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Glacial meltwater drives high CH 4 supersaturation in Maxwell Bay, King George Island (Southern Ocean)
No full textCoastal waters exhibit the highest and most dynamic dissolved CH 4 concentrations in marine environments, but significant knowledge gaps on the distribution and emissions, particularly in the Southern Ocean, still exist. We quantified dissolved CH 4 concentrations and sea–air fluxes in the coastal waters of Maxwell Bay, King George Island, Antarctica, in December 2023. Surface waters showed exceptionally high CH 4 supersaturations (213–2342%), associated with lower salinity and higher turbidity, which were attributed primarily to meltwater discharge from a retreating tidewater glacier. Our findings suggest that glacial melt may significantly increase CH 4 emissions from Antarctic coastal waters, highlighting the need for further research to understand CH 4 dynamics and improve emission estimates in the context of accelerating climate‐driven glacial melt
Winter flood significantly changes salinity and nutrient export from land to sea
No full textFlood events caused by high rainfall can have profound biogeochemical impacts on riverine systems but also on the receiving coastal waters. The winter flood in Germany in December 2023/January 2024 affected the Elbe and Weser River systems. We obtained unique data during the peak of the flood and compared these with the monthly means from previous years (2018-2023). Hydrographic parameters and nutrients were determined by standard methods. Low salinity values were observed in the Elbe estuary and the adjacent German Bight (part of North Sea). At Helgoland the lowest average salinity was observed in January 2024 with 31.3 ± 0.5 compared to an average salinity of 32.7 ± 0.7 for the years 2016 to 2023. Nutrient loads (nitrate, phosphate) in the rivers showed a six- to 11-fold increase in the Elbe and Weser rivers compared to years without flood events. Enhanced concentrations of nitrate and silicate were found in the German Bight in January. Nutrients were diluted with North Sea waters, indicating a conservative behavior of nutrients in winter. Atypical prevailing meteorological conditions in January 2024, with predominantly easterly winds, potentially affect the dispersal of the river plume and the nutrients in the North Sea. In March 2024 the chlorophyll-a concentration strongly increased to 2.9 ± 1.8 µmol/L and was twice as high compared to only 1.5 ± 0.7 µmol/L observed in previous years. The observed intensified spring bloom in March in the German Bight near the island of Helgoland indicates the impacts of the flood-derived nutrient inputs three months after the flood event, as the timing of light and nutrient availability was optimal. It is assumed that seasonality and magnitude of flooding in the Elbe estuary and adjacent coastal region will change in future due to climate warming. Thus, the timing of light and nutrient availability will also change, with unconstrained impacts on primary producers and higher trophic levels
Hydrography of intertidal environments in Schleswig-Holstein, Germany
No full textThe current status of intertidal waters in the wake of ongoing global change was assessed in a baseline study with a 36 month time series of water level, temperature, and salinity measurements from Bottsand lagoon on the Baltic Sea coast, and on the mudflats off Schobüll at the North Sea coast of Schleswig-Holstein, Germany. Extreme events, storm surges and heat waves were also recorded in a temporal resolution of 20 minutes. At Bottsand lagoon, the temperatures followed the air temperatures in winter, and were higher than the air temperatures in spring and summer. The annual averages varied from 12.1 to 12.6 °C, the air temperatures varied from 11.1 to 11.2 °C. The salinities showed one or two months periods of consistently higher or lower values in winter and spring. The annual averages ranged from 14.7 to 16.9 units. The lagoon showed a different variability than that of the open Baltic surface waters, where the temperatures and salinities were lower in summer and higher in winter. The seasonal salinity differences were less developed in the mid 1960s, when the connectivity of the lagoon with the Baltic Sea was less restricted, and a sandy shoal in the lagoon was not present. In Husum Bight off Schobüll, water temperatures were lower than the air temperatures in winter and higher in spring and summer. The annual average water temperatures ranged from 10.8 to 11.4 °C, and the air temperatures from 9.9 to 10.2 °C. High waters were warmer during the day than at night-time in spring and early summer only. The annual average salinities off Schobüll ranged from 24.0 to 27.2 units. The values were higher in summer and lower in winter. This seasonal cycle was related to variations in the Elbe river runoff, which largely influences the salinity in the south-eastern German Bight. The same seasonal cycle was recorded in the Sylt Roads time series. Cross-correlations of the records revealed that it takes seven weeks for an Elbe river freshwater pulse to reach Schobüll, and three weeks more to proceed to Sylt. On average, the salinities were 2.7 units lower off Schobüll than off Sylt, which mirrors a pervasive gradient of landward decreasing salinities in the Wadden Sea. They were induced by a local, low-salinity lens on top of tidal waters, fed by groundwater seepage or by freshwater runoff. A cross correlation with the precipitation record revealed salinity decreases about one week after high precipitation. The cumulative salt marsh submergence times per period of observation, i.e. inundation frequencies, were very variable at the lower boundaries of the lower and upper salt marsh vegetation zones. The inundation frequencies were consistently higher at Bottsand than at Schobüll, where the same halophyte assemblages prevailed. As the average salinity was 10 units higher at Schobüll, the differences of inundation frequencies suggest that a certain salinity has to be maintained in the soils to sustain specific halophyte assemblages. A mass occurrence of small Pacific oyster shells was observed before the vegetation boundary off Schobüll in spring 2024. The data suggested an oyster spatfall triggered by the North Sea heat waves in summer 2023, with temperatures exceeding 23 °C, and a subsequent wipe-out during a period of salinities lower than 18 units after an Elbe river discharge event in January 2024. The biotic responses to environmental extremes highlighted the vulnerability of Wadden Sea ecosystems at times of Global Change
Fluxes of Biogenic and Oxygenated VOCs From In Situ Mesocosm Studies of Seawaters From the South‐West Pacific Ocean
No full textVolatile organic compounds (VOCs) are key atmospheric species influencing oxidative capacity and secondary organic aerosol formation. Oceans emit a variety of VOCs via complex biological, chemical, and physical processes. Although dimethyl sulfide (DMS) is a known precursor in marine aerosol formation, marine emissions of organic gases are more diverse. Here, we quantify semi‐controlled sea‐to‐air net fluxes of isoprene (0.50 ± 0.30 ng m −2 s −1 ), monoterpenes (0.93 ± 0.73 ng m −2 s −1 ), and oxygenated organics (methanol: 2.50 ± 1.13 ng m −2 s −1 ) using in situ mesocosm studies of natural seawaters in the south‐west Pacific Ocean. Under wind speeds <3 m s −1 , flux compositions varied between Frontal, Subtropical, and Subantarctic seawaters, with several VOCs exhibiting fluxes comparable to or exceeding DMS (0.75 ± 0.86 ng m −2 s −1 ). Significant associations were observed among biogenic VOC fluxes and phytoplankton groups, notably with nanophytoplankton. The impact of atmospheric ozone changes was tested by introducing additional ozone into one mesocosm, which increased methanol emissions while decreasing monoterpene and acetaldehyde fluxes, making the ocean a sink for the latter. Such studies provide quantitative links between natural phytoplankton assemblages and emissions of climatically relevant marine VOCs, offering the potential to use satellite oceanographic data to improve the representation of these emissions in chemistry‐climate models.
Plain Language Summary
Volatile organic compounds (VOCs) are gases that are important in atmospheric chemistry, and are emitted from the ocean via complex biological, chemical and physical processes. Many marine biogenic VOCs emission pathways are not yet well characterized. Here we quantify sea‐to‐air fluxes of biogenic VOCs from a series of large incubation studies of natural seawaters in the South‐west Pacific Ocean. Large fluxes were measured, especially in the more productive waters where significant associations were observed between the composition of biogenic VOC fluxes and phytoplanktonic groups in the seawater and notably with nanophytoplankton. Understanding the specific contributions of nanophytoplankton to biogenic VOCs emissions is essential for accurately modeling their impact on atmospheric chemistry and climate. As research progresses, it becomes increasingly clear that these microorganisms are integral to the biogeochemical cycling of VOCs, influencing both marine ecosystems and atmospheric dynamics.
Key Points
Sea‐to‐air fluxes of volatile organic compounds were quantified under semi‐controlled fixed equivalent wind‐speed conditions
Marine biogenic emission fluxes of isoprene, monoterpenes, and methanol were equivalent to those of dimethylsulfide
Fluxes of biogenic volatile organic compounds were correlated to nanophytoplankton cell abundances rather than to chlorophyll‐
Foresee: ML-Driven, Communication-Efficient Time-Series Forecasting
No full textIn the Internet of Things, a multitude of sensors continuously collect data and transmit it to the cloud for analysis. However, frequent transfer of measurements is impractical for battery-powered sensors due to the high energy-costs of wireless communication. Therefore, sensors often collect data and send it at periodic intervals, while a state-of-the-art cloud-based predictive model estimates intermediate values between transmissions. This paper introduces Foresee, which improves data quality on the cloud without additional communication overhead compared to periodic and model-drives approaches. Foresee makes local predictions on the sensor by employing a small, resource-efficient neural network. Upon detecting significant deviations between predicted and measured data, Foresee communicates these measurements to the cloud. Thus, Foresee notifies the cloud whenever predictions are difficult. On the cloud side, Foresee uses a state-of-the-art transformer model to make predictions between transmissions. Our results demonstrate the effectiveness of Foresee across different datasets. For instance, on the AlSolar dataset, with a prediction length of 48, we observe a 26% improvement in the Mean Absolute Error without any additional communication, compared to periodic communication every 39 timesteps. Additionally, Foresee achieves a 63% reduction in Mean Absolute Error compared to a model-driven approach with the same communication overhead
Characterization of protein, carbohydrate and lipid digestion in larvae of the sea urchin Strongylocentrotus purpuratus
No full textThe dissertation investigates the digestive physiology of the larvae of the sea urchin Strongylocentrotus purpuratus, in particular the degradation of proteins, carbohydrates and lipids. Extracellular digestion is considered a crucial step in the evolution of multicellularity and heterotrophy. While digestion is well described in adult sea urchins, it has been little studied in planktonic larvae.
Molecular, biochemical and physiological methods were used to investigate the activity and gene expression of digestive enzymes under different feeding conditions (high vs. low food supply). The results show that larvae already have a fully developed digestive machinery at an early stage (from day 7). Gene expression was age-dependent and responded to food availability. The expression of protease genes was particularly high, followed by lipases and significantly lower levels of glycosidases.
Enzymatic analyses showed that proteases responded rapidly to feeding - even with a low diet - while lipases were only activated with a high diet. Glycosidases, on the other hand, showed a slower, continuous activation.
The pH optima of the enzymes correspond to the conditions in the larval intestine: Proteases and lipases worked best under alkaline conditions (pH 9.0-9.5), whereas glycosidases worked best at neutral to slightly acidic pH (pH 5.0-6.0), indicating a possible localisation outside the midgut.
Overall, the work provides new insights into the functional development and adaptability of the digestive system of sea urchin larvae. It forms a basis for further studies on dietary changes during metamorphosis and the reaction of these organisms to environmental changes
1. Wochenbericht SO314
No full textForschungsfahrt des FS SONNE SO 314: T-SECTOR Southeast Pacific Rise:
13.08.2025 (Papeete/Tahiti) – 05.10.2025 (Antofagasta/Chile
Kronotsky Volcano – A low-K end-member frontal volcano in Kamchatka: Geological structure and composition of rocks and minerals
No full textHighlights
• First systematic geological and geochemical data for Kronotsky volcano.
• Kronotsky tholeiitic basalts have the lowest K, Ti, P, Zr, Nb and LREE in Kamchatka.
• Petrography and mineral phenocrysts recorded complex evolution of tholeiitic magmas.
• Parental Kronotsky magmas originate by ~25 % melting of very depleted mantle.
• Kronotsky magmas have potential contribution from the subducting Krusenstern fracture zone.
Abstract
Kronotsky volcano is the largest but poorly studied stratovolcano in the frontal zone of the Kamchatka arc. Here we present the first systematic data on the geological structure of this volcano and the composition of its rocks and minerals. Kronotsky lavas are predominantly low-K, high-Fe tholeiitic basalts to basaltic andesites with SiO2 = 47.0–53.2 wt%, K2O = 0.24–0.65 wt%, FeO⁎ = 9.1–13.4 wt% and MgO = 3.7–11.2 wt%. Andesites (SiO2 = 59.9–60.5 wt%, K2O = 0.65 wt%, FeO⁎ = 7.7–7.6 wt%, MgO = 2.4–2.6 wt%) are rare and occur among the lava cones and necks from the latest stage of activity. The major phenocrysts in Kronotsky basalts are olivine (Fo91.9–67), plagioclase (An95–40) and high-Ca pyroxene (Mg#89.3–50). Orthopyroxene occurs as phenocrysts (Mg#61–67) in the andesites and rarely in the basaltic andesites, and as inclusions (Mg#83) in the high Ca-pyroxene glomerocrysts of the most mafic varieties of basalts. Ti-magnetite (Fe2+/Fe3+ = 0.98–1.51, TiO2 = 11.0–16.5 wt%) forms subphenocrysts in andesites and microlites in the groundmass of basalts. Inclusions of Cr-spinel (Cr/Cr + Al = 0.19–0.79, TiO2 = 0.18–2.81 wt% and Al2O3 = 8.7–33.2 wt%) are found in olivine phenocrysts. Variations of whole rock and mineral compositions reflect the existence of long-lived magma chamber(s) under the volcano and the processes of crystal differentiation, accumulation and magma mixing as well as crystallization associated with magma degassing during ascent and decompression.
Compared to all Quaternary volcanoes on Kamchatka, Kronotsky basalts are the most depleted in K2O (down to 0.24 wt%) and a number of other incompatible elements (Ti, Zr, Nb, LREE), and are characterized by the lowest Nb/Zr (≤0.02) and Nb/Yb (≤0.5) ratios. In contrast, Ba/Nb (up to 280) and especially Ba/Th (up to 938) ratios are relatively high compared to other Kamchatka volcanoes. The composition of high-Mg olivine (Fo ≥ 87.5 mol%, Ni ≤2500 ppm, Fe/Mn = 56–71) indicates that the primary magmas of Kronotsky volcano originated from a peridotite mantle source. Trace element modeling suggests that the mantle was melted to a high degree (up to 25 %) and was more depleted than the source of typical MORB and of most parental magmas in Kamchatka. The exceptionally high degree of melting, combined with a strong relative enrichment in fluid mobile elements, suggests an enhanced fluid flux from the subducting Pacific plate beneath Kronotsky volcano, which is responsible for the extensive mantle melting. The Krusenstern fracture zone on the Pacific plate subducting beneath central Kamchatka may be a potential source of abundant hydrous fluids in the mantle wedge beneath Kronotsky volcano, which makes this volcano distinct in the Kamchatka arc
The Сanadian Basin (Arctic Ocean): Models of Its Geological Structure, History, and Geodynamics of Formation
No full textThe Amerasian and Eurasian basins are distinguished in the Arctic Ocean and are separated by the Lomonosov Ridge. The Canadian Basin, with Cretaceous oceanic and transitional crust, is located in the southern part of the Amerasian Basin. The Alpha-Mendeleev Rise and its associated deep-sea basins (Podvodnikov, Makarov, Toll, Nautilus, and Stefansson) lie to the north of the Canadian Basin. The Alpha-Mendeleev Rise and associated basins have continental crust that has been altered to varying degrees. Their major formation occurred about 125–90 Ma. We discuss three models for the formation of the Canadian Basin. Model-1: the entire Amerasian Basin with the oceanic and transitional crust was formed first (before 125 Ma). The Alpha-Mendeleev Rise region was then formed on the earlier oceanic crust as a volcanic formation (125–90 Ma). Model-2: the Canadian Basin formed first (before 125 Ma). The Alpha-Mendeleev Rise area and associated basins were then formed due to the significant transtension of the continental crust and magmatism (125–90 Ma). Model-3: The Alpha-Mendeleev rise area and associated basins formed first above a mantle plume (125–100 Ma). Subsequently, along one of the branches of continental rifting, spreading of the transitional and oceanic crust began and the Canadian Basin was formed (100–70 Ma). We find Model-1 to be the least probable, because it is now proven that the Alpha-Mendeleev Rise is underlain by continental crust. Model-2 and Model-3 are both possible. According to these models, the Canadian Basin formed as a backarc basin of the Pacific subduction zone
