scholarly journals Persistent effects of sand extraction on habitats and associated benthic communities in the German Bight

2020 ◽  
Author(s):  
Finn Mielck ◽  
Rune Michaelis ◽  
H. Christian Hass ◽  
Sarah Hertel ◽  
Caroline Ganal ◽  
...  
Keyword(s):  
Benthic Communities ◽  
Effective Means ◽  
Local Population ◽  
Benthic Fauna ◽  
Cost Effective ◽  
Habitat Characteristics ◽  
Long Term Effects ◽  
Successional Stage ◽  
Protection Measures ◽  
Sand Extraction

Abstract. Sea-level rise demands for protection measures of endangered coastlines crucial for the local population. At the island of Sylt in the SE North Sea, shoreline erosion is compensated by replenishment with sand dredged from an offshore excavation site. We studied the long-term effects of sand extraction on bathymetry, geomorphology, habitats, and benthic fauna. Hydroacoustic surveys revealed that changes of bathymetry and habitat characteristics caused by sand extraction can be still detected after > 35 years while the investigation of grab samples revealed persistent changes in sediment composition and benthic faunal composition. The comparison of recently dredged areas ( 10 years ago) and undisturbed sites exposed significant differences in the number of individuals and species of macrozoobenthic organisms as well as in the mud content, indicating a persistent successional stage of the communities in the dredged areas. The slow backfill of the dredging pits results from low ambient sediment availability and relatively calm hydrodynamic conditions, despite high wave energy during storms. Based on current sedimentation rates, we conclude that a complete backfill of the deep excavation sites and re-establishment of the benthic communities is likely to take centuries in this area. Since re-establishment of the benthic communities depends on previous re-establishment of habitat characteristics, habitat mapping with remote sensing techniques is suggested as a cost-effective means to monitor the state of regeneration.

scholarly journals Impact of marine sand extraction on benthic communities west off Sylt (SE North Sea)

2020 ◽  
Author(s):  
Finn Mielck ◽  
Rune Michaelis ◽  
Werner Armonies ◽  
H. Christian Hass
Keyword(s):  
North Sea ◽  
Benthic Communities ◽  
Habitat Characteristics ◽  
Western Coast ◽  
Long Term Effects ◽  
Successional Stage ◽  
Grab Sampling ◽  
Effective Measure ◽  
Marine Sand ◽  
Sand Extraction

<p>Ongoing erosion at coasts, beaches and dunes accompanied by a climate change-induced sea-level rise requires extensive protection measures. At the Island of Sylt (SE North Sea) beach nourishments were conducted for almost 50 years to protect the exposed western coast against erosion. Since 1984, the materials for the sand replenishments were dredged from an offshore excavation site approx. 7 km west off Sylt in the German Bight. In this study, we investigate the long-term effects of sand extraction on the local geomorphology, the associated benthic habitats and fauna. Hydroacoustic surveys and grab sampling revealed that after more than 35 years changes in bathymetry (with dredging pits of down to ~15 m below sea floor) and also changes in habitat characteristics are still present. Additionally, the sediment and benthic faunal compositions have changed. A comparison between dredged areas and undisturbed seafloor revealed significant differences in mud content (increasing), the number of individuals and species of macrozoobenthic organisms (decreasing). This indicates that the benthic communities in the dredging areas are in a persistent successional stage. Mud-loving species (e. g. <em>Notomastus latericeus</em> and<em> Kurtiella bidentate</em>) profit from the changed habitats, however sand-preferring organisms (e.g. <em>Pisione remota</em> and <em>Aonides paucibranchiata</em>) largely disappeared. Because of the slow backfill rates, we conclude that a complete backfill of the deep dredging pits is likely to take centuries. The same is expected to apply for the regeneration of the benthic communities. However, since rather coarse-to-medium sand was removed from this area and re-accumulation of this Pleistocene material is not possible because of weak transport rates, a re-establishment of benthic communities that prefer coarser sand seems to be unlikely. Since benthic communities are strongly linked to the habitat characteristics, habitat mapping using hydroacoustic techniques is an efficient and cost-effective measure to monitor the state of regeneration in this study site.</p>

scholarly journals Persistent effects of sand extraction on habitats and associated benthic communities in the German Bight

2021 ◽  
Vol 18 (12) ◽  
pp. 3565-3577
Author(s):  
Finn Mielck ◽  
Rune Michaelis ◽  
H. Christian Hass ◽  
Sarah Hertel ◽  
Caroline Ganal ◽  
...  
Keyword(s):  
Benthic Communities ◽  
Local Population ◽  
Habitat Type ◽  
Coarse Sand ◽  
Habitat Characteristics ◽  
Mitigation Measures ◽  
Sediment Layer ◽  
Long Term Effects ◽  
Sand Surface ◽  
Sand Extraction

Abstract. Sea-level rise demands for protection measures of endangered coastlines crucial for the local population. At the island of Sylt in the SE North Sea, shoreline erosion is compensated by replenishment with sand dredged from an offshore extraction site. We studied the long-term effects of sand extraction on bathymetry, geomorphology, habitats and benthic fauna. Sand extraction created dredging holes about 1 km in diameter and up to 20 m below the ambient seafloor level. Directly after dredging the superficial sediment layer, inside the pits was dominated by coarse sand and stones. Hydroacoustic surveys revealed only minor changes of bathymetry > 35 years after sand extraction. Obviously, backfill of the dredging pits was very slow, at a rate of a few millimeters per year, presumably resulting from low ambient sediment availability and relatively calm hydrodynamic conditions despite high wave energy during storms. Thus, a complete backfill of the deep extraction sites is likely to take centuries in this area. Hydroacoustic surveys and ground truthing showed that the backfilled material is mainly very fine sand and mud, turning the previously coarse sand surface into a muddy habitat. Accordingly, grab samples revealed significant differences in macrozoobenthos community composition, abundance and species density between recently dredged areas (< 10 years ago), recovery sites (dredging activity > 10 years ago) and undisturbed sites (control sites). Overall, dredging turned the original association of sand-dwelling species into a muddy sediment association. Since re-establishment of disturbed benthic communities depends on previous re-establishment of habitat characteristics, the low sedimentation rates indicate that a return to a pre-dredging habitat type with its former benthic community and habitat characteristics is unlikely. Since coarse sand is virtually immobile in this area, a regeneration towards pre-dredging conditions is also unlikely without human interference (e.g., mitigation measures like depositing coarse material on the seafloor to restore the sessile epifauna).

Description of a Remote Still Photography System for Collection of Benthic Photo-Quadrats

2010 ◽  
Vol 44 (2) ◽  
pp. 56-63 ◽  
Author(s):  
Kris I. Waddington ◽  
Ben W. Piek ◽  
Antony D. Payne ◽  
Simon L. Grove ◽  
Euan S. Harvey ◽  
...  
Keyword(s):  
Anthropogenic Impacts ◽  
Benthic Communities ◽  
Effective Means ◽  
Cost Effective ◽  
Taxonomic Resolution ◽  
Benthic Assemblages ◽  
Differential Gps ◽  
Short Baseline ◽  
Wide Range ◽  
Distribution And Ecology

AbstractQuantitative sampling of benthic communities is central to a wide range of ecological research, from understanding spatial distribution and ecology to impact studies. With the need to sample deep as well as shallow regions, limited sampling capabilities of diver-based methods and the expanding footprint of human activity, there is a need for an effective system capable of classifying benthic assemblages and able to monitor potential anthropogenic impacts. Here we describe a remote system capable of collecting benthic photo-quadrats to depths of 100 m. A procedure for the classification of these images into 64 abiotic and biotic categories is also described. During a 64-day sampling program that included sampling at seven locations along 1,200 km of coastline that resulted in the collection of over 9,000 images, only one day of sampling was lost due to equipment malfunction, with 99.5% of points able to be classified to the taxonomic resolution required, demonstrating the reliability and accuracy of this system. Furthermore, the incorporation of differential GPS and ultra-short baseline positioning system allowed collected images to be geo-referenced to within 0.5 m. Such precision allows the system to be used in conjunction with hydroacoustic habitat mapping techniques and potentially for repeated monitoring of areas with a small spatial extent. Development of this system provides a cost-effective means of quantifying benthic assemblages over broad scales.

scholarly journals Ross Sea Benthic Ecosystems: Macro- and Mega-faunal Community Patterns From a Multi-environment Survey

2021 ◽  
Vol 8 ◽  
Author(s):  
Vonda J. Cummings ◽  
David A. Bowden ◽  
Matthew H. Pinkerton ◽  
N. Jane Halliday ◽  
Judi E. Hewitt
Keyword(s):  
Environmental Changes ◽  
Marine Protected Area ◽  
Ross Sea ◽  
Spatial Scales ◽  
Benthic Communities ◽  
Benthic Fauna ◽  
Habitat Characteristics ◽  
Physical Habitat ◽  
Distribution Models ◽  
Suspension Feeders

The Ross Sea, Antarctica, is amongst the least human-impacted marine environments, and the site of the world’s largest Marine Protected Area. We present research on two components of the Ross Sea benthic fauna: mega-epifauna, and macro-infauna, sampled using video and multicore, respectively, on the continental shelf and in previously unsampled habitats on the northern continental slope and abyssal plain. We describe physical habitat characteristics and community composition, in terms of faunal diversity, abundance, and functional traits, and compare similarities within and between habitats. We also examine relationships between faunal distributions and ice cover and productivity, using summaries of satellite-derived data over the decade prior to our sampling. Clear differences in seafloor characteristics and communities were noted between environments. Seafloor substrates were more diverse on the Slope and Abyss, while taxa were generally more diverse on the Shelf. Mega-epifauna were predominantly suspension feeders across the Shelf and Slope, with deposit feeder-grazers found in higher or equal abundances in the Abyss. In contrast, suspension feeders were the least common macro-infaunal feeding type on the Shelf and Slope. Concordance between the mega-epifauna and macro-infauna data suggests that non-destructive video sampling of mega-epifauna can be used to indicate likely composition of macro-infauna, at larger spatial scales, at least. Primary productivity, seabed organic flux, and sea ice concentrations, and their variability over time, were important structuring factors for both community types. This illustrates the importance of better understanding bentho-pelagic coupling and incorporating this in biogeographic and process-distribution models, to enable meaningful predictions of how these ecosystems may be impacted by projected environmental changes. This study has enhanced our understanding of the distributions and functions of seabed habitats and fauna inside and outside the Ross Sea MPA boundaries, expanding the baseline dataset against which the success of the MPA, as well as variability and change in benthic communities can be evaluated longer term.

Parallel Computing for Tire Simulations

2011 ◽  
Vol 39 (3) ◽  
pp. 193-209 ◽  
Author(s):  
H. Surendranath ◽  
M. Dunbar
Keyword(s):  
High Performance ◽  
Effective Means ◽  
Cost Effective ◽  
Turnaround Time ◽  
Careful Consideration ◽  
Rolling Contact ◽  
Element Analysis ◽  
Parallel Solvers ◽  
Design Changes ◽  
Highly Nonlinear

Abstract Over the last few decades, finite element analysis has become an integral part of the overall tire design process. Engineers need to perform a number of different simulations to evaluate new designs and study the effect of proposed design changes. However, tires pose formidable simulation challenges due to the presence of highly nonlinear rubber compounds, embedded reinforcements, complex tread geometries, rolling contact, and large deformations. Accurate simulation requires careful consideration of these factors, resulting in the extensive turnaround time, often times prolonging the design cycle. Therefore, it is extremely critical to explore means to reduce the turnaround time while producing reliable results. Compute clusters have recently become a cost effective means to perform high performance computing (HPC). Distributed memory parallel solvers designed to take advantage of compute clusters have become increasingly popular. In this paper, we examine the use of HPC for various tire simulations and demonstrate how it can significantly reduce simulation turnaround time. Abaqus/Standard is used for routine tire simulations like footprint and steady state rolling. Abaqus/Explicit is used for transient rolling and hydroplaning simulations. The run times and scaling data corresponding to models of various sizes and complexity are presented.

Exploring the Benefits of Early Contractor Involvement (ECI) and the Mechanism for Automated 5D BIM Quantification Process in Offsite Modular Construction

2016 ◽  
Author(s):  
Tochukwu Moses ◽  
David Heesom ◽  
David Oloke ◽  
Martin Crouch
Keyword(s):  
Effective Means ◽  
Cost Effective ◽  
Modular Construction ◽  
Automated Quantification ◽  
Building Information ◽  
Project Risks ◽  
Value Add ◽  
The Uk ◽  
The Impact ◽  
Level 2

The UK Construction Industry through its Government Construction Strategy has recently been mandated to implement Level 2 Building Information Modelling (BIM) on public sector projects. This move, along with other initiatives is key to driving a requirement for 25% cost reduction (establishing the most cost-effective means) on. Other key deliverables within the strategy include reduction in overall project time, early contractor involvement, improved sustainability and enhanced product quality. Collaboration and integrated project delivery is central to the level 2 implementation strategy yet the key protocols or standards relative to cost within BIM processes is not well defined. As offsite construction becomes more prolific within the UK construction sector, this construction approach coupled with BIM, particularly 5D automated quantification process, and early contractor involvement provides significant opportunities for the sector to meet government targets. Early contractor involvement is supported by both the industry and the successive Governments as a credible means to avoid and manage project risks, encourage innovation and value add, making cost and project time predictable, and improving outcomes. The contractor is seen as an expert in construction and could be counter intuitive to exclude such valuable expertise from the pre-construction phase especially with the BIM intent of äóÖbuild it twiceäó», once virtually and once physically. In particular when offsite construction is used, the contractoräó»s construction expertise should be leveraged for the virtual build in BIM-designed projects to ensure a fully streamlined process. Building in a layer of automated costing through 5D BIM will bring about a more robust method of quantification and can help to deliver the 25% reduction in overall cost of a project. Using a literature review and a case study, this paper will look into the benefits of Early Contractor Involvement (ECI) and the impact of 5D BIM on the offsite construction process.

scholarly journals mRNA-Based Vaccines

Vaccines ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 390
Author(s):  
Frank Kowalzik ◽  
Daniel Schreiner ◽  
Christian Jensen ◽  
Daniel Teschner ◽  
Stephan Gehring ◽  
...  
Keyword(s):  
Large Scale ◽  
New Technologies ◽  
Vaccine Development ◽  
Effective Means ◽  
Cost Effective ◽  
Clinical Applications ◽  
Cell Mediated Immunity ◽  
Healthy Individuals ◽  
Emerging Pathogens ◽  
Cell Genome

Increases in the world’s population and population density promote the spread of emerging pathogens. Vaccines are the most cost-effective means of preventing this spread. Traditional methods used to identify and produce new vaccines are not adequate, in most instances, to ensure global protection. New technologies are urgently needed to expedite large scale vaccine development. mRNA-based vaccines promise to meet this need. mRNA-based vaccines exhibit a number of potential advantages relative to conventional vaccines, namely they (1) involve neither infectious elements nor a risk of stable integration into the host cell genome; (2) generate humoral and cell-mediated immunity; (3) are well-tolerated by healthy individuals; and (4) are less expensive and produced more rapidly by processes that are readily standardized and scaled-up, improving responsiveness to large emerging outbreaks. Multiple mRNA vaccine platforms have demonstrated efficacy in preventing infectious diseases and treating several types of cancers in humans as well as animal models. This review describes the factors that contribute to maximizing the production of effective mRNA vaccine transcripts and delivery systems, and the clinical applications are discussed in detail.

The Southern Ocean benthic fauna and climate change: a historical perspective

1992 ◽  
Vol 338 (1285) ◽  
pp. 299-309 ◽  
Keyword(s):  
Global Warming ◽  
Southern Ocean ◽  
Environmental Change ◽  
Benthic Communities ◽  
Benthic Fauna ◽  
Marine Fauna ◽  
Short Term Change ◽  
Term Change ◽  
Continental Ice Sheets

Environmental change is the norm and it is likely that, particularly on the geological timescale, the temperature regime experienced by marine organisms has never been stable. These temperature changes vary in timescale from daily, through seasonal variations, to long-term environmental change over tens of millions of years. Whereas physiological work can give information on how individual organisms may react phenotypically to short-term change, the way benthic communities react to long-term change can only be studied from the fossil record. The present benthic marine fauna of the Southern Ocean is rich and diverse, consisting of a mixture of taxa with differing evolutionary histories and biogeographical affinities, suggesting that at no time in the Cenozoic did continental ice sheets extend sufficiently to eradicate all shallow-water faunas around Antarctica at the same time. Nevertheless, certain features do suggest the operation of vicariant processes, and climatic cycles affecting distributional ranges and ice-sheet extension may both have enhanced speciation processes. The overall cooling of southern high-latitude seas since the mid-Eocene has been neither smooth nor steady. Intermittent periods of global warming and the influence of Milankovitch cyclicity is likely to have led to regular pulses of migration in and out of Antarctica. The resultant diversity pump may explain in part the high species richness of some marine taxa in the Southern Ocean. It is difficult to suggest how the existing fauna will react to present global warming. Although it is certain the fauna will change, as all faunas have done throughout evolutionary time, we cannot predict with confidence how it will do so.

A method for correcting acoustic finite-difference amplitudes for elastic effects

Geophysics ◽  
2014 ◽  
Vol 79 (4) ◽  
pp. T243-T255 ◽  
Author(s):  
James W. D. Hobro ◽  
Chris H. Chapman ◽  
Johan O. A. Robertsson
Keyword(s):  
Wave Equation ◽  
Finite Difference ◽  
Effective Means ◽  
Cost Effective ◽  
P Wave ◽  
S Waves ◽  
Velocity Models ◽  
Acoustic Simulation ◽  
Wide Range ◽  
Elastic Simulation

We present a new method for correcting the amplitudes of arrivals in an acoustic finite-difference simulation for elastic effects. In this method, we selectively compute an estimate of the error incurred when the acoustic wave equation is used to approximate the behavior of the elastic wave equation. This error estimate is used to generate an effective source field in a second acoustic simulation. The result of this second simulation is then applied as a correction to the original acoustic simulation. The overall cost is approximately twice that of an acoustic simulation but substantially less than the cost of an elastic simulation. Because both simulations are acoustic, no S-waves are generated, so dispersed converted waves are avoided. We tested the characteristics of the method on a simple synthetic model designed to simulate propagation through a strong acoustic impedance contrast representative of sedimentary geology. It corrected amplitudes to high accuracy for reflected arrivals over a wide range of incidence angles. We also evaluated results from simulations on more complex models that demonstrated that the method was applicable in realistic sedimentary models containing a wide range of seismic contrasts. However, its accuracy was reduced for wide-angle reflections from very high impedance contrasts such as a shallow top-salt interface. We examined the influence of modeling at coarse grid resolutions, in which converted S-waves in the equivalent elastic simulation are dispersed. These results provide some validation for the accuracy of the method when applied using finite-difference grids designed for acoustic modeling. The method appears to offer a cost-effective means of modeling elastic amplitudes for P-wave arrivals in a useful range of velocity models. It has several potential applications in imaging and inversion.

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