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Natural ocean alkalinization through erosion of glacial till and weathering at the seafloor: coastal cliff

Climate change-driven deglaciation and erosion in high-latitude regions enhance the flux of terrigenous material to the coastal ocean. Newly exposed land surfaces left behind by retreating glaciers are covered by glacial till, which is rich in fine-grained minerals. Many of these minerals are undersaturated in seawater and thus prone to dissolution (i.e., seafloor weathering). Consequently, intensified erosion and mineral weathering may act as an additional CO₂ sink while supplying alkalinity to coastal waters. To evaluate this hypothesis, we carried out a sediment geochemical study in the southwestern Baltic Sea, where coastal erosion of glacial till is the dominant source of terrigenous material to offshore depocenters. We analyzed glacial till from coastal cliffs, sediments, and pore waters for major element composition using inductively coupled plasma optical emission spectroscopy and an elemental analyzer. Water samples were further analyzed for dissolved redox species and dissolved silica by photometry and ion chromatography. These data were then used to quantify mineral dissolution and precipitation processes and to assess their net effect on inorganic carbon cycling.

Forschergruppe (FOR) 1525: INUIT - Ice Nuclei research UnIT, Heterogende Eisnukleation ausgelöst durch poröse Materialien

Die Nukleation von Eispartikeln spielt eine wichtige Rolle bei der Wolken- und Niederschlagsbildung, mit Konsequenten für die atmosphärische Chemie, die Wolkenphysik und das Erdklima. Für eine Quantifizierung und Vorhersage des Einflusses von Wolken in Wettervorhersage- und Klimamodellen muss die Bildung von Eispartikeln daher in einer realistischen Art und Weise beschrieben werden. Einer der wichtigen Bildungsmechanismen ist dabei die heterogene Eisnukleation im Immersionsmodus, bei dem Eis an der Oberfläche eines in einem wässrigen Tröpfchen suspendierten Eiskeims - zum Beispiel eines Mineralstaub- Partikels - gebildet wird. Wir werden im Rahmen dieses Forschungsprojekts zahlreiche Gefrierexperimente im Immersionsmodus durchführen. So werden eine Reihe verschiedener, als Aerosolpartikel in der Atmosphäre vorkommende Materialien auf ihre Eisnukleationseigenschaften hin untersucht werden. Insbesondere sollen hier die Temperatur- und Zeitabhängigkeit der von diesen Materialien ausgelösten Eisnukleation quantifiziert werden. Dabei werden wir spezielles Augenmerk auf die systematische Untersuchung der von porösen Materialien ausgelösten Eisnukleation legen. Es sollen sowohl synthetische Materialien wie beispielsweise mesoporöse Silikate untersucht werden, als auch natürlich vorkommende Materialien wie etwa mikroporöse Zeolithe.

Schwerpunktprogramm (SPP) 1158: Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; Bereich Infrastruktur - Antarktisforschung mit vergleichenden Untersuchungen in arktischen Eisgebieten, Controls on and paleoceanographic utility of the valve size frequency distribution of the Southern Ocean diatom, Fragilariopsis kerguelensis

Unraveling the role of the Southern Ocean's biological pump in regulating climate would be enhanced by the development of paleoceanographic proxies specific to carbon or silica cycling. Observations that the average size of valves of the diatom, Fragilariopsis kerguelensis, varies seasonally, with latitude, and over glacial-interglacial cycles in the Southern Ocean suggest that the valve size frequency distribution in sediments could be used to reconstruct aspects of paleoproductivity and silica cycling. We aim to develop this proxy by using culture, field and sediment samples to determine the exact controls on valve size frequency distributions, the most important of which is likely to be the frequency of auxospore formation within the population. The controls on auxospore formation are as yet unknown and both mating experiments in culture as well as in situ iron fertilization experiments are likely to unravel the mechanisms determining auxospore formation under both controlled and field conditions. The valve size frequency distribution can then be used to indicate the intensity of the environmental and/or biological conditions triggering auxospore formation.

KOSMOS 2023 Helgoland mesocosm study on ocean alkalinity enhancement: sediment trap particle flux data and water column biogeochemistry

The data presented herein originates from a mesocosm study conducted as part of the BMBF CDRmare, Retake project (grant agreement no. 03F0895A), aimed at investigating the ecological ramifications of ocean alkalinity enhancement (OAE). Twelve mesocosms were deployed in Helgoland South Harbor, Germany, and systematically sampled using integrated water samplers over the period spanning from March 12th to April 20th, 2023. Six alkalinity levels under two dilution scenarios were established to differentiate between localized and uniform OAE additions. Alkalinity was increased stepwise to ΔTAmax = 1250 μmol kg-1 (250 μmol TA kg-1 increments) using sodium hydroxide (NaOH) with calcium chloride (CaCl2) to simulate cation release during calcium-based mineral dissolution, causing strong carbonate chemistry perturbations (e.g., pHT > 9.25). The dataset encompasses a spectrum of sediment trap particle flux data, water column biogeochemistry including pigment variables, inorganic nutrients, carbonate chemistry parameters. The study and data set offer insights into impacts of alkalinity enhancement on marine ecosystems and their associated biogeochemistry.

Seawater carbonate chemistry and mass fluxes and elemental composition of particulate export in KOSMOS mesocosm experiments (2010-2014)

Diatoms account for up to 40% of marine primary production and require silicic acid to grow and build their opal shell. On the physiological and ecological level, diatoms are thought to be resistant to, or even benefit from, ocean acidification. Yet, global-scale responses and implications for biogeochemical cycles in the future ocean remain largely unknown. Here we conducted five in situ mesocosm experiments with natural plankton communities in different biomes and find that ocean acidification increases the elemental ratio of silicon (Si) to nitrogen (N) of sinking biogenic matter by 17 ± 6 per cent under pCO2 conditions projected for the year 2100. This shift in Si:N seems to be caused by slower chemical dissolution of silica at decreasing seawater pH. We test this finding with global sediment trap data, which confirm a widespread influence of pH on Si:N in the oceanic water column. Earth system model simulations show that a future pH-driven decrease in silica dissolution of sinking material reduces the availability of silicic acid in the surface ocean, triggering a global decline of diatoms by 13–26 per cent due to ocean acidification by the year 2200. This outcome contrasts sharply with the conclusions of previous experimental studies, thereby illustrating how our current understanding of biological impacts of ocean change can be considerably altered at the global scale through unexpected feedback mechanisms in the Earth system.

Mesocosm experiment on the influence of heatwave on plankton

In the context of global change, marine organisms are subjected not only to gradual changes in abiotic parameters, but also to an increasing number of extreme events, such as heatwaves. However, we still know little about the influence of heatwaves on the structure of marine communities, and experimental studies are needed to test the impact of heatwaves alone, and in combination with other environmental drivers. Here, we conducted a mesocosm experiment and applied an integrated multiple driver design to assess the potential impact of heatwaves under ambient and future environmental conditions on natural coastal plankton communities. To represent future environmental conditions, temperature and pH were manipulated based on the Representative Concentration Pathway 8.5 proposed by the IPCC for 2100, and dissolved N:P ratios were increased to simulate the conditions expected in European coastal zones. Throughout the experiment, we measured abiotic conditions as well as the abundance of bacterioplankton, phytoplankton, and microzooplankton.

Physical and chemical parameters of sediment core SAC05 from Sacrower See (NE Germany) provide a robust reconstruction of climate change and human impact since 13,000 cal. BP

The 11.8 m-long composite sediment record from the hardwater lake of Sacrower See, located near the city of Potsdam (north-eastern Germany), has been characterised by a range of analytical techniques. These include magnetic susceptibility, chemical parameters (XRF core scanning, CNS analysis, biogenic silica) and stable isotopes (13C, 15N). The chronology covers the entire Holocene and the concluding Lateglacial (Alleröd, Younger Dryas) and is based on age-depth modelling using radiocarbon dates refined by the onset of the local varve chronology in 1870 CE (Lüder et al., 2006) and by the Laacher See Tephra, an isochrone dated to 13,000 cal. BP. It offers a detailed environmental reconstruction providing insights into depositional processes influenced by both natural climatic variations and human activities (Enters et al., 2009; Kirilova et al., 2009). The Lateglacial and Early Holocene are distinguished by the stabilisation of natural landscapes characterised by the presence of pine-birch (Alleröd) and mixed oak forests (Early Holocene). This development was interrupted by the climatic deterioration of the Younger Dryas, which resulted in a destabilisation of vegetation and increased natural soil erosion. It is evident that, for the first time around 5500 cal. BP, anthropogenic forest clearing became a factor, which subsequently led to increasing cultural soil erosion further accelerating during the Bronze Age (3600-3200 cal. BP), the Early Iron Age (2800-2600 cal. BP) and the Middle Ages (900-600 cal. BP). In the course of industrialisation since the 19th century, human impact underwent a transition from the destabilisation of soils to the phenomenon of eutrophication. This transition resulted in the occurrence of hypolimnetic anoxia, accompanied by the formation of carbonaceous varves.

Updated global compilation of coccolithophore calcification measurements from unperturbed water samples including ancillary data

This database expands the Poulton et al., 2018 (doi:10.1594/PANGAEA.888182) database of pelagic calcium carbonate (CP) rate measurements from isotopic tracer uptake in incubated discrete water samples, as discussed in Daniels et al., 2018 (doi:10.5194/essd-10-1859-2018), and accompanies Marsh et al. (in prep.). The database now includes more CP (new data n = 400; complete database n = 3165), net primary production rate (PP) (new data n = 399; complete database n = 3150), total coccolithophore cell counts (new data n = 240; complete database n = 1512), and Emiliania huxleyi cell counts (new data n = 27; complete database n = 612). This expanded database maintains the record of data, including the principal investigator, expedition, OS region, doi reference (where available), collection date and year, sample ID, latitude, longitude, sampling and light depth, and method of measuring CP. We further expand the Poulton et al. (2018) data collection by including ancillary and environmental data, including: optical depth (OD, n = 3165), pHtotal (hereinafter referred to as pHT, n = 398), temperature (n = 1160), salinity (n = 1161), and the concentrations of chlorophyll a (n = 1363), NOx (NO3 or the sum of NO3 + NO2, n = 1161), silicic acid (Si(OH)4, n= 1156), phosphate (PO4, n = 1232), dissolved inorganic carbon (DIC, n = 318), total alkalinity (TA, n = 307), bicarbonate ion concentration (n = 349), and carbonate ion concentration (n = 352). All data was matched to CP, sample bottle identifiers (Niskin bottle numbers), and/or sampling depth values. This global database (81 °N - 64 °S, 132 °E - 174 °W) now covers expeditions and upper ocean measurements (0 - 193 m) from 1989 to 2024. Global in-situ geolocated data spanning time is valuable for modelling, satellite algorithms, and capturing calcium carbonate production in the global ocean. This expanded database, including the environmental, nutrient, chlorophyll a, and carbonate chemistry data, also allows for analysis of factors influencing calcium carbonate production on a global scale. This data amalgamation contributes to understanding the biogeochemistry of the oceans, global carbon cycle, and ocean acidification.

Elementkarte der Digitalen Lithogeochemischen Karte von Bayern 1:25.000 (dLGK25) - Siliziumdioxid (P90)

Die Elementkarte stellt die räumliche Verteilung der klassifizierten Gehalte des 90. Perzentils von Siliziumdioxid (in Gew.-%) innerhalb der 184 geochemischen Gesteinseinheiten in Bayern dar. In die Auswertung gehen dabei nur die Daten der ersten (von maximal drei) Lithologien einer geochemischen Gesteinseinheit ein. Für Informationen im Hinblick auf die Auswertung der Daten sowie auf die kartenmäßige Darstellung wird auf die Metadaten der digitalen Lithogeochemischen Karte 1:25 000 von Bayern (dLGK25) verwiesen.

Elementkarte der Digitalen Lithogeochemischen Karte von Bayern 1:25.000 (dLGK25) - Siliziumdioxid (P50)

Die Elementkarte stellt die räumliche Verteilung der klassifizierten Gehalte des 50. Perzentils von Siliziumdioxid (in Gew.-%) innerhalb der 184 geochemischen Gesteinseinheiten in Bayern dar. In die Auswertung gehen dabei nur die Daten der ersten (von maximal drei) Lithologien einer geochemischen Gesteinseinheit ein. Für Informationen im Hinblick auf die Auswertung der Daten sowie auf die kartenmäßige Darstellung wird auf die Metadaten der digitalen Lithogeochemischen Karte 1:25 000 von Bayern (dLGK25) verwiesen.

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