1,721,117 research outputs found
Controls on planktonic foraminifera apparent calcification depths for the northern equatorial Indian Ocean
Get PDFWithin the world’s oceans, regionally distinct ecological niches develop due to differences in water temperature, nutrients, food availability, predation and light intensity. This results in differences in the vertical dispersion of planktonic foraminifera on the global scale. Understanding the controls on these modern-day distributions is important when using these organisms for paleoceanographic reconstructions. As such, this study constrains modern depth habitats for the northern equatorial Indian Ocean, for 14 planktonic foraminiferal species (G. ruber, G. elongatus, G. pyramidalis, G. rubescens, T. sacculifer, G. siphonifera, G. glutinata, N. dutertrei, G. bulloides, G. ungulata, P. obliquiloculata, G. menardii, G. hexagonus, G. scitula) using stable isotopic signatures (δ18O and δ13C) and Mg/Ca ratios. We evaluate two aspects of inferred depth habitats: (1) the significance of the apparent calcification depth (ACD) calculation method/equations and (2) regional species-specific ACD controls. Through a comparison with five global, (sub)tropical studies we found the choice of applied equation and δ18Osw significant and an important consideration when comparing with the published literature. The ACDs of the surface mixed layer and thermocline species show a tight clustering between 73–109 m water depth coinciding with the deep chlorophyll maximum (DCM). Furthermore, the ACDs for the sub-thermocline species are positioned relative to secondary peaks in the local primary production. We surmise that food source plays a key role in the relative living depths for the majority of the investigated planktonic foraminifera within this oligotrophic environment of the Maldives and elsewhere in the tropical oceans
Hydrography and plankton abundance of horizontal plankton hauls sampled off Northwest Africa (Table 1b)
No full textHydrography and plankton abundance of horizontal plankton hauls sampled off Northwest Africa (Table 1b
Hydrography and plankton abundance of vertical plankton haul profile GIK15658-2, off NW Africa (Table 1c)
No full textHydrography and plankton abundance of vertical plankton haul profile GIK15658-2, off NW Africa (Table 1c
Hydrography and plankton abundance of vertical plankton haul profile GIK15679-2, off NW Africa (Table 1c)
No full textHydrography and plankton abundance of vertical plankton haul profile GIK15666-8, off NW Africa (Table 1c
Stable isotopic measurement on planktonic foraminifera of vertical plankton haul samples GIK15666-8, off NW Africa (Table 1d)
No full textStable isotopic measurement on planktonic foraminifera of vertical plankton haul samples GIK15679-2, off NW Africa (Table 1d
Stable isotopic measurements on planktonic foraminifera of plankton haul samples off Northwest Africa (Table 1d)
No full textStable isotopic measurements on planktonic foraminifera of plankton haul samples off Northwest Africa (Table 1d
Die spätquartäre pelagische Aragoniterhaltung im Arabischen Meer und ihre paläozeanographischen Auswirkungen
No full textIn the course of the Quaternary the carbon dioxide concentrations of the atmosphere showed large fluctuations related to the oceanic carbon cycle and carbonate system. The production, accumulation, and dissolution of pelagic aragonite constitutes a considerable part of the oceanic carbonate system. Variations in water mass properties, atmospheric and oceanic circulation, which lead to changes in bioproductivity in the upwelling areas influence the preservation of aragonite and therefore the preservation of pteropod shells. This project is concerned with Late Quaternary preservation of pteropods in sediments of the Arabian Sea. To this purpose 15 surface sediment samples and two high resolution sediment cores from the Arabian Sea have been analysed by means of the pteropod shell preservation index LDX (Limacina inflata dissolution index, Gerhard and Henrich, 2001) in respect to the aragonite preservation state. One objective was to test and apply the newly developed LDX on sediments from the Arabian Sea and to trace spatial and temporal variations in pteropod preservation
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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