Animals shape Earth surface processes and landforms by displacing Earth surface materials and by making them more or less susceptible to geophysical processes. Despite increased recognition of the global significance of animal landscape "signatures", analysis of their magnitude and generality has not been possible until now. We present a meta-analysis of zoogeomorphic effect sizes using a comprehensive data set derived from a systematic review of published research. Our analysis provides unequivocal statistical evidence that wild animal agents substantially change geomorphic properties, on average by 136% in freshwaters and 66% in terrestrial ecosystems. Irrespective of ecosystem type, the presence of an animal agent increased substrate porosity and reduced the absolute or relative amount of fine material, properties that influence water and sediment fluxes and potentially landscape resilience. Livestock effect size data were scarce (two taxa), so analysis was focused on 61 wild animal species. While our analysis is the most extensive to-date, spanning nine taxonomic classes across freshwater and terrestrial ecosystem types, hundreds more animal geomorphic agents are not represented due to a lack of effect size data. In contrast to prevailing hypotheses, we found little evidence of reduced effect sizes in settings with higher potential geophysical energy; instead, relationships with energy context were nuanced and dependent on geomorphic signature. Our findings show that wild animal geomorphic effects are not of low magnitude, nor are they limited to a handful of species, ecosystem types, or energy contexts. These findings challenge orthodox assumptions that geophysical drivers dominate Earth surface processes, and landform and landscape evolution.
The bacterial genus Endozoicomonas is prevalent and abundant in the microbiome of many corals, but the combination of environmental and host factors shaping its distribution remains uncertain. In this study, we used 16S rRNA gene sequencing to examine the distribution of Endozoicomonas across hard (Porites astreoides, Montastraea cavernosa, Agaricia spp.) and soft coral (Muricea spp., Gorgoniidae, Cladiellidae, Malacalcyonacea) microbiomes across a depth gradient from shallow (4.5 m) to upper mesophotic zones (36.6 m) at four sites around the Little Cayman Island, including two marine protected areas. Endozoicomonas was abundant across all coral microbiomes, with soft corals exhibiting near-total dominance (relative abundance range 0.1–99
Shear zone systems exposed in the crystalline rocks of Colorado record Proterozoic deformation episodes documenting strain partitioning, reactivation and the progressive tectonic evolution of SW Laurentia. These structures, and their equivalents throughout the southwestern USA, provide insight into the structural evolution of the North American craton, and inform tectonic models for an active, but challenging to decipher period in Earth's history. NE-SW-trending mylonitic bands record regional fold formation and establishment of sub-vertical D-1/D-2 shear zones occurred during the successive c. 1720-1600 Ma Yavapai and Mazatzal orogenies, and D-3/D-4 reactivation of these structures during the c. 1450-1300 Ma Picuris Orogeny. The shallowly dipping Slide Lake Shear Zone (SLSZ), in Colorado's Sawatch Range, is adjacent to the steeply dipping Homestake Shear Zone (HSZ), allowing for comparison between high- and low-angle faulting in mid-crustal positions associated with the long-lived Laurentian orogenic margin throughout the Proterozoic. Both structures record similar deformational conditions and bulk NW-SE-verging kinematics. Newly obtained in situ electron microprobe monazite U-Th-Pb geochronology and trace element geochemistry constrain the timing and nature of SLSZ activity, allowing direct comparison with established HSZ activity. Core domains in a steeply dipping segment of the SLSZ record mineral growth during the Yavapai Orogeny (D-1) at c. 1700 +/- 14 Ma, and support continued SLSZ activation during the Mazatzal Orogeny (D-2). Low-angle segments preserve deformation associated with the Mesoproterozoic Picuris Orogeny (D-3/D-4) at c. 1450-1300 Ma. The age progression of the SLSZ parallels the structural evolution of the HSZ, indicating that sub-horizontal, transtensional, D-3/D-4 slip on the SLSZ was coeval with sub-vertical, transpressional, D-3/D-4 slip on the HSZ. Cumulatively, the existing structural and newly established temporal history of the HSZ-SLSZ system is interpreted to indicate that oblique extensional and compressional strain were competing in the middle crust within the Laurentian interior during the Picuris Orogeny, lending credence to models of plateau-style crustal thickening and collapse during this event.
ABSTRACT Gallium nitride (GaN) is near ubiquitous in modern day technologies, forming the backbone of solid‐state lighting and high‐power electronics. Engineering the physical properties of GaN has been investigated to some degree by the incorporation or doping of most of the elements of the periodic table, but the actinides remain unexplored. Molecular beam epitaxy is used to demonstrate uranium doping of GaN single crystals. High structural quality of the host matrix is maintained despite partial elemental segregation of the uranium dopant into 1D structures at the levels presented here. Electronic transport measurements reveal relatively high conductivity, which persists down to cryogenic temperature and is characterized by the formation of narrow gaps in the electronic band structures very close to the Fermi level. Photoluminescence measurements reveal that the U‐doped GaN exhibits optical behavior similar to that of the GaN substrate. The addition of actinide materials to a non‐centrosymmetric, optically active, radiation‐hard, and electronically tunable host matrix opens a world of possibilities for investigating and leveraging elements with high electron correlations in the pursuit of novel devices.
In agricultural landscapes, increasing groundwater nitrate concentrations are common and reflect leaching from cultivated soils, often into adjacent riparian zones within stream corridors. High nitrate concentrations may be attenuated in riparian groundwater, where abundant organic matter and saturated anoxic soils and sediments (collectively "substrate") support denitrifying activity. Variable substrate and the resulting residence time distribution in shallow groundwater can drive redox status and net nitrate removal, yet can be challenging to simulate in detail. This study explores how spatial variation in the texture of riparian aquifer substrate may influence groundwater residence times and biogeochemical behaviour of a riparian aquifer subject to chronic nitrate loading from non-irrigated wheat production in the semiarid Northern Great Plains. This is addressed using a novel combination of physicochemical measurements, geophysical observation of a groundwater tracer injection, and a simplified groundwater mixing model analysis. Higher and more variable nitrate concentrations were documented in wells completed in coarser substrates, suggesting generally shorter residence times compared to finer substrates, which exhibited lower nitrate concentrations suggestive of longer residence times. Therefore, we hypothesised that net nitrate consumption could be captured with a simple simulation approach using (a) the proportion of finer-textured riparian aquifer substrate to quantify redoximorphic processes that result in net nitrate consumption and (b) the proportion of coarser riparian substrate to quantify the groundwater residence time distribution. We tested this hypothesis by first exploring spatial patterns in groundwater chemistry and hydraulic characteristics at 16 shallow (< 1.5 m) wells and then by directly observing residence time of solutes in groundwater flow, using high frequency monitoring of groundwater specific conductivity and time-lapse electrical resistivity tomography imaging of a cross-section of a riparian groundwater flow path. Mixing models informed by geophysical imaging and tracer breakthrough constrain the potential influence of exchanges between fine and coarse substrates on the net nitrate transformation occurring along riparian groundwater flow paths. Dual-textured groundwater mixing model simulations illustrate how the proportion of coarse textured material may dictate the total amount of flow through riparian substrate while the proportion of flow through the finer-textured material that mixes with flow through coarse material may dictate the extent of net nitrate consumption processes. This work leverages novel geophysical observations to contribute a simple bimodal approach exploring how hydrologic complexity in riparian subsurface flow systems may influence the overall potential of riparian groundwaters to process nutrients before watershed export.
