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  • 1
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    Diatom fluxes in the NW Mediterranean: evidence from a 12-year sediment trap record and surficial sediments (2013)
    Oxford University Press
    Details
    Publikationsdatum: 2013-08-28
    Beschreibung: We examined the total diatom flux and species composition, total coccolith flux and total mass flux collected with a sediment trap between October 1993 and January 2006 in the northeastern entrance of the Gulf of Lions (North Western Mediterranean). The average daily diatom and coccolith fluxes (3 x 10 7 valves m 2 d –1 and 6.1 x 10 8 coccoliths m 2 day –1 , respectively) are comparable in magnitude with previously reported data sets in other high productivity areas of the Western Mediterranean. The temporal particle flux pattern reflected the variations in surface oceanographic conditions and primary productivity, which showed strong annual cycling. Highest diatom, coccolith and total mass fluxes always occurred during the winter–spring transition, while minima were observed during summer. Changes in the diverse diatom communities reflected the water column conditions throughout the record. The intensity of the diatom winter–spring blooms seemed to be enhanced in those years with intense and cold winds during winter, whereas years with low winter wind stress were liable to be less productive for diatoms. Coccolith fluxes exhibited a more stable interannual pattern than diatom fluxes. Significant discrepancies were found between the sediment trap and surficial sediment diatom assemblages.
    Print ISSN: 0142-7873
    Digitale ISSN: 1464-3774
    Thema: Biologie
    Publiziert von Oxford University Press
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
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    Latitudinal and temporal distributions of diatom populations in the pelagic waters of the Subantarctic and Polar Frontal Zones of the Southern Ocean and their role in the biological pump (2015)
    Copernicus
    Details
    Publikationsdatum: 2015-06-11
    Beschreibung: The Subantarctic and Polar Frontal zones (SAZ and PFZ) represent a large portion of the total area of the Southern Ocean and serve as a strong sink for atmospheric CO2. These regions are central to hypotheses linking particle fluxes and climate change, yet multi-year records of modern flux and the organisms that control it are, for obvious reasons, rare. In this study, we examine two sediment trap records of the flux of diatoms and bulk components collected by two bottom-tethered sediment traps deployed at mesopelagic depths (~ 1 km) in the SAZ (two-year record) and in the PFZ (six-year record) along the 140° E meridian. These traps provide a direct measure of transfer below winter mixed layer depths, i.e. at depths where effective sequestration from the atmosphere occurs, in contrast to study of processes in the surface ocean. Total mass fluxes were about two-fold higher in the PFZ (24 ± 13 g m−2 yr−1) than in the SAZ (14 ± 2 g m−2 yr−1). Bulk chemical composition of the particle fluxes mirrored the composition of the distinct plankton communities of the surface layer, being dominated by carbonate in the SAZ and by biogenic silica in the PFZ. POC export was similar for the annual average at both sites (1.0 ± 0.1 and 0.8 ± 0.4 g m−2 yr−1, for the PFZ and SAZ, respectively), indicating that the particles in the SAZ were relatively POC rich. Seasonality in the particle export was more pronounced in the PFZ. Peak fluxes occurred during summer in the PFZ and during spring in the SAZ. The strong summer pulses in the PFZ are responsible for a large fraction of the variability in carbon sequestration from the atmosphere in this region. The latitudinal variation of the total diatom flux was found to be in line with the biogenic silica export with an annual flux of 31 ± 5.5 × 108 valves m−2 yr−1 at the PFZ compared to 0.5 ± 0.4 × 108 m−2 yr−1 of the SAZ. Fragilariopsis kerguelensis dominated the annual diatom export at both sites (43 at the SAZ and 59% in the PFZ). POC fluxes displayed a strong positive correlation with the relative contribution of a group of weakly-silicified and bloom-forming species in the PFZ. Several lines of evidence suggest that the development of these species during the growth season facilitates the formation of aggregates and carbon export. Our results confirm previous work suggesting that F. kerguelensis is a major aspect of the decoupling of the carbon and silicon cycles in the high-nutrient low-chlorophyll waters of the Southern Ocean.
    Print ISSN: 1810-6277
    Digitale ISSN: 1810-6285
    Thema: Biologie , Geologie und Paläontologie
    Publiziert von Copernicus im Namen von European Geosciences Union.
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
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    Latitudinal and temporal distributions of diatom populations in the pelagic waters of the Subantarctic and Polar Frontal zones of the Southern Ocean and their role in the biological pump (2015)
    Copernicus
    Details
    Publikationsdatum: 2015-09-17
    Beschreibung: The Subantarctic and Polar Frontal zones (SAZ and PFZ) represent a large portion of the total area of the Southern Ocean and serve as a strong sink for atmospheric CO2. These regions are central to hypotheses linking particle fluxes and climate change, yet multi-year records of modern flux and the organisms that control it are, for obvious reasons, rare. In this study, we examine two sediment trap records of the flux of diatoms and bulk components collected by two bottom-tethered sediment traps deployed at mesopelagic depths (~ 1 km) in the SAZ (2-year record; July 1999–October 2001) and in the PFZ (6-year record; September 1997–February 1998, July 1999–August 2000, November 2002–October 2004 and December 2005–October 2007) along the 140° E meridian. These traps provide a direct measure of transfer below winter mixed layer depths, i.e. at depths where effective sequestration from the atmosphere occurs, in contrast to study of processes in the surface ocean. Total mass fluxes were about twofold higher in the PFZ (24 ± 13 g m−2 yr−1) than in the SAZ (14 ± 2 g m−2 yr−1). Bulk chemical composition of the particle fluxes mirrored the composition of the distinct plankton communities of the surface layer, being dominated by carbonate in the SAZ and by biogenic silica in the PFZ. Particulate organic carbon (POC) export was similar for the annual average at both sites (1.0 ± 0.1 and 0.8 ± 0.4 g m−2 yr−1 for the PFZ and SAZ, respectively), indicating that the particles in the SAZ were relatively POC rich. Seasonality in the particle export was more pronounced in the PFZ. Peak fluxes occurred during summer in the PFZ and during spring in the SAZ. The strong summer pulses in the PFZ are responsible for a large fraction of the variability in carbon sequestration from the atmosphere in this region. The latitudinal variation of the total diatom flux was found to be in line with the biogenic silica export with an annual flux of 31 ± 5.5 × 108 valves m−2 yr−1 at the PFZ compared to 0.5 ± 0.4 × 108 m−2 yr−1 at the SAZ. Fragilariopsis kerguelensis dominated the annual diatom export at both sites (43 % at the SAZ and 59 % in the PFZ). POC fluxes displayed a strong positive correlation with the relative contribution of a group of weakly silicified and bloom-forming species in the PFZ. Several lines of evidence suggests that the development of these species during the growth season facilitates the formation of aggregates and carbon export. Our results confirm previous work suggesting that F. kerguelensis plays a major role in the decoupling of the carbon and silicon cycles in the high-nutrient low-chlorophyll waters of the Southern Ocean.
    Print ISSN: 1726-4170
    Digitale ISSN: 1726-4189
    Thema: Biologie , Geologie und Paläontologie
    Publiziert von Copernicus im Namen von European Geosciences Union.
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
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    Full annual monitoring of Subantarctic Emiliania huxleyi populations reveals highly calcified morphotypes in high-CO2 winter conditions (2020)
    Springer Nature
    Details
    Publikationsdatum: 2020-02-13
    Digitale ISSN: 2045-2322
    Thema: Allgemeine Naturwissenschaft
    Publiziert von Springer Nature
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
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    Postglacial sedimentary processes on the Storfjorden and Kveithola trough mouth fans: impact of extreme glacimarine sedimentation (2014)
    Elsevier Science Limited
    Details
    Publikationsdatum: 2022-06-14
    Beschreibung: The depositional history of the Storfjorden and Kveithola trough-mouth fans (TMFs) in the northwestern Barents Sea has been investigated within two coordinated Spanish and Italian projects in the framework of the International Polar Year (IPY) Activity 367, NICE STREAMS. The investigation has been conducted using a multidisciplinary approach to the study of sediment cores positioned on high-resolution multibeam bathymetry and TOPAS/CHIRP sub-bottom profiles. Core correlation and the age model were based on 27 AMS 14C samples, rock magnetic parameters, lithofacies sequences, and the presence of marker beds including two oxidized layers marking the post Last Glacial Maximum (LGM) inception of deglaciation (OX-2) and the Younger Dryas cold climatic event (OX-1). Sediment facies analysis allowed the distinction of a number of depositional processes whose onset appears closely related to ice stream dynamics and oceanographic patterns in response to climate change. The glacigenic diamicton with low water content, high density, and high shear strength, deposited during glacial maxima, indicates ice streams grounded at the shelf edge. Massive release of IRD occurred at the inception of deglaciation in response to increased calving rates with possible outer ice streams lift off and collapse. The presence of a several-meter-thick sequence of interlaminated sediments deposited by subglacial outbursts of turbid meltwater (plumites) indicates rapid ice streams' melting and retreat. Crudely-layered and heavily-bioturbated sediments were deposited by contour currents under climatic/environmental conditions favorable to bioproductivity. The extreme sedimentation rate of 3.4 cm a− 1 calculated for the plumites from the upper-slope area indicates a massive, nearly instantaneous (less than 150 years), terrigenous input corresponding to an outstanding meltwater event. We propose these interlaminated sediments to represent the high-latitude marine record of MeltWater Pulse 1a (MWP-1a). Different bathymetric and oceanographic conditions controlled locally the mode of glacial retreat, resulting in different thickness of plumites on the upper continental slope of the Storfjorden and Kveithola TMFs. It is possible that the southern part of Storfjorden TMF received additional sediments from the deglaciation of the neighboring Kveithola ice stream.
    Beschreibung: Published
    Beschreibung: 309–326
    Beschreibung: 2.2. Laboratorio di paleomagnetismo
    Beschreibung: 3.8. Geofisica per l'ambiente
    Beschreibung: JCR Journal
    Beschreibung: restricted
    Schlagwort(e): Barents Sea ; sedimentary processes ; LGM ; meltwater plumes ; gullies ; MWP-1a ; 03. Hydrosphere::03.01. General::03.01.06. Paleoceanography and paleoclimatology ; 04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport ; 04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy ; 04. Solid Earth::04.05. Geomagnetism::04.05.09. Environmental magnetism
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Standort Signatur Erwartet Verfügbarkeit
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