ALBERT

Description: Benthic foraminifera from Bottsand coastal lagoon, western Baltic Sea, have been studied since the mid-1960s. They were monitored annually in late autumn since 2003 at the terminal ditch of the lagoon. There were 12 different species recognised, of which three have not been recorded during earlier investigations. Dominant species showed strong interannual fluctuations and a steady increase in population densities over the last decade. Elphidium incertum, a stenohaline species of the Baltic deep water fauna, colonised the Bottsand lagoon in 2016, most likely during a period of salinities 〉19 units and water temperatures of 18 °C on average in early autumn. The high salinities probably triggered their germination from a propagule bank in the ditch bottom sediment. The new E. incertum population showed densities higher by an order of magnitude than those of the indigenous species. The latter did not decline, revealing that E. incertum used another food source or occupied a different microhabitat. Elphidium incertum survived transient periods of lower salinities in late autumn 2017, though with reduced abundances, and became a regular faunal constituent at the Bottsand lagoon.

Description: The quantitative reconstruction of past seawater salinity has yet to be achieved and the search for a direct and independent salinity proxy is ongoing. Recent culture and field studies show a significant positive correlation of Na/Ca with salinity in benthic and planktonic foraminiferal calcite. For accurate paleoceanographic reconstructions, consistent and reliable calibrations are necessary, which are still missing. In order to assess the reliability of foraminiferal Na/Ca as a direct proxy for seawater salinity, this study presents electron microprobe Na/Ca data, measured on cultured specimens of Trilobatus sacculifer. The culture experiments were conducted over a wide salinity range of 26 to 45, while temperature was kept constant. To further understand potential controlling factors of Na incorporation, measurements were also performed on foraminifera cultured at various temperatures in the range of 19.5 °C to 29.5 °C under constant salinity conditions. Foraminiferal Na/Ca ratios positively correlate with seawater salinity (Na/Caforam = 0.97 + 0.115 ⋅ Salinity, R = 0.97, p 〈 0.005). Temperature on the other hand exhibits no statistically significant relationship with Na/Ca ratios indicating salinity to be the dominant factor controlling Na incorporation. The culturing results are corroborated by measurements on T. sacculifer from Caribbean and Gulf of Guinea surface sediments. In conclusion, planktonic foraminiferal Na/Ca can be applied as a reliable proxy for reconstructing sea surface salinities, albeit species-specific calibrations might be necessary.

Description: Past ocean temperatures and salinities can be approximated from combined stable oxygen isotopes (δ18O) and Mg ∕ Ca measurements in fossil foraminiferal tests with varying success. To further refine this approach, we collected living planktic foraminifers by net sampling and pumping of sea surface water from the Caribbean Sea, the eastern Gulf of Mexico and the Florida Straits. Analyses of δ18O and Mg ∕ Ca in eight living planktic species (Globigerinoides sacculifer, Orbulina universa, Neogloboquadrina dutertrei, Pulleniatina obliquiloculata, Globorotalia menardii, Globorotalia ungulata, Globorotalia truncatulinoides and Globorotalia tumida) were compared to measured in situ properties of the ambient seawater (temperature, salinity and δ18Oseawater) and fossil tests of underlying surface sediments. “Vital effects” such as symbiont activity and test growth cause δ18O disequilibria with respect to the ambient seawater and a large scatter in foraminiferal Mg ∕ Ca. Overall, ocean temperature is the most prominent environmental influence on δ18Ocalcite and Mg ∕ Ca. Enrichment of the heavier 18O isotope in living specimens below the mixed layer and in fossil tests is clearly related to lowered in situ temperatures and gametogenic calcification. Mg ∕ Ca-based temperature estimates of G. sacculifer indicate seasonal maximum accumulation rates on the seafloor in early spring (March) at Caribbean stations and later in the year (May) in the Florida Straits, related to the respective mixed layer temperatures of ∼26 ∘C. Notably, G. sacculifer reveals a weak positive linear relationship between foraminiferal derived δ18Oseawater estimates and both measured in situ δ18Oseawater and salinity. Our results affirm the applicability of existing δ18O and Mg ∕ Ca calibrations for the reconstruction of past ocean temperatures and δ18Oseawater reflecting salinity due to the convincing accordance of proxy data in both living and fossil foraminifers, and in situ environmental parameters. Large vital effects and seasonally varying proxy signals, however, need to be taken into account.

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: Während des Spätpleistozäns und Holozäns werden auf der langgestreckten Sulu-See Tiefsee-Ebene Turbidite mit einer Häufigkeit von 3 bis 94 Ereignissen pro 1000 Jahre im Wechsel mit hemipelagischem Sediment abgelagert. Eine Tephralage und isotopenstratigraphische Untersuchungen ermöglichten es, 10 untersuchte Kolbenlotkerne zu korrelieren und in fünf bis ins letzte Hochglazial reichende Zeitscheiben zu gliedern. Entsprechend dem Gefüge der Basislagen der terrigenen Turbidite können im nördlichen Teil der Tiefsee-Ebene proximale und im Süden distale Ablagerungsbereiche unterschieden weren. Die Turbidithäufigkeiten bleiben bis ins Spätpleistozän konstant, nehmen jedoch regional von 94 Turbiditen/1000 Jahre im Norden auf 11 Turbidite/1000 Jahre im Südteil der Tiefsee-Ebene ab. Dieser Gradient und die Gefügemerkmale zeigen, daß die meisten Turbiditströme die Tiefsee-Ebene durch den sich nördlich anschließenden Panay-Canyon erreichen. Von allen berücksichtigten Faktoren ist der taifuninduzierte Einstrom dichterer Wassermassen aus dem Südchinesischen Meer durch die Mindoro-Straße und den Panay-Canyon der wahrscheinlichste Auslöser für hochfrequente terrigene Turbiditströme. A narrow deep-sea abyssal plain is situated in the deepest part of the south-eastern Sulu Sea subbasin. The trench sediments which were recovered with piston cores during RV Sonne cruises SO 49 and SO 58 comprise numerous Late Pleistocene to Holocene turbidites with intercalated hemipelagic mud layers. While a proximal turbidite facies is recognized only in the northern trench, distal terrigenous turbidites are frequent in the whole basin. The occurrence of calcareous turbidites is restricted, however, to the southern trench. Although terrigenous turbidite frequencies remain rather constant over the past 22,000 years, they show a decrease from 94 in the northern trench to 11 turbidites/ka in the southern part of the basin. This gradient points to the Panay Canyon north of the trench as the main source for terrigenous turbidites. Features of erosion and gravity-driven downslope-transport are observed on the Panay Canyon floor. From all factors considered, typhoon-induced water inflow from the South China Sea through the Mindoro Strait seems to be the most important trigger mechanism for the frequent release of terrigenous turbiditic flows passing through the Panay Canyon to the Sulu Sea abyssal plain.

Description: In der Schreibkreide von Helgoland (NW-Deutschland) wurden leitende Foraminiferenarten an einer Profiltraverse im Seegebiet südwestlich der Insel (Görtel) untersucht. Die Kenntnis der Lagerungsverhältnisse der Kreideschichten und der genauen Probenpositionen erlaubte unter Berücksichtigung der Bathymetrie die Konstruktion eines synthetischen Prof1les für die höhere Oberkreide (Unter-Coniac bis Ober-Santon) und die Festlegung der stratigraphischen Lage für die einzelnen Proben. Eine Aufstellung der Vertikalreichweiten leitender Arten führte zur Untergliederung in sechs Foraminiferen-Zonen, die bereits im Schreibkreide-Richtprofil von Lägerdarf/Holstein an der Makroinvertebraten-Gliederung geeicht wurden. Stark reduzierte Mächtigkeiten im Unter-Santon und aufgearbeitete Gehäuse von Stensioeina granulata polonica WITWICKA im Ober-Santonweisen in Verbindung mit Grobkreidelagen im Coniac und Ober-Santon auf wiederholte Erosionsphasen hin.

Description: The long-term climate cooling during Campanian - Maastrichtian times is not well understood to date, especially because of the uncertainty introduced by low temporal resolution of biostratigraphy and the pronounced provincialism between tropical and temperate taxa. Two new high-resolution carbon isotope records derived from the boreal shelf-sea section at Lägerdorf-Kronsmoor-Hemmoor, northern Germany and the tropical Pacific at Deep Sea Drilling Project Site 305, Shatsky Rise, reduce these uncertainties. The records can be correlated with an accuracy not achieved by biostratigraphic methods so far. Distinct carbon isotope events in the late Campanian and the early Maastrichtian can be identified at both localities suggesting to represent global carbon cycle perturbations. Especially, the negative carbon isotope excursion in the early Maastrichtian, a pronounced feature of open-ocean records from the Pacific and Southern oceans, is recognized for the first time at a shelf-sea locality related to the North Atlantic Ocean. Furthermore, two short-term positive excursions are identified as superimposed signals to this event. The improved stratigraphy provides the unique opportunity to recognize leads and lags between the carbon cycle and ocean circulation of different marine settings and ecosystems, leading to a better understanding of their causes and effects.