Alfred Wegener Institute for Polar and Marine Research
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Selective purification of catecholate, hydroxamate and α-hydroxycarboxylate siderophores with titanium dioxide affinity chromatography
Get PDFSiderophores, high affinity iron chelators, play a key role in the uptake of iron by microorganisms and regulate many biological functions. Siderophores are categorized by their chelating group, e.g., catecholates, hydroxamates, α-hydroxycarboxylates. Natural concentrations of siderophores are often either too low or sample matrices are too complex for direct analysis by, e.g., liquid chromatography – mass spectrometry. Therefore, both concentration and purification are prerequisite for reliable analyses. However, a chromatographic technique that is selective for all siderophore classes and affords high levels of purification is lacking. We developed a titanium dioxide affinity chromatography (TDAC) solid-phase extraction (SPE) that affords the selective purification of these siderophore classes from complex sample matrices with recoveries up to 82%. The one-step purification removed most non-ligand sample ‘contaminants’, therefore, affording the straightforward identification of siderophore peaks in base peak chromatograms. As a proof of concept, the bioinformatic processing, dereplication of known features and selection of significant features in the TDAC eluates afforded a fast identification of six novel siderophores (woodybactines) from bacterial supernatants. We propose TDAC SPE as a fast and cost-effective methodology to screen for known or discover novel siderophores in natural samples in combination with untargeted bioinformatic processing by, e.g., XCMS. The method is scalable and yielded large amounts of highly purified siderophores from bacterial culture supernatants, providing an effective quantitative sample clean-up for, e.g., NMR structure elucidation
Fast Ice Thickness Distribution in the Western Ross Sea in Late Spring
Get PDFWe present a 700 km airborne electromagnetic survey of late-spring fast ice and sub-ice platelet
layer (SIPL) thickness distributions from McMurdo Sound to Cape Adare, providing a first-time inventory
of fast ice thickness close to its annual maximum. The overall mode of the consolidated ice (including snow)
thickness was 1.9 m, less than its mean of 2.6 ± 1.0 m. Our survey was partitioned into level and rough ice,
and SIPL thickness was estimated under level ice. Although level ice, with a mode of 2.0 m and mean of
2.0 ± 0.6 m, was prevalent, rough ice occupied 41% of the transect by length, 50% by volume, and had a
mode of 3.3 m and mean of 3.2 ± 1.2 m. The thickest 10% of rough ice was almost 6 m on average, inclusive
of a 2 km segment thicker than 8 m in Moubray Bay. The thickest ice occurred predominantly along the
northwestern Ross Sea, due to compaction against the coast. The adjacent pack ice was thinner (by ∼1 m)
than the first-year fast ice. In Silverfish Bay, offshore Hells Gate Ice Shelf, New Harbor, and Granite Harbor,
the SIPL transect volume was a significant fraction (0.30) of the consolidated ice volume. The thickest 10%
of SIPLs averaged nearly 3 m thick, and near Hells Gate Ice Shelf the SIPL was almost 10 m thick, implying
vigorous heat loss to the ocean (∼90 W m −2). We conclude that polynya-induced ice deformation and
interaction with continental ice influence fast ice thickness in the western Ross Sea
Justicia en territorios pesqueros: Violaciones a los derechos humanos en la pesca artesanal en la Corte Constitucional de Colombia
Get PDFLos mares y aguas continentales han sido espacios de luchas sociales históricamente invisibilizadas. Este artículo ofrece un análisis interdisciplinario de todas las decisiones de la Corte Constitucional Colombiana relacionadas con violaciones de derechos humanos en la pesca artesanal. Por medio del Enfoque Basado en Derechos Humanos estudiamos 79 sentencias y construimos una base de datos digital llamada Justicia en Territorios Pesqueros. Identificamos y analizamos los derechos reivindicados con mayor frecuencia. En su mayoría, las decisiones de la Corte indican que el sector de la pesca artesanal no es tenido en cuenta en la aprobación de proyectos de desarrollo. Concluimos que el Estado colombiano privilegia los intereses de los sectores económicos industriales en detrimento de los derechos de las poblaciones pesqueras.</jats:p
Effect of post-thaw hydrological changes during the degradation process of a palsa
Get PDFWith climate change, discontinuous permafrost is thawing rapidly and is predicted to reach a “tipping point” in the next decade. Permafrost affected peatlands store about 185±66 Pg C. Due to permafrost thaw, the landscape topographies and hydrologic conditions could change quickly and thus, release carbon (C) stored in soils. However, there is a current lack of understanding regarding the C lability after post- thaw and how the microbial community and labile C in the water will affect methane (CH4) and carbon dioxide (CO2) fluxes. Here, we quantified and qualified the effect of hydrologic changes on CH4 and CO2 emissions and production during the thawing process of a palsa (peaty permafrost mounts, mainly in discontinuous permafrost areas). We did a chronosequence study by measuring CH4 and CO2 emissions along a thawing transect from an intact palsa to a thawed wetland site during fall. Additionally, we mimicked a palsa degradation by incubating 1 m soil cores from the palsa and the wetland sites. We inoculated the incubation with water from the thawed site to study the effect of hydrological changes after permafrost thaw. The CO2 and CH4 emissions were continuously measured for 60 days. Additionally, dissolved gas, as well as nutrients were sampling over the entirety of the incubation time. The preliminary results from the field measurements showed that the intact palsa and the intermediate site behaved as a net C sink whereas, the thawed wetland site had the highest CH4 emissions (20 – 40 ppm). Furthermore, we showed that this mesocosm-scale incubation setup is an efficient and robust way to study C cycle dynamics and more accurately upscale laboratory results to the field. With permafrost thaw and former areas turning into wetlands more greenhouse gases will be emitted. Therefore, bridging scale is necessary to better estimate the future C emissions
Helicopter-borne RGB orthomosaics and photogrammetric digital elevation models from the MOSAiC Expedition
Get PDFThe Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition took place between October 2019 and September 2020 giving the rare opportunity to monitor sea-ice properties over a full annual cycle. Here we present 24 high-resolution orthomosaics and 14 photogrammetric digital elevation models of the sea-ice surface around the icebreaker RV Polarstern between March and September 2020. The dataset is based on >34.000 images acquired by a helicopter-borne optical camera system with survey flights covering areas between 1.8 and 96.5 km2 around the vessel. Depending on the flight pattern and altitude of the helicopter, ground resolutions of the orthomosaics range between 0.03 and 0.5 m. By combining the photogrammetric products with contemporaneously acquired airborne laser scanner reflectance measurements selected orthomosaics could be corrected for cloud shadows which facilitates their usage for sea-ice and melt pond classification algorithms. The presented dataset is a valuable data source for the interdisciplinary MOSAiC community building a temporal and spatially resolved baseline to accompany various remote sensing and in situ research projects
Derivation and compilation of lower-atmospheric properties relating to temperature, wind, stability, moisture, and surface radiation budget over the central Arctic sea ice during MOSAiC
Get PDFAtmospheric measurements taken over the span of an entire year between October 2019 and September 2020 during the icebreaker-based Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition provide insight into processes acting in the Arctic atmosphere. Through the merging of disparate yet complementary in situ observations, we can derive information about these thermodynamic and kinematic processes with great detail. This paper describes methods used to create a lower-atmospheric properties dataset containing information on several key features relating to the central Arctic atmospheric boundary layer, including properties of temperature inversions, low-level jets, near-surface meteorological conditions, cloud cover, and the surface radiation budget. The lower-atmospheric properties dataset was developed using observations from radiosondes launched at least four times per day, a 10 m meteorological tower and radiation station deployed on the sea ice near the research vessel Polarstern, and a ceilometer located on the deck of the Polarstern. This lower-atmospheric properties dataset, which can be found at 10.1594/PANGAEA.957760 (Jozef et al., 2023), contains metrics which fall into the overarching categories of temperature, wind, stability, clouds, and radiation at the time of each radiosonde launch. The purpose of the lower-atmospheric properties dataset is to provide a consistent description of general atmospheric boundary layer conditions throughout the MOSAiC year, which can aid in research applications with the overall goal of gaining a greater understanding of the atmospheric processes governing the central Arctic and how they may contribute to future climate change
At the interface between scientists and local practitioners - presenting climate index projections to reindeer herders
Get PDFComparing Loon Superpressure Balloon Observations of Gravity Waves in the Tropics With Global Storm‐Resolving Models
Get PDFSuperpressure balloons, which drift approximately on isopycnal surfaces, get displaced by gravity waves and are thus capable of detecting gravity wave signatures. The project Loon provides superpressure balloon data in the upper troposphere and lower stratosphere from 2011 to 2021. We compare Loon data from the 6 years of best data coverage with output of global storm-resolving models from the DYnamics of the Atmospheric general circulation Modeled On Non-hydrostatic Domains winter initiative in the tropics. We study the variance of the vertical velocity and, for the models, the gravity wave momentum flux as function of distance to closest convection. The models show large differences in the variance of the vertical wind velocity, which is crucial for calculating vertical gravity wave momentum fluxes. We find large differences between the models with respect to simulated convection, lateral propagation, and the wave background away from sources. We then sample balloons as models by optimizing the match of vertical wind distributions using a temporal low pass filter. The average distance the balloons travel during the optimum low pass filtering time turns out to correspond approximately to four times the model grid spacing. The functional dependence of the vertical velocity variance on distance to closest convection is similar between the models and the observations sampled as models. The robustness of this result across all models suggests that storm-resolving models provide a useful resource for machine learning some characteristics of convectively generated gravity waves
Nutrient and carbon dynamics along the river-estuary-ocean continuum on Central European scale
Get PDFNutrient and carbon dynamics within the river-estuary-coastal water systems are key processes to understand the matter fluxes from the terrestrial environment to the ocean. In a large-scale study we analysed those dynamics with the focus of the prevailing low water conditions by following a sampling approach based on the travel time of water.
We started with a nearly Lagrangian sampling along the River Elbe (German part; 580 km within 8 days travel time). After a subsequent investigation of the estuary, the plume of the river was followed by raster sampling the German Bight (North Sea) using three ships simultaneously. In the river, intensive growth of phytoplankton was determined connected with high oxygen saturation and pH values as well as under-saturation of CO2, whereas concentrations of dissolved nutrients declined. In the estuary, the Elbe shifted from an autotrophic to a heterotrophic system: Phytoplankton died off upstream of the salinity gradient causing minima in oxygen saturation and pH, supersaturation of CO2, and a release of nutrients. In the coastal region, phytoplankton and nutrient concentrations were low, oxygen close to saturation, and pH in a typical marine range. We detected a positive relationship between pH values and oxygen saturation and a negative one between pCO2 and oxygen saturation. Corresponding to the significant particulate nutrient flux via phytoplankton, flux rates of dissolved nutrients from the river into the estuary were low and determined by depleted concentrations. In contrast, fluxes from the estuary to the coastal waters were higher and the pattern was determined by tidal currents.
Overall, the presented observation approach is appropriate to better understand land-ocean fluxes, particularly if it is performed under different hydrological conditions including extremes and seems to be suitable to investigate the impact of such events in freshwater on coastal systems in future.
The study was conducted within the frame of the Helmholtz MOSES initiative (Modular Observation Solutions for Earth Systems) targeting processes and impacts of hydrological extremes