Environmental Reconstruction Research Articles

Hash Encoding and Brightness Correction in 3D Industrial and Environmental Reconstruction of Tidal Flat Neural Radiation.

We present an innovative approach to mitigating brightness variations in the unmanned aerial vehicle (UAV)-based 3D reconstruction of tidal flat environments, emphasizing industrial applications. Our work focuses on enhancing the accuracy and efficiency of neural radiance fields (NeRF) for 3D scene synthesis. We introduce a novel luminance correction technique to address challenging illumination conditions, employing a convolutional neural network (CNN) for image enhancement in cases of overexposure and underexposure. Additionally, we propose a hash encoding method to optimize the spatial position encoding efficiency of NeRF. The efficacy of our method is validated using diverse datasets, including a custom tidal flat dataset and the Mip-NeRF 360 dataset, demonstrating superior performance across various lighting scenarios.

Testing and refinement of elemental proxies in tropical lakes from the Indian subcontinent

AbstractThe conventional approach of using modern values of lake hydrochemistry and sediment composition as key parameters for identifying proxies for environmental reconstruction is complicated by regional climate, catchment geology, lake morphometry and anthropogenic input. In contrast to modern studies from lakes in the north‐temperate regions, reliable proxy indicators for past environmental change from tropical lake systems are still lacking. In this study, we compare new surface geochemical and mineralogical data from the Manasbal Lake, Kashmir (India), with other lakes situated in climatically and geomorphologically distinct regimes with varying degrees of pollution (Tso Moriri in north‐western Himalaya and Lonar in central India). We characterise external (e.g., geology and weathering), internal (e.g., lake water mixing and evaporation) factors and human activities influencing sediment composition and spatial distribution of proxies in each of these lakes to evaluate the usefulness of some of the commonly used proxies, as well as ascertain conditions where they might be applicable. Our results show that (i) morphometric parameters (such as lake size, water depth and catchment vs. lake area) variably influence the spatial distribution of sediments and proxies on the lake bottom highlighting the limitations of using single cores for long‐term palaeoclimate reconstruction; (ii) hydrochemical proxies (such as Na+/Na++Ca2+ and Mg/Ca) can delineate endogenic (Lonar and Tso Moriri lakes) versus allogenic (Manasbal Lake) influence on modern sediment characteristics; (iii) the compilation of heavy metal data (e.g., Fe, Zn, Mn, Cr and Ni) from all three lake basins with varying degrees of pollution highlights the limitations of using them to characterise weathering conditions in these basins; and (iv) human impact must be precluded before using the most promising endogenic minerals (calcite, aragonite, gypsum and pyrite) as palaeoenvironmental/palaeoclimate indicators.

ADVANCING ANTARCTIC SEDIMENT CHRONOLOGY THROUGH COMBINED RAMPED PYROLYSIS OXIDATION AND PYROLYSIS-GC-MS

ABSTRACT Radiocarbon (14C) dating of sediment deposition around Antarctica is often challenging due to heterogeneity in sources and ages of organic carbon in the sediment. Chemical and thermochemical techniques have been used to separate organic carbon when microfossils are not present. These techniques generally improve on bulk sediment dates, but they necessitate assumptions about the age spectra of specific molecules or compound classes and about the chemical heterogeneity of thermochemical separations. To address this, the Rafter Radiocarbon Laboratory has established parallel ramped pyrolysis oxidation (RPO) and ramped pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) systems to thermochemically separate distinct carbon fractions, diagnose the chemical composition of each fraction, and target suitable RPO fractions for radiocarbon dating. Three case studies of sediment taken from locations around Antarctica are presented to demonstrate the implementation of combined RPO-AMS and Py-GC-MS to provide more robust age determination in detrital sediment stratigraphy. These three depositional environments are good examples of analytical and interpretive challenges related to oceanographic conditions, carbon sources, and other factors. Using parallel RPO-AMS and Py-GC-MS analyses, we reduce the number of radiocarbon measurements required, minimize run times, provide context for unexpected 14C ages, and better support interpretations of radiocarbon measurements in the context of environmental reconstruction.

Investigating human impacts on rocky reefs using measures of complexity and relief from 3D photogrammetry

AbstractThe structural complexity of a habitat is linked with the health and biodiversity of the ecosystem. Computational methods analyzing 3D representations of the environment allow for accurate measurement; however, rocky reef environments that feature gullies, arches, stacks, and ledges may be inaccurately represented using standard measures of complexity. This article presents a novel assessment of structural complexity through relief calculated from 3D reconstructions of marine environments, tailored for rocky reefs with vertical features. This method is tested in two case studies: a tropical coral reef in Indonesia and a rocky (chalk) reef in the United Kingdom. Chalk reef relief was not correlated with vector dispersion or fractal dimension and was weakly correlated with rugosity (); however, in two comparison tropical reef datasets, relief correlated moderately with vector dispersion on both coral reefs () and moderately‐strongly with rugosity (). On the chalk reef, tailored complexity metrics confirmed the previous finding that catch‐size Cancer pagurus abundance (≥115 mm) was correlated with fractal dimension (), indicating that adults preferred elevated, complex reefs. Analysis showed correlations between relief and low‐severity chalk damage () and between relief and abrasion damage (), whereas previous research had indicated that damage was not correlated with complexity (assessed computationally with rugosity, fractal dimension, and vector dispersion). Surveying marine environments with multicamera arrays and 3D photogrammetry can drastically reduce the time and cost of fieldwork surveys and provide accurate measures of complexity across survey sites. Adapting complexity metrics to habitat‐specific topography provides valuable insight (in this case, into rocky reef marine habitats). Findings from the UK case study support the continued monitoring of the Cromer Shoal Chalk Bed Marine Conservation Zone (MCZ).

The relationship between the loess stratigraphy in the Vojvodina region of northern Serbia and the Saalian and Rissian Stage glaciations – a review

The regional loess stratigraphy in the Vojvodina region, in the southeastern Carpathian Basin, has often been successfully correlated to the global palaeoclimate. This is a quasi‐continuous sedimentary record that provides detailed environmental reconstruction during the last four glacial/interglacial cycles. In this study, we present a standardized loess stratigraphy and illustrate how it correlates with the marine oxygen isotope and Chinese loess stratigraphical records. We argue that the loess stratigraphy in Vojvodina region is an important link in the integration of European terrestrial stratigraphical schemes and the deep‐sea stratigraphical model. We highlight how the loess record can better illustrate terrestrial environmental change through multiple glacial cycles than other records, such as glacial records. The investigated loess record enables direct links to be made between the loess sediments and their glacial sources. This reveals evidence of glaciations during every glacial cycle of the Saalian Stage complex, equivalent to Marine Isotope Stage (MIS) 10, 8 and 6. Therefore, Serbian loess has the potential to provide a direct link between terrestrial glaciations and wider records of global climate change, which is an enigma for many other continental records. These loess records display a strong relationship with the intensity of European glaciations during different glacial cycles. Loess sedimentation rates are highest in the most intensive European glaciation of the Saalian complex (MIS 6) and much lower during the weaker ‘missing’ glaciations equivalent to MIS 8 and 10. A key observation from the Vojvodina loess is the gradual increase in interglacial aridity through the late Middle Pleistocene. The explanation for the progressively increasing aridity in the investigated region at this time is still unclear. However, this trend is consistent with the idea of the Saalian complex as representing a 400 ka mega glacial cycle modulated by shorter classic 100 ka glacial cycles.

Stable isotopes in the shell organic matrix for (paleo)environmental reconstructions

Stable isotope ratios of mollusc shell carbonates have long been used to reconstruct past environmental conditions. Although shells also contain organics, they are seldom used in (paleo)climatic studies. Here, we extract the acid-soluble and insoluble fractions of the organic matrix of modern Mytilus galloprovincialis shells from three sites along a coast–to-upper-estuary environmental gradient to measure their hydrogen (δ2H) and oxygen (δ18O) isotope compositions. Both organic fractions showed isotopic signatures significantly different from those of carbonate and water at each site, indicating the involvement of different fractionation mechanisms. The soluble fraction showed gradual differences in isotope values along the gradient, while the insoluble fraction showed δ2H-δ18O correlation regressions subparallel to the Global and Local Meteoric Water Lines. These results showed the great potential of the shell organic matrix stable isotopes as possible (paleo)environmental proxies, stimulating further research to better define the fractionation mechanisms involved.

Self-Interested Coalitional Crowdsensing for Multi-Agent Interactive Environment Monitoring.

As a promising paradigm, mobile crowdsensing (MCS) takes advantage of sensing abilities and cooperates with multi-agent reinforcement learning technologies to provide services for users in large sensing areas, such as smart transportation, environment monitoring, etc. In most cases, strategy training for multi-agent reinforcement learning requires substantial interaction with the sensing environment, which results in unaffordable costs. Thus, environment reconstruction via extraction of the causal effect model from past data is an effective way to smoothly accomplish environment monitoring. However, the sensing environment is often so complex that the observable and unobservable data collected are sparse and heterogeneous, affecting the accuracy of the reconstruction. In this paper, we focus on developing a robust multi-agent environment monitoring framework, called self-interested coalitional crowdsensing for multi-agent interactive environment monitoring (SCC-MIE), including environment reconstruction and worker selection. In SCC-MIE, we start from a multi-agent generative adversarial imitation learning framework to introduce a new self-interested coalitional learning strategy, which forges cooperation between a reconstructor and a discriminator to learn the sensing environment together with the hidden confounder while providing interpretability on the results of environment monitoring. Based on this, we utilize the secretary problem to select suitable workers to collect data for accurate environment monitoring in a real-time manner. It is shown that SCC-MIE realizes a significant performance improvement in environment monitoring compared to the existing models.

Fossil soils from abrasive southern Baltic coastal sections and problems with their classification: A case study from Ustka Bay, Poland

This study aimed to identify the main depositional and soil-forming phases in the middle section of the Polish Baltic coast and determine the history of its landscape development. An attempt was also made to define new qualifiers to describe these compacted and eroded soils (including fossil soils), which have not previously been included in the WRB classification. The study was conducted in cliff sections located in the southern Baltic coastal zone. Selected physical and chemical properties were determined from four soil profiles using standard methods. Additionally, peat, peat-like material, mursh, and charcoals were dated using the radiocarbon method. Environmental reconstructions based on fossil soils have provided information about the development of the coast in the context of periods of relative climate stability that allowed the formation of soils of various types. The presence of sediments of different origin (glacial till, fluvioglacial and aeolian sands, interbeddings of peat, mursh and peat-like material) in the profiles compared with the obtained radiocarbon dates allowed for an assessment of the impact of environmental conditions on the potential for soil formation over thousands of years. The oldest soils, represented by Akrofluvic Stagnic Gleysols and Fluvic Stagnic Gleysols, were dated back to the Preboreal/Boreal period,whereas the youngest fossil soils (Albic Podzols (Arenic) and Aeolic Dystric Arenosols)) were developed in the SA2 phase of the Subatlantic period. The contemporary soil cover was represented by poorly developed Aeolic Dystric Arenosols with initial features of the podzolization process. No soils dated to the Atlantic period were found. Our findings are complementary to those of other studies on the history of the Polish Baltic coast and can be used for comparing with the soil cover development in other coastal regions of the Baltic Sea.

A Novel Approach for Simultaneous Localization and Dense Mapping Based on Binocular Vision in Forest Ecological Environment

The three-dimensional reconstruction of forest ecological environment by low-altitude remote sensing photography from Unmanned Aerial Vehicles (UAVs) provides a powerful basis for the fine surveying of forest resources and forest management. A stereo vision system, D-SLAM, is proposed to realize simultaneous localization and dense mapping for UAVs in complex forest ecological environments. The system takes binocular images as input and 3D dense maps as target outputs, while the 3D sparse maps and the camera poses can be obtained. The tracking thread utilizes temporal clue to match sparse map points for zero-drift localization. The relative motion amount and data association between frames are used as constraints for new keyframes selection, and the binocular image spatial clue compensation strategy is proposed to increase the robustness of the algorithm tracking. The dense mapping thread uses Linear Attention Network (LANet) to predict reliable disparity maps in ill-posed regions, which are transformed to depth maps for constructing dense point cloud maps. Evaluations of three datasets, EuRoC, KITTI and Forest, show that the proposed system can run at 30 ordinary frames and 3 keyframes per second with Forest, with a high localization accuracy of several centimeters for Root Mean Squared Absolute Trajectory Error (RMS ATE) on EuRoC and a Relative Root Mean Squared Error (RMSE) with two average values of 0.64 and 0.2 for trel and Rrel with KITTI, outperforming most mainstream models in terms of tracking accuracy and robustness. Moreover, the advantage of dense mapping compensates for the shortcomings of sparse mapping in most Smultaneous Localization and Mapping (SLAM) systems and the proposed system meets the requirements of real-time localization and dense mapping in the complex ecological environment of forests.

First flower inclusion and fossil evidence of Cryptocarya (Laurales, Lauraceae) from Miocene amber of Zhangpu (China)

Lauraceae have one of the oldest fossil records of angiosperms with the earliest known evidence from the mid-Cretaceous. However, most of these records are based on leaves, especially from the Cenozoic of Asia, which are often challenging to assign to extinct or extant genera or species. In contrast, fossils of reproductive organs are more informative, but remain scarce. We here described the first Cenozoic Lauraceae flower of Asia and confirmed the presence of Cryptocarya in the Miocene Zhangpu flora (Fujian Province, south-eastern China) based on an amber inclusion. We scanned the specimen using synchrotron radiation-based micro-computed tomography (SRμCT) and then compared the fossil with extant flowers of the genus. The present fossil flower is small, bisexual, and polysymmetric, with a whorled and trimerous perianth and androecium along with a hypanthium around the gynoecium. The perianth comprises six undifferentiated tepals, the androecium consists of nine stamens and three innermost staminodes, and the gynoecium of a single carpel with a superior, unilocular (and uniovulate) ovary. Our study also shows that the fossil shares an unusual position of the typical staminal glands and a short androecial tube on the rim of the hypanthium with at least one extant Australian species of Cryptocarya, which have not been reported before. Nowadays, Lauraceae are still present in tropical to subtropical regions, mostly in American and Asian rainforests. The discovery of many Lauraceae leaf fossils in Zhangpu, as well as the amber flower of this study, is consistent with the current reconstruction of the amber source environment as a megathermal seasonal rainforest during the Mid-Miocene.

A new indicator for estimating the degree of mining-induced land subsidence: the overburden’s average GSI value

Underground coal mining leads to land subsidence, which, in turn, results in damage to buildings and infrastructure, disturbs the original ecological environment, and hinders the sustainable development of coal mining cities. A reasonable estimation of land subsidence, on the other hand, is the foundation for building protection, land reclamation, and ecological environment reconstruction. However, when we applied the existing land subsidence estimation theory to the deep mining areas of the Ordos coalfield in western China, there was a significant deviation between the estimations and the measurements. To explain such unusual case, we propose using the overburden’s average GSI (Geological Strength Index) value instead of the compressive strength (UCS) of rock specimens for a better representation of the overburden’s overall properties. By using on-site subsidence monitoring results and historical data, we provided evidence which supports that the overburden’s average GSI value has a much greater impact on subsidence rates than the UCS. Subsequently, we investigated the relationship between three typical overburden’s GSI values and the subsidence rates via a calibrated numerical model, revealing the variation patterns of maximum surface subsidence when the overburden’s average GSI value is set at 30, 50, and 75, respectively. Finally, on the basis of the measured and simulated results, we discussed a non-conventional strip mining method for mining subsidence control in the deep mining areas of the Ordos coalfield in western China, and explained why it is possible and what are the significant advantages behind. The proposed methods, findings, and suggestions in this paper are therefore quite helpful for researchers and engineers who wish to estimate and control the mining-induced land subsidence, as well as for those who are particularly interested in the study of environment science related to land subsidence.

Active Iterative Optimization for Aerial Visual Reconstruction of Wide-Area Natural Environment

Active Iterative Optimization for Aerial Visual Reconstruction of Wide-Area Natural Environment

Cultivating staff equality, diversity, and inclusion in higher education in the post-pandemic era: an organizational compassion perspective.

The COVID-19 pandemic has exacerbated pre-existing challenges faced by academic staff in UK higher education and drawn attention to issues of Equality, Diversity, and Inclusion (EDI). Amidst global competitiveness and workplace pressures, challenges such as managerialism, increased workload, and inequalities have worsened, significantly impacting mental health. This paper presents a conceptual analysis connecting EDI with organizational compassion within the context of Higher Education. The prioritization of organizational compassion is presented as a means to enhance sensitivity to EDI in the reconstruction of post-pandemic learning environments. Anchored in the organizational compassion theory and the NEAR Mechanisms Model, our study contributes to the intersection of the organizational compassion, EDI and higher education literatures by exploring how fostering compassion relations can contribute to enhancing EDI. This offers a new perspective to creating a more humane and supportive higher education environment.

Holocene and postglacial lake sedimentation in the central part of the Karelian Isthmus as an example of Lake Krasnoye in the Leningrad region

This paper deals with the issue of changing the conditions of the geographical environment in the postglacial and Holocene in the central part of the Karelian Isthmus. Toward paleogeographic reconstruction, a survey of the sediments of the bottom of Lake Krasnoye (Leningrad Oblast, Russian Federation) was conducted, since the lake deposits represent a reliable source of information about natural events from the past. A large amount of data obtained by X-ray fluorescence analysis of the core sample was analyzed, a lithostratigraphic description of the sediments was carried out and geophysical characteristics of the bottom sediments were interpreted. They were divided into several units that differed in the number of properties and reflected different sedimentation conditions. In the reconstruction of the past natural environment, special attention is paid to paleoclimatic and paleosedimentological issues.

3D Trajectory Planning for Real-Time Image Acquisition in UAV-Assisted VR

Nowadays, unmanned aerial vehicles (UAVs), empowered with the capability of high-definition image transmission, are used to capture the rapidly changing physical environment by leveraging its high flexibility to reconstruct an immersive realistic virtual environment for metaverse users. In this paper, we consider a novel UAV-assisted image acquisition system where a UAV is dispatched to take off from an initial location to capture real-time images of multiple ground targets and then transfer the captured images back to the ground user for virtual environment reconstruction. We aim to minimize the time for the UAV to complete the image acquisition task by optimizing the three-dimensional UAV trajectory under the constraints of image quality, information causality and energy consumption. To this end, we first formulate the investigated scenario into a mixed integer optimization problem, which, however, is difficult to solve due to the infinite time-varying variables closely coupled with each other. Then, a three-stage progressive algorithm is proposed to obtain an efficient solution to the formulated mixed integer optimization problem, where the constraints of image quality, information causality and energy consumption can be sequentially satisfied. Finally, comprehensive performance evaluation is conducted to verify the effectiveness of the proposed three-stage progressive trajectory design algorithm, and the results show that the proposed algorithm significantly outperforms the benchmark schemes.

Late Quaternary human-environment relationship in the Ganga Plain, India

Here, we present the first-ever attempt to combine palaeoenvironmental records (n = 17) from dated stratigraphic sequences with Geographic Information System (GIS) spatial modelling of archaeological sites (3 phases; n = 306 sites) in the Ganga Plain. The spatial modelling assesses the distribution of archaeological sites and phases on maps showing changing elevation, geology, geomorphology, biome, and rainfall variability within the Ganga Plain, aiming to evaluate the human-environment relationship during the Late Quaternary Period.The compilation of oxygen and hydrogen isotopic composition (δ18O and δD values) and pollen-based environment reconstructions for the last ∼100 ka indicates high rainfall conditions during ∼100–75 ka, ∼10–5 ka, and ∼3.6–1.3 ka. Fluctuating rainfall conditions were observed during ∼75–25 ka and ∼18–15 ka, while the period from ∼25 to 18 ka was the weakest monsoon phase, marking the Last Glacial Maximum. Arid conditions were also observed during ∼15–10 ka and ∼5–3.6 ka. The archaeological review suggests the presence of the Acheulian culture, diverse Mesolithic cultures, and the Neolithic phase marked by advanced agriculture and pottery production in the Ganga Plain. The past environmental analyses show changes in settlement areas correlating with rainfall variations. Frequent climate changes and increasing population density during the Late Pleistocene-Early Holocene boundary probably forced prehistoric humans to adopt agricultural practices. The distribution of archaeological sites representing different cultural phases on the modern spatial maps of landscape variability (e.g., elevation, rainfall, geomorphology, and geology) reflects an intricate relationship between prehistoric human settlements, monsoonal rainfall, and climate-driven landform processes.Our assessment suggests that the integration of archaeological sites, geological mapping, vegetation analysis, and palaeoclimate records has the potential to provide valuable insights into ancient human-environment interactions. Therefore, we recommend continued interdisciplinary research in these fields to further enhance our knowledge of prehistoric societies and their responses to changing landscapes and climates in the Ganga Plain.

Tropical Mountain Peatlands from Southern Espinhaço Range, Brazil: Ecosystem Services, Biodiversity and Paleoenvironmental Reconstruction

Peatlands are transition ecosystems between terrestrial and aquatic environments, formed over time and space by the accumulation of plant materials under conditions of excessive moisture, low nutrient availability, low pH and oxygen scarcity, in which organic matter undergoes slow processes of humification. Peatland ecosystems from the Southern Espinhaço Range (SdEM), located in the State of Minas Gerais, were formed by the sui generis combination of environmental factors, setting the stage for their vast biodiversity, endemic and peculiar. For thousands of years these ecosystems have been developing, preserving proxies for environmental reconstitution, sequestering more and more carbon, and increasing their capacity to store water (spongelike effect) and regulate the water discharge from streams. Environmental reconstruction studies carried out in these ecosystems have revealed various regional paleoclimatic changes in the last 35,000 years. The carbon stock sequestered is 8.7 Mt, and 255 million m3 of water are stored in 25,385 hectares of these peatlands. These ecosystems constitute the headwaters of the most important rivers in Eastern Brazil: the São Francisco, Jequitinhonha, and Doce River basins, and regulate their flows during the dry season. However, peatlands located outside of conservation units are threatened by human activity. The Long-Term Ecological Research Program “Peatlands of the Southern Espinhaço Range: Ecosystem Services and Biodiversity” (PELDturf; funded by National Council of Scientific and Technologic Development - CNPq and Minas Gerais State Research Support Foundation - Fapemig), initiated in 2021, has intensified the characterization and monitoring of biodiversity and ecosystem services of peatlands. The results of two decades of research have revealed the importance of these ecosystems for biodiversity, the global carbon cycle, regional water resources, and paleoenvironmental reconstruction. It has also become evident that the rapid degradation of these ecosystems, mainly caused by human activity, can irreversibly compromise their ecosystem services, biodiversity, and paleoenvironmental reconstruction studies in the medium term. Therefore, it is imperative to empower local and regional communities regarding the importance of peatland ecosystems for the environment, socio-economy, and quality of life for their populations, as well as for the planet.

Environmental reconstruction and dating of Shixiakou Locality 1 on China’s West Loess Plateau: implications for human adaptive changes apparent during the Last Glacial Maximum (LGM) and post-LGM periods

Environmental reconstruction and dating of Shixiakou Locality 1 on China’s West Loess Plateau: implications for human adaptive changes apparent during the Last Glacial Maximum (LGM) and post-LGM periods

Organic matter enrichment and palaeo-sedimentary environment reconstruction of lacustrine shale in the second member of the Middle Jurassic Qiketai Formation in the Shengbei Sub-sag, Turpan–Hami Basin, NW China

Lacustrine organic-rich shales in the second member of the Jurassic Qiketai Formation (J 2 q 2 ) in the Shengbei Sub-sag, Turpan–Hami Basin, NW China exhibit strong heterogeneity due to frequent alternations of sedimentary environments. The distinct shale environments present in both upper and lower units of J 2 q 2 provide an ideal example for studying the enrichment mechanism of organic matter (OM) under a complex sedimentary background. In this study, petrological, mineralogical, major/trace element and isotopic analyses were used to reconstruct the palaeo-environment and reveal the mechanisms of OM enrichment. The results indicate that the J 2 q 2 shale was deposited in a lacustrine mixed carbonate–siliciclastic environment and the palaeo-environment indicators suggesting an oxic–dysoxic, mildly brackish water condition. Based on a comprehensive comparison of both members of J 2 q 2 , an OM enrichment model is established and the main controlling factor of the formation of the organic-rich shale is elucidated. Under the background of a warm-humid climate, the lower unit of J 2 q 2 was deposited in a deeper and more restricted water body with stronger chemical weathering, resulting in limited terrestrial input compared to that of the upper unit. Inorganic geochemical analysis indicates a higher primary productivity in the lower unit of J 2 q 2 with local fluctuations. High primary productivity and favourable preservation conditions domain the OM enrichment in the study area. Supplementary material: Raw data of carbon and oxygen isotopic analysis, TOC, Rock-Eval pyrolysis, and major and trace element analysis are available at https://doi.org/10.6084/m9.figshare.c.6901480

Taphonomic damage of molluscan shells in the Nile Delta under natural and anthropogenic sources of environmental variability

Environmental reconstruction can benefit from the interpretation of the postmortem history of shell remains. The molluscan death assemblages obtained from grab samples at forty-nine sites in the Manzala lagoon, the largest lagoon in the Nile Delta, were analyzed to infer the taphonomic alteration. The preservation of shells at each site has been semi-quantitatively ranked based on the taphonomic features formed by encrustation, bioerosion, abrasion, dissolution, precipitation, fragmentation, discoloration, and loss of sheen (low, moderate, high). A significant difference has been observed between sites of low and high environmental stress. Water depth and substrate type (hydrodynamics) correlate significantly to the percent number of altered shells. The southern parts of the lagoon, which are characterized by lower water energy and higher rates of sedimentation, are highly polluted by heavy metals (Cd, Pb, Zn) and organic pollutants. The southern parts receive much sediment from the agricultural drains, which increases burial of shelly material and decreases their time on the TAZ. The northern parts of the lagoon have slower rates of sedimentation, so that the molluscan shells remain longer at the sediment-water interface (Taphonomic Active zone; TAZ), where fragmentation is enhanced by winnowing under higher water-energy. The long residence in the TAZ also favored both bioerosion (Trypanites and Oichnus) and encrustation by bryozoan colonies, polychaetes, and oysters. Therefore, the taphonomic processes have the potential to cause severe damage and taphonomic loss of shell materials. Chemical dissolution and precipitation of shell remains may be related to acidic pore water. Moreover, high alkalinities in the southern polluted parts may also reduce the dissolution in contrast to the acidic water in the northern parts of the lagoon.