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Frank Schmieder - One of the best experts on this subject based on the ideXlab platform.
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Occurrence of thick Ethmodiscus Oozes associated with a terminal Mid-Pleistocene Transition event in the oligotrophic subtropical South Atlantic
Palaeogeography Palaeoclimatology Palaeoecology, 2006Co-Authors: Oscar E Romero, Frank SchmiederAbstract:Abstract Within generally calcareous sediment sequences, layers of variable thickness of the giant diatom Ethmodiscus were found in five cores recovered in the Subtropical South Atlantic between 23° and 33°S from both sides of the Mid-Atlantic Ridge. Two types of Oozes occur: (almost) monospecific layers of Ethmodiscus and layers dominated by Ethmodiscus, with several accompanying tropical/subtropical, oligotrophic-water diatoms. The two thickest Ethmodiscus layers occur in GeoB3801-6 around 29°S, and accumulated during late MIS 14 and MIS 12, respectively. Downcore concentrations of Ethmodiscus valves range between 3.4 ⁎ 104 and 2.3 ⁎ 107 valves g− 1. We discuss the Ooze formation in the context of migration of frontal systems and changes in the thermohaline circulation. The occurrence of Ethmodiscus Oozes in sediments underlying the present-day pelagic, low-nutrient waters is associated with a terminal event of the Mid-Pleistocene Transition at around 530 ka, when the ocean circulation rearranged after a period of reduced NADW production.
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Occurrence of thick Ethmodiscus Oozes associated with a terminal Mid-Pleistocene Transition event in the oligotrophic subtropical
2006Co-Authors: Oscar E Romero, Frank SchmiederAbstract:Within generally calcareous sediment sequences, layers of variable thickness of the giant diatom Ethmodiscus were found in five cores recovered in the Subtropical South Atlantic between 238 and 338S from both sides of the Mid-Atlantic Ridge. Two types of Oozes occur: (almost) monospecific layers of Ethmodiscus and layers dominated by Ethmodiscus, with several accompanying tropical/subtropical, oligotrophic-water diatoms. The two thickest Ethmodiscus layers occur in GeoB3801-6 around 298S, and accumulated during late MIS 14 and MIS 12, respectively. Downcore concentrations of Ethmodiscus valves range between 3.4*10 4 and 2.3*10 7 valves g 1 . We discuss the Ooze formation in the context of migration of frontal systems and changes in the thermohaline circulation. The occurrence of Ethmodiscus Oozes in sediments underlying the present-day pelagic, low-nutrient waters is associated with a terminal event of the Mid-Pleistocene Transition at around 530 ka, when the ocean circulation rearranged after a period of reduced NADW production. D 2005 Elsevier B.V. All rights reserved.
Oscar E Romero - One of the best experts on this subject based on the ideXlab platform.
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Occurrence of thick Ethmodiscus Oozes associated with a terminal Mid-Pleistocene Transition event in the oligotrophic subtropical South Atlantic
Palaeogeography Palaeoclimatology Palaeoecology, 2006Co-Authors: Oscar E Romero, Frank SchmiederAbstract:Abstract Within generally calcareous sediment sequences, layers of variable thickness of the giant diatom Ethmodiscus were found in five cores recovered in the Subtropical South Atlantic between 23° and 33°S from both sides of the Mid-Atlantic Ridge. Two types of Oozes occur: (almost) monospecific layers of Ethmodiscus and layers dominated by Ethmodiscus, with several accompanying tropical/subtropical, oligotrophic-water diatoms. The two thickest Ethmodiscus layers occur in GeoB3801-6 around 29°S, and accumulated during late MIS 14 and MIS 12, respectively. Downcore concentrations of Ethmodiscus valves range between 3.4 ⁎ 104 and 2.3 ⁎ 107 valves g− 1. We discuss the Ooze formation in the context of migration of frontal systems and changes in the thermohaline circulation. The occurrence of Ethmodiscus Oozes in sediments underlying the present-day pelagic, low-nutrient waters is associated with a terminal event of the Mid-Pleistocene Transition at around 530 ka, when the ocean circulation rearranged after a period of reduced NADW production.
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Occurrence of thick Ethmodiscus Oozes associated with a terminal Mid-Pleistocene Transition event in the oligotrophic subtropical
2006Co-Authors: Oscar E Romero, Frank SchmiederAbstract:Within generally calcareous sediment sequences, layers of variable thickness of the giant diatom Ethmodiscus were found in five cores recovered in the Subtropical South Atlantic between 238 and 338S from both sides of the Mid-Atlantic Ridge. Two types of Oozes occur: (almost) monospecific layers of Ethmodiscus and layers dominated by Ethmodiscus, with several accompanying tropical/subtropical, oligotrophic-water diatoms. The two thickest Ethmodiscus layers occur in GeoB3801-6 around 298S, and accumulated during late MIS 14 and MIS 12, respectively. Downcore concentrations of Ethmodiscus valves range between 3.4*10 4 and 2.3*10 7 valves g 1 . We discuss the Ooze formation in the context of migration of frontal systems and changes in the thermohaline circulation. The occurrence of Ethmodiscus Oozes in sediments underlying the present-day pelagic, low-nutrient waters is associated with a terminal event of the Mid-Pleistocene Transition at around 530 ka, when the ocean circulation rearranged after a period of reduced NADW production. D 2005 Elsevier B.V. All rights reserved.
Quan Zeng - One of the best experts on this subject based on the ideXlab platform.
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Early events in fire blight infection and pathogenesis of Erwinia amylovora
Journal of Plant Pathology, 2020Co-Authors: Quan Zeng, Joanna Puławska, Jeffrey SchachterleAbstract:When viewing the fire blight disease from the perspective of a disease cycle, it is clear that the pathogen Erwinia amylovora goes through different infection stages on an annual basis. These stages include the initial infection of flowers and shoot tips with Ooze as the inoculum; systemic spread through the plant vasculature; production of Ooze on plant surfaces as the secondary inoculum, and formation of annual cankers to tolerate winter stresses. Among them, the stage of initial infection of flowers and shoot tips drew most research attention, as in this stage, E. amylovora transits from epiphytic colonization on the plant surface to endophytic infection internally in the plant tissue. Limiting the epiphytic colonization of E. amylovora on flower surfaces is also the focus of fire blight management, as only the epiphytic cells of E. amylovora can be targeted by the antimicrobial sprays. In this review, we focus on some of these “early events” during the initial infection of flowers and shoot tips. We define these “early events” as any events that occur from the production of inoculum to before the systemic spread of the pathogen through the xylem. This includes the production and transfer of the inoculum (Ooze) to flowers and shoot tips; epiphytic proliferation of E. amylovora on flower / leaf surfaces; entry of the pathogen cells into host through natural openings or wounds; and initial proliferation immediately after entering the host. In the first half of this review, we summarize findings of some recent pathological investigations of these early events. In the second half of this review, we discuss the pathogenesis of E. amylovora in the context of these early events, particularly how E. amylovora modulates its virulence expression to induce disease symptoms. We focus on recent findings published within the past five years.
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microbiological examination of erwinia amylovora exopolysaccharide Ooze
Phytopathology, 2017Co-Authors: Suzanne M Slack, Quan Zeng, Cory Outwater, George W. SundinAbstract:Fire blight, caused by the pathogen Erwinia amylovora, is the most devastating bacterial disease of pome fruit in North America and worldwide. The primary method of dispersal for E. amylovora is through Ooze, a mass of exopolysaccharides and bacterial cells that is exuded as droplets from infected host tissue. During the 2013 and 2014 field seasons, 317 Ooze droplets were collected from field-inoculated apple trees. Populations of E. amylovora in Ooze droplets were 108 CFU/μl on average. Ooze droplets harboring larger (>108 CFU/μl) cell populations were typically smaller in total volume and had darker coloring, such as orange, red, or dark red hues. Examination of apple host tissue at the site of emergence of Ooze droplets using scanning electron microscopy revealed that Ooze was not exuding through natural openings; instead, it was found on erumpent mounds and small (10-μm) tears in tissue. These observations suggested that E. amylovora-induced wounds in tissue provided the exit holes for Ooze extrusion ...
Torsten Bickert - One of the best experts on this subject based on the ideXlab platform.
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Persisting maximum Agulhas leakage during MIS 14 indicated by massive Ethmodiscus Oozes in the subtropical South Atlantic
Paleoceanography, 2011Co-Authors: Nick Rackebrandt, Henning Kuhnert, Jeroen Groeneveld, Torsten BickertAbstract:[1] The glacial marine isotope stage 14 (MIS 14) appears in many climate records as an unusually warm glacial. During this period an almost monospecific, up to 1.5 m thick, laminated layer of the giant diatom Ethmodiscus rex has been deposited below the South Atlantic Subtropical Gyre. This oligotrophic region is today less favorable for diatom growth with sediments typically consisting of calcareous nannofossil Oozes. We have reconstructed temperatures and the stable oxygen isotopic compositions of sea surface and thermocline water (δ18Ow) from planktonic foraminiferal (Globigerinoides ruber and Globorotalia inflata) Mg/Ca and stable oxygen isotopes to test whether perturbations in surface ocean conditions contributed to the deposition of the diatom layer at ∼530 kyr B.P. Temperatures and δ18Ow values reconstructed from this diatom Ooze interval are highly variable, with maxima similar to interglacial values. Since the area of the Ethmodiscus Oozes resembles the region where Agulhas rings are present, we interpret these hydrographic changes to reflect the varying influence of warm and saline water of Indian Ocean origin that entered the Subtropical Gyre trapped in Agulhas rings. The formation of the Ethmodiscus Oozes is associated with a period of maximum Agulhas leakage and a maximum frequency of Agulhas ring formation caused by a termination-type position of the Subtropical Front during the unusual warm MIS 14. The input of silica through the Agulhas rings enabled the shift in primary production from calcareous nannoplankton to diatoms, leading to the deposition of the massive diatom Oozes.
George W. Sundin - One of the best experts on this subject based on the ideXlab platform.
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microbiological examination of erwinia amylovora exopolysaccharide Ooze
Phytopathology, 2017Co-Authors: Suzanne M Slack, Quan Zeng, Cory Outwater, George W. SundinAbstract:Fire blight, caused by the pathogen Erwinia amylovora, is the most devastating bacterial disease of pome fruit in North America and worldwide. The primary method of dispersal for E. amylovora is through Ooze, a mass of exopolysaccharides and bacterial cells that is exuded as droplets from infected host tissue. During the 2013 and 2014 field seasons, 317 Ooze droplets were collected from field-inoculated apple trees. Populations of E. amylovora in Ooze droplets were 108 CFU/μl on average. Ooze droplets harboring larger (>108 CFU/μl) cell populations were typically smaller in total volume and had darker coloring, such as orange, red, or dark red hues. Examination of apple host tissue at the site of emergence of Ooze droplets using scanning electron microscopy revealed that Ooze was not exuding through natural openings; instead, it was found on erumpent mounds and small (10-μm) tears in tissue. These observations suggested that E. amylovora-induced wounds in tissue provided the exit holes for Ooze extrusion ...
