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From the Surface Ocean to the Seafloor: Linking Modern and Paleo-Genetics at the Sabrina Coast, East Antarctica (IN2017_V01)
(American Geophysical Union, 2023) Armbrecht, Linda; Focardi, Amaranta; Lawler, Kelly; O'Brien, Phillip; Leventer, Amy; Noble, T L; Opdyke, Bradley; Duffy, Meghan; Evangelinos, Dimitris; George, Simon; Lieser, Jan; Lopez-Quiros, Adrian; Post, A; Armand, Leanne
With ongoing climate change, research into the biological changes occurring in particularly vulnerable ecosystems, such as Antarctica, is critical. The Totten Glacier region, Sabrina Coast, is currently experiencing some of the highest rates of thinning across all East Antarctica. An assessment of the microscopic organisms supporting the ecosystem of the marginal sea-ice zone over the continental rise is important, yet there is a lack of knowledge about the diversity and distribution of these organisms throughout the water column, and their occurrence and/or preservation in the underlying sediments. Here, we provide a taxonomic overview of the modern and ancient marine bacterial and eukaryotic communities of the Totten Glacier region, using a combination of 16S and 18S rRNA amplicon sequencing (modern DNA) and shotgun metagenomics (sedimentary ancient DNA, sedaDNA). Our data show considerable differences between eukaryote and bacterial signals in the water column versus the sediments. Proteobacteria and diatoms dominate the bacterial and eukaryote composition in the upper water column, while diatoms, dinoflagellates, and haptophytes notably decrease in relative abundance with increasing water depth. Little diatom sedaDNA is preserved in the sediments, which are instead dominated by Proteobacteria and Retaria. We compare the diatom microfossil and sedaDNA record and link the weak preservation of diatom sedaDNA to DNA degradation while sinking through the water column to the seafloor. This study provides the first assessment of DNA transfer from ocean waters to sediments and an overview of the microscopic communities occurring in the climatically important Totten Glacier region.
On the age of Ain Hanech Oldowan locality (Algeria): First numerical dating results
(Academic Press, 2023) Duval, Mathieu; Sahnouni, Mohamed; Pares, Josep M.; Zhao, Jian-Xin; Grun, Rainer; Abdessadok, Salah; Perez-Gonzalez, Alfredo; Derradji, Abdelkader; Harichane, Zoheir; Mazouni, Nacim; Boulaghraief, Kamel
Our current understanding of early human settlements in North Africa relies on a few well-contextualized Oldowan and Acheulean sites (e.g., Ain Hanech, El Kherba, Ain Boucherit Lw and Up, Tighennif in Algeria; Thomas Quarry in Morocco). In particular, the site of Ain Hanech has documented for many decades the earliest evidence of human presence in North Africa (e.g., Sahnouni and de Heinzelin, 1998), until older stone tools were recently reported at the nearby Ain Boucherit locality (Sahnouni et al., 2018).
Community recommendations for geochemical data, services and analytical capabilities in the 21st century
(Elsevier Ltd., 2023) Klocking, Marthe; Wyborn, Lesley; Lehnert, Kerstin; Ware, D. Bryant; Prent, Alexander M.; Profeta, Lucia; Kohlmann, Fabian; Noble, Wayne; Bruno, Ian; Lambart, Sarah; Ananuer, Halimulati; Gao, Yajie
The majority of geochemical and cosmochemical research is based upon observations and, in particular, upon the acquisition, processing and interpretation of analytical data from physical samples. The exponential increase in volumes and rates of data acquisition over the last century, combined with advances in instruments, analytical methods and an increasing variety of data types analysed, has necessitated the development of new ways of data curation, access and sharing. Together with novel data processing methods, these changes have enabled new scientific insights and are driving innovation in Earth and Planetary Science research. Yet, as approaches to data-intensive research develop and evolve, new challenges emerge. As large and often global data compilations increasingly form the basis for new research studies, institutional and methodological differences in data reporting are proving to be significant hurdles in synthesising data from multiple sources. Consistent data formats and data acquisition descriptions are becoming crucial to enable quality assessment, reusability and integration of results fostering confidence in available data for reuse. Here, we explore the key challenges faced by the geo- and cosmochemistry community and, by drawing comparisons from other communities, recommend possible approaches to overcome them. The first challenge is bringing together the numerous sub-disciplines within our community under a common international initiative. One key factor for this convergence is gaining endorsement from the international geochemical, cosmochemical and analytical societies and associations, journals and institutions. Increased education and outreach, spearheaded by ambassadors recruited from leading scientists across disciplines, will further contribute to raising awareness, and to uniting and mobilising the community. Appropriate incentives, recognition and credit for good data management as well as an improved, user-oriented technical infrastructure will be essential for achieving a cultural change towards an environment in which the effective use and real-time interchange of large datasets is common-place. Finally, the development of best practices for standardised data reporting and exchange, driven by expert committees, will be a crucial step towards making geo- and cosmochemical data more Findable, Accessible, Interoperable and Reusable by both humans and machines (FAIR).
Some animals make plant sterols
(American Association for the Advancement of Science, 2023) Brocks, Jochen; Bobrovskiy, Ilya
Cholesterol is a flat, rigid molecule that slots into animal cell membranes, controlling physical properties such as membrane rigidity, fluidity, permeability, and curvature. Other eukaryotes have taken sterol biosynthesis further by adding alkyl groups to the side chain, such as phytosterols found in plants. However, it remains an enigma why the membranes of nearly all animals use cholesterol alone, whereas most other eukaryotes, including plants and fungi, contain complex mixtures of various sterols in their membranes. On page 520 of this issue, Michellod et al. (1) report the discovery of gutless worms (Olavius algarvensis) that endogenously produce cholesterol as well as phytosterols that are usually found in plants. By searching for the remains of such sterols in fossils, it may be possible to map the evolution of sterol biosynthesis in the animal kingdom and eventually understand why humans exclusively produce cholesterol.
Cenozoic upper mantle flow history of the Atlantic realm based on Couette/Poiseuille models: Towards paleo-mantle-flowgraphy
(Elsevier, 2023) Ray Wang, Zhirui; Stotz, I; Bunge, Hans-Peter; Vilacis, Berta; Hayek, Jorge; Ghelichkhan, Siavash; Lebedev, Sergei
Mantle convection is a fundamental process in the Earth's system, yet its history remains poorly known. Sophisticated inverse geodynamic Earth models are available to retrodict past mantle states, but their high computational cost and complex parameterizations limit their ability to isolate key effects and interpret simulated paleo-mantle-flow patterns. This calls for an approach to conceptualize paleo-mantle-flow at a simple analytical level. The existence of weak asthenosphere allows one to formulate a Couette/Poiseuille model of upper mantle flow, where flow is linked to movements of overlying tectonic plates, and to lateral pressure gradients induced by rising plumes and sinking slabs. Here we present results from such models for the Atlantic realm in the Cenozoic, and link them to seismically inferred anisotropy along with mantle flow retrodictions from inverse geodynamic modeling. Our analytical paleo-mantle-flow indicates that (1) material sourced by plumes is carried towards slab locations, as expected, (2) it is broadly consistent with the orientation of seismic azimuthal anisotropy, and (3) it agrees with the large-scale flow patterns and amplitudes from mantle flow retrodictions. Our results suggest using a hierarchy of models together with growing geological constraints on past plate motions and dynamic topography to gain a better understanding of paleo-mantle-flow.