scholarly journals Radiocarbon dating supports bivalve-fish age coupling along a bathymetric gradient in high-resolution paleoenvironmental studies

Geology ◽  
2020 ◽  
Vol 48 (6) ◽  
pp. 589-593 ◽  
Author(s):  
Paolo G. Albano ◽  
Quan Hua ◽  
Darrell S. Kaufman ◽  
Adam Tomašových ◽  
Martin Zuschin ◽  
...  
Keyword(s):  
Time Averaging ◽  
Depth Gradient ◽  
Surficial Sediments ◽  
Radiocarbon Age ◽  
Order Of Magnitude ◽  
Infaunal Bivalve ◽  
Temporal And Spatial ◽  
Trophic Webs ◽  
Warm Temperate ◽  
Comparable Time

Abstract Studies of paleocommunities and trophic webs assume that multispecies assemblages consist of species that coexisted in the same habitat over the duration of time averaging. However, even species with similar durability can differ in age within a single fossil assemblage. Here, we tested whether skeletal remains of different phyla and trophic guilds, the most abundant infaunal bivalve shells and nektobenthic fish otoliths, differed in radiocarbon age in surficial sediments along a depth gradient from 10 to 40 m on the warm-temperate Israeli shelf, and we modeled their dynamics of taphonomic loss. We found that, in spite of the higher potential of fishes for out-of-habitat transport after death, differences in age structure within depths were smaller by almost an order of magnitude than differences between depths. Shell and otolith assemblages underwent depth-specific burial pathways independent of taxon identity, generating death assemblages with comparable time averaging, and supporting the assumption of temporal and spatial co-occurrence of mollusks and fishes.

Distribution of mercury and methylmercury in the sediments of a lowland river system

2005 ◽  
Vol 461 (2057) ◽  
pp. 1335-1355 ◽  
Author(s):  
Jason W Birkett ◽  
John N Lester
Keyword(s):  
Point Source ◽  
Total Mercury ◽  
Sewage Treatment ◽  
River System ◽  
Initial Increase ◽  
Surficial Sediments ◽  
Spatial Trends ◽  
The Mean ◽  
Temporal And Spatial ◽  
Temporal And Spatial Trends

Concentrations of total mercury (T-Hg) and methylmercury (MeHg) were determined in surficial sediments from the River Yare, Norfolk, UK over the period 1986–1998, to assess the temporal and spatial trends of contamination arising from a historical point source discharge. The results demonstrate that the spatial distribution pattern follows that of a distinct pollution plume in the sediments with an initial increase 2–3 km downstream from the point source discharge at Whitlingham sewage treatment works (STW) outfall. Temporally, this pollution plume remains evident, although there has been an overall decline in the mean T-Hg concentrations from 5.4 in 1986 to 1.8 mg kg −1 in 1998. The major factor for this improvement has been the reduction in discharge of metals from the STW, together with burial by a fresh overlay of uncontaminated sediments. MeHg concentrations also exhibited a dispersed pollution plume. Mean concentrations of MeHg fluctuated during the study period between 3.3 and 8.5 μg kg −1 . There has been no concomitant decline in MeHg concentrations over this period. MeHg was found to constitute less than 1% of T-Hg concentrations in the sediments. The weak correlations observed between T-Hg and MeHg concentrations indicate external environmental factors have a significant influence on determining MeHg concentrations in the sedimentary compartment.

scholarly journals Temporal and spatial variations in CH4 concentrations in a Japanese warm-temperate mixed forest

2010 ◽  
Vol 66 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Takafumi MIYAMA ◽  
Taro HASHIMOTO ◽  
Yuji KOMINAMI ◽  
Kenta NAKAGAWA ◽  
Motonori OKUMURA ◽  
...  
Keyword(s):  
Mixed Forest ◽  
Spatial Variations ◽  
Temporal And Spatial Variations ◽  
Temporal And Spatial ◽  
Temperate Mixed Forest ◽  
Warm Temperate

Time averaging and stratigraphic unmixing: reconstructing ecological decline in molluscan production (Holocene, Brijuni, NE Adriatic)

2020 ◽  
Author(s):  
Adam Tomašových ◽  
Martin Zuschin ◽  
Ivo Gallmetzer ◽  
Alexandra Haselmair
Keyword(s):  
Accumulation Rate ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Coralline Algae ◽  
Time Averaging ◽  
Sedimentation Rates ◽  
Amino Acid Racemization ◽  
Ecological History ◽  
Shell Bed ◽  
Warm Temperate

<p>The northeastern Adriatic seafloor is formed by warm-temperate bioclastic carbonates with coralline algae, bryozoans and mollusks. These sediments represent a mixture of past and present-day production owing to low sedimentation rates and bioturbation. Although low sedimentation rates do not allow resolution of ecological history at centennial or even millennial scales on the basis of raw stratigraphic data, age unmixing based on radiocarbon-calibrated amino acid racemization shows that one of the major molluscan sediment producers – the infaunal suspension-feeder Timoclea ovata  – markedly peaked in production ~5,000 years during the maximum flooding and earliest highstand phase and significantly diminished in abundance during the late highstand phase at Brijuni, with a large proportion of dead shells now present in surface sediments representing shells that are several centuries old. This species still occurs in living assemblages but our analyses indicate that its former production was by several orders of magnitude higher. In contrast, stratigraphic trends in absolute and proportional abundance of this species in ~1.5 m-thick sediment cores show a gradual or a very mild upcore decline, indicating that raw stratigraphic data do not efficiently detect millennial-scale ecological dynamic. The temporal decline in production of Timoclea ovata is associated with an increase in water depth and an increase in sediment-accumulation rate, and led to a transition from molluscan oyster-scallop shell bed to late highstand bryomol sediments.</p>

scholarly journals Embracing the uncertainty: the evolution of SOFI into a diverse family of fluctuation-based super-resolution microscopy methods

2021 ◽  
Author(s):  
Monika Pawlowska ◽  
Ron Tenne ◽  
Bohnishikha Ghosh ◽  
Adrian Makowski ◽  
Radek Lapkiewicz
Keyword(s):  
3D Imaging ◽  
Deep Neural Networks ◽  
Fluorescent Proteins ◽  
Super Resolution ◽  
Significant Progress ◽  
Spatial Correlations ◽  
Order Of Magnitude ◽  
Temporal And Spatial ◽  
Microscopy Techniques ◽  
Super Resolution Microscopy

Abstract Super-resolution microscopy techniques have pushed the limits of resolution in optical imaging by more than an order of magnitude. However, these methods often require long acquisition times as well as complex setups and sample preparation protocols. Super-resolution Optical Fluctuation Imaging (SOFI) emerged over ten years ago as an approach that exploits temporal and spatial correlations within the acquired images to obtain increased resolution with less strict requirements. This review follows the progress of SOFI from its first demonstration to the development of a branch of methods that treat fluctuations as a source of contrast, rather than noise. Among others, we highlight the implementation of SOFI with standard fluorescent proteins as well as the microscope modification that facilitate 3D imaging and the application of modern cameras. Going beyond the classical framework of SOFI, we explore different innovative concepts from deep neural networks all the way to a quantum analogue of SOFI, antibunching microscopy. While SOFI has not reached the same level of ubiquity as other super-resolution methods, our overview finds significant progress and substantial potential for the concept of leveraging fluorescence fluctuations to obtain super-resolved images.

Analysis of the Inter-Row Flow Field Within a Transonic Axial Compressor: Part 2 — Unsteady Flow Analysis

2000 ◽  
Author(s):  
Xavier Ottavy ◽  
Isabelle Trébinjac ◽  
André Vouillarmet
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Flow Analysis ◽  
Axial Compressor ◽  
Leading Edge ◽  
Rotor Blades ◽  
Time Averaging ◽  
Flow Phenomena ◽  
Order Of Magnitude ◽  
Transonic Axial Compressor

An analysis of the experimental data, obtained by laser two-focus anemometry in the IGV-rotor inter-row region of a transonic axial compressor, is presented with the aim of improving the understanding of the unsteady flow phenomena. A study of the IGV wakes and of the shock waves emanating from the leading edge of the rotor blades is proposed. Their interaction reveals the increase in magnitude of the wake passing through the moving shock. This result is highlighted by the streamwise evolution of the wake vorticity. Moreover, the results are analyzed in terms of a time averaging procedure and the purely time-dependent velocity fluctuations which occur are quantified. It may be concluded that they are of the same order of magnitude as the spatial terms for the inlet rotor flow field. That shows that the temporal fluctuations should be considered for the 3D rotor time-averaged simulations.

Verification of a conceptual model of water quality for small temporarily open/closed estuaries: East Kleinemonde Estuary, South Africa

2009 ◽  
Vol 60 (3) ◽  
pp. 234 ◽  
Author(s):  
Susan Taljaard ◽  
Gavin Snow ◽  
Phumelele Gama ◽  
Lara van Niekerk
Keyword(s):  
South Africa ◽  
Water Quality ◽  
Conceptual Model ◽  
Complex Dynamics ◽  
Inorganic Nitrogen ◽  
Spatial Scales ◽  
Chemical Parameters ◽  
Physico Chemical ◽  
Temporal And Spatial ◽  
Warm Temperate

The dynamics of the world’s larger permanently open estuaries have been well documented, but much less is known about the complex dynamics of smaller temporarily open/closed estuaries (TOCEs). Seventy per cent of South Africa’s 250 estuaries are classified as TOCEs, and many are less than 50 ha. A conceptual model of the water-quality dynamics of TOCEs has been proposed, primarily considering three hydrodynamic states (closed, semi-closed and open). This paper uses data from the East Kleinemonde Estuary, a small TOCE in the warm-temperate region of South Africa, to verify the model, focusing on physico-chemical parameters (salinity, temperature, pH, dissolved oxygen and turbidity) and inorganic macronutrients (dissolved inorganic nitrogen and dissolved inorganic phosphate) for the open and closed states. The results generally fitted the model in terms of the behaviour of the physico-chemical parameters and macronutrients in the water column. This knowledge provides a first approach to predict the water-quality dynamics in small TOCEs, thereby ensuring that the often limited resources are targeted at resolving uncertainties at appropriate temporal and spatial scales. TOCEs are not unique to South Africa and also occur along other coasts (Mediterranean and south-western Australia) where this type of model could also be applied.

Sclerochronological evidence of pronounced seasonality from the Pliocene of the southern North Sea Basin, and its implication

2021 ◽  
Author(s):  
Andrew Johnson ◽  
Annemarie Valentine ◽  
Melanie Leng ◽  
Bernd Schöne ◽  
Hilary Sloane ◽  
...  
Keyword(s):  
Surface Temperature ◽  
North Sea ◽  
High Surface ◽  
Time Averaging ◽  
Arctica Islandica ◽  
Late Pliocene ◽  
Southern North Sea ◽  
Winter Temperatures ◽  
Cool Temperate ◽  
Warm Temperate

<p>Various elements of the biota of the early Pliocene Coralline Crag Formation (southern North Sea Basin, eastern England) have been taken to indicate a warm temperate marine climate, with summer surface temperatures above 20 °C and winter temperatures above 10 °C [1]. However, summer and winter temperature estimates from oxygen-isotope (δ<sup>18</sup>O) sclerochronology of benthic invertebrates are typically in the respective cool temperate range when calculated using a plausible modelled value for water δ<sup>18</sup>O of +0.1‰. For instance, examples of the bivalve mollusc <em>Aequipecten opercularis</em> from the Ramsholt Member indicate summer maximum temperatures of 11.0–15.7 °C and winter minimum temperatures of 4.4–7.1 °C [2]. Amongst other evidence, the pattern of microgrowth-increment variation in Ramsholt-Member <em>A. opercularis</em> points to a depth below the summer thermocline, hence the temperatures recorded for that season provide an underestimate of surface temperature; this may well have been in the warm temperate summer range [2], as suggested by the pelagic dinoflagellate biota [3]. However, the cool temperate benthic winter temperatures indicated by isotopic data are likely also to have obtained at the surface, pointing to a greater seasonal range in surface temperature (perhaps > 15 °C) than in the modern North Sea (< 13 °C) [2]. This conclusion is not changed by adoption of a different (invariant) value for water δ<sup>18</sup>O and also follows from data for a specific late Pliocene interval (Mid-Piacenzian Warm Period) elsewhere in the southern North Sea Basin (Belgium, Netherlands [4]). Here we present isotopic evidence of a seasonal range in surface temperature higher than now at other times in the late Pliocene. Examples of <em>A. opercularis</em> from several horizons in the Lillo Formation (Belgium) and the Oosterhout Formation (Netherlands) indicate seasonal ranges in benthic temperature of 10–14 °C. Seasonal variation in water δ<sup>18</sup>O can only plausibly account for about 1 °C of these ranges. Taking into consideration microgrowth-increment evidence of a setting below the summer thermocline, the seafloor ranges imply that the surface seasonal range was sometimes 17 °C or more. Other bivalves (<em>Atrina fragilis</em>, <em>Arctica islandica,</em> <em>Pygocardia rustica</em>, <em>Glycymeris radiolyrata</em>) do not indicate such a high seasonal range in benthic (and hence surface) temperature but this can be attributed to inadequate sampling—time-averaging or a failure to recover evidence of seasonal extremes because of growth breaks. The high surface temperature range could reflect a reduction in vigour of the North Atlantic Current and hence diminished oceanic supply of heat in winter.</p><p>References:</p><p>[1] Vignols et al. (2019), Chem. Geol. 526, 62–83. https://doi.org/10.1016/j.chemgeo.2018.05.034.</p><p>[2] Johnson et al. (2020), Palaeogeogr. Palaeoclimatol. Palaeoecol. 561. https://doi.org/10.1016/j.palaeo.2020.110046.</p><p>[3] Head (1997), J. Paleontol. 71, 165–193. https://doi.org/10.1017/S0022336000039123.</p><p>[4] Valentine et al. (2011), Palaeogeogr. Palaeoclimatol. Palaeoecol. 309, 9–16. https://doi.org/10.1016/j.palaeo.2011.05.015.</p>

Aminochronology and time averaging of Quaternary land snail assemblages from colluvial deposits in the Madeira Archipelago, Portugal

2019 ◽  
Vol 92 (2) ◽  
pp. 483-496 ◽  
Author(s):  
Evan New ◽  
Yurena Yanes ◽  
Robert A.D. Cameron ◽  
Joshua H. Miller ◽  
Dinarte Teixeira ◽  
...  
Keyword(s):  
Land Snail ◽  
Time Averaging ◽  
Radiocarbon Age ◽  
Amino Acid Racemization ◽  
Madeira Archipelago ◽  
Dating Methods ◽  
Dating Method ◽  
Volcanic Islands ◽  
Geologic Record ◽  
Age Estimates

AbstractUnderstanding the properties of time averaging (age mixing) in a stratigraphic layer is essential for properly interpreting the paleofauna preserved in the geologic record. This work assesses the age and quantifies the scale and structure of time averaging of land snail-rich colluvial sediments from the Madeira Archipelago (Portugal) by dating individual shells using amino acid racemization calibrated with graphite-target and carbonate-target accelerator mass spectrometry radiocarbon methods. Gastropod shells of Actinella nitidiuscula were collected from seven sites on the volcanic islands of Bugio and Deserta Grande (Desertas Islands), where snail shells are abundant and well preserved in Quaternary colluvial deposits. Results show that the shells ranged in age from modern to ~48 cal ka BP (calibrated radiocarbon age), covering the last glacial and present interglacial periods. Snail shells retrieved from two of the colluvial sites exhibit multimillennial age mixing (>6 ka), which significantly exceeds the analytical error from dating methods and calibration. The observed multimillennial mixing of these assemblages should be taking into consideration in upcoming paleoenvironmental and paleoecological studies in the region. The extent of age mixing may also inform about the time span of colluvial deposition, which can be useful in future geomorphological studies. In addition, this study presents the first carbonate-target radiocarbon results for land snail shells and suggests that this novel, rapid, and more affordable dating method offers reliable age estimates for small land snail shells younger than ~20 cal ka BP.

scholarly journals Thermodynamics at Very Long Time and Space Scales

Entropy ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. 1090 ◽  
Author(s):  
Bjarne Andresen ◽  
Christopher Essex
Keyword(s):  
Large Time ◽  
Additional Constraint ◽  
Time Averaging ◽  
Length Scale ◽  
Slow Time ◽  
The Past ◽  
New Concepts ◽  
Molecular Scale ◽  
Long Time ◽  
Order Of Magnitude

Any observation, and hence concept, is limited by the time and length scale of the observer and his instruments. Originally, we lived on a timescale of minutes and a length scale of meters, give or take an order of magnitude or two. Therefore, we devloped laboratory sized concepts, like volume, pressure, and temperature of continuous media. The past 150 years we managed to observe on the molecular scale and similarly nanoseconds timescale, leading to atomic physics that requires new concepts. In this paper, we are moving in the opposite direction, to extremely large time and length scales. We call this regime “slow time”. Here, we explore which laboratory concepts still apply in slow time and which new ones may emerge. E.g., we find that temperature no longer exists and that a new component of entropy emerges from long time averaging of other quantities. Just as finite-time thermodynamics developed from the small additional constraint of a finite process duration, here we add a small new condition, the very long timescale that results in a loss of temporal resolution, and again look for new structure.

Sign in / Sign up

Export Citation Format

Share Document