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Foraminifera census counts at salt-marsch archive GeoHH-FK (Friedrichskoog, south-eastern North Sea)
No full textHere we have evaluated and compared two benthic foraminiferal records derived from sedimentary salt-marsh archives from the south-eastern North Sea coast, covering the past ~100 years. The particular focus was on the agglutinated benthic salt-marsh foraminifera Entzia macrescens, finding a rising number of deformed tests at times of strengthened North Sea storminess and associated more frequent salt-marsh flooding between the mid-century and late 1980s. The study is based on sediment sequences GeoHH-FK (Friedrichskoog, Dithmarschen) and TB13-1 (Bay of Tümlau, Eiderstedt Peninsula; Müller-Navarra et al., 2019; doi:10.1016/j.ecss.2018.12.022) that were retrieved from the salt marshes' erosional cliffs in November 2016 and August 2013. Sediment sequence GeoHH-FK was sampled at 0.5 cm spacing, with every second sample considered for benthic foraminiferal analysis, resulting in a total of 116 samples. All samples were wet-sieved for the 63–500 µm sediment fraction and benthic foraminiferal analysis was based on allocate splits in order to obtain approximately 100 individuals per split. Subsequent taxonomical identification was carried out on the wet sediment samples. Normal and irregular tests of E. macrescens were distinguished and counted separately. The benthic foraminiferal record of TB13-1 was provided by Müller-Navarra et al. (2019; doi:10.1016/j.ecss.2018.12.022). As benthic foraminifera are very sensitive to environmental changes, the consideration of deformed tests of the salt-marsh indicator species E. macrescens allowed for the evaluation of the salt marshes' vulnerability to changing climate conditions, in dependence on the degree of their modification by human interventions
Seasonal, diel and vertical distribution of zooplankton in Comau Fjord, Chilean Patagonia
No full textSeasonal, diel and vertical distribution of mesozooplankton was described over the entire water column of Comau Fjord, northern Chilean Patagonia. Stratified vertical hauls we taken with a Nansen net (100 μm mesh) between the surface and the bottom (0-50-100-200-300-400-450 m) in spring, summer, autumn and winter. Samples were scanned with a ZooScan, and abundance, biovolume and biomass were determined for 41 taxa identified on the web-based platform EcoTaxa 2.0. This dataset was generated in the frame of the co-operation between the Universidad Austral de Chile (https://www.uach.cl), the Huinay Scientific Field Station (http://www.huinay.cl) and the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (http://www.awi.de) in the frame of the project PACOC Plankton- And cold-water COral ecology in Comau Fjord, Chile. The study was also embedded in activities of the Research Center Dynamics of High Latitude Marine Ecosystems (IDEAL) (http://www.centroideal.cl/eng/)
Global compilation of the first occurrence of Gephyrocapsa huxleyi and other Gephyrocapsa species from sediment core samples
No full textThe data compilation includes the first occurrence of G. huxleyi and other species of Gephyrocapsa as revealed by Quaternary sediment samples from the world oceans. This new synthesis includes previously published data, all with rigorous relationships of their emergence events with marine isotope stages based on good quality oxygen isotope stratigraphy and/or astronomical tuning from each sediment core
Strong local, not global, controls on marine pyrite sulfur isotopes
No full textUnderstanding variation in the sulfur isotopic composition of sedimentary pyrite (δ34Spyr) is motivated by the key role of sulfur biogeochemistry in regulating Earth's surface oxidation state. Until recently, the impact of local depositional conditions on δ34Spyr has remained underappreciated, and stratigraphic variations in δ34Spyr were interpreted mostly to reflect global changes in biogeochemical cycling. We present two coeval δ34Spyr records from shelf and basin settings in a single sedimentary system. Despite their proximity and contemporaneous deposition, these two records preserve radically different geochemical signals. Swings of ~65‰ in shelf δ34Spyr track short-term variations in local sedimentation and are completely absent from the abyssal record. In contrast, a long-term ~30‰ decrease in abyssal δ34Spyr reflects regional changes in ocean circulation and/or sustained pyrite formation. These results highlight strong local controls on δ34Spyr, calling for reevaluation of the current practice of using δ34Spyr stratigraphic variations to infer global changes in Earth's surface environment
