ALBERT

Description: The eastern Pacific benthic foraminifer Nonionella stella Cushman & Moyer, 1930 was recorded for the first time in the Skagerrak (North Sea) and its fjords. In this short note we evaluate its migration, considering both dispersal by propagules and ship ballast tanks. We suggest that the predominantly southward surface currents along the western European seaboard and Morocco would impede a wide-range dispersal of N. stella propagules and hypothesize transportation by ship ballast tanks as the possible vector of N. stella immigration into northern European seas.

Description: Highlights • Review of sediment archives from the Peruvian margin since the LGM. • Focus on the evolutionary feature of the hiatus found in archives. • Modern analogue for current-dominated environments for paleo reconstructions. • New results for erosional potential of the non-linear internal waves (NLIWs). Abstract The Peruvian continental margin is characterized by the presence of one of the strongest and most distinct Oxygen Minimum Zones (OMZs) in today's oceans. Therefore, it has long been in the focus of oceanographic and geological investigations. Observations indicate that OMZs are expanding in relation with currently changing climate. To advance understanding of the temporal evolution of OMZs and climate change, complete paleoceanographic and palaeoclimatological reconstructions are needed. However, the development of paleoenvironmental scenarios for the period since the Last Glacial Maximum at this region was hampered by a ubiquitous hiatus and short-term interruptions of the stratigraphical record. In the present study, we combined the stratigraphical information from 31 sediment cores from the Peruvian margin located between 3 and 18°S and water depths of 90 to 1300 m within and below today's OMZ, in order to determine the extent of the hiatus and assess the responsible mechanisms. A widespread unconformity and related erosional features, omission surfaces and phosphorites, were observed in sediment cores from the area south of 7°S, depicting a prograding feature on the continental slope from south to north during the deglaciation. Combining recent oceanographic and sedimentological observations, it is inferred that, tide-topography interaction and resulting non-linear internal waves (NLIWs) shape the slope by erosion, carry sediments upslope or downslope and leave widespread phosphoritic lag sediments, while the Peru Chile Undercurrent (PCUC) transports the resuspended sediments southward causing non-deposition. This exceptional sedimentary regime makes the Peruvian margin a modern analogue for such environments. Overall, our compilation of downcore records showed that enhanced bottom currents due to tide-topography interaction were progressively evolving and affected a wider area with the onset of the last deglaciation. Elevated tidal amplitudes and variability of mid-depth water masses (i.e.; density changes) and hydrodynamics in relation with changing climate were potential reasons of this evolving feature of erosion and reworking. Additionally, erosion and non-deposition was observed widest and even was encountered on the continental shelf during the early Holocene, potentially indicating a strong phase of the PCUC mirroring today's El Niño-like conditions.

Description: Highlights • Foraminiferal species were assigned to ecological groups according to AMBI procedure. • The benthic foraminifera-based Foram-AMBI was calculated using the AMBI formula. • Foram-AMBI was successfully tested on independent data sets. • Foram-AMBI correlates well with Shannon's diversity and TOC in test data sets. • Foram-AMBI reflects a stress gradient caused by increased organic carbon. The present study follows up the FOraminiferal BIo-MOnitoring (FOBIMO) working group's aim to explore methods which will improve the usefulness of benthic foraminifera in environmental monitoring. An internationally well-established marine biotic index, AMBI, commonly applied to assess ecological quality status was adapted for use on benthic foraminifera. As required by the AMBI formula, species were assigned to one of five ecological groups according to their sensitivity/tolerance to conditions along an increasing stress gradient (here increasing organic matter enrichment). For the assignments, we used 19 published data sets on fully marine NE Atlantic and Arctic fjord, continental shelf, and slope assemblages for which total organic carbon (TOC) data were available. Assignments were based on the relative abundance of the different species along associated TOC gradients. Of the 128 assigned species, the majority was assigned to Groups I–III dominating in low to moderately organic enriched environments with a high to good ecological quality status. Groups IV and V, representing strongly organically enriched environments with a moderate to poor ecological quality status, had 1 and 2 species, respectively. The resulting foraminifera-based Foram-AMBI was calculated using the AMBI formula and tested on four independent foraminiferal data sets from the same geographical region. The validation included correlations of the Foram-AMBI with Shannon's diversity (H′log2) as well as with the organic carbon content in the validation data sets. In two validation data sets from the Norwegian Skagerrak coast, a high proportion of the assemblages consisted of assigned species. The results showed a good correlation between the Foram-AMBI and both the TOC and Shannon's diversity H′log2. In two more southern validation data sets all TOC values were low and the abundance of unassigned species was too high for the Foram-AMBI to provide trustworthy results. The Foram-AMBI of the two validation data sets with high abundance of assigned species clearly reflected an increasing organic carbon-induced stress gradient. Hence, this first attempt to apply the AMBI formula on benthic foraminiferal data shows promising results. However, to improve the applicability of Foram-AMBI, there is a need to assign more species by obtaining data from studies along wide organic carbon pressure gradients, particularly from the southern North Sea and southwards.

Description: Alexander Volker Altenbach was born in 1953 in Frankfurt/Main, Germany. Alex attended school in Königstein/Taunus, where he passed his Abitur in 1974. He then studied Geology and Paleontology at Goethe University, Frankfurt. During an internship on an oil rig in Denmark, he first experienced a professional working environment and the adventures of hydrocarbon exploration in the North Sea. For his diploma thesis Alex worked on the stratigraphy and tectonics of the Sierra de Montgai, in the Pyrenees, Spain, under the supervision of Rolf Schroeder, Senckenberg Museum, Frankfurt/M. The subject comprised a genuine geological mapping exercise and biostratigraphic dating of the exposed formations. Stratigraphic ages were determined with the Mesozoic orbitoids and planktonic foraminifera in thin sections. Alex shared the long travels to Spain with his two companions Hans-Joachim Wallrabe-Adams (aka Kolli) and Peter Brinnel, enjoying an old “concha naranja” Volkswagen van, as well as field work in the spectacular scenery of the Sierra de Montsec, and living the Catalonian lifestyle. As late as 1993, the theme of Alex’s habilitation defense again was the geology of the Sierra de Montsec, for which he had kept his fascination (cf. Wallrabe-Adams et al., 2005). Being challenged by disentangling the complicated tectonic structure of the Sierra de Montgai, Alex learnt Fortran78 to produce a virtual Schmid net on the central university computer, visualizing different deformation styles of the different tectonic units. His early professional computer programming probably gave rise to his later endeavor in computing. Attracted by the developments in Marine Geosciences at Kiel University during the early 1980s, Alex joined the Micropaleontology Group of Gerhard Friedrich Lutze, and commenced …

Description: The distribution and microhabitat of living benthic fora- minifera (15 calcareous and 6 agglutinated) have been studied in two box cores from the Tagus Prodelta. Stable oxygen and carbon isotopes were analysed for eight different species from six surface samples from the Tagus Prodelta and Estuary. At the two box core stations, most of the living foraminifera were restricted to the oxygenated top cm of the sediment and generally show a shallow infaunal behavior. Those taxa are e.g. Rectuvigerina phlegeri, Stainforthia fusiformis and species of the genus Bolivina, which is the most abundant genus in the Tagus Prodelta. Infaunal species are found down to 10 cm depth, and some infaunal taxa, e.g. Bulimina marginata, Globobulimina auriculata and Nonionella turgida, inhabit the low oxic or anoxic sediments. The deep infaunal species are suggested to feed selectively, on refractory organic matter or on the bacterial stocks, while the opportunistic shallow infaunal species are believed to feed on fresh phytodetritus or labile organic matter. Our data show that there is a close connection between the concentration of foraminifera and the distribution of organic matter in the area. The highest abundance of living benthic foraminifera was found in sediments close to the Tagus river plume, where the sediments have relatively high organic carbon contents. The spatial distribution of the stable isotope values of different benthic foraminifera reflects the distribution of the low salinity and relatively high temperature water with high organic carbon fluxes within the Tagus Estuary.