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Simulated density reorganization on the Weddell Sea continental shelf sensitive to atmospheric forcing
No full textThe strong Antarctic Slope Front in the southern Weddell Sea limits the present-day transport of modified Warm Deep Water (mWDW) onto the continental shelf and is associated with a characteristic V-shape in the density structure across the continental slope. The mechanisms controlling today's V-shape are well studied, but its future development is not yet well constrained. In this study, we run ocean model simulations for a 21st century Shared Socioeconomic Pathways (SSP) 3-7.0 emission scenario. The forcing is retrieved from atmospheric model output from simulations with a global climate model and from a higher-resolved regional atmospheric model respectively. We find that the resolution of the atmospheric model component influences the simulated future transport of mWDW onto the continental shelf into the Filchner Trough in the southern Weddell Sea through differences in the evolution of the depth and symmetry of the V-shape over the 21st century. In both simulations, reduced sea-ice formation and weakened Ekman downwelling reduce the depth of the V-shape and increase the sensitivity of its position above the slope to seasonal variations in sea-ice production and in the wind field. Using forcing data from an atmosphere model with higher resolution leads to an acceleration of the density redistribution on the continental shelf compared to the simulations forced with coarse-resolution data. This indicates that the SSP3-7.0 climate scenario may have a greater potential for a regime shift from a cold to a warm Filchner Trough through a cross-slope current before the end of the 21st century than suggested by other ocean simulations for the same scenario but with lower atmospheric resolution. As cross-slope currents disturb the continuity of the V-shape, we define a spatial grade of connectivity to quantify the lateral integrity of the V-shape along the continental slope. We find that the integrity of the V-shape reduces with a delay of 3 months after a strong cross-slope current of mWDW enters Filchner Trough. Atmospheric downscaling increases the potential for a regime shift, dominated by warmer summer air temperatures. The Antarctic Slope Front is temporarily disturbed by cross-slope currents but the primary reason for the regime shift is the cross-slope density gradient
Littorina ZOBLUC - Zostera als Blue Carbon Speicher Cruise “SeagrassMonitoring_summer_2025”
No full textLittorina June/July 2025
22 June – 1 July 2025, Kiel – Kie
Lessons Learned from the Sea Star Wasting Disease Investigation
No full textMarine invertebrate mass mortality events (MMEs) threaten biodiversity and have the potential to catastrophically alter ecosystem structure. A proximal question around acute MMEs is their etiologies and/or environmental drivers. Establishing a robust cause of mortality is challenging in marine habitats due to the complexity of the interactions among species and the free dispersal of microorganisms from surrounding waters to metazoan microbiomes. The 2013–2014 sea star wasting disease (SSWD) MME in the northeast Pacific Ocean highlights the difficulty in establishing responsible agents. In less than a year of scientific investigation, investigators identified a candidate agent and provided at the time convincing data of pathogenic and transmissible disease. However, later investigation failed to support the initial results, and critical retrospective analyses of experimental procedures and reinterpretation of early findings disbanded any candidate agent. Despite the circuitous path that the investigation and understanding of SSWD have taken, lessons learned from the initial investigation—improving on approaches that led to misinterpretation—have been successfully applied to the 2022 Diadema antillarum investigation. In this review, we outline the history of the initial SSWD investigation, examine how early exploration led to spurious interpretations, summarize the lessons learned, provide recommendations for future work in other systems, and examine potential links between the SSWD event and the Diadema antillarum MME
Warming effects on a nonindigenous predator are not conserved across seasons
No full textThe global proliferation of nonindigenous species remains a critical stressor driving both biodiversity loss and socioeconomic costs. These impacts frequently depend on environmental contexts, but few studies have investigated how seasonal variations coupled with climate changes, like warming, could modulate nonindigenous species ecological impacts. The Japanese brush‐clawed shore crab Hemigrapsus takanoi is a successful nonindigenous species in northern European waters and is currently spreading in the Baltic Sea. In this study, we used generalized linear models and the comparative functional response approach to examine the predatory impact of H. takanoi toward blue mussels Mytilus sp. across four seasons under current and future temperature scenarios (i.e., ambient and + 6°C warming). We further integrated H. takanoi Q 10 values and field abundances across seasons to examine population‐level feeding impacts toward blue mussels. The nonindigenous species exhibited a consistent type II functional response (i.e., inversely prey density‐dependent response) across all seasons, temperatures and sexes, with males consistently consuming more mussels than females across all seasons. Warming generally decreased handling times and increased attack rates, but these effects varied by season and sex, with the most pronounced temperature responses observed in autumn and spring. Population‐level impact calculations integrating field abundance data of H. takanoi indicated that under ambient conditions, feeding impacts toward blue mussels currently peak in the summer months, but as temperature increases, this feeding impact is anticipated to shift later in the year into autumn. These findings underline the critical need for multifaceted research approaches to better understand and predict the context‐dependent ecological impacts of nonindigenous species, particularly in the face of ongoing climate change and shifting population characteristics
The Amazonian mangrove systems accumulate and release dissolved neodymium and hafnium to the oceans
No full textMangroves are essential tropical ecosystems nurturing a wide range of marine biodiversity and counteracting global warming by sequestering atmospheric carbon dioxide. Hence, the export mechanisms and fluxes of particulate and dissolved organic carbon and trace elements from mangroves directly influence coastal productivity, the global carbon cycle and thus global climate, which are, however, not well constrained. Here we find consistent radiogenic neodymium and hafnium isotopic compositions of porewater, sedimentary iron-manganese oxyhydroxides and coastal seawater, suggesting that the Amazonian mangrove belt supplies trace elements through porewater discharge, dissolution of iron-manganese oxyhydroxides and their interactions with seawater. Together, these processes supply 8.4 x 106 g yr-1 dissolved neodymium, equivalent to 64% of the total sources of neodymium to the Amazonian coastal seawater. Globally, mangrove systems along the continental margins contribute 6-9% of the net neodymium input to the ocean, which is similar to the contributions from atmospheric deposition. A contribution of this magnitude is potentially also the case for other trace elements, given the strong correlations between neodymium and iron (Pearson r = 0.92), and manganese (r = 0.75) concentrations across the entire river-ocean section, emphasizing the crucial role of mangrove system inputs in micro-nutrient cycling
Distinct phytoplankton assemblages underlie hotspots of primary production in the eastern North Pacific Ocean
No full textMarine eastern boundary current ecosystems, such as the California Current System (CCS), involve productive, mesotrophic transition zones. The CCS exhibits highly variable primary production (PP), yet factors driving the variability and underlying phytoplankton communities remain poorly understood. We integrated physicochemical and biological data from surface waters sampled during 10 CCS expeditions, spanning 13 yr, and resolved regimes with distinct phytoplankton communities. Additional to an oligotrophic regime (OR), mesotrophic waters beyond the coastal area partitioned into Meso-High and Meso-Low regimes, differing in nitrate concentrations and PP. The OR was dominated by Prochlorococcus High-Light I (HLI), and eukaryotic phytoplankton were largely predatory mixotrophs. Eukaryotes dominated Meso-Low and Meso-High phytoplankton biomass. Within the Meso-Low, Pelagomonas calceolata was important, and Prochlorococcus Low-Light I (LLI) rose in prominence. In the Meso-High, the picoprasinophyte Ostreococcus lucimarinus was abundant, and Synechococcus Clade IV was notable. The Meso-High exhibited the highest PP (38 ± 16 mg C m−3 d−1; p < 0.01) and higher growth rates for photosynthetic eukaryotes (0.84 ± 0.02 d−1) than for Prochlorococcus (0.61 ± 0.01 d−1) and Synechococcus (0.31 ± 0.05 d−1). An experiment simulating seasonal oligotrophic seawater intrusion into the Meso-High resulted in growth rates reaching 1.18 ± 0.10 d−1 (O. lucimarinus), 0.75 ± 0.21 d−1 (Prochlorococcus LLI), and 0.50 ± 0.04 d−1 (Synechococcus EPC2). Thus, variable PP is underpinned by distinct phytoplankton communities across CCS mesotrophic regimes, and their dynamic nature is influenced by the rapidity with which specific taxa respond to changing environmental conditions or possibly transient nutrient release from viral encounters. Future work should assess whether these dynamics are consistent across eastern boundary current ecosystems and over temporal variations
Origin of maar clusters at the type locality Eifel (Germany): H2O or CO2?
No full textThe closely spaced late glacial Daun and Gillenfeld maar clusters at the maar type locality in western Eifel (Germany) are commonly interpreted to be of phreatomagmatic origin powered by thermohydraulic explosions occurring initially at a depth of 200–300 m below the surface. Our reconnaissance work focusing on the iconoclastic water-filled Pulvermaar (PM) deposits (a funnel-shaped crater 74 m deep and 700 m in diameter surrounded by a tephra ring) and other nearby maars has provided intriguing evidence that CO2-dominated pyroclastic processes at a depth of several kilometers may have been a fundamental factor in generating the volumetrically abundant volcanic pellets (aka subspherical lava lapilli) and the rounded, lava-coated fragments of plutonic and metamorphic rocks (named nodules here) in these deposits. Phreatomagmatic explosions probably contributed to near-surface country rock fragmentation and crater foundering. Supporting lines of evidence for the role of CO2 include the following: (1) the likely high CO2-concentration of the melilite-nephelinite magma; (2) fragments of carbonatite (alkali feldspar intergrown with carbonate) in several maar deposits including the nearby ca. 11 000-year-old Ulmen maar deposits, the youngest volcano in Germany; (3) strongly rounded plutonic and gneiss nodules up to ca. 35 cm in diameter, both interpreted to be of mid-crustal derivation at ca. 20 km depth. The nodules record a complex multiphase dynamic history at depth that commences with an earlier phase of intruded melilite nephelinite into a metamorphic gneissic carapace that was largely crystallized at the time of the eruption. Subsequently, these plutonic as well as the metamorphic rocks were fragmented, followed by thorough milling and rounding of the fragments and eventual lava spray-coating of both types of nodules by a later phase of intruded gas-rich nephelinite magma that was compositionally identical to the older resident intrusion. The prominent role of these processes is reflected by the abundance of volcanic pellets in the lower exposed PM tephra ring deposits and by their dominance in the upper finer-grained well-bedded maar deposits. The pellets are composed of agglutinated smaller nephelinite lapilli and crystal fragments that were possibly derived from collided and fragmented plutonic nodules. The collection of nodules and pellets was most likely transported upward, largely by CO2-flushing and by continuous milling in the transport system, and joined by Devonian rock fragments closer to the surface. In the final stages of ascent, this was probably accompanied by near-surface phreatomagmatic processes including crater-formation
Virtual fieldwork in immersive environments using game engines
No full textHighlights
• Game Engines such as the Unreal Engine are modern 3D creation tools allowing to visualize photogrammetri- 30 cally scanned and reconstructed geospatial data, and to implement many forms of interaction with them.
• Interactive analysis, measurement, and understanding of geospatial data can benefit from extended reality e.g. when located in spatially immersive environments.
Abstract
Fieldwork still is the first and foremost source of insight in many disciplines of the geosciences. Virtual fieldwork is an approach meant to enable scientists trained in fieldwork to apply these skills to a virtual representation of outcrops that are inaccessible to humans e.g. due to being located on the seafloor. For this purpose we develop a virtual fieldwork software in the game engine and 3D creation tool Unreal Engine. This software is developed specifically for a large, spatially immersive environment as well as virtual reality using head-mounted displays. It contains multiple options for quantitative measurements of visualized 3D model data. We visualize three distinct real-world datasets gathered by different photogrammetric and bathymetric methods as use cases and gather initial feedback from domain experts
Non‐native species have higher consumption rates than their native counterparts
No full textNon-native species can be major drivers of ecosystem alteration, especially through changes in trophic interactions. Successful non-native species have been predicted to have greater resource use efficiency relative to trophically analogous native species (the Resource Consumption Hypothesis), but rigorous evidence remains equivocal. Here, we tested this proposition quantitatively in a global meta-analysis of comparative functional response studies. We calculated the log response ratio of paired non-native and native species functional responses, using attack rate and maximum consumption rate parameters as response variables. Explanatory variables were consumer taxonomic group and functional feeding group, habitat, native assemblage latitude, and non-native species taxonomic distinctiveness. Maximum consumption rates for non-native species were 70% higher, on average, than those of their native counterparts; attack rates also tended to be higher, but not significantly so. The magnitude of maximum consumption rate effect sizes varied with consumer taxonomic group and functional feeding group, being highest in favour of non-natives for molluscs and herbivores. Consumption rate differences between non-native and native species tended to be greater for freshwater taxa, perhaps reflecting sensitivity of insular freshwater food webs to novel consumers; this pattern needs to be explored further as additional data are obtained from terrestrial and marine ecosystems. In general, our results support the Resource Consumption Hypothesis, which can partly explain how successful non-native species can reduce native resource populations and restructure food webs
CAU Kiel Institute of Geosciences: Measuring Techniques in Shallow Water - Cruise No. AL612, 8.05.2024 – 18.05.2024, Kiel (Germany) – Kiel (Germany), MScMarineMeasure
No full textCruise AL612 was a teaching course for students of the MSc Marine Geosciences and BSc
Geowissenschaften at Kiel University. In this cruise also PhD students and PostDocs were trained.
They had hands-on experience on standard marine geoscientific research procedures on the
expeditions from Kiel to the Kiel and Mecklenburg Bay, Western Baltic Sea.
The research program focussed on water column measurements and sedimentological
observations of the seafloor and subseafloor structures. Work areas were located North and East
of Fehmarn Island, in Mecklenburg Bay, and Kiel Bay. CTD profiles (plus density, oxygen) were
taken. ADCP measurements (velocities) were carried out at different cross-sections. Different
areas were mapped with multibeam echosounder (MBES) and sediment echosounder (SES). Grab
samples and gravity cores were taken and described