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  • 2000-2004  (36)
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  • 1
    Online Resource
    Online Resource
    Kalzifizierung der Coccolithophoride Emiliania huxleyi (Proymnesiophyceae) unter Betrachtung des Zellzyklus (2004)
    Kiel
    Details Availability
    Keywords: Hochschulschrift ; Sargassosee ; Coccolithophoridae ; Verkalkung
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (97 Seiten = 5 MB) , Illustrationen, Graphen
    Edition: Online-Ausgabe 2021
    URL: https://oceanrep.geomar.de/54401/
    Language: German
    Note: Zusammenfassung in deutscher und englischer Sprache
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  • 2
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    The seafloor as the ultimate sediment trap - using sediment properties to constrain benthic-pelagic exchange processes at the Goban Spur (2001)
    Pergamon Press
    In:  Deep Sea Research Part II: Topical Studies in Oceanography, 48 (14-15) . pp. 3245-3264.
    Details
    Publication Date: 2020-08-05
    Description: The benthic diagenetic model OMEXDIA has been used to reproduce observed benthic pore water and solid phase profiles obtained during the OMEX study in the Goban Spur Area (N.E. Atlantic), and to dynamically model benthic profiles at site OMEX III (3660-m depth), with the sediment trap organic flux as external forcing. The results of the dynamic modelling show that the organic flux as determined from the lowermost sediment trap (400 metres above the bottom) at OMEX III is insufficient to explain the organic carbon and pore water profiles. The best fitting was obtained by maintaining the seasonal pattern as observed in the traps, while multiplying the absolute values of the flux by a factor of 1.85. The “inverse modelling” of diagenetic processes resulted in estimates of total mineralisation rate and of degradability of the organic matter at the different stations. These diagenetic model-based estimates are used to constrain the patterns of lateral and vertical transports of organic matter. Using the observed degradability as a function of depth, we show that the observed organic matter fluxes at the different depths are consistent with a model where at all stations along the gradient the same vertical export flux occurs at 200 m, and where organic matter sinks with a constant sinking rate of around 130 m d−1. If sinking rates were higher, in the order of 200 m d−1, the observations could be consistent with an off-slope gradient in export production of approximately a factor of 1.5 between the shallowest and deepest sites. The derived high degradability of the arriving organic matter and the consistency of the mass fluxes at the different stations exclude the possibility of a massive deposition, on the margin, of organic matter produced on the shelf or shelf break. However, other hypotheses to explain the patterns found in the sediment trap data of both OMEX and other continental margin study sites also suffer from different inconsistencies. Further, close examination of the flow patterns at the margin will be needed to examine the question.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0967-0645(01)00039-X
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Taxon-specific growth and selective microzooplankton grazing of phytoplankton in the Northeast Atlantic (2001)
    Elsevier
    In:  Journal of Marine Systems, 30 . pp. 241-261.
    Details
    Publication Date: 2017-07-12
    Description: Taxon-specific microzooplankton dynamics were studied along a transect through the North Atlantic Drift from 70°N 04°E to 40°N 20°W during July 1997 using serial dilution and nutrient-enrichment experiments. Nutrient concentrations and microzooplankton composition indicated postbloom conditions at 40°N, 47°N, and 50°N, a transitional system at 54°N, and bloom conditions at 62°N and 70°N. The ratio of microzooplankton to phytoplankton biomass was inversely related to nitrate and phosphate concentrations. Potential grazing thresholds were observed in four of nine experiments at 40–66% of the initial phytoplankton concentration. Grazing losses were determined for six pigment-specific classes of phytoplankton. Selective grazing losses of phytoplankton taxa ranged from 73% to 248% of the nonselective grazing losses predicted according to their biomass contributions. The grazing selectivity varied considerably between communities, with the microherbivores showing positive selection for cyanobacteria and dinoflagellates and predominantly avoidance of chlorophyta and bacillariophyceae. Microzooplankton did not show a preference for the dominant phytoplankton taxa, but grazed preferentially on fast-growing phytoplankton with minor contributions (〈15%) to the phytoplankton biomass. However, bacillariophyceae were the major contributors to phytoplankton biomass and accounted for major fractions of the total losses through microzooplankton grazing. Microzooplankton consumed the equivalent of 0.12–5.5 times their own biomass daily on a carbon basis, amounting to 65–197% of gross phytoplankton production. With the conservative assumption that 20% of the consumed phytoplankton was converted to microzooplankton biomass, the latter was estimated to contribute 27–381% to the net production of the entire microzooplankton community. We therefore conclude that the taxonomic structure and the net production of the microzooplankton communities were significantly affected by the intensity and selectivity of herbivorous microzooplankton grazing.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0924-7963(01)00061-6
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Particle flux variability in the polar and Atlantic biogeochemical provinces of the Nordic Seas (2001)
    Springer
    In:  In: The Northern North Atlantic: A Changing Environment. , ed. by Schäfer, P., Ritzrau, W., Schlüter, M. and Thiede, J. Springer, Berlin, Germany, pp. 69-79.
    Details
    Publication Date: 2020-04-01
    Description: A decade of particle flux measurements providse the basis for a comparison of the eastem and westem provinces ofthe Nordic Seas. Ice-related physical and biological seasonality as well as pelagic settings jointly control fluxes in the westem Polar Province which receives southward flowing water of Polar origin. Sediment trap data from this realm highlight a predominantly physical flux control which leads to exports of siliceous particles within the biological marginal ice zone as a prominent contributor. In the northward flowing waters of the eastem Atlantic Province, feeding Strategie . life histories and the succession of dominant mesozooplankters (copepods and pteropods) are central in controlling fluxes. Furthermore, more calcareous matter is exported here with a shift in flux seasonality towards surnrner/autumn. Dominant pelagic processes modeled numerically as to their impact on annual organic carbon exports for both provinces confirrn that interannual flux variability is related to changes in the respective control mechanisms. Annual organic carbon exports are strikingly similar in the Polar and Atlantic Provinces (2.4 and 2.9 g m-2 y-1 at 500 m depth). despite major differences in flux control. The Polar and Atlantic Provinces. however, can be distinguished according to annual fluxes of opal ( l.4 and 0.6 g m-2 y-1) and carbonate (6.8 and 10.4 g m-2 y-1). lnterannual variability may blur this in single years. Thus. it is vital to use multi-annual data sets when including particle exports in general biogeochemical province descriptions. Vertical flux profiles (collections from 500 m, l000 min both provinces and 300-600 m above the seafloor deviate from the general vertical decline of fluxes due to particle degradation during sinking. At depths 〉 1000 m secondary fluxes (laterally advected/re uspended particles) are often juxtaposed to primary (pelagic) fluxes, a pattem which is most prominent in the Atlantic Province. Spatial variability within theAtlantic Province remains poorly understood. and the same holds true for interannual variability. No proxies are at hand for this province to quantitatively relate fluxes to physical or biological pelagic properties. For the easonally ice-covered Polar Province a robust relationship exists between particle export and ambient ice-regime (Ramseier et al. this volume; Ramseier et al. 1999). Spatial flux pattems may be differentiated and interannual variability can be analyzed in this manner to improve our ability to couple pelagic export pattems with benthic and geochemical sedimentary processes in seasonally ice-covered seas.
    Type: Book chapter , NonPeerReviewed
    Format: text
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  • 5
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    Coupled biogeochemical cycling and controling factors (2003)
    Springer Verlag
    In:  In: Marine Science Frontiers for Europe. , ed. by Wefer, G., Lamy, F. and Mantoura, F. Springer Verlag, Berlin, Germany, pp. 147-162. ISBN 3-540-40168-7
    Details
    Publication Date: 2019-09-05
    Description: The changing climate of the planet is closely linked to biogeochemical processes in the oceans with important feedbacks between oceanic, atmospheric and terrestrial components of the earth system. This chapter identifies key processes that mediate the response of marine ecosystems to a changing environment and recommends implementation strategies for future studies. Technological and methodological advances such as the use of new biochemical and molecular techniques have led to the discovery of unknown metabolic pathways and identification of genetic diversity in marine systems. Ecosystem changes, reflected in shifts in dominant plankton groups are likely to have a !arge global but also regional impact in the European context. In terms of marine biogeochemical cycling, key processes that respond to a changing climate include photosynthesis (and its modulation by trace meta! availability and nitrogen fixation), calcification and the production and release of a suite of volatile, climate-reactive gasses. Implementation of future research strategies should focus on the ability to monitor key variables from stationary platforms and ships of opportunity with sufficient stability and accuracy to resolve natural and anthropogenic signals. Large-scale in situ manipulation experiments and mesocosm studies are also recommended as well as the application of molecular and genetic techniques that are a powerful means to investigate physiological and biogeochemical transformations that drive the oceans's response to climate change.
    Type: Book chapter , PeerReviewed
    Format: text
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    OceanRep: Book chapter
  • 6
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    Export of POC from the surface mixed layer (2001)
    Vreie Universiteit Brussels
    In:  In: European Network for Integrated Marine Science Analysis. , ed. by Dehairs, F. and Goeyens, L. Vreie Universiteit Brussels, Brüssel, Belgium.
    Details
    Publication Date: 2019-09-13
    Type: Book chapter , PeerReviewed
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  • 7
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    Export production in the Bay of Biscay as estimated from barium – barite in settling material: a comparison with new production (2000)
    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 47 (4). pp. 583-601.
    Details
    Publication Date: 2020-08-05
    Description: We present barium data for sediment traps deployed in a northeast Atlantic margin environment (Bay of Biscay). Fluxes of excess barium were measured with the objective of calculating carbon export production rates from the surface mixed layer and thus contribute to the understanding of organic carbon transport in a margin environment. Therefore, it was necessary to properly understand the different processes that affected the barium fluxes in this margin environment. Seasonal variability of POC/Ba flux ratios and decrease of barium solubilisation in the trap cups with increasing depth in the water column probably indicate that the efficiency of barite formation in the organic micro-environment varies with season and that the process is relatively slow and not yet completed in the upper 600 m of water column. Thus barite presence in biogenic aggregates will significantly depend on water column transit time of these aggregates. Furthermore, it was observed that significant lateral input of excess-Ba can occur, probably associated with residual currents leaving the margin. This advected excess-Ba affected especially the recorded fluxes in the deeper traps (〉1000 m) of the outer slope region. We have attempted to correct for this advected excess-Ba component, using Th (reported by others for the same samples) as an indicator of enhanced lateral flux and assigning a characteristic Ba/Th ratio to advected material. Using transfer functions relating excess-Ba flux with export production characteristic of margin areas, observed Ba fluxes indicate an export production between 7 and 18 g C m−2 yr−1. Such values are 3–7 times lower than estimates based on N-nutrient uptake and nutrient mass balances, but larger and more realistic than is obtained when a transfer function characteristic of open ocean systems is applied. The discrepancy between export production estimates based on excess-Ba fluxes and nutrient uptake could be resolved if part of the carbon is exported as dissolved organic matter. Results suggest that margin systems function differently from open ocean systems, and therefore Ba-proxy rationales developed for open ocean sites might not be applicable in margin areas.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0967-0637(99)00072-2
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  • 8
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    Spatial and temporal variability of particle flux at the N.W. European continental margin (2001)
    Elsevier
    In:  Deep Sea Research Part II: Topical Studies in Oceanography, 48 (14-15) . pp. 3083-3106.
    Details
    Publication Date: 2020-08-05
    Description: A synopsis of results from two sediment trap moorings deployed at the mid- and outer slope (water depths 1450 and 3660 m, respectively) of the Goban Spur (N.E. Atlantic Margin) is presented. Fluxes increase with trap deployment depth; below 1000 m resuspended and advected material contributes increasingly to bulk flux. Fluxes of dry weight, POC and diatoms in the traps 400 m above bottom (mab) are smaller than those recorded at the sediment surface due to lateral fluxes in the benthic nepheloid layer. These near-bottom fluxes are larger at shallower water depths. 231Pa/230Th ratios in sedimenting material suggest that boundary scavenging is not significant at the Goban Spur. Fluxes of 210Pb in the intermediate and deep traps are comparable to the 210Pb supply rate at this site. At the outer slope, sediment 210Pb fluxes are similar to those measured in the traps 400 mab; at the mid-slope they are a factor of 2 higher, once again indicating large near-bottom lateral particle input. Based on POC-normalised biomarkers in sedimenting material, we followed changes in the quality of sedimenting material with differing trap depth and on seasonal and event-related time scales. In spring fresh, diatom-dominated sedimentation occurs, with progressive degradation of POC with time (to winter) and depth (from 600 to 3220 m). Deeper traps are distinguished on the basis of opal and aluminium fluxes that are dominant in lateral input. A storm event during late September 1993 was clearly reflected in the δ15N isotope ratio of sedimenting material, with a time lag of 2–3 weeks. Diatom and opal fluxes were elevated in this storm-related signal, and its biomarker composition in the 600-m trap was similar to that during spring. An estimate made of upward nitrate flux (new production) at the shelf break and at the outer slope indicated a 2-fold higher new (export) production at the shelf break. Particulate organic carbon export from the shelf break to below the depth of maximal seasonal mixing ranges between 3 and 9% of primary production.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0967-0645(01)00033-9
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  • 9
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    Distribution, composition and flux of particulate material over the European margin at 47°-50°N (2001)
    Pergamon Press
    In:  Deep Sea Research Part II: Topical Studies in Oceanography, 48 (14-15) . pp. 3107-3139.
    Details
    Publication Date: 2020-08-05
    Description: In the framework of the Ocean Margin Exchange project, a multi-disciplinary study has been conducted at the shelf edge and slope of the Goban Spur in order to determine the spatial distribution, quantity and quality of particle flux, and delineate the transport mechanisms of the major organic and inorganic components. We present here a synthesis view of the major transport modes of both biogenic and lithogenic material being delivered to the open slope of the Goban Spur. We attempt to differentiate between the direct biogenic flux from the surface mixed layer and the advective component, both biogenic and lithogenic. Long-term moorings, instrumented with sediment traps, current meters and transmissometers have yielded samples and near-continuous recordings of hydrographic variables (current direction and speed, temperature and salinity) and light transmission for a period of 2.5 years. Numerous stations have been occupied for CTD casts with light transmission and collection of water samples. The sedimenting material has been analysed for a variety of marker compounds including phytoplankton pigments, isotopic, biomineral and trace metal composition and microscopical analyses. These samples are augmented by seasonal information on the distribution and composition of fine particles and marine snow in the water column. The slope shows well-developed bottom nepheloid layers always present and intermediate nepheloid layers intermittently present. Concentrations are mainly in the range 50–130 mg m−3 in nepheloid layers and 6–25 mg m−3 in clear water. A seasonal variability in the concentration at the clear water minimum is argued to be related to seasonal variations in vertical flux and aggregate break-up in transit during summer months. It is suggested that the winter sink for this seasonal change in particulate matter involves some re-aggregation and scavenging, and some conversion of particulate to dissolved organic matter. This may provide a slow seasonal pump of dissolved organic carbon to the deep ocean interior. Differences in trapped quantities at different water depths are interpreted as due to lateral flux from the continental margin. There is a major lateral input between 600 and 1050 m at an inner station and between 600 and 1440 m at an outer one. The transport is thought to be related to intermediate nepheloid layers, but those measured are too dilute to be able to supply the flux. Observed bottom nepheloid layers are highly concentrated very close to the bed (up to 5 g m−3), with a population of large aggregates. Some of these are capable of delivering the flux seen offshore during intermittent detachment of nepheloid layers into mid-water. Concentrated bottom nepheloid layers are also able to deliver large particles with unstable phytoplankton pigments to the deep sea floor in a few tens of days. Calculated CaCO3 fluxes are adjusted for dissolution, which is inferred from Ca/Al ratios to be occurring in the CaCO3-saturated upper water column where up to 80% of the CaCO3 resulting from primary production is dissolved.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0967-0645(01)00034-0
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Basin-wide particulate carbon flux in the Atlantic Ocean: regional export patterns and potential for atmospheric CO2 sequestration (2001)
    AGU (American Geophysical Union)
    In:  Global Biogeochemical Cycles, 15 (4). pp. 845-862.
    Details
    Publication Date: 2018-03-15
    Description: Particle flux data from 27 sites in the Atlantic Ocean have been compiled in order to determine regional variations in the strength and efficiency of the biological pump and to quantify carbon fluxes over the ocean basin, thus estimating the potential oceanic sequestration of atmospheric CO2. An algorithm is derived relating annual particulate organic carbon (POC) flux to primary production and depth that yields variations in the export ratio (ER = POC flux/primary production) at 125 m of between 0.08 and 0.38 over the range of production from 50 to 400 g C m−2 yr−1. Significant regional differences in changes of the export ratio with depth are related to the temporal stability of flux. Sites with more pulsed export have higher export ratios at 125 m but show more rapid decreases of POC flux with depth, resulting in little geographic variation in fluxes below ∼3000 m. The opposing effects of organic carbon production and calcification on ΔpCO2 of surface seawater are considered to calculate an “effective carbon flux” at the depth of the euphotic zone and at the base of the winter mixed layer. POC flux at the base of the euphotic zone integrated over the Atlantic Ocean between 65°N and 65°S amounts to 3.14 Gt C yr−1. Of this, 5.7% is remineralized above the winter mixed layer and thus does not contribute to CO2 sequestration on climatically relevant timescales. The effective carbon flux, termed Jeff, amounts to 2.47 Gt C yr−1 and is a measure of the potential sequestration of atmospheric CO2 for the area considered. A shift in the composition of sedimenting particles (seen in a decrease of the opal:carbonate ratio) is seen across the entire North Atlantic, indicating a basin-wide phenomenon that may be related to large-scale changes in climatic forcing.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2000GB001376
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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