Alfred Wegener Institute for Polar and Marine Research
Electronic Publication Information CenterNot a member yet
52828 research outputs found
Sort by
Enhanced Primary Productivity in the Brazil Malvinas Confluence Zone during the Mis 3
Get PDFMicropaleontological analyses from the western South Atlantic core AU-Geo02-GC20 (45° 55' S; 58° 30' W, 2589 m water depth) revealed changes in the primary productivity and sea surface temperature (SST) during MIS 3 that point to significant changes in the Brazil Malvinas Confluence Zone dynamics. These changes led to a marked increase in the SST and the primary productivity between 44.0-36.1 ka BP, as indicated by the quantitative reconstruction of the subsurface temperature and the high relative abundance of the planktonic foraminifera Globigerina bulloides and the eutrophic index. The increase in the SST and the primary productivity could indicate frequent or more persistent southward penetration of subtropical waters over the north Patagonian margin due to a southward extension of the Brazil Current and a weakening of the Malvinas Current. The high primary productivity resulted in the intensive use of phosphate during spring. Conversely, benthic assemblages do not reflect high surface productivity. The dominance of calcareous nannoplankton over diatoms as primary producers, which allows inferring the shoaling of the nutricline and the thermocline, justifies the decoupling between planktonic and benthic communities as a consequence of reduced efficiency of the biological pump. The deposition of the pelagites during the period of enhanced primary productivity indicates a slowing down of the bottom circulation, probably due to a weakening of the Atlantic Meridional Overturning Circulation
Manifiesto para la protección de los derechos humanos de las comunidades pesqueras artesanales en Colombia
Get PDFEstimado editor,
En el 2019, investigadoras de la Universidad del Magdalena (Colombia), en colaboración con una investigadora del Instituto Helmholtz para la Biodiversidad Marina Funcional (HIFMB, Alemania), implementaron el proyecto Vulneración de Derechos Humanos en la Pesca Artesanal en Colombia, gracias al cual se generó una línea de trabajo interdisciplinario (Justicia en Territorios Pesqueros) enfocada en investigar y denunciar diferentes injusticias en espacios marinos y costeros. Por medio del análisis sistemático de 91 sentencias de tutelas revisadas por la Corte Constitucional de Colombia, se identificaron violaciones a derechos humanos asociados a las comunidades de pescadores artesanales en todo el país.
Uno de los resultados de este proyecto ha sido la construcción de una base de datos digital denominada Justicia en Territorios Pesqueros (disponible en http://pescayjusticia.unimagdalena.edu.co/) que busca visibilizar estas violaciones y facilitar acciones futuras para la protección de los derechos humanos en el sector de la pesca artesanal en Colombia (ver Figueroa et al. 2023).
El 10 de marzo de 2023, se llevó a cabo el Primer Conversatorio Nacional Pescando Justicia: Violaciones a Derechos Humanos en Territorios Pesqueros, en donde se hizo el lanzamiento de la base de datos y se socializaron los resultados del proyecto con líderes y lideresas de comunidades pesqueras, miembros de la academia, funcionarios de las agencias gubernamentales de pesca, medio ambiente, derechos humanos y miembros de organizaciones no gubernamentales. Luego de dialogar sobre los resultados socializados y discutir su relevancia en el país, se redactó un manifiesto que presentamos a continuación.</jats:p
Within- and among-colony variation in non-breeding dispersion of Magellanic penguins breeding along the coast of Argentina
Get PDFMagellanic penguins Spheniscus magellanicus are upper trophic level predators and play a key role within their marine ecosystems. However, we lack detailed understanding of their non-breeding distribution where they might be impacted by human threats and climate change. Using geolocator tracking devices deployed in 2021, we analyzed individual non-breeding movements, and differences in the spatial, environmental, and trophic niches of Magellanic penguins breeding along the Atlantic coast of Argentina. The results show that movement characteristics, including trip lengths and dispersal distance, were similar among individuals and across colonies. However, the temporal pattern, including the timing of arrival to the breeding sites, differed between colonies. During the non-breeding season, distributions showed considerable overlap between colonies, notably between individuals from the central and the northernmost breeding sites. Individuals from the northern and central colonies faced similar oceanographic features (i.e. sea surface temperature, chlorophyll a, salinity, depth) and used similar foraging niches while within the anchovy geographic domain. In contrast, individuals breeding farther south were feeding within the geographically distinct sprat domain. Our results indicate that Magellanic penguins breeding along the latitudinal range of Argentina express a broad variation in habitat use during the non-breeding period, and make use of a large proportion of the Patagonian Shelf. The latitudinal location of the breeding colony seems to define the trophic niche and where individuals move during the non-breeding season.</jats:p
Matrix‐independent boron isotope analysis of silicate and carbonate reference materials by ultraviolet femtosecond laser ablation multi‐collector inductively coupled plasma mass spectrometry with application to the cold‐water coral Desmophyllum dianthus
Get PDFRationale: Boron isotopes are a powerful tool for pH reconstruction in marine
carbonates and as a tracer for fluid–mineral interaction in geochemistry.
Microanalytical approaches based on laser ablation multi-collector inductively
coupled plasma mass spectrometry (LA-MC-ICP-MS) often suffer from effects
induced by the sample matrix. In this study, we investigate matrix-independent
analyses of B isotopic ratios and apply this technique to cold-water corals.
Methods: We employ a customized 193 nm femtosecond laser ablation system
(Solstice, Spectra-Physics) coupled to a MC-ICP-MS system (Nu Plasma II, Nu
Instruments) equipped with electron multipliers for in situ measurements of B
isotopic ratios (11B/10B) at the micrometric scale. We analyzed various reference
materials of silicate and carbonate matrices using non-matrix matched calibration
without employing any correction. This approach was then applied to investigate
defined increments in coral samples from a Chilean fjord.
Results: We obtained accurate B isotopic ratios with a reproducibility of ±0.9‰
(2 SD) for various reference materials including silicate glasses (GOR132-G,
StHs6/80-G, ATHO-G and NIST SRM 612), clay (IAEA-B-8) and carbonate (JCp-1)
using the silicate glass NIST SRM 610 as calibration standard, which shows that
neither laser-induced nor ICP-related matrix effects are detectable. The application
to cold-water corals (Desmophyllum dianthus) reveals minor intra-skeleton variations
in δ11B with average values between 23.01‰and 25.86‰.
Conclusions: Our instrumental set-up provides accurate and precise B isotopic ratios
independently of the sample matrix at the micrometric scale. This approach opens a
wide field of application in geochemistry, including pH reconstruction in biogenic
carbonates and deciphering processes related to fluid–mineral interaction
Nitrous Oxide Fluxes in Permafrost Peatlands Remain Negligible After Wildfire and Thermokarst Disturbance
Get PDFThe greenhouse gas (GHG) balance of boreal peatlands in permafrost regions will be affected by climate change through disturbances such as permafrost thaw and wildfire. Although the future GHG balance of boreal peatlands including ponds is dominated by the exchange of both carbon dioxide (CO2) and methane (CH4), disturbance impacts on fluxes of the potent GHG nitrous oxide (N2O) could contribute to shifts in the net radiative balance. Here, we measured monthly (April to October) fluxes of N2O, CH4, and CO2 from three sites located across the sporadic and discontinuous permafrost zones of western Canada. Undisturbed permafrost peat plateaus acted as N2O sinks (−0.025 mg N2O m−2 d−1), but N2O uptake was lower from burned plateaus (−0.003 mg N2O m−2 d−1) and higher following permafrost thaw in the thermokarst bogs (−0.054 mg N2O m−2 d−1). The thermokarst bogs had below-ambient N2O soil gas concentrations, suggesting that denitrification consumed atmospheric N2O during reduction to dinitrogen. Atmospheric uptake of N2O in peat plateaus and thermokarst bogs increased with soil temperature and soil moisture, suggesting sensitivity of N2O consumption to further climate change. Four of five peatland ponds acted as N2O sinks (−0.018 mg N2O m−2 d−1), with no influence of thermokarst expansion. One pond with high nitrate concentrations had high N2O emissions (0.30 mg N2O m−2 d−1). Overall, our study suggests that the future net radiative balance of boreal peatlands will be dominated by impacts of wildfire and permafrost thaw on CH4 and CO2 fluxes, while the influence from N2O is minor
Gridded pollen-based Holocene regional plant cover in temperate and northern subtropical China suitable for climate modelling
Get PDFWe present the first gridded and temporally continuous quantitative pollen-based plant-cover reconstruction for temperate and northern subtropical China over the Holocene (11.7 ka to present) obtained by applying the Regional Estimates of VEgetation Abundance from Large Sites (REVEALS) model. The objective is to provide a dataset of pollen-based land cover for the last ca. 12 millennia that is suitable for palaeoclimate modelling and for the evaluation of simulated past vegetation cover from dynamic vegetation models and anthropogenic land-cover change (ALCC) scenarios. The REVEALS reconstruction was achieved using 94 selected pollen records from lakes and bogs at a 1× 1 spatial scale and a temporal resolution of 500 years between 11.7 and 0.7 ka and in three recent time windows (0.7-0.35 ka, 0.35-0.1 ka, and 0.1 ka to present). The dataset includes REVEALS estimates of cover and their standard errors (SEs) for 27 plant taxa in 75 1 × 1 grid cells distributed within the study region. The 27 plant taxa were also grouped into 6 plant functional types and 3 land-cover types (coniferous trees CT, broadleaved trees BT, and C3 herbs/open land (C3H/OL)), and their REVEALS estimates of cover and related SEs were calculated. We describe the protocol used for the selection of pollen records and the REVEALS application (with parameter settings) and explain the major rationales behind the protocol. As an illustration, we present, for eight selected time windows, gridded maps of the pollen-based REVEALS estimates of cover for the three land-cover types (CT, BT, and C3H/OL). We then discuss the reliability and limitations of the Chinese dataset of Holocene gridded REVEALS plant cover, and its current and potential uses. The dataset is available at the National Tibetan Plateau Data Center (TPDC; Li, 2022; 10.11888/Paleoenv.tpdc.272292)
Implications of Snowpack Reactive Bromine Production for Arctic Ice Core Bromine Preservation
Get PDFSnowpack emissions are recognized as an important source of gas-phase reactive bromine in the Arctic and are necessary to explain ozone depletion events in spring caused by the catalytic destruction of ozone by halogen radicals. Quantifying bromine emissions from snowpack is essential for interpretation of ice-core bromine. We present ice-core bromine records since the pre-industrial (1750 CE) from six Arctic locations and examine potential post-depositional loss of snowpack bromine using a global chemical transport model. Trend analysis of the ice-core records shows that only the high-latitude coastal Akademii Nauk (AN) ice core from the Russian Arctic preserves significant trends since pre-industrial times that are consistent with trends in sea ice extent and anthropogenic emissions from source regions. Model simulations suggest that recycling of reactive bromine on the snow skin layer (top 1 mm) results in 9–17% loss of deposited bromine across all six ice-core locations. Reactive bromine production from below the snow skin layer and within the snow photic zone is potentially more important, but the magnitude of this source is uncertain. Model simulations suggest that the AN core is most likely to preserve an atmospheric signal compared to five Greenland ice cores due to its high latitude location combined with a relatively high snow accumulation rate. Understanding the sources and amount of photochemically reactive snow bromide in the snow photic zone throughout the sunlit period in the high Arctic is essential for interpreting ice-core bromine, and warrants further lab studies and field observations at inland locations
Biologically Inspired Girder Structure for the Synchrotron Radiation Facility PETRA IV
Get PDFLightweight structures are widely used across different industry sectors. However, they get easily excited by external influences, such as vibrations. Undesired high vibration amplitudes can be avoided by shifting the structural eigenfrequencies, which can be achieved adapting the structural design considering optimisation procedures and structures primarily inspired by diatoms. This procedures has been applied to the development process of a girder structure installed in a synchrotron radiation facility to support heavy magnets and other components. The objective was to design a 2.9 m long girder structure with high eigenfrequencies, a high stiffness and a low mass. Based on a topology optimisation result, a parametric beam–shell model including biologically inspired structures (e.g., Voronoi combs, ribs, and soft and organic-looking transitions) was built up. The subsequent cross-sectional optimisation using evolutionary strategic optimisation revealed an optimum girder structure, which was successfully manufactured using the casting technology. Eigenfrequency measurements validated the numerical models. Future changes in the specifications can be implemented in the bio-inspired development process to obtain adapted girder structures
Genetic and Structural Diversity of Prokaryotic Ice-Binding Proteins from the Central Arctic Ocean
Get PDFIce-binding proteins (IBPs) are a group of ecologically and biotechnologically relevant enzymes produced by psychrophilic organisms. Although putative IBPs containing the domain of unknown function (DUF) 3494 have been identified in many taxa of polar microbes, our knowledge of their genetic and structural diversity in natural microbial communities is limited. Here, we used samples from sea ice and sea water collected in the central Arctic Ocean as part of the MOSAiC expedition for metagenome sequencing and the subsequent analyses of metagenome-assembled genomes (MAGs). By linking structurally diverse IBPs to particular environments and potential functions, we reveal that IBP sequences are enriched in interior ice, have diverse genomic contexts and cluster taxonomically. Their diverse protein structures may be a consequence of domain shuffling, leading to variable combinations of protein domains in IBPs and probably reflecting the functional versatility required to thrive in the extreme and variable environment of the central Arctic Ocean
A molecular and epidemiological study of Grillotia (Cestoda: Trypanorhyncha) larval infection in Etmopterus spinax (Elasmobranchii: Squaliformes) in the Mediterranean Sea and Northeast Atlantic Ocean
Get PDFAmongst other factors, topographic features can influence the genetic variability among populations of marine organisms. This applies to host species but also to their parasites, which are poorly studied regarding this aspect, as well as with regard to their use as bioindicators. In the present work, the ribosomal DNA (28S rDNA) was used to assess genetic diversity of Grillotia (Cestoda, Trypanorhyncha) larvae in one of its paratenic hosts, namely Etmopterus spinax, across five different regions (off Scotland, Celtic, Alboran and Balearic Seas and off Cyprus) belonging to three major geographic areas (Northeast Atlantic, western and eastern Mediterranean). The obtained sequences revealed a total of 18 polymorphic sites and 17 haplotypes, as well as significant values of variance throughout the five different regions. Reconstructed phylogenetic trees highlighted that all Grillotia sp. sequences formed a monophyletic group, but divergent lineages split into different main clades which were in relation to the area of origin, with a consistent cluster of sequences from the Atlantic Ocean, as well as another from the Eastern Mediterranean. In contrast, low genetic differentiation was observed between samples from Balearic and Alboran Seas, and with respect to Grillotia sp. larvae from the Gulf of Naples analysed in a previous study. Geographical differences in parasite infection descriptors (prevalence, abundance, and intensity) were assessed, revealing significant differences among the sampled regions. The present study indicates that geographical distance and submarine barriers affect not only the connectivity of hosts but also their parasite infrapopulations by limiting interpopulation dispersal. It underlines the usefulness of parasites as biological tags for the study of susceptible and data-poor host species such as deep-water sharks and its potential implications for host population management and protection measures