Alfred Wegener Institute for Polar and Marine Research
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Assessment of nine markers for phylogeny, species and haplotype identification of Kappaphycus species and Eucheuma denticulatum (Solieriaceae, Rhodophyta)
Get PDFMolecular studies have contributed to the taxonomy of carrageenan-producing Kappaphycus spp. and Eucheuma denticulatum. However, unresolved species complexes and the lack of standardization in the use of genetic markers impede the identification of specimens and the delineation of a robust taxonomic framework. Here, nine molecular markers (cox1, cox2–3 spacer, cox2, cox3, COB, ITS, psbA, UPA and rbcL) were used to generate a multilocus phylogeny for 113 fresh eucheumatoid samples and four herbarium specimens. Analyses of species delineation and genetic distances confirmed the monophyly of currently accepted taxa. These analyses suggest that clades previously reported as K. striatus KS1 and KS2 are conspecific, and that E. denticulatum EDA ‘spinosum’ and EDB ‘endong/cacing’ are also conspecific. The results also unveiled possible new taxa from Hawaii and Indonesia. Each molecular marker and combinations thereof were assessed with regard to species identification, ease of amplification and sequencing, and haplotype characterization. All genetic markers recorded at least 94% success in the amplification and sequencing of fresh specimens, with cox1 being the most phylogenetically informative. Automatic partitioning, phylogenetic and tree-based assessments showed cox1, cox2–3 spacer, cox2 and rbcL were able to correctly identify species while cox1+ rbcL, COB+rbcL, cox2+ rbcL or cox1+ COB+rbcL trees best represented the phylogeny with consistently high nodal support. Among individual markers, cox1 identified the greatest number of haplotypes, while UPA, partial rbcL (750 bp), ITS, cox3 and cox2–3 spacer were able to retrieve information from herbarium specimens of 12–16 years of age. These molecular results provide a basis for a database essential for the taxonomic framework, cultivar development and germplasm conservation of eucheumatoids
Biocalcification in porcelaneous foraminifera
Get PDFLiving organisms control the formation of mineral skeletons and other structures through biomineralization. Major phylogenetic groups usually consistently follow a single biomineralization pathway. Foraminifera, which are very efficient marine calcifiers, making a substantial contribution to global carbonate production and global carbon sequestration, are regarded as an exception. This phylum has been commonly thought to follow two contrasting models of either in situ ‘mineralization of extracellular matrix’ attributed to hyaline rotaliid shells, or ‘mineralization within intracellular vesicles’ attributed to porcelaneous miliolid shells. Our previous results on rotaliids along with those on miliolids in this paper question such a wide divergence of biomineralization pathways within the same phylum of Foraminifera. We have found under a high-resolution scanning electron microscopy (SEM) that precipitation of high-Mg calcitic mesocrystals in porcelaneous shells takes place in situ and form a dense, chaotic meshwork of needle-like crystallites. We have not observed calcified needles that already precipitated in the transported vesicles, what challenges the previous model of miliolid mineralization. Hence, Foraminifera probably utilize less divergent calcification pathways, following the recently discovered biomineralization principles. Mesocrystalline chamber walls in both models are therefore most likely created by intravesicular accumulation of pre-formed liquid amorphous mineral phase deposited and crystallized within the extracellular organic matrix enclosed in a biologically controlled privileged space by active pseudopodial structures. Both calcification pathways evolved independently in the Paleozoic and are well conserved in two clades that represent different chamber formation modes.</jats:p
Assimilation of ground-based GNSS data using a local ensemble Kalman filter
Get PDFTropical cyclones become increasingly nonlinear and dynamically unstable in high-resolution models. The initial conditions are typically sub-optimal, leaving scope to improve the accuracy of forecasts with improved data assimilation. Simultaneously, the lack of real ground-based GNSS observations over the ocean poses significant challenges when evaluating the assimilation results in oceanic regions. In this study, an Observation System Simulation Experiment is carried out based on a tropical cyclone case. Assimilation experiments using the WRF-PDAF framework are conducted. Conventional and GNSS observation operators are implemented. A diverse array of synthetic observations, encompassing temperature (T), wind components (U and V), precipitable water (PW), and zenith total delay (ZTD), are assimilated utilizing the Local Error-Subspace Transform Kalman filter (LESTKF). The findings highlight the improvement in forecast accuracy achieved through the assimilation process over the ocean. Multiple observation types further improve the forecast accuracy. The study underscores the crucial role of GNSS data assimilation techniques. The assimilation of GNSS data presents potential for advancing weather forecasting capabilities. Thus, the construction of ground-based GNSS observation stations over the ocean is promising
Spatialising ‘carceral mobilities’: extracting census data for analysis of prisoner inflow, transfer and release
Get PDFResponding to the dearth of fully-comprehensive or summary data on prisoner or ‘carceral mobilities’, this paper provides the first comprehensive case study analysis of the flow into, between and out from prisons. By uniquely extracting data from the 2011 UK Census to identify and visualise trends in movement, highlight centrality of institutions and observe the self-containedness of regions of operation, findings reveal specific volumes and geographies of prisoner flow as well as discrepancies with the expected practices of prison category transfers and disparities between the distances travelled by prisoners in establishments with different functions. Such analysis is a critical tool in appraising (in)efficiencies with the governance of prisons at the regional and national level. In conclusion, Census Data is revealed as a viable source of data for analysis in situations where institutional data is not forthcoming/available, which provides significant potential for the advancement of the range and scope of studies in carceral mobilities and criminological research more broadly
What do glass sponges do when no one is looking? Vazella pourtalesii: Responses to sediment deposition, passive locomotion, and contracting behavior
Get PDFBehavioral response of deep-sea sponges can provide crucial insights into the mechanisms shaping energy fluxes and ecosystem functioning. Although some advances have been made, the behavior of deep-sea Hexactinellid still remain widely unknown. In the present study we address the glass sponge Vazella pourtalesii behavior. High-temporal resolution imaging and environmental data were acquired with an autonomous lander deployed in the Sambro Bank Sponge Conservation Area (Scotian Shelf) at a depth of 150 m, representing the upper limit of this deep-sea species' distribution and what is commonly regarded as the deep sea. For 94 days, a V. pourtalesii individual was monitored, providing quantitative information on its response to sediment deposition triggered by a storm, as well as on its passive locomotion and contractive behavior. Sediment was cleared from its surface within 72 h, which is highly relevant for its filtering capacity, indicating that this sponge species can cope with high suspended sediment concentrations. This enables it to occur on sedimentary environments like the Scotian Shelf. As observed in other deep-sea hexactinellids, the monitored individual engaged in rhythmic contractions, which appear to be driven by physiological process/es rather than environmental factors. During the study period, strong bottom currents (>37 cm/s) toppled and displaced the monitored individual several times. Despite changes in position and orientation that can negatively impact the filtering capacity of sponges, no signs of deterioration were observed. V. pourtalesii's vase-like body morphology and attachment to cobbles, as a gravitational center, may allow it to have a more homogeneous interaction with currents which may permit them to better cope with positional changes. Overall, this study highlights that deep-sea Porifera display a wide array of phenological changes in response to both biotic and abiotic factors
Long-term measurements reveal a 100-day lag between peaks in phytoplankton chlorophyll and benthic bacterial abundance in the Fram Strait
Get PDFAbstract
Repeated measurements of benthic and pelagic parameters in the rapidly changing Arctic Ocean provide a unique insight into spatial and interannual trends and changes in the ecosystem. Here, we compiled biogenic and biogeochemical measurements collected from sediment cores at the Long-Term Ecological Research Observatory HAUSGARTEN located in the Fram Strait. A total of 21 stations were visited yearly over a period of 18 years (2002–2019). The time series highlighted an increase in bacterial numbers for samples collected 50 days after the peak phytoplankton bloom. Although bacterial abundances were not bathymetric depth-dependent when viewed across all years, we observed a seasonal trend in benthic microbial abundance closely related to the timing of the phytoplankton bloom with a time-lag of 100 days between the surface phytoplankton peak and the peak in bacterial abundance in the sediment. Considering the residence time of phytoplankton in the upper ocean and the water depth, we estimated an average settling velocity for phytodetritus of 30 m.d−1, which is similar to previous observations from Fram Strait. This suggests that settling organic matter promotes vertical microbial connectivity and benthic bacterial abundance in the deep ocean, shaping the microbial biogeography, diversity, and biogeochemical processes.</jats:p
Glacial history of the King Haakon trough system, sub-Antarctic South Georgia
Get PDFThe glaciated island of South Georgia in the sub-Antarctic is a key area for climate reconstructions, because it is positioned in the Southern Ocean amidst the core belt of the Southern Westerlies and the main fronts of the Antarctic Circumpolar Current. This makes it particularly susceptible to changes in local, regional, but also Southern Hemisphere-wide climate conditions. Marine-geological records recovered from its continental shelf therefore offer unique potential to constrain how ice masses in this part of the Southern Ocean responded to Quaternary climate change, but despite this, little glacial-geomorphological and sedimentological research has been done offshore South Georgia. Here, we present a new suite of glacial landforms, identified from high-resolution bathymetry data, supplemented with acoustic facies from sub-bottom profiles, in order to reconstruct the pre-Holocene glacial history of the King Haakon Trough System on the southwestern South Georgia continental shelf. Our data show numerous landforms common for phases of ice advance and retreat, which are interpreted to document the confluence of two major trunk glaciers during peak glaciation. Progressively elongated linear bedforms imply accelerated ice flow and/or softer sediment substrate towards the shelf edge and suggest that the South Georgia Ice Cap experienced streaming ice and behaved similarly to other palaeo-ice sheets. A grounding-zone wedge close to the shelf edge marks the position of maximum ice extent during a peak glaciation, while clusters of recessional moraines and three large morainal banks indicate repeated phases of staggered retreat. Multiple extensive ice advances are indicated by stacked till sequences within the sub-bottom profiles of the mid- and outer shelf. The second-to-last till generation appears to be slightly more extensive than the most recent glacial till, and could suggest that South Georgia may have had a similar glacial evolution to other sub-Antarctic islands. This paper complements two studies focusing on the Holocene depositional environments and their associated sedimentary processes in the same trough system, in an effort to elucidate an important part of the Quaternary evolution of South Georgia's marine environment
Miocene Climatic Optimum and Middle Miocene Climate Transition: a foraminiferal record from the central Ross Sea, Antarctica
Get PDFAbstract. The Ross Sea record of the Miocene Climatic Optimum (MCO; ∼ 16.9–14.7 Ma) and the Middle Miocene Climate Transition (MMCT; ∼ 14.7–13.8 Ma) provides critical insights into Antarctic ocean–cryosphere interactions during a time of extreme warmth and subsequent cooling. Here we report on Lower to Middle Miocene foraminiferal assemblages from the International Ocean Discovery Program (IODP) Site U1521 on the outer shelf of the central Ross Sea to identify regional shifts in environmental and water mass conditions and trace continental shelf evolution. We identified seven benthic biofacies clusters, dominated by abundant Globocassidulina subglobosa (a proposed indicator of proto-Circumpolar Deep Water, pCDW), Uvigerina cf. U. fueguina (high productivity and enhanced bottom-water currents), Nonionella spp. (high productivity), or Melonis spp. (high productivity) using a Q-mode cluster analysis to develop preliminary regional paleoenvironmental interpretations. Four unique assemblages, including Globobulimina cf. G. auriculata (high productivity and low oxygen), are also identified. Unit IV (representing the early MCO event) is a short-lived (∼ 80 ka), progradational, clast-poor sandy diamictite, likely deposited during deglaciation; the upper part of Unit IV is transitional with overlying Unit III. Unit IV sediments contain the most persistently abundant and diverse foraminiferal assemblages recovered at U1521 because they are mud-rich and diatom-poor, despite very high sedimentation rates. The benthic assemblages shift between Globocassidulina and Uvigerina dominance, suggesting changes in the pCDW influence relative to productivity and/or current activity. We suggest the abundance of Uvigerina (a shelf-edge proxy) in Unit IV records the northward progradation of the Ross continental shelf at this location during the late Early to Middle Miocene. Unit III (MCO) was deposited in an open-marine setting, evident by the ice-rafted detritus or debris (IRD) clast-free, diatom-rich/diatom-bearing muds. The sporadic nature of foraminiferal abundances in Unit III is likely due to intervals of terrigenous mud alternating with more diatom-rich/diatom-bearing muds. As in Unit IV, the muddier lithologies (higher natural gamma ray (NGR) values) are more likely to preserve calcareous foraminifera, whereas the most diatom-rich sediments (lower NGR values) are more corrosive to carbonate. We interpret the muddier intervals as interglacials with incursions of pCDW, as indicated by increased Globocassidulina subglobosa, and sporadic occurrences of rare warmer-water planktic foraminifera. Collectively, these multiple incursions of warmer-water planktic foraminifera provide evidence for polar amplification in the Ross Sea during the MCO and MMCT. The diatom-rich muds are interpreted as glacials during the MCO with open-marine conditions and higher productivity. The dominance of Globobulimina in the upper part of Unit III corresponds with the carbon maximum of Carbon Maxima 2 (CM2) and low-oxygen conditions in the sediments at ∼ 16.1 Ma. Subsequent glaciation (including Mi2, Miocene Isotope event 2), marine-based ice sheet grounding, and erosion on the shallow shelf are recorded by the widespread Ross Sea Unconformity 4 (RSU4; ∼ 15.95–14.2 Ma) at Site U1521. Unit II (MMCT) likely represents sedimentation in the interval between the RSU4 and the Mi3 (Miocene Isotope event 3) glaciation at ∼ 13.9–13.8 Ma. The benthic biofacies composition of Unit II shows a further increase in neritic taxa, including Elphidium magellanicum and Epistominella vitrea, suggesting continued shoaling of the continental shelf, which facilitated the growth of marine-based ice sheets during the Middle Miocene. Our initial correlation between Site U1521 and the ANtarctic geological DRILLing Project (ANDRILL) site, AND-2A, yields similar environmental interpretations, including peak warm events 3 and 4 during the MCO, supported by the foraminifera and unit lithologies. Suspected glacial intervals during the MCO, including Mi2 at the top of Unit III, correlate well with the reconstructed deep-sea estimates of ice volume changes (seawater δ18Osw record) from the Ocean Drilling Program (ODP) Site 1171 on the South Tasman Rise.
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Climate change driven effects on transport, fate and biogeochemistry of trace element contaminants in coastal marine ecosystems
Get PDFHuman activities and climate change substantially threaten coastal areas, impacting ecosystem functions, services, and human-wellbeing. Trace elements, from both natural and anthropogenic sources, can contaminate coastal regions, and at high concentrations may become toxic to marine biota. Climate change is likely to affect the sources, sinks and cycling of trace elements in coastal systems: for example, riverine runoff is set to increase as precipitation in the Arctic intensifies, and more frequent extreme floods are expected to activate previously deeply buried trace elements. Furthermore, changes in human activity under a warming climate, such as increased Arctic shipping and potential geoengineering projects such as ocean alkalinity enhancement, will likely introduce more trace elements to coastal ecosystems. Advancing our understanding of trace element cycling is at present limited by factors including lack of data coverage in the Global South, challenges in studying multi-stressor effects and ecosystem responses, lack of long-term data, and the difficulty in parametrizing robust models in coastal environments
