffalli, Jérémie Vidal-dupiol, Guillaume Mitta, Mehdi Adjeroud, Marine Pratlong, Didier Aurelle, François Bonhomme, Camille Clerissi, Eve ToulzaAbstract:BackgroundAlthough the term holobiont has been popularized in corals with the advent of the hologenome theory of evolution, the underlying concepts are still a matter of debate. Indeed, the relative contribution of host and environment and especially Thermal Regime in shaping the microbial communities should be examined carefully to evaluate the potential role of symbionts for holobiont adaptation in the context of global changes. We used the sessile, long-lived, symbiotic and environmentally sensitive reef-building coral Pocillopora damicornis to address these issues.ResultsWe sampled Pocillopora damicornis colonies corresponding to two different mitochondrial lineages in different geographic areas displaying different Thermal Regimes: Djibouti, French Polynesia, New Caledonia, and Taiwan. The community composition of bacteria and the algal endosymbiont Symbiodinium were characterized using high-throughput sequencing of 16S rRNA gene and internal transcribed spacer, ITS2, respectively. Bacterial microbiota was very diverse with high prevalence of Endozoicomonas, Arcobacter, and Acinetobacter in all samples. While Symbiodinium sub-clade C1 was dominant in Taiwan and New Caledonia, D1 was dominant in Djibouti and French Polynesia. Moreover, we also identified a high background diversity (i.e., with proportions
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Thermal Regime and host clade rather than geography drive symbiodinium and bacterial assemblages in the scleractinian coral pocillopora damicornis sensu lato
Microbiome, 2018Co-Authors: Kelly Brenerraffalli, Guillaume Mitta, Mehdi Adjeroud, Marine Pratlong, Didier Aurelle, François Bonhomme, Camille Clerissi, Jeremie Vidaldupiol, Eve ToulzaAbstract:Although the term holobiont has been popularized in corals with the advent of the hologenome theory of evolution, the underlying concepts are still a matter of debate. Indeed, the relative contribution of host and environment and especially Thermal Regime in shaping the microbial communities should be examined carefully to evaluate the potential role of symbionts for holobiont adaptation in the context of global changes. We used the sessile, long-lived, symbiotic and environmentally sensitive reef-building coral Pocillopora damicornis to address these issues. We sampled Pocillopora damicornis colonies corresponding to two different mitochondrial lineages in different geographic areas displaying different Thermal Regimes: Djibouti, French Polynesia, New Caledonia, and Taiwan. The community composition of bacteria and the algal endosymbiont Symbiodinium were characterized using high-throughput sequencing of 16S rRNA gene and internal transcribed spacer, ITS2, respectively. Bacterial microbiota was very diverse with high prevalence of Endozoicomonas, Arcobacter, and Acinetobacter in all samples. While Symbiodinium sub-clade C1 was dominant in Taiwan and New Caledonia, D1 was dominant in Djibouti and French Polynesia. Moreover, we also identified a high background diversity (i.e., with proportions < 1%) of A1, C3, C15, and G Symbiodinum sub-clades. Using redundancy analyses, we found that the effect of geography was very low for both communities and that host genotypes and temperatures differently influenced Symbiodinium and bacterial microbiota. Indeed, while the constraint of host haplotype was higher than temperatures on bacterial composition, we showed for the first time a strong relationship between the composition of Symbiodinium communities and minimal sea surface temperatures. Because Symbiodinium assemblages are more constrained by the Thermal Regime than bacterial communities, we propose that their contribution to adaptive capacities of the holobiont to temperature changes might be higher than the influence of bacterial microbiota. Moreover, the link between Symbiodinium community composition and minimal temperatures suggests low relative fitness of clade D at lower temperatures. This observation is particularly relevant in the context of climate change, since corals will face increasing temperatures as well as much frequent abnormal cold episodes in some areas of the world.
