Low-energy Environment Research Articles

The sclerobionts of the Bajocian Oolithe ferrugineuse de Bayeux Formation from Calvados (Paris Basin, Normandy, France)

Silicified fossils collected in ploughed fields at Gavrus (Calvados, France), mainly mollusc shells, are Bajocian in age, and come from the Oolithe ferrugineuse de Bayeux Formation. The entire formation is highly condensed and most fossils are reworked. Their silicification allowed treatment with dilute hydrochloric acid. This treatment brought to light numerous encrusting sclerobionts: Porifera (3 taxa), Bryozoa (n), Polychaeta (9), Brachiopoda (n), Bivalvia (5). The borings and bioerosional traces are described using the “categories of architectural design” as defined by Buatois et al. (2017). Among the 28 ichnotaxa described (corresponding to an ichnodisparity of 14), Planavolites wisshaki isp. nov., Kleithrichnus belemnophilus igen. nov., isp. nov. and Foggara foggara igen. nov., isp. nov. are new. Some Gastrochaenolites dijugus Kelly and Bromley, 1984 borings accommodate the shell of the presumed borer Lithophaga fabella J.-A. Eudes-Deslongchamps, 1838. A group of Nododendrina europaea (Fischer, 1875) on a belemnite rostrum provides a good instance of an ichnogenetic series. Encrusting sclerobionts and macroscopic boring and bioerosional trace-makers are dominantly suspension feeders. The ichnofacies is a peculiar Entobia-ichnofacies, found in deeper, lower-energy environments than the “classical” coastal Entobia-ichnofacies, on deep shell-grounds far from the coast, in the deep euphotic zone.

Exploring bacterial pathogen community dynamics in freshwater beach sediments: A tale of two lakes.

Pathogenic bacteria associated with freshwater ecosystems can pose significant health risks particularly where recreational water use is popular. Common water quality assessments involve quantifying indicator Escherichia coli within the water column but neglect to consider physical and geochemical factors and contributions from the sediment. In this study, we used high-throughput sequencing to investigate sediment microbial communities at four freshwater public beaches in southern Ontario, Canada and analysed community structure, function, and gene expression with relation to geographical characteristics. Our results indicate that beach sediments at the sediment-water interface could serve as potential sources of bacterial contamination under low-energy environments with tightly packed small sediment particles compared with high-energy environments. Further, the absence of pathogens but expression of pathogenic transcripts suggests occurrence of alternate gene acquisition. Pathogenicity at these locations included expression of Salmonella virulence factors, genes involved in pertussis, and antimicrobial resistance. Finally, we introduce a proposed universal bacterial pathogen model to consider the combined and synergistic processes used by these microbes. To our knowledge, this is the first study of its kind to investigate chemolithotrophic activity related to pathogens within bed sediment at freshwater beaches. This work helps advance current understanding of health risks in these environments.

COMP-01. MODELING THE EVOLUTION OF PLOIDY IN A RESOURCE RESTRICTED ENVIRONMENT

Abstract Progression of lower-grade gliomas (LGG) to glioblastoma (GBM) is accompanied by a phenotypic switch to an invasive cell phenotype. Converging evidence from colorectal-, breast-, and lung-cancers, suggests a strong enrichment of high ploidy cells among metastatic lesions as compared to the primary. Even in normal development: trophoblast giant cells are responsible for invading the placenta during embryogenesis and these cells often have tens of copies of the genome. We formulate a mechanistic Grow-or-go model that postulates higher energy demands of high-ploidy cells as driver of invasive behavior. The unit we are modeling is a cell, that comes with a certain ploidy, proliferation-, and death-rate. Variations in ploidy emerge as a result of chromosome missegregations. For each cell we calculate the probability of cell-division as a function of energy availability in the neighborhood vs. ploidy-dependent energy demand of the cell. Underlying this comparison is the dual role of integrin signaling: integrin-mediated signals allow cells to progress from G1 to S-phase. At the same time integrins mediate cell migration. The model was implemented as a cellular automaton and 2,500 simulations were ran at variable energies and missegregation rates. In low-energy environments high-ploidy clones were enriched at the leading edge of the tumor. This was not the case in high-energy environments. We applied the model to analyze previously published exome sequencing data from 14 multi-spatial and longitudinal LGG biopsies. Using the size and ploidy of co-existing clones as summary statistics for Approximate Bayesian Computation, we infer relative chromosome missegregation rates in primary LGG. A higher missegregation rate was predictive of faster progression of LGG to GBM (multivariate Cox: HR = 7.96, P = 0.041). Future validation experiments will evaluate the potential of the model to explain differences in the prognostic power of integrin signaling and cell cycle progression between males and females.

Stratigraphic setting of fossil log sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA

The outcrop belt of the Upper Jurassic Morrison Formation in the northeastern Uinta Basin and southeastern flank of the Uinta Mountains is particularly rich in dinosaurian and non-dinosaurian faunas, as well as in fossil plants. The discovery of several well-preserved, relatively intact, fossil logs at several locations in Rainbow Draw and one location in Miners Draw, both near Dinosaur National Monument (Utah), has provided an opportunity to study the local paleobotany, stratigraphy, and sedimentology of the Morrison Formation in northeastern Utah. The Morrison Formation in northeastern Utah consists of four members. In ascending chronostratigraphic order, they are the Windy Hill, Tidwell, Salt Wash, and Brushy Basin Members. The lithology (including the presenceof glauconite grains) and fossil assemblage of the lower two members (Windy Hill and Tidwell) indicate a marine to marginal marine (coastal plain) depositional environment, whereas the lithology, fossil flora and faunaassemblage of the upper two members (Salt Wash and Brushy Basin) indicate a fluvial–lacustrine depositional environment. At least 10 fossil log sites in Rainbow Draw have been documented so far, and geologic mapping indicates that the logs and wood all occur in the same stratigraphic interval within the Salt Wash Member, approximately 17 to 27 m above the base of the member. The unit containing the logs and wood is about 11 m thick and consists of very fine to fine-grained sandstone and siltstone with indistinct bedding and no discernible sedimentary features.The logs are siliceous, some have a coaly exterior, and they range in exposed length from 0.5 to 11 m and reach diameters up to 1.1 m. In the Miners Draw area, a single siliceous log is documented in the upper part of the Salt Wash Member within a silty sandstone unit that is 4 m thick; its exposed length is about 6 m. Although the correlation of the Miners Draw log-bearing interval to the interval in Rainbow Draw is uncertain, both units are lithologically similar and both occur in the upper part of the Salt Wash Member. The logs have been identified as araucariaceous conifers that pertain to the same taxon originally described as Araucarioxylon hoodii Tidwell et Medlyn 1993 from Mt. Ellen in the Henry Mountains of southern Utah. Concurrent systematic work will prompt a nomenclatural transfer of this species to the genus Agathoxylon. Based on the abundance of large fossil logs and wood in the same stratigraphic interval in Rainbow Draw, wehypothesize that the area was covered by stands of moderately large trees of araucariaceous conifers. The sedimentological evidence suggests that the trees were not transported far from their original site of growth before they were deposited in a low-energy floodplain environment.

Spatial Abundance and Colour Morphotype Densities of the Rock-Boring Sea Urchin (Echinometra lucunter) at Two Different Habitats

The rock-boring sea urchin Echinometra lucunter is a common echinoderm found throughout the intertidal zone along the northeastern coast of, Toco, Trinidad. Sea urchin abundance, size distribution, and colour morphotypes at two sites: Pequelle Bay (SB) and Grande L’Anse (GA) were quantified using 1 m2 quadrats, accessible during extreme low tides, and in two environments, notably low and high wave action. Percent coverage of cnidarian and macroalgae were estimated in each quadrat. Sea urchin densities were 9.9–17.8 urchins/m2 in high wave action, and 25.2–60.7 urchins/m2 in low wave action environments. Size (measured as maximum sea urchin diameter) are highest between 21 and 50 mm for both black and red colour morphotypes. Black colour morphs were significantly larger than red morphs (ANOVA, F2, 175 = 5.55, p < 0.05). Sea urchins at low energy environments were significantly larger than those found in high energy environments for all years (p < 0.05). Mean hard coral, soft coral, and macroalgae cover did not show any relationship with habitat type or urchin densities. Although sea urchin abundance and distribution were variable, larger urchins were more likely to be found in low wave action environments, and smaller urchins were mostly found in the open, and exposed to high wave action.

The genus Dallocardia (Mollusca: Bivalvia: Cardiidae) in the Southwestern Atlantic Ocean

Fil: Signorelli, Javier Hernan. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Centro Nacional Patagonico. Instituto de Biologia de Organismos Marinos; Argentina

Differences in vegetation characteristics with shoreline position on a tropical pocket beach

ABSTRACT Composition and richness of coastal vegetation differs with distance from the water and sheltering by topography. Transition from pioneer beach plants to mature forests is expected to be narrow on low wave energy coasts with a tropical climate favorable to vegetation growth. The goal of this paper is to determine whether vegetation on the beach and foredune will be denser and have a greater number of species and more woody shrubs near the water as wave and wind stresses diminish because of favorable shoreline orientation within a pocket beach. Field data on beach width, beach mobility, dune height, vegetation species, vegetation height and percent vegetation cover were collected in Puerto Rico along six cross-shore transects. Beaches are more stable at transects in the lee of an eolianite barrier and a tombolo. The vegetation gradient there is compressed, with denser, taller, more diverse vegetation and more tree species close to the waterline than at more exposed sites. The lack of mobility of the beaches and dunes and lack of geomorphically significant disturbance events is in contrast to the conspicuous feedbacks between overwash, topography, and vegetation on exposed mid-latitude coasts, revealing the need for more study of low-energy beach environments.

Environmental trends between 2400 and 1200 BP in Barrancas, Argentinean Puna: Impacts on local resource variability and socioeconomic organization

AbstractThis paper presents a multiproxy analysis—geomorphology, organic matter, and carbonate content, diatoms, pollen, and magnetic properties of sediments—of the Barrancas Pueblo profile, located in Barrancas, Jujuy, Argentina (S 23°18′08,7; W 66°05′15,2; 3666 m.a.s.l.) to explore local environmental change over the last few millennia. This study is part of a broader investigation of the environmental conditions that facilitated and/or triggered the development of a mixed herding and hunting economic strategy during the late Holocene. The results suggest ongoing local moisture availability for most of the late Holocene; between 2400 and 1500 BP there was a stable, low energy environment that supported a vegetated floodplain, resulting in high availability of pasture and water. However, throughout most of the studied period, there were punctual arid episodes and erosion of the river catchment. High environmental variability post‐3000 cal BP could have put a premium on strategies to reduce the risk associated with resource unpredictability, such as economic specialization and intensification and storage practices designed to control and mitigate resource variability. This process could have ultimately lead to the consolidation of the Andean pastoralist way of life ca. 3000–2500 BP.

Shoal environment as a biodiversity hotspot: A case from the Barremian-Albian strata of Gabal Lagama (North Sinai, Egypt)

Recent studies demonstrated that shoal habitats include exceptionally diverse marine communities. Therefore, understanding the dynamics of these shoals under natural climatic changes is essential for biodiversity conservation. The Barremian-Albian succession of Gabal Lagama (North Sinai, Egypt) represents high-energy carbonates deposited on a complex oolite shoal. Behind these shoals, restricted lagoons and inter/supratidal mudflats environments of lesser extent were formed. Both rock and fossil samples were subjected to quantitative analyses. Nonmetric Multidimensional Scaling (NMDS) based on quantitative data from the microfacies suggested that the percentage of ooids, echinoderms, and benthic foraminifers are the major contributors to the variation in the facies association. Based on macrofaunal samples, three main benthic communities were identified. These communities display a clear connection to hydrodynamics and substrate type (grain size and consistency level). Indeed, high-energy shoal environment is characterized by a polyspecific association, which is dominated by epifaunal suspension-feeders (Amphidonte association). In contrast, two associations of low-energy environment is dominated by few species (i.e. paucispecific) and therefore, they reflect stressed environments; the lagoonal (Nucula association) and the middle ramp (Trigonia association). The facies architecture arranged the Barremian-Albian succession into five Type 2 sequences, which document 3rd order sea-level oscillation. The Barremian delta-dominated setting changed into a tide-dominated homoclinal ramp in the early Aptian and finally to a wave-dominated ramp by the late Aptian, which continued to the early Albian. The functional attributes of the benthic communities (epifauna/infauna and deposit/suspension feeders) have cyclic pattern correlated to the third order sea-level fluctuations.

The characteristics and controlling factors of facies-controlled coastal eogenetic karst: insights from the Fourth Member of Neoproterozoic Dengying Formation, Central Sichuan Basin, China

Karst porosity system is widely developed in the Fourth Member of Neoproterozoic Dengying Formation in Central Sichuan Basin of China. The result of the previous exploration in this area based on the theory of telogenetic karst, which mainly focused on the fracture/fault belt especially in the karst slope, leaves much to be desired. Though a systematically geological research in this study, it is found that the dissolution holes are mainly concentrated on the mud mound deposits and granular rocks. Both of them have a greater primitive porosity and permeability than the micrite that originally formed in low-energy environments, which is facies controlled. On the basis of the above and the fact that a tectonic movement has caused a massive subaerial exposure of the formation that only experienced a shallow burial, it is proposed that the paleokarst porosity system is the product of eogenetic karst. Two-stage eogenetic karsts have been interpreted: the syngenetic exposure caused by the short-term relative sea-level fluctuation and the exposure caused by the uplift of the second phase of Tongwan tectonic movement. The meteoric alteration in syngenetic period is commonly marked by the development of intergranular pores but on a small scale. It is believed to be important for providing a good pore-permeability foundation for the later eogenetic karst. The later exposure occurs immediately at the end of the deposition of the Fourth Member of Dengying Formation that only experienced a shallow burial. Since the effect of compaction and cementation in this shallow burial before uplift is relatively weak, only the micrite has been densified and retaining the majority of original pores in the carbonate mounds and grain shoals as paths for karst flow. Moreover, combined with the geological background and seismic profile, it can be ascertained that the karst occurs in a coastal environment. Twelve meteoric lenses have been interpreted after recovering the karst palaeogeomorphology. The scale of the meteoric lens and the reservoir performance have shown a decreasing tendency from the coastal to the inland area, which also confirms this view. The results of this research have put emphasis on the lithologic differentiation in eogenetic karst and the geographical location of karst development thus might provide a reference for further reservoir prediction in this area and other similar places.

Resveratrol cytotoxicity is energy-dependent.

Resveratrol is a phytochemical that may promote health. However, it has also been reported to be a toxic compound. The molecular mechanism by which resveratrol acts remains unclear. The inhibition of the oxidative phosphorylation (OXPHOS) pathway appears to be the molecular mechanism of resveratrol. Taking this into account, we propose that the cytotoxic properties of resveratrol depend on the energy (e.g., carbohydrates, lipids, and proteins) availability in the cells. In this regard, in a condition with low energy accessibility, resveratrol could enhance ATP starvation to lethal levels. In contrast, when cells are supplemented with high quantities of energy and resveratrol, the inhibition of OXPHOS might produce a low-energy environment, mimicking the beneficial effects of caloric restriction. This review suggests that investigating a possible complex relationship between caloric intake and the differential effects of resveratrol on OXPHOS may be justified. PRACTICAL APPLICATIONS: A low-calorie diet accompanied by significant levels of resveratrol might modify cellular bioenergetics, which could impact cellular viability and enhance the anti-cancer properties of resveratrol.

Inkjet printing of zinc oxide and P3HT:ICBA in ambient conditions for inverted bulk heterojunction solar cells

The third-generation organic solar cells have the benefits of low-cost, solution processability, low energy payback time, environment friendliness and appropriateness for mass production via large area printing techniques. The electron transport layer improves the ohmic contact between the cathode and the photoactive layer. In this research article, we demonstrate a drop on demand inkjet printing of the zinc oxide electron transport layer and the photoactive layer blend consisting of a donor poly(3-hexylthiophene-2,5-diyl) (P3HT) and acceptor Indene C-60 bisadduct (ICBA) of an organic solar cell. Consequently, all inkjet printed solar cell achieved a power conversion efficiency of 4.7% under ambient conditions. We highlighted that drop spacing, substrate temperature and the waveform parameters such as voltage and time are the important parameters for printing. Moreover, we observed a difference in morphology between spin coated and inkjet printed devices as characterized via UV–Visible absorbance, atomic force microscopy and scanning electron microscopy. Furthermore, we applied device characterization from impedance spectroscopy to elucidate the difference in device performance. Particularly, the effective lifetime and global mobilities calculated from the impedance spectroscopy Nyquist plots at 1 Voltage bias in the dark for all inkjet-printed devices are 0.0374 μs and 57.5 × 10−3 cm2/V–S respectively, and for all, spin-coated devices are 0.0628 μs and 115.3 × 10−3 cm2/V–S respectively.

Cellulose acetate based biopolymeric mixed matrix membranes with various nanoparticles for environmental remediation-A comparative study

Aluminium oxide (Al2O3) and nano zerovalent iron (nZVI) nanoparticles blended cellulose acetate-polysulfone (CA-PSF) ultrafiltration mixed matrix membranes (MMMs) were successfully prepared via phase inversion method for the removal of dyes and metal ions from wastewater. The dye degradation is very difficult because of structure and low biodegradability nature. At the same time, removal of heavy metals from water also a challenging task. In this study, removal of methylene blue (MB) dye and Cu (II) metal ions as a great environmental concern. There are many techniques available for the removal of these pollutants such as chemical precipitation, adsorption etc. Now-a-days, membrane separation has been extensively used for the treatment of wastewater due to their operational simplicity, low energy consumption and environment friendly nature. In this study, bare CA-PSF (M1) and nanoparticles incorporated MMMs like CA-PSF/Al2O3 (M2) and CA-PSF/nZVI (M3) were prepared, characterized and compared for their rejection and filtration performances. The modified membranes have high rejection values 91 and 94% for MB dye and for Cu (II) the rejection values of 84 and 88% for M2 and M3 membranes respectively than bare membrane. Surface roughness, morphology, cross sectional structure and nanoparticles distribution in the membranes were examined by AFM, SEM and TEM. Membrane performances in terms of pure water permeability and antifouling were also assessed. The fabricated membranes showed outstanding capacity to take care for contaminated water.

Litho-, bio-, and chemostratigraphy of the Middle Triassic carbonate succession in the North-Central Coast Region of Vietnam

Middle Triassic carbonates extend from the North-Central Coast region of Vietnam to northern Laos. We conducted sedimentological, paleontological, and geochemical analyses on the carbonates of the Hoang Mai Formation in Nghe An province, Vietnam. The carbonates consist of the following six lithostratigraphic units (from bottom to top): sandy limestone (unit 1), peloidal packstone with a microbialite interlayer (unit 2), peloidal packstone and oncoidal floatstone (unit 3), peloidal–bioclastic packstone (unit 4), peloidal packstone with variable quantities of bioclasts and microbialite (unit 5), and peloidal packstone with variable quantities of bioclasts (unit 6). The sandy nature of unit 1 and of three of the interlayers in unit 2 indicates a supply of terrigenous material during the early stages of formation of the Hoang Mai carbonate platform. The dominance of carbonates with a fine-grained matrix throughout the overlying succession implies a low-energy depositional environment. Common occurrences of dasycladalean algae in units 4–6 indicate a back-reef lagoon environment. A total of 24 foraminiferal taxa, including Citaella dinarica and C. deformata, were identified. These two age-diagnostic species occur in units 3–6, suggesting that this interval is correlated with the Pelsonian and that the lower units (units 1–2) are potentially correlated with the Bithynian. Thus, the entire core section can be assigned to the middle Anisian (lower Middle Triassic). An assessment of the diagenetic alteration using geochemical parameters indicates that the carbonates of the studied succession have not retained their initial strontium (87Sr/86Sr) and oxygen (δ18O) isotope compositions. In contrast, the carbonates in the lower (units 1–2) and middle (units 2–5) intervals have retained their initial carbon isotope compositions (δ13C), making them suitable for C isotopic analyses. In the lower interval, we observe a slight δ13C-enrichment, followed by a gradual δ13C-depletion upwards into the middle interval. The observed trend in δ13C values from the Hoang Mai Formation can be correlated with similar trends reported from South China and Romania. Samples within the upper interval (units 5–6) of the Vietnamese δ13C profile are relatively δ13C-depleted, which is likely the result of diagenetic overprinting.

The Early–Middle Ordovician graptolite genus Azygograptus in South China: New material and paleogeographic implications

This study presents a new analysis of three species of the Ordovician graptolite genus Azygograptus Nicholson & Lapworth from the Wenxiakou section in the Zhongxiang area of Hubei Province. The paleogeographic occurrences of the genus within South China were plotted on an up-to-date paleogeographic map based on a revised data set of graptolite occurrences from 68 localities compiled by the online Geobiodiversity Database (GBDB). The paleogeographic distribution of Azygograptus follows a nearshore-offshore trend, and the taxonomic diversity of Azygograptus is higher in nearshore high-energy environments than in offshore low-energy environments. However, graptolites also gathered in deeper-water environments surrounding oldlands partly due to the high-nutrient inputs and rapid deposition. Azygograptus is found not only in high-latitude cold-water regions as endemic taxa but also in low-latitude regions. Oceanic circulation may account for the rapid dispersal of Azygograptus from high-latitude regions, such as Britain and Scandinavia, to low-latitude regions, such as South China, eventually resulting in their observed paleogeographic distribution.

A structure model for phase separated fluoroaluminosilicate glass system by molecular dynamic simulations

Oxyfluoride glass and glass ceramics have been widely used in optical devices with Ln3+ doping. Especially, fluoride phase separation is considered as the initial stage of nanocrystallization that can help to realize the controllable crystallization and also provide the low phonon energy environment in oxyfluoride glass. Therefore, a structure model to describe this phase separated glass system is in great help for designing optical materials with high luminescence. In this study, large-scale molecular dynamics (MD) simulations were performed to understand the structural heterogeneity and make attempt to propose a structure model for fluoroaluminosilicate glass. The simulation results reveal immiscible behaviors of the fluoroaluminosilicate glass that separate into fluoride-rich phase and aluminosilicate-rich residual matrix, which have structural features analogous to fluoride and aluminosilicate glass, respectively. Besides, Al3+ plays an essential role to inter-connect oxygen and fluorine ions on the oxide-fluoride phase interface, maintaining the stability of the glass system.

Exploring geophysical and palynological proxies for paleoenvironmental reconstructions in the Miocene of western Amazonia (Solimões Formation, Brazil)

Western Amazonia underwent important landscape changes during the Miocene due to the Andean uplift. Vast wetlands developed during this period and prevailed until the late Miocene. The evolution of this environment has been studied on the basis of sedimentology and paleontology. Here, we explore geophysical proxies (Gamma Ray, Electric Resistivity and Spontaneous Potential) from cores of the Solimões Formation (Brazil) to support paleoenvironmental reconstructions and potentially validate pollen taxa as environmental indicators. We show a general tendency from geophysical profiles to increasing energies in the depositional settings in agreement with lithologies during the accumulation history of the Solimões Formation. Moreover, ACME zone of the fossil palm Mauritia (Mauritiidites franciscoi) is associated with low energy environments, ACME of the extinct palm Grimsdalea magnaclavata is associated with similar environments but of a transitional nature, oscillating between high and low energies, and ACMEs of fossil Poaceae (Monoporopollenites annulatus) are mostly associated with high-energy environments of more active fluvial dynamics. These three phases appear in order from early, early/middle and middle/late Miocene in the cores, which we believe reflects the climax development and subsequent demise of the wetland system. Additionally, marine surfaces are detectable in the geophysical logging what could help sampling strategies for future studies on cores aiming to detecte these marine events.

Evaluating the effects of morphology and orientation on feeding in atrypide brachiopods using 3-D printed models

The brachiopod order Atrypida was one of the most diverse and abundant clades of marine organisms across North America during the Silurian and Devonian. Atrypide brachiopods were active sessile suspension feeders that used their lophophores to capture food particles from the water. Within the subfamily Variatrypinae, there are two end-member morphotypes associated with either high or low energy environments. It has further been suggested shape played an important role in enhancing feeding efficiency. The first morphotype is shield-shaped, weakly convex, and associated with low-energy systems. The second morphotype is globose and associated with high-energy systems. Furthermore, both pedicle-attached and liberosessile life orientations have been suggested for atrypides, based on both fossil material and biomechanical experiments. Any change in orientation could radically affect feeding efficiency. Our study uses biomechanical experiments on morphologically accurate 3-D printed atrypide models to evaluate the effects of shape and orientation on feeding current strength in the shield-shaped and globose morphotypes. We used 3-D scanning and printing to construct two morphologically accurate gaping models of the end-member shapes. The models included simulated body tissue, a flexible scale lophophore and valves of accurate thickness. A recirculating flume tank and dye streams were used to visualize ambient flow within the models in multiple pedicle-attached and pedicle-absent orientations to flow. During the trials the shield shape produced better ambient flow than the globose shape in pedicle-attached orientations. Further, pedicle-attached orientations produced better ambient flow than pedicle-absent orientations. Our results suggest that, shield-shaped atrypides benefited from enhanced ambient flow, while globose atrypides would have relied more on active pumping when in a pedicle attached orientation. As well, the results suggest a pedicle was required to orient atrypides for efficient feeding.

Stromatolite Provinces of Hamelin Pool: Physiographic Controls On Stromatolites and Associated Lithofacies

Recent studies recognized distinct stromatolite provinces in Hamelin Pool, Western Australia, each with morphologically distinct stromatolite structures paired with characteristic shelf physiography. In the present paper, we couple detailed lithofacies mapping with Hamelin Pool bathymetry and consider physiography as a control of sedimentation processes, including stromatolite development. Bathymetric transects, derived from a high-resolution bathymetry map with depths from 0 to 11 meters, allow calculation of slope gradients in the provinces. As in other settings, bathymetry is linked to energy regimes, which in turn appear to be coupled with variations in stromatolite morphologies and associated lithofacies as follows: (1) low-gradient ramps with low-energy settings are associated with sheet mats and elongate-clustered stromatolites that exhibit regular spatial patterns, possibly indicative of self-organization; (2) low gradients coupled with high-energy settings resulting from strong winds result in seif stromatolites with pronounced directional bands; (3) medium to steep gradients coupled with medium to high energy are associated with individual and merged stromatolites, often with thin basal necks; (4) headlands and promontories where the topography deflects currents are associated with elongate-nested stromatolites; and (5) medium- to high-energy slopes typically found at promontory edges and shelf margins are dominated by blocky pavement. Observations linking stromatolite morphology to physiography in a modern microbial system provide insight into the long-lived debate about biology versus environment in controlling stromatolite morphology. When physiography leads to a high-energy regime, environmental controls are the main factor determining stromatolite morphology. In contrast, when physiography promotes a low-energy environment, the response of biological communities becomes the main driver of macroscale stromatolite morphology.

Dissecting the paleocontinental and paleoenvironmental dynamics of the great Ordovician biodiversification

AbstractThe Ordovician was a time of drastic biological and geological change. Previous work has suggested that there was a dramatic increase in global diversity during this time, but also has indicated that regional dynamics and dynamics in specific environments might have been different. Here, we contrast two paleocontinents that have different geological histories through the Ordovician, namely Laurentia and Baltica. The first was situated close to the equator throughout the whole Ordovician, while the latter has traversed tens of latitudes during the same time. We predict that Baltica, which was under long-term environmental change, would show greater average and interval-to-interval origination and extinction rates than Laurentia. In addition, we are interested in the role of the environment in which taxa originated, specifically, the patterns of onshore–offshore dynamics of diversification, where onshore and offshore areas represent high-energy and low-energy environments, respectively. Here, we predict that high-energy environments might be more conducive for originations.Our new analyses show that the global Ordovician spike in genus richness from the Dapingian to the Darriwilian Stage resulted from a very high origination rate at the Dapingian/Darriwilian boundary, while the extinction rate remained low. We found substantial interval-to-interval variation in the origination and extinction rates in Baltica and Laurentia, but the probabilities of origination and extinction are somewhat higher in Baltica than Laurentia. Onshore and offshore areas have largely indistinguishable origination and extinction rates, in contradiction to our predictions. The global spike in origination rates at the Dapingian/Darriwilian boundary is apparent in Baltica, Laurentia, and onshore and offshore areas, and abundant variability in diversification rates is apparent over other time intervals for these paleocontinents and paleoenvironments. This observation hints at global mechanisms for the spike in origination rates at the Dapingian/Darriwilian boundary but a domination of more regional and local mechanisms over other time intervals in the Ordovician.