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Khalsa, Noah S., Kyle P. Gatt, Trent M. Sutton et Amanda L. Kelley. « Characterization of the abiotic drivers of abundance of nearshore Arctic fishes ». Ecology and Evolution 11, no 16 (22 juillet 2021) : 11491–506. http://dx.doi.org/10.1002/ece3.7940.
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Goodbody-Gringley, Gretchen, Emma Strand et Joanna M. Pitt. « Molecular characterization of nearshore baitfish populations in Bermuda to inform management ». PeerJ 7 (4 juillet 2019) : e7244. http://dx.doi.org/10.7717/peerj.7244.
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Small-bodied marine fishes play an important role in the food web, feeding both larger fishes and seabirds. Often referred to as baitfishes, they concentrate seasonally in coastal areas in large, often heterospecific assemblages that are targeted by both commercial and recreational fishers. Given apparent declines in at least some of Bermuda’s baitfish species over the past 40 years, it is useful to determine the species composition of baitfish assemblages, and how it varies among sites, in order to inform management. Using genetic barcoding of the Cytochrome c oxidase 1 gene (COI), we confirm species identity, assess intraspecific genetic diversity locally, and determine rates of broader genetic connectivity for baitfish assemblages in Bermuda. Species analyzed includedHypoatherina harringtonensis,Anchoa choerostoma,Jenkinsia lamprotaenia,Harengula humeralis,Opisthonema oglinumandSardinella aurita. Species identification based on molecular barcoding revealed some misidentification of individuals based solely on gross morphological characteristics, with an error rate of 11%, validating the usefulness of this approach. Interestingly, sequence results for the endemic Bermuda anchovy,A. choerostoma, were within 1% similarity to the more broadly distributed big-eye anchovy,A. lamprotaenia, and thus additional analyses are warranted to evaluate the genetic basis for endemism. Estimates of genetic diversity within and among baitfish assemblages in Bermuda were high, indicating high rates of local connectivity among sites for all species. As such, management should consider Bermuda’s baitfish species as single, highly mixed populations. However, with the exception ofH. humeralisand the endemicA. choerostoma, significant genetic differentiation and population structure were found when comparing Bermuda’s baitfish populations with those from other regions, suggesting limited gene flow between other regions and Bermuda for these species. Limited regional connectivity has implications for management, as strong genetic divergence suggests that populations in Bermuda are predominantly self-seeding and thus not likely to be replenished from distant populations. These results therefore support precautionary management of baitfish species in Bermuda.
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Nie, Ding, Ning Li, Min Zhang, Wangqiang Jiang et Xin Wang. « Characterization of Electromagnetic Scattering From Water-Depth-Changed Nearshore Sea Surface ». IEEE Antennas and Wireless Propagation Letters 15 (2016) : 472–75. http://dx.doi.org/10.1109/lawp.2015.2453336.
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Raubenheimer, Britt. « DEVELOPMENT OF A NEARSHORE EXTREME EVENTS RECONNAISSANCE COMMUNITY ». Coastal Engineering Proceedings, no 36v (31 décembre 2020) : 12. http://dx.doi.org/10.9753/icce.v36v.keynote.12.
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Extreme events have significant impacts on the nearshore water-land system - where ocean, sound, and estuary processes interact with the nearby land - that pose high risk to society. Observations before, during, and after these events are critical to improve understanding of the interactions and feedbacks among the natural and built environments during major storms, and the corresponding human actions and reactions. The goal of the Nearshore Extreme Events Reconnaissance (NEER) Association is to organize and coordinate a national network of scientists spanning many disciplines to perform rapid, pre-and post-event site characterization, to deploy instruments to observe event processes, and to gather virtual data about the event and provide support to field teams. This presentation provides information about NEER's motivation, event-response and coordination activities, data-distribution plans, and lessons learned to date. Funding for NEER is provided by the U.S. National Science Foundation Coastlines and People Program.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/9I9Z3OLGszU
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Gonzalez, Raul, Qingping Zou et Shunqi Pan. « MODELLING OF THE IMPACT OF A WAVE FARM ON NEARSHORE SEDIMENT TRANSPORT ». Coastal Engineering Proceedings 1, no 33 (9 octobre 2012) : 66. http://dx.doi.org/10.9753/icce.v33.sediment.66.
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This paper presents the results from an integrated modelling system investigating the effects of a wave farm on nearshore sediment transport. Wave Hub project is a large scale demonstration site for the development of the operation of arrays of wave energy generation devices located at the southwest coast of the UK where multiple field measurements took place. The two-way coupled SWAN and ROMS models with nested modelling system were set up at the Wave Hub site and run with and without a wave farm. The model results show that the presence of the wave farm has significant impacts on the nearshore circulation, bed shear stresses and sediment transport. The morphological changes are also altered by the wave farm. The study is the key element for the wave resource characterization and environmental impact assessment of the wave farm.
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Tsai, Chia-Cheng, et Chun-Hung Lin. « Review and Future Perspective of Geophysical Methods Applied in Nearshore Site Characterization ». Journal of Marine Science and Engineering 10, no 3 (1 mars 2022) : 344. http://dx.doi.org/10.3390/jmse10030344.
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Seabed surveying is the basis of engineering development in shallow waters. At present, geophysical survey methods mainly utilize sonars for qualitative surveying, which requires the calibration of the results found through in situ drilling and sampling. Among them, the parameters required for engineering designs are obtained from either in situ tests or laboratory experiments of soil samples retrieved from drilling. However, the experience from onshore applications shows that the physical quantities obtained through quantitative geophysical survey methods for shallow waters can be indirectly used to estimate engineering parameters or directly as parameters for engineering evaluation, which has high application potential. This review analyzes various geophysical survey methods for nearshore site characterization (i.e., side-scan sonar, single/multi- beam sonar, sub-bottom profiler, seismic reflection method, and underwater magnetometer) and challenges in their application, and introduces quantitative geophysical survey methods (including the underwater seismic refraction method, seismic surface wave method and underwater electrical resistivity tomography) that are worth focusing on for future development. Three application difficulties have been identified, namely, the lack of operational efficiency, appropriate operational equipment and systems, and sufficient guidance for experimental shallow sea applications. It is hoped that comprehensive discussion of these challenges will increase awareness leading to engineering improvements in the surveying and measuring capabilities in shallow waters, further reducing the risk of geotechnical hazards.
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Lowe, Alexander T., Aaron W. E. Galloway, J. Sean Yeung, Megan N. Dethier et David O. Duggins. « Broad sampling and diverse biomarkers allow characterization of nearshore particulate organic matter ». Oikos 123, no 11 (17 juin 2014) : 1341–54. http://dx.doi.org/10.1111/oik.01392.
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Ahn, Seongho, Vincent S. Neary, Mohammad Nabi Allahdadi et Ruoying He. « Nearshore wave energy resource characterization along the East Coast of the United States ». Renewable Energy 172 (juillet 2021) : 1212–24. http://dx.doi.org/10.1016/j.renene.2021.03.037.
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Waples, James T., Robert Paddock, John Janssen, David Lovalvo, Boris Schulze, Jerry Kaster et J. Val Klump. « High Resolution Bathymetry and Lakebed Characterization in the Nearshore of Western Lake Michigan ». Journal of Great Lakes Research 31 (janvier 2005) : 64–74. http://dx.doi.org/10.1016/s0380-1330(05)70290-2.
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Hotto, A. M., M. F. Satchwell et G. L. Boyer. « Molecular Characterization of Potential Microcystin-Producing Cyanobacteria in Lake Ontario Embayments and Nearshore Waters ». Applied and Environmental Microbiology 73, no 14 (25 mai 2007) : 4570–78. http://dx.doi.org/10.1128/aem.00318-07.
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ABSTRACT The distribution and genotypic variation of potential microcystin (MC) producers along the southern and eastern shores of Lake Ontario in 2001 and 2003 were examined using a suite of PCR primers. Cyanobacterial, Microcystis sp., and Microcystis-specific toxin primer sets identified shoreline distribution of cyanobacterial DNA (in 97% of the stations) and MC synthetase genes (in 50% of the stations). Sequence analysis of a partial mcyA amplicon targeting Microcystis, Anabaena, and Planktothrix species indicated that the Microcystis sp. genotype was the dominant MC genotype present and revealed a novel Microcystis-like sequence containing a 6-bp insert. Analysis of the same samples with genus-specific mcyE primers confirmed that the Microcystis sp. genotype was the dominant potential MC producer. Genotype compositions within embayments were relatively homogenous compared to those for shoreline and tributary samples. MC concentrations along the shoreline exhibited both temporal and spatial differences as evidenced by the protein phosphatase inhibition assay, at times exceeding the World Health Organization guideline value for drinking water of 1.0 μg MC-LReq liter−1. MC genotypes are widespread along the New York State shoreline of Lake Ontario, appear to originate nearshore, and can be carried through the lake via wind and surface water current patterns.
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You, J. L., L. X. Cao, G. F. Liu, S. N. Zhou, H. M. Tan et Y. C. Lin. « Isolation and characterization of actinomycetes antagonistic to pathogenic Vibrio spp. from nearshore marine sediments ». World Journal of Microbiology and Biotechnology 21, no 5 (juillet 2005) : 679–82. http://dx.doi.org/10.1007/s11274-004-3851-3.
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Clarke, Laurence J., Leonie Suter, Bruce E. Deagle, Andrea M. Polanowski, Aleks Terauds, Glenn J. Johnstone et Jonathan S. Stark. « Environmental DNA metabarcoding for monitoring metazoan biodiversity in Antarctic nearshore ecosystems ». PeerJ 9 (15 novembre 2021) : e12458. http://dx.doi.org/10.7717/peerj.12458.
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Antarctic benthic ecosystems support high biodiversity but their characterization is limited to a few well-studied areas, due to the extreme environment and remoteness making access and sampling difficult. Our aim was to compare water and sediment as sources of environmental DNA (eDNA) to better characterise Antarctic benthic communities and further develop practical approaches for DNA-based biodiversity assessment in remote environments. We used a cytochrome c oxidase subunit I (COI) metabarcoding approach to characterise metazoan communities in 26 nearshore sites across 12 locations in the Vestfold Hills (East Antarctica) based on DNA extracted from either sediment cores or filtered seawater. We detected a total of 99 metazoan species from 12 phyla across 26 sites, with similar numbers of species detected in sediment and water eDNA samples. However, significantly different communities were detected in the two sample types at sites where both were collected (i.e., where paired samples were available). For example, nematodes and echinoderms were more likely to be detected exclusively in sediment and water eDNA samples, respectively. eDNA from water and sediment core samples are complementary sample types, with epifauna more likely to be detected in water column samples and infauna in sediment. More reference DNA sequences are needed for infauna/meiofauna to increase the proportion of sequences and number of taxa that can be identified. Developing a better understanding of the temporal and spatial dynamics of eDNA at low temperatures would also aid interpretation of eDNA signals from polar environments. Our results provide a preliminary scan of benthic metazoan communities in the Vestfold Hills, with additional markers required to provide a comprehensive biodiversity survey. However, our study demonstrates the choice of sample type for eDNA studies of benthic ecosystems (sediment, water or both) needs to be carefully considered in light of the research or monitoring question of interest.
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Baron, Robert M., Lance K. B. Jordan et Richard E. Spieler. « Characterization of the marine fish assemblage associated with the nearshore hardbottom of Broward County, Florida, USA ». Estuarine, Coastal and Shelf Science 60, no 3 (juillet 2004) : 431–43. http://dx.doi.org/10.1016/j.ecss.2004.02.002.
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Nichols, PD, et QI Espey. « Characterization of organic matter at the air-sea interface, in subsurface water, and in bottom sediments near the Malabar sewage outfall in Sydney's coastal region ». Marine and Freshwater Research 42, no 4 (1991) : 327. http://dx.doi.org/10.1071/mf9910327.
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The lipid and related-chemical compositions of samples from the air-sea interface, subsurface water and sediments collected adjacent to Sydney's Malabar nearshore sewage outfall during January and February 1990 were analysed in detail. A novel sampling scheme made use of a rotating-drum microlayer sampler, a towed Seastar sampler for filtration and extration of subsurface water in situ, and sediment collection in Teflon bags by divers. Particulate and dissolved organic matter was examined for four distinct aquatic environments: the surface microlayer in a no-slick zone (ML), the microlayer in a plume slick (PS), the microlayer in a banded slick (BS) and subsurface waters (SS). The concentrations of lipid classes and of many individual components in particulate matter from water samples generally followed the trend PS > ML > BS > SS, although in several instances the sequence began with ML > PS. A similar pattern was seen for the dissolved organic fractions. The composition of the ML sample differed from the compositions of the other water samples for several of the lipid classes analysed; the very high relative abundance of cholesterol and the presence of significant portions of long-chain saturated and monounsaturated fatty acids indicate a substantial marine origin for the lipids in the ML sample. The concentrations of most components were generally an order of magnitude higher in sediment 0.5 km from the Malabar outfall than in sediment 0.85 km away (Long Bay). The faecal indicator coprostanol was present in all samples at concentrations ranging from 0.1 to 7 �g L-1 in water and from 0.1 to 1.1�g g-1 in sediments. Petroleum contamination was also apparent in all samples, based on a number of distinctive features of the hydrocarbon profiles: the occurrence of a high abundance of unresolved complex material, little or no odd-over-even predominance in the distribution of n-alkanes, and the presence of hopanes and steranes characteristic of crude oil. Polycyclic aromatic hydrocarbons (PAHs) derived from combustion sources were detected in sediments at both distances from the outfall. PAH concentrations in water samples were at the limits of detection of this study. With the commissioning of deep-water outfalls to replace the nearshore ones, a decrease in nearshore contamination is expected. This study provides baseline chemical data for future comparative examination of the efficacy of Sydney's deep-water sewage outfalls.
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Stark, Nina, Brendan Green, Nick Brilli, Emily Eidam, Kevin W. Franke et Kaleb Markert. « Geotechnical Measurements for the Investigation and Assessment of Arctic Coastal Erosion—A Review and Outlook ». Journal of Marine Science and Engineering 10, no 7 (1 juillet 2022) : 914. http://dx.doi.org/10.3390/jmse10070914.
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Geotechnical data are increasingly utilized to aid investigations of coastal erosion and the development of coastal morphological models; however, measurement techniques are still challenged by environmental conditions and accessibility in coastal areas, and particularly, by nearshore conditions. These challenges are exacerbated for Arctic coastal environments. This article reviews existing and emerging data collection methods in the context of geotechnical investigations of Arctic coastal erosion and nearshore change. Specifically, the use of cone penetration testing (CPT), which can provide key data for the mapping of soil and ice layers as well as for the assessment of slope and block failures, and the use of free-fall penetrometers (FFPs) for rapid mapping of seabed surface conditions, are discussed. Because of limitations in the spatial coverage and number of available in situ point measurements by penetrometers, data fusion with geophysical and remotely sensed data is considered. Offshore and nearshore, the combination of acoustic surveying with geotechnical testing can optimize large-scale seabed characterization, while onshore most recent developments in satellite-based and unmanned-aerial-vehicle-based data collection offer new opportunities to enhance spatial coverage and collect information on bathymetry and topography, amongst others. Emphasis is given to easily deployable and rugged techniques and strategies that can offer near-term opportunities to fill current gaps in data availability. This review suggests that data fusion of geotechnical in situ testing, using CPT to provide soil information at deeper depths and even in the presence of ice and using FFPs to offer rapid and large-coverage geotechnical testing of surface sediments (i.e., in the upper tens of centimeters to meters of sediment depth), combined with acoustic seabed surveying and emerging remote sensing tools, has the potential to provide essential data to improve the prediction of Arctic coastal erosion, particularly where climate-driven changes in soil conditions may bias the use of historic observations of erosion for future prediction.
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Atkinson, John, Luciana S. Esteves, Jon W. Williams, David L. McCann et Paul S. Bell. « The Application of X-Band Radar for Characterization of Nearshore Dynamics on a Mixed Sand and Gravel Beach ». Journal of Coastal Research 85 (mai 2018) : 281–85. http://dx.doi.org/10.2112/si85-057.1.
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Evans, Rob L. « Using CSEM techniques to map the shallow section of seafloor : From the coastline to the edges of the continental slope ». GEOPHYSICS 72, no 2 (mars 2007) : WA105—WA116. http://dx.doi.org/10.1190/1.2434798.
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Many important processes occur within the shallow section of the seafloor on the continental shelf and slope, yet conventional geophysical constraints on the physical properties within this critical boundary layer are limited. Some of the key constraints involve quantification of fluids within the seafloor, which can be provided by electrical methods. This paper reviews the application of a towed EM system to map the uppermost [Formula: see text] of seafloor in a variety of settings ranging from nearshore regions in water depths of approximately [Formula: see text] on the continental shelf out to water depths of [Formula: see text]. The system is a mapping tool that provides areal maps of seafloor resistivity and has been used for a variety of purposes, including sedimentary characterization and facies mapping, evaluation of groundwater discharge, and mapping seafloor mounds in the Gulf of Mexico, thought to contain massive deposits of gas hydrate.
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Fantinato, Lucas, Adriano Ranierin, Pedro Martins et Gustavo Lutz. « Brazil Case Study - Tactical Response Plans and Voo's Program - A New Approach to Shoreline Protection Preparedness ». International Oil Spill Conference Proceedings 2014, no 1 (1 mai 2014) : 14–25. http://dx.doi.org/10.7901/2169-3358-2014.1.14.
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ABSTRACT In the past, Brazilian Oil Spill Response Plans focused on the definition of response strategies in offshore environments, but were insufficient when it came to shoreline protection. After the occurrence of major oil spill accidents around the world and events of great repercussion in Brazil and with the intensification of oil and gas E&P activities in locations close to the coast and near environmentally sensitive areas in the country (such as Camamu-Almada and the Jequitinhonha basin), the need for additional nearshore response studies became of the utmost importance. Recently developed documents address the environmental characterization of the coast and indicate the appropriate response strategies, but a more action-oriented approach is needed. For that purpose, based on the best practices in shoreline protection worldwide, a methodology is being implemented so as to provide consistent preparedness support for the protection of nearshore resources. The methodology uses the Brazilian licensing mandatory documents in order to identify the appropriate level of protection preparedness for each of the vulnerable segments of shoreline within the domain of the E&P activity. Once the proper level of preparedness has been identified, the method indicates how to attain such result by presenting a set of tools, such as: TRP (Tactical Response Plan), VoOs (Vessel of Oportunity) Program, Advances Bases and Full Deployment Exercises. This paper provides an overview of the methodology, followed by a case study in Brazil which helps illustrate how the level of preparedness is determined and how the proposed tools help achieve such result. Therefore, it allows assessing the effectiveness of this new approach in the country. Considering Brazil's growing E&P potential, the long extent of its coastline and the abundance of sensitive resources alongshore, the methodology should be applied to other E&P projects developed in the country.
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Diaz-Hernandez, Gabriel, Fernando J. Mendez et Roberto Mínguez. « Numerical Analysis and Diagnosis of the Hydrodynamic Effects Produced by Hurricane Gordon along the Coast of Spain ». Weather and Forecasting 29, no 3 (1 juin 2014) : 666–83. http://dx.doi.org/10.1175/waf-d-13-00130.1.
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Abstract This paper presents a detailed hindcast for the generation and propagation of sea state variables—significant wave height Hs, peak period Tp, mean direction θ, and spectral shape γ –σ —associated with cyclonic events to numerically diagnose their possible hydrodynamic effects over the northeastern Atlantic. An example of such cyclonic events is Hurricane Gordon, which occurred during the second half of August 2012. Extreme hurricane-strength winds produced new and atypically low-frequency (about 14 s) packs of energy. The preexistent wave spectrum suddenly experienced an addition of low-frequency energy along the coast of Cádiz, Spain. This study presents the results of a comprehensive analysis developed to reconstruct the events produced by Hurricane Gordon (2012) along the coast of Cádiz. The analysis features the use of (i) parametric models for the characterization of hurricane winds and pressure fields, (ii) implementation of the Simulating Waves Nearshore (SWAN) model for the generation and propagation of waves in the northeast Atlantic Ocean, and (iii) its coupling with the MOPLA—taken from the Spanish acronym for wave propagation model, current, and morphodynamic evolution of beaches—model for the evaluation of longshore currents. The numerical wave characterization, generation, and propagation were validated with instrumental data from deep-water and coastal buoys.
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Winterfeld, M., T. Laepple et G. Mollenhauer. « Characterization of particulate organic matter in the Lena River delta and adjacent nearshore zone, NE Siberia – Part I : Radiocarbon inventories ». Biogeosciences 12, no 12 (19 juin 2015) : 3769–88. http://dx.doi.org/10.5194/bg-12-3769-2015.
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Abstract. Particulate organic matter (POM) derived from permafrost soils and transported by the Lena River represents a quantitatively important terrestrial carbon pool exported to Laptev Sea sediments (next to POM derived from coastal erosion). Its fate in a future warming Arctic, i.e., its remobilization and remineralization after permafrost thawing as well as its transport pathways to and sequestration in marine sediments, is currently under debate. We present one of the first radiocarbon (14C) data sets for surface water POM within the Lena Delta sampled in the summers of 2009–2010 and spring 2011 (n = 30 samples). The bulk Δ14C values varied from −55 to −391 ‰ translating into 14C ages of 395 to 3920 years BP. We further estimated the fraction of soil-derived POM to our samples based on (1) particulate organic carbon to particulate nitrogen ratios (POC : PN) and (2) on the stable carbon isotope (δ13C) composition of our samples. Assuming that this phytoplankton POM has a modern 14C concentration, we inferred the 14C concentrations of the soil-derived POM fractions. The results ranged from −322 to −884 ‰ (i.e., 3060 to 17 250 14C years BP) for the POC : PN-based scenario and from −261 to −944 ‰ (i.e., 2370 to 23 100 14C years BP) for the δ13C-based scenario. Despite the limitations of our approach, the estimated Δ14C values of the soil-derived POM fractions seem to reflect the heterogeneous 14C concentrations of the Lena River catchment soils covering a range from Holocene to Pleistocene ages better than the bulk POM Δ14C values. We further used a dual-carbon-isotope three-end-member mixing model to distinguish between POM contributions from Holocene soils and Pleistocene Ice Complex (IC) deposits to our soil-derived POM fraction. IC contributions are comparatively low (mean of 0.14) compared to Holocene soils (mean of 0.32) and riverine phytoplankton (mean of 0.55), which could be explained with the restricted spatial distribution of IC deposits within the Lena catchment. Based on our newly calculated soil-derived POM Δ14C values, we propose an isotopic range for the riverine soil-derived POM end member with Δ14C of −495 ± 153 ‰ deduced from our δ13C-based binary mixing model and δ13C of −26.6 ± 1 ‰ deduced from our data of Lena Delta soils and literature values. These estimates can help to improve the dual-carbon-isotope simulations used to quantify contributions from riverine soil POM, Pleistocene IC POM from coastal erosion, and marine POM in Siberian shelf sediments.
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Winterfeld, M., et G. Mollenhauer. « Characterization of particulate organic matter in the Lena River Delta and adjacent nearshore zone, NE Siberia – Part 2 : Radiocarbon inventories ». Biogeosciences Discussions 11, no 10 (8 octobre 2014) : 14413–51. http://dx.doi.org/10.5194/bgd-11-14413-2014.
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Abstract. Particulate organic matter (POM) derived from permafrost soils and transported by the Lena River represents a quantitatively important terrestrial carbon pool exported to Laptev Sea sediments (next to POM derived from coastal erosion). Its fate in a future warming Arctic, i.e. its remobilization and remineralization after permafrost thawing as well as its transport pathways to and sequestration in marine sediments is currently under debate. We present the first radiocarbon (14C) data set of surface water POM within the Lena Delta sampled in summers 2009–2010 and spring 2011 (n = 30 samples). The bulk Δ14C concentrations varied from −55 to −391‰ translating into 14C ages of 395 to 3920 yr BP. We further estimated the fraction of phytoplankton-derived POM to our samples based on (1) particulate organic carbon to particulate nitrogen ratios (POC:PN) and (2) on the stable carbon isotope (Δ13C) composition of our samples. Assuming that this phytoplankton POM has a modern 14C signature we inferred the 14C concentrations of the soil-derived POM fractions. The results ranged from −258 to −768‰ (i.e. 2340 to 11 700 14C yr BP) for the POC:PN-based scenario and from −191 to −704‰ (i.e. 1640 to 9720 14C yrs BP). Despite the limitations of our approach, the estimated Δ14C concentrations of the soil-derived POM fractions seem to reflect the heterogeneous 14C signal of the Lena River catchment soils covering a range from Holocene to Pleistocene ages. We therefore propose a typical isotopic signature of riverine soil-derived POM with a Δ13C of −26.6 ± 1.1‰ deduced from our data of Lena Delta soils and published values, and a Δ14C concentration of −362 ± 123‰ deduced from our Δ13C-based estimates. These data can help to improve the dual-carbon-isotope simulations used to quantify contributions from riverine soil POM, Pleistocene ice complex POM from coastal erosion, and marine POM in Siberian shelf sediments.
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Blossier, Brice, Christophe Brière, J. A. Roelvink et D. J. R. Walstra. « CHARACTERIZATION OF PROCESSES INVOLVED IN THE RESET OF A SUBTIDAL BAR ». Coastal Engineering Proceedings 1, no 33 (15 décembre 2012) : 101. http://dx.doi.org/10.9753/icce.v33.sediment.101.
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Sand beach profiles can exhibit nearshore sandbars with complex 3D patterns. Under energetic conditions, these patterns disappear and the bars get to a certain extent alongshore uniform. This phenomenon is called a reset. The existing literature mainly concerns the development of the bar patterns (3D) or the cross-shore migration of sandbars (2D). Studies on reset-events from a three dimensional point of view are limited but can be found for instance in Reniers et al. (2004) and Smit (2010). This paper describes an analysis that is aimed at determining the relevant processes involved in the reset of three dimensional subtidal bars and at describing the relative influence of each of these processes. To perform this study, data collected during the ECORS campaign at Le Truc Vert (France) in 2008 are analyzed. In addition, a numerical approach is performed using a research Delft3D model forced by the Xbeach wave generator to investigate the processes involved in a reset-event. The effects of the hydrodynamic external conditions on the flow patterns in the surfzone are investigated. Then the reset is studied in details in order to understand the role of the different processes taken into account by the numerical model. The incident wave energy controls the intensity of the reset. The bar cross-shore migration is controlled by the wave breaking process. The wave breaking position and the dissipation rate of the roller energy controls the generation of Shoreward Propagating Accretionary Waves (SPAW). The straightening of the subtidal bar occurs when the conditions induce a significant longshore current in the surfzone.
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Deering, Robert, Trevor Bell, Donald L. Forbes, Calvin Campbell et Evan Edinger. « Morphological characterization of submarine slope failures in a semi-enclosed fjord, Frobisher Bay, eastern Canadian Arctic ». Geological Society, London, Special Publications 477, no 1 (24 mai 2018) : 367–76. http://dx.doi.org/10.1144/sp477.35.
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AbstractSubmarine slope failures in the nearshore waters of SE Baffin Island, eastern Canadian Arctic, present a challenge to coastal and seabed development. Submarine slope failures are a known geohazard in fjords in Norway, Chile, Alaska, British Columbia and elsewhere, but have received little attention in the coastal waters of Arctic Canada. Over the past 6 years, there has been a rapid expansion of multibeam echosounder (MBES) mapping in Canadian Arctic fjords, leading to the discovery of many submarine slope failures. One area that has been mapped in detail is inner Frobisher Bay. This macrotidal, seasonally ice-covered, semi-enclosed embayment has a glacially scoured bed, ice-contact deposits, including recessional moraines, and stratified glaciomarine and post-glacial silts and clays with abundant dropstones. The prevalence of submarine slope failures in the inner bay (one per 20 km2) appears to be anomalous. To date, MBES mapping has imaged at least 246 failures, ranging in size from 0.007 to 2.1 km2 and all within the glaciomarine and post-glacial succession. Morphometric analysis of these features based on high-resolution MBES bathymetry provides an insight into their spatial distribution, relative chronology, triggers and flow characteristics; factors essential to understanding the mechanisms underlying their abundance in this Canadian Arctic fjord.
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Ebersole, Bruce A., Donald T. Resio et Joannes J. Westerink. « A Community Approach to Improved Prediction and Characterization of Coastal Storm Hazards ». Marine Technology Society Journal 40, no 4 (1 décembre 2006) : 56–68. http://dx.doi.org/10.4031/002533206787353114.
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This paper discusses the value of a community approach to characterizing the coastal storm hazard, e.g., hurricane water levels and wave conditions, through field measurements, data analysis, and modeling. Value is illustrated using experiences and results from recent and ongoing projects. One example is recently completed work by the Interagency Performance Evaluation Task Force (IPET), which was commissioned by the U.S. Army Corps of Engineers. The IPET was charged with gathering the facts regarding performance of the hurricane protection system in Southeast Louisiana in response to Hurricane Katrina. A second example is ongoing work being lead by the Corps to design projects that can greatly reduce the likelihood and consequences of flooding for coastal Louisiana and Mississippi. These investigations are being closely coordinated with work of the Federal Emergency Management Agency to update flood insurance rate maps for the region. Findings and lessons learned are discussed, and challenges in making accurate surge and wave predictions are identified, including: 1) inaccuracy in coastal and estuarine wind fields, 2) specification of a wind drag law in shallow coastal areas, and 3) problems in treating nearshore wave set-up and coupling into surge models. A new Corps research program that is addressing many of these issues, also a community effort, is described as are results from early progress in selected problem areas. The paper presents advantages to developing open-source, community-based computer software for coastal storm wave and surge predictions, and some problems with today's over-reliance on proprietary software.
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Holzmann, Maria, et Jan Pawlowski. « Taxonomic relationships in the genus <i>Ammonia</i> ; (Foraminifera) based on ribosomal DNA sequences ». Journal of Micropalaeontology 19, no 1 (1 mai 2000) : 85–95. http://dx.doi.org/10.1144/jm.19.1.85.
Texte intégralRésumé :
Abstract. The genus Ammonia is a common benthic foraminifer which is widely distributed in nearshore marine environments. Its large morphological variability causes considerable difficulties in species identification. In the present study, we investigated taxonomic relationships in Ammonia by using a molecular approach based on ribosomal DNA sequences. We obtained 149 partial large subunit ribosomal DNA (LSU rDNA) sequences and 23 small subunit ribosomal DNA (SSU rDNA) sequences from 88 living Ammonia specimens which were collected from free-living populations in 14 localities. Sequence analysis revealed the presence of eight distinct genotypic groups (T1–T7, T9) and one distinct genotype that is represented by one specimen (T8). Examination of morphological characters shows that only one genotypic group can be clearly distinguished by its morphology. Biogeographical and ecological features are used for an additional characterization and it seems that the different groups live in relatively well defined environmental conditions and that only one genotypic group is cosmopolitan, while the others have a rather restricted geographical distribution. According to our study, three of the genotypic groups can be regarded as distinct species.
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García-Medina, Gabriel, Zhaoqing Yang, Wei-Cheng Wu et Taiping Wang. « Wave resource characterization at regional and nearshore scales for the U.S. Alaska coast based on a 32-year high-resolution hindcast ». Renewable Energy 170 (juin 2021) : 595–612. http://dx.doi.org/10.1016/j.renene.2021.02.005.
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Neary, Vincent S., Seongho Ahn, Bibiana E. Seng, Mohammad Nabi Allahdadi, Taiping Wang, Zhaoqing Yang et Ruoying He. « Characterization of Extreme Wave Conditions for Wave Energy Converter Design and Project Risk Assessment ». Journal of Marine Science and Engineering 8, no 4 (18 avril 2020) : 289. http://dx.doi.org/10.3390/jmse8040289.
Texte intégralRésumé :
Best practices and international standards for determining n-year return period extreme wave (sea states) conditions allow wave energy converter designers and project developers the option to apply simple univariate or more complex bivariate extreme value analysis methods. The present study compares extreme sea state estimates derived from univariate and bivariate methods and investigates the performance of spectral wave models for predicting extreme sea states at buoy locations within several regional wave climates along the US East and West Coasts. Two common third-generation spectral wave models are evaluated, a WAVEWATCH III® model with a grid resolution of 4 arc-minutes (6–7 km), and a Simulating WAves Nearshore model, with a coastal resolution of 200–300 m. Both models are used to generate multi-year hindcasts, from which extreme sea state statistics used for wave conditions characterization can be derived and compared to those based on in-situ observations at National Data Buoy Center stations. Comparison of results using different univariate and bivariate methods from the same data source indicates reasonable agreement on average. Discrepancies are predominantly random. Large discrepancies are common and increase with return period. There is a systematic underbias for extreme significant wave heights derived from model hindcasts compared to those derived from buoy measurements. This underbias is dependent on model spatial resolution. However, simple linear corrections can effectively compensate for this bias. A similar approach is not possible for correcting model-derived environmental contours, but other methods, e.g., machine learning, should be explored.
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Beigzadeh, Keon, Julie M. Rieland, Catherine B. Eastman, David J. Duffy et Brian J. Love. « Characterization of Ingested Plastic Microparticles Extracted from Sea Turtle Post-Hatchlings at Necropsy ». Microplastics 1, no 2 (13 avril 2022) : 254–62. http://dx.doi.org/10.3390/microplastics1020018.
Texte intégralRésumé :
Inadvertent consumption of latent microplastics is a lethal challenge for developing creatures in aquatic environments. There are compelling needs to classify which kinds of plastics are most likely to be encountered by sea creatures and to develop mitigation strategies to reduce exposure. We analyzed an ensemble of microplastic particle fragments isolated from sea turtle post-hatchlings to identify their composition and other features and attributes. These microplastic particles were likely consumed by post-hatchlings because of the adsorbed biofilm formation mimicking normal food sources. Of the hundreds of particles that were collected, 30 were selected for analysis using differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and density assessment to identify them compared with other compositional libraries. These thermophysical measurements were also compared with observational assessments via optical microscopy. Of the particles tested, nearly all were polyolefins such as polyethylene and polypropylene. The melting points of the extracted polymers were typically lower than for product grades of these resins, indicative of some level of degradation. Spectral analysis by FTIR often showed absorption indicative of new chemistries likely from both hydrolysis and biofilm growth observed on the surface that was subsequently investigated through surface abrading. Separate assessments of density of these particles were conducted and tended to reinforce identification via FTIR and DSC. The density results can be misleading if additives, fillers or biofilms that form alter the particle density relative to those of the neat resins. We suggest that since post-hatchlings commonly feed in the neritic or nearshore environment, less dense polymers are more likely to convey, thereby threatening sea turtle hatchlings who consume them inadvertently.
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Winterfeld, M., M. A. Goñi, J. Just, J. Hefter et G. Mollenhauer. « Characterization of particulate organic matter in the Lena River delta and adjacent nearshore zone, NE Siberia – Part 2 : Lignin-derived phenol compositions ». Biogeosciences 12, no 7 (15 avril 2015) : 2261–83. http://dx.doi.org/10.5194/bg-12-2261-2015.
Texte intégralRésumé :
Abstract. The Lena River in central Siberia is one of the major pathways translocating terrestrial organic matter (OM) from its vast catchment area to the coastal zone of the Laptev Sea and the Arctic Ocean. The permafrost soils of its far south-stretching catchment, which store huge amounts of OM, will most likely respond differently to climate warming and remobilize previously frozen OM with distinct properties specific for the source vegetation and soil. To characterize the material discharged by the Lena River, we analyzed the lignin phenol composition in total suspended matter (TSM) from surface water collected in spring and summer, surface sediments from Buor Khaya Bay along with soils from the Lena Delta's first (Holocene) and third terraces (Pleistocene ice complex), and plant samples. Our results show that lignin-derived cinnamyl : vanillyl (C / V) and syringyl : vanillyl (S / V) ratios are > 0.14 and 0.25, respectively, in TSM and surface sediments, whereas in delta soils they are > 0.16 and > 0.51, respectively. These lignin compositions are consistent with significant inputs of organic matter from non-woody angiosperm sources mixed with organic matter derived from woody gymnosperm sources. We applied a simple linear mixing model based on the C / V and S / V ratios, and the results indicate the organic matter in delta TSM samples and Buor Khaya Bay surface sediments contain comparable contributions from gymnosperm material, which is primarily derived from the taiga forests south of the delta, and angiosperm material typical for tundra vegetation. Considering the small catchment area covered by tundra (~ 12%), the input is substantial and tundra-derived OM input is likely to increase in a warming Arctic. The similar and high acid to aldehyde ratios of vanillyl and syringyl (Ad / AlV, S) in Lena Delta summer TSM (> 0.7 and > 0.5, respectively) and Buor Khaya Bay surface sediments (> 1.0 and > 0.9, respectively) suggest that the OM is highly degraded and Lena River summer TSM could be a possible source of the surface sediments. The Ad / AlV, S ratios of the first and third delta terraces were generally lower (mean ratios > 0.4 and > 0.4, respectively) than summer TSM and surface sediments. This implies that TSM contains additional contributions from a more degraded OM source (southern catchment and/or finer more degraded particle size). Alternatively, OM degradation on land after permafrost thawing and subaqueously during transport and sedimentation could be considerable. Despite the high natural heterogeneity of OM stored in delta soils and exported by the Lena River, the catchment-characteristic vegetation is reflected by the lignin biomarker composition. Climate-warming-related changes in the Lena River catchment may be detectable in changing lignin biomarker composition and diagenetic alteration.
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Winterfeld, M., M. A. Goñi, J. Just, J. Hefter et G. Mollenhauer. « Characterization of particulate organic matter in the Lena River Delta and adjacent nearshore zone, NE Siberia – Part 1 : Lignin-derived phenol compositions ». Biogeosciences Discussions 11, no 10 (8 octobre 2014) : 14359–411. http://dx.doi.org/10.5194/bgd-11-14359-2014.
Texte intégralRésumé :
Abstract. The Lena River in central Siberia is one of the major pathways translocating terrestrial organic matter (OM) from its vast catchment area to the coastal zone of the Laptev Sea and the Arctic Ocean. The permafrost soils of its far south stretching catchment, which store huge amounts of OM, will most likely respond differently to climate warming and remobilize previously frozen OM with distinct properties specific for the source vegetation and soil. To characterize the material discharged by the Lena River, we analyzed the lignin phenol composition in total suspended matter (TSM) from surface water collected in spring and summer, surface sediments from the Buor Khaya Bay along with soils from the Lena Delta's first (Holocene) and third terraces (Pleistocene ice complex), and plant samples. Our results show that lignin-derived cinnamyl:vanillyl (C/V) and syringyl:vanillyl (S/V) ratios are >0.14 and 0.25, respectively, in TSM and surface sediments, whereas in delta soils they are >0.16 and >0.51, respectively. These lignin compositions are consistent with significant inputs of organic matter from non-woody angiosperm sources mixed with organic matter derived from woody gymnosperm sources. We applied a simple linear mixing model based on the C/V and S/V ratios and the results indicate the organic matter in delta TSM samples and Buor Khaya Bay surface sediments contain comparable contributions from gymnosperm material, which is primarily derived from the taiga forests south of the delta, and angiosperm material typical for tundra vegetation. Considering the small catchment area covered by tundra (∼12%), the input is substantial and tundra-derived OM input is likely to increase in a warming Arctic. The similar and high acid to aldehyde ratios of vanillyl and syringyl (Ad/AlV, S) in Lena Delta summer TSM (>0.7 and >0.5, respectively) and Buor Khaya Bay surface sediments (>1.0 and >0.9, respectively) suggest that the OM is highly degraded and Lena River summer TSM could be a possible source for the surface sediments. The Ad/AlV, S ratios of the first and third delta terraces were generally lower (mean ratios >0.4 and >0.4, respectively) than summer TSM and surface sediments. This implies that TSM contains additional contributions from a more degraded OM source (southern catchment and/or finer more degraded particle size). Alternatively, OM degradation on land after permafrost thawing and subaqueously during transport and sedimentation could be considerable. Despite the high natural heterogeneity of OM stored in delta soils and exported by the Lena River, the catchment characteristic vegetation is reflected by the lignin biomarker composition. Climate warming related changes in the Lena River catchment may be detectable in changing lignin biomarker composition and diagenetic alteration.
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Wang, Ying, Xue Li, Baohua H. Li, Zhenyao Y. Shen, Chenghong H. Feng et Yaxin X. Chen. « Characterization, sources, and potential risk assessment of PAHs in surface sediments from nearshore and farther shore zones of the Yangtze estuary, China ». Environmental Science and Pollution Research 19, no 9 (15 mai 2012) : 4148–58. http://dx.doi.org/10.1007/s11356-012-0952-7.
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Kim, Jinah, Jaeil Kim, Taekyung Kim, Dong Huh et Sofia Caires. « Wave-Tracking in the Surf Zone Using Coastal Video Imagery with Deep Neural Networks ». Atmosphere 11, no 3 (21 mars 2020) : 304. http://dx.doi.org/10.3390/atmos11030304.
Texte intégralRésumé :
In this paper, we propose a series of procedures for coastal wave-tracking using coastal video imagery with deep neural networks. It consists of three stages: video enhancement, hydrodynamic scene separation and wave-tracking. First, a generative adversarial network, trained using paired raindrop and clean videos, is applied to remove image distortions by raindrops and to restore background information of coastal waves. Next, a hydrodynamic scene of propagated wave information is separated from surrounding environmental information in the enhanced coastal video imagery using a deep autoencoder network. Finally, propagating waves are tracked by registering consecutive images in the quality-enhanced and scene-separated coastal video imagery using a spatial transformer network. The instantaneous wave speed of each individual wave crest and breaker in the video domain is successfully estimated through learning the behavior of transformed and propagated waves in the surf zone using deep neural networks. Since it enables the acquisition of spatio-temporal information of the surf zone though the characterization of wave breakers inclusively wave run-up, we expect that the proposed framework with the deep neural networks leads to improve understanding of nearshore wave dynamics.
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Clark, J. I., et J. Y. Guigné. « Twenty-fifth anniversary special paper : Marine geotechnical engineering in Canada ». Canadian Geotechnical Journal 25, no 2 (1 mai 1988) : 179–98. http://dx.doi.org/10.1139/t88-023.
Texte intégralRésumé :
Marine geotechnical engineering in Canada is over one hundred years old, having started with overwater drilling and testing for bridges and nearshore structures. Its growth has been sporadic, with not much attention being directed to the geotechnical properties of marine soils until the late 1970's when design of artificial islands made up of large caissons started to develop. For about the last 15 years, marine geotechnical engineering has been driven by the oil and gas industry. Most of the action has been in the Beaufort Sea, where complex site conditions have necessitated detailed geotechnical field drilling, sampling programs, and in situ testing. Very little geotechnical engineering research work or site investigation has been carried out off the east coast except for the Hibernia site on the Grand Banks. In the coming years we can expect to see dramatic changes in site investigation methods. The use of robotics and expert systems coupled with innovative geophysical techniques could dramatically change our methods of site characterization and measurement of geotechnical properties. Key words: marine geotechnical engineering, Beaufort Sea, Grand Banks, Scotian Shelf, in situ testing, geophysical – geotechnical relationship, future trends.
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Nolan, E. T., D. K. A. Barnes, J. Brown, K. Downes, P. Enderlein, E. Gowland, O. T. Hogg et al. « Biological and physical characterization of the seabed surrounding Ascension Island from 100–1000 m ». Journal of the Marine Biological Association of the United Kingdom 97, no 4 (juin 2017) : 647–59. http://dx.doi.org/10.1017/s0025315417000820.
Texte intégralRésumé :
Recent studies have improved our understanding of nearshore marine ecosystems surrounding Ascension Island (central Atlantic Ocean), but little is known about Ascension's benthic environment beyond its shallow coastal waters. Here, we report the first detailed physical and biological examination of the seabed surrounding Ascension Island at 100–1000 m depth. Multibeam swath data were used to map fine scale bathymetry and derive seabed slope and rugosity indices for the entire area. Water temperature and salinity profiles were obtained from five Conductivity, Temperature, Depth (CTD) deployments, revealing a spatially consistent thermocline at 80 m depth. A camera lander (Shelf Underwater Camera System; SUCS) provided nearly 400 images from 21 sites (100 m transects) at depths of 110–1020 m, showing high variability in the structure of benthic habitats and biological communities. These surveys revealed a total of 95 faunal morphotypes (mean richness >14 per site), complemented by 213 voucher specimens constituting 60 morphotypes collected from seven targeted Agassiz trawl (AGT) deployments. While total faunal density (maximum >300 m−2 at 480 m depth) increased with rugosity, characteristic shifts in multivariate assemblage structure were driven by depth and substratum type. Shallow assemblages (~100 m) were dominated by black coral (Antipatharia sp.) on rocky substrata, cup corals (Caryophyllia sp.) and sea urchins (Cidaris sp.) were abundant on fine sediment at intermediate depths (250–500 m), and shrimps (Nematocarcinus spp.) were common at greater depths (>500 m). Other ubiquitous taxa included serpulid and sabellid polychaetes and brittle stars (Ophiocantha sp.). Cold-water corals (Lophelia cf. pertusa), indicative of Vulnerable Marine Ecosystems (VMEs) and representing substantial benthic carbon accumulation, occurred in particularly dense aggregations at <350 m but were encountered as deep as 1020 m. In addition to enhancing marine biodiversity records at this locality, this study provides critical baseline data to support the future management of Ascension's marine environment.
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Khan, Ahmad A., Ivan Chang-Yen et Lutchminarine Chatergoon. « SOURCE IDENTIFICATION OF AN OIL SPILL ON TRINIDAD'S EAST COAST ». International Oil Spill Conference Proceedings 1989, no 1 (1 février 1989) : 555–62. http://dx.doi.org/10.7901/2169-3358-1989-1-555.
Texte intégralRésumé :
ABSTRACT In April 1986, a large quantity of unrefined crude oil was released into the nearshore marine environment on Trinidad's east coast. The oil was observed to have affected approximately 20 kilometers of coastline. Physical examination of the oil collected revealed that it had the appearance of a light grade crude, was golden brown in color, and had a characteristic gassy odor. Also observed was a mass mortality of the bivalve Donax sp (chip-chip), which inhabits sandy areas of the intertidal zone. Oil was extracted from samples of water, beach sand, and chip-chip collected from selected stations along the affected area. Also collected were samples of oil from possible sources located both offshore and at land-based facilities. Chemical characterization of the oil extracts, using capillary gas chromatography, atomic absorption and fluorescence spectroscopy, and carbon-13 nuclear magnetic resonance spectrometry, yielded data sets that distinguished the oils in the environment from the suspect source oils investigated. Application of statistical pattern recognition techniques, utilizing a hierarchical clustering procedure, to data from both environmental and suspect source samples yielded a high probability match between the spill samples and samples from one of the two oil companies operating in the area.
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Liu, Yang, Xiaofang Liu et Jun Sun. « Response of Chlorophyll Fluorescence Characteristics and Dissolved Organic Matter for Marine Diatom Skeletonema dohrnii under Stress from Penicillin and Zn2+ ». Plants 10, no 12 (7 décembre 2021) : 2684. http://dx.doi.org/10.3390/plants10122684.
Texte intégralRésumé :
Skeletonema dohrnii is a good model diatom for studying environmental stress and has promising applications and prospects in various fields. Antibiotics and heavy metals are commonly exceeded in the nearshore marine habitats. In this work, we investigated the effects of an antibiotic (penicillin, 2 µg/L) and a heavy metal ion (Zn2+, 10 µmol/L) stress on marine diatom S. dohrnii, mainly using excitation-emission matrices (EEMs) fluorescence methods and OJIP test. Results indicated that algal cells grown with the antibiotic showed higher biomass, specific growth rate, doubling time, chlorophyll a, and chlorophyll fluorescence variables. Moreover, excess zinc had negative effects on S. dohrnii. We found that zinc not only inhibited the relative photosynthetic electron transfer efficiency but also reduced the Chl a content, which ultimately affected algal growth and organic matter production. In addition, the combined effect of penicillin and Zn2+ further affected the physiological state of S. dohrnii. The dissolved organic matter (DOM) characteristics of the four cultures were also different, including fluorescence indices (fluorescence index, biological index, β/α, and humification index) and fluorescence peaks (peaks A, C, M and T). In brief, characterization of chlorophyll fluorescence characteristics and DOM-related variables are important for understanding the effects of environmental stress on microalgae.
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Massey, Lynn M., Shannon Penna, Eric Zahn, Dan Lawson et Cassandra M. Davis. « Monitoring Green Sea Turtles in the San Gabriel River of Southern California ». Animals 13, no 3 (27 janvier 2023) : 434. http://dx.doi.org/10.3390/ani13030434.
Texte intégralRésumé :
Effective conservation of endangered species relies on the characterization of habitat use and tracking of long-term population trends, which can be especially challenging for marine species that migrate long distances and utilize a diversity of habitats throughout their lives. Since 2012, citizen science volunteers at the Aquarium of the Pacific in Long Beach, California, have been monitoring an urban population of East Pacific green sea turtles (Chelonia mydas) that resides near the mouth of the San Gabriel River (SGR) in Southern California, USA, in order to gain insights about how the population uses this area. Here, we collate and analyze nine years of citizen science data, including observed sightings collected across 10 observation stations. Our results confirm that green sea turtles are frequently present around warm water effluent from power plants, similar to research results reported for other locations in the eastern Pacific Ocean. Importantly, observational data also show notable green sea turtle activity around the outfalls for a small wetland habitat bordering the SGR, highlighting the importance of wetland ecosystems as a key habitat and foraging area for this threatened population. Finally, our results showcase the benefits of using citizen science to monitor sea turtle populations in easily accessible nearshore habitats.
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Medina, J. M., R. L. Jalbuena, R. A. B. Torres et A. C. Blanco. « SPATIO-TEMPORAL CHARACTERIZATION OF MANILA BAY USING OPTICAL WATER TYPE AND WATER QUALITY MAPPING USING SENTINEL-3 OLCI IMAGES ». International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLVIII-4/W6-2022 (7 février 2023) : 223–30. http://dx.doi.org/10.5194/isprs-archives-xlviii-4-w6-2022-223-2023.
Texte intégralRésumé :
Abstract. Optical water type (OWT) classification provides a way to delineate surface waters according to spectral properties caused by optically active constituents. This classification is useful in mapping out spatial variability and describing changes in water quality over time as it uses inherent optical properties to discriminate areas of a water body. We used Sentinel-3 OLCI images from July 2017 to December 2020 to classify OWT in Manila Bay and to generate chlorophyll-a and total suspended matter (TSM) concentration layers using C2RCC algorithm. Nine coastal OWT classes for Manila Bay having consistent presence and spatial distribution seasonally were identified. The most dominant class, OWT 6, (3.50 µg/cm3 chlorophyll-a; 4.93 g/m3 TSM) was concentrated around the central area of the bay, covering as much as 79% of it. Chlorophyll-a and TSM concentrations were higher in the nearshore areas and were decreasing offshore. The class with the second highest concentrations, OWT 7, (9.11 µg/cm3 chlorophyll-a; 26.80 g/m3 TSM) were found near river outlets, where high nutrient and sediment loadings coming from the watershed enter the bay. Lowest concentrations (0.26–0.70 µg/cm3 chlorophyll-a; 0.64–1.10 g/m3 TSM) were found in OWT 1, OWT 2, and OWT 3, all located farthest from the shore, such as the mouth of the bay leading to the open sea. Validation using in situ observations showed that C2RCC produced relatively good estimates for chlorophyll-a concentrations of up to 12 µg/cm3 (RMSE=1.71 µg/cm3). No conclusion was drawn for TSM due to insufficient data.
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Brinkerhoff, Riley, Michael Vanden Berg et Mark Millard. « Using pore system characterization to subdivide the burgeoning Uteland Butte Play, Green River Formation, Uinta Basin, Utah ». Geosites 50 (1 septembre 2022) : 1–27. http://dx.doi.org/10.31711/ugap.v50i.105.
Texte intégralRésumé :
Over 240 horizontal wells with highly variable production results have been drilled in the Uteland Butte member (UBm) of the lower Green River Formation in the Uinta Basin, Utah. The best wells have each produced more than 300,000 barrels of oil in the first 12 months of production, with conservative Estimated Ultimate Recoveries (EURs) for several wells above a million barrels. Conversely, the poorest UBm wells have initial production rates of less than 10,000 barrels of oil in the first year and will never recoup their drilling costs. Pore pressure, oil viscosity, well length, and well completion are recognized as important controls on well productivity. Less understood, but of equal importance, is the variability in reservoir types across the UBm play. The UBm can be divided into sub-plays by district using the dominant pore systems in each area. We defined four distinct sub-plays within the Uinta Basin: 1) intergranular-dominated porosity, 2) intercrystalline- pore-dominated dolomite, 3) mixed intercrystalline-organic porosity, and 4) organic porosity. Reservoirs in the intergranular-dominated porosity sub-play are mostly present in the form of nearshore siliciclastic and carbonate bars, such as ooid and ostracod shoals, fluvial mouth bars, and nearshore siliciclastic bars. The normal pressure and charge in these reservoirs are due to hydrocarbon migration out of the deeper basin. Source rocks in this sub-play have an average maturity of 0.5 to 0.7 vitrinite reflectance (VRo), too low for mainstage oil generation for these lacustrine shales (Ruble and others, 2001), and produce highly viscous black wax with very low gas-to-oil ratios (GORs). To date, horizontal wells drilled in this sub-play have not been economically successful. The intercrystalline-pore-dominated sub-play consists of thin (<2 to 8+ feet), laterally continuous, high-porosity dolomites that act as the best reservoirs. The reservoir is normally to slightly overpressured and is predominately charged with hydrocarbons that migrated out of the deeper basin. This sub-play was the first to be drilled horizontally, with the dolomite beds being identified as the highest quality targets. The UBm is thick in the intercrystalline-pore-dominated fairway, consisting of over 130 feet of carbonates and black shales, with only a fraction of the interval being high-porosity dolomites. This sub-play has an average VRo of 0.6 to 0.8, still too low for mainstage oil generation in these rocks and produces a migrated black wax with low GORs. The mixed intercrystalline-organic porosity sub-play is largely self-sourced and significantly overpressured. This sub-play has the thickest gross section and is dominated by thin dolomite beds, thicker argillaceous limestones, and thicker shaley beds, with the latter units contributing significant production. Maturities in this sub-play range from 0.8 to 1.0 VRo. This sub-play produces a yellow to gray wax with moderate GORs. Finally, the organic-porosity-dominated sub-play is highly overpressured and completely self-sourced. There is relatively little reservoir-quality dolomite, the limestones are more argillaceous, and the organic-rich carbonate shales are thicker. The productive reservoir in this sub-play consists of organic porosity largely contained in bitumen that has been expelled at lower maturity, then continued to thermally degrade with higher maturity, converting to zones of interconnected organic porosity. Maturities range from 1.0 to 1.2 VRo and the hydrocarbons produced are a bright yellow wax with relatively high GORs. To be economically developed, each of these sub-plays requires individually tailored drilling, completion, and production strategies. By recognizing the important differences these pore systems exert on best development practices and then accurately mapping them across the basin, operators, interest owners, and regulatory agencies can more efficiently plan operations.
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Taylor, Elliott, Andy Graham, Jose Rios, Jean-Yves Huet, Lindsay Page-Jones et Gabriel Ivaba. « Angola Coastal Mapping and Tactics for Oil Spill Response ». International Oil Spill Conference Proceedings 2017, no 1 (1 mai 2017) : 850–62. http://dx.doi.org/10.7901/2169-3358-2017.1.850.
Texte intégralRésumé :
ABSTRACT The Angolan oil and gas industry workgroup (ACEPA-Associação das Companhias de Exploração e Produção de Angola) continues to collaborate in the development and completion of oil spill response initiatives as responsible operators and committed participants in the IMO-IPIECA Global Initiative for West, Central and Southern Africa (GI WACAF). Between 2012–2015, a comprehensive program of oil spill response planning, geodatabase development, mapping, and guides were completed for the entire coast of Angola. Low altitude aerial video surveys that combine oblique imagery and a verbal commentary record were recorded as the foundation for mapping coastal sensitivities, ESI characterization, shore zone and backshore operational definition, and shoreline segmentation. Other information added to the coastal geodatabase includes operational and logistical considerations such as land access and boat launch locations, proposed sites for staging, holding of temporary wastes, industrial and human use (fishing, recreational), and nearshore access constraints. A key aspect of the shoreline mapping effort was to build the information into a stand-alone pre-shoreline cleanup assessment technique (SCAT)-database that provides layered information for each of the 1999 shoreline segments. Digital video and high-resolution oblique aerial photos for 2400 km of coastline are geo-referenced and integrated into the GIS system with viewer software that allows the user to “fly” the shoreline. Shoreline attributes for biological, socioeconomic, and human use were used to rank 117 sensitive sites. The 45 highest priority sensitive sites were surveyed and detailed geographic response plans (GRPs) for site protection strategies and tactics were compiled into two atlases. The comprehensive coastal characterization, segmentation, and priority site protection plans provide the Angola government and oil industry with spill preparedness tools that are world-class.
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Raffa, Francesco, Giovanni Ludeno, Giuseppa Buscaino, Gianmaria Sannino, Adriana Carillo, Rosario Grammauta, Domenico Spoto, Francesco Soldovieri, Salvatore Mazzola et Francesco Serafino. « Coupling of Wave Data and Underwater Acoustic Measurements in a Maritime High-Traffic Coastal Area : A Case Study in the Strait of Sicily ». Journal of Atmospheric and Oceanic Technology 34, no 12 (décembre 2017) : 2589–99. http://dx.doi.org/10.1175/jtech-d-17-0046.1.
Texte intégralRésumé :
AbstractUnderwater acoustic monitoring combined with real-time sea surface observations and numerical model forecasts could improve the efficiency of natural and anthropogenic sound source discrimination. In this work, acoustic sound pressure levels at different frequencies were compared with significant wave heights, measured using an X-band radar system, and then matched against independent data derived from a Simulating Waves Nearshore (SWAN) model in order to confirm their reliability. The acoustic data were recorded from a fixed buoy located in the Sicilian Channel at 4.9 km from the coast and 33 km from the X-band radar system installed at Cape San Marco (in the southwest region of Sicily). All data were acquired during two different periods: 28 February–16 March 2015 and 23 April–27 May 2015. The level of noise at the 16-Hz octave band showed the best linear correlation , with in situ radar observations of significant wave height. Radar measurements of wave height coupled with in situ acoustic measurements give a characterization of the level of noise as result of sea state in a specific area. These measurements could be used to discriminate natural sources of noise (waves) from other sound sources, such as biological and anthropogenic sources. This discrimination contributes to understanding the impact of acoustic pollution on marine environments and provides a monitoring plan protocol for safeguarding biodiversity in the Mediterranean coastal areas.
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Lee, Wonhyun, et James M. Kaihatu. « EFFECTS OF DESALINATION ON HYDRODYNAMIC PROCESS IN PERSIAN GULF ». Coastal Engineering Proceedings, no 36 (30 décembre 2018) : 3. http://dx.doi.org/10.9753/icce.v36.papers.3.
Texte intégralRésumé :
Desalination is a significant source of potable water to the Persian Gulf (simply, the Gulf) region. At present, the Gulf countries are the biggest users of seawater desalination with over 50% of the world’s installed capacity. While, as ground- and surface water sources may become scarce or endangered in the Middle East and North Africa (MENA) region, water desalination activities are expected to continue growing in quantity and capacity, particularly in the Gulf region. However, it is not yet clear what the environmental effects are of increased brine discharge to the nearshore and offshore environments, as reliance on mass exchange through the Strait of Hormuz may be insufficient for necessary levels of flushing. To study this, a three-dimensional characterization of the Gulf has been developed using the Delft3D-FLOW hydrodynamic model. This model was used to obtain the hydrodynamics and flow transporting characteristics in the Gulf. In addition to meteorological and oceanographic forcing, the seasonal discharges of four major rivers and numerous desalination plants in the Gulf region were considered to the modeling system. Field measurements from Texas A&M University at Galveston (TAMUG) Microstructure Group in 2013 provided the validation for the model. The maximum 4.21 ppt and 4.32℃ increases in salinity and temperature, respectively, due to the brine discharge of desalination were obtained at the adjacent area to six desalination plants in the Gulf.
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Staley, Christopher, et Michael J. Sadowsky. « Regional Similarities and Consistent Patterns of Local Variation in Beach Sand Bacterial Communities throughout the Northern Hemisphere ». Applied and Environmental Microbiology 82, no 9 (26 février 2016) : 2751–62. http://dx.doi.org/10.1128/aem.00247-16.
Texte intégralRésumé :
ABSTRACTRecent characterization of the bacterial community structure in beach sands has revealed patterns of biogeography similar to those observed in aquatic environments. Studies to date, however, have mainly focused on subtidal sediments from marine beaches. Here, we investigate the bacterial diversity, using Illumina-based sequencing of the V5-V6 region of the 16S rRNA gene, at 11 beaches representing those next to the Great Lakes, Florida, and the Pacific Ocean. The alpha diversity differed significantly among regions (P< 0.0001), while the within-region diversity was more similar. The beta diversity also differed by region (P< 0.001), where freshwater sands had significantly higher abundances of taxa within theActinobacteria,Betaproteobacteria, andVerrucomicrobiathan marine environments. In contrast, marine sands harbored greater abundances ofGammaproteobacteriaandPlanctomycetes, and those from Florida had moreDeltaproteobacteriaandFirmicutes. Marine beaches had significantly different phylogenetic community structures (P≤ 0.018), but freshwater and Florida beaches showed fewer within-region phylogenetic differences. Furthermore, regionally distinct patterns in taxonomic variation were observed in backshore sands, which had communities distinct from those in nearshore sands (P< 0.001). Sample depth minimally influenced the community composition. The results of this study reveal distinct bacterial community structures in sand on a broad geographic scale but moderate regional similarity and suggest that local variation is primarily related to the distance from the shoreline. This study offers a novel comparison of the bacterial communities in freshwater and marine beach sands and provides an important basis for future comparisons and analyses to elucidate factors affecting microbial ecology in this underexplored environment.IMPORTANCEThis study presents a large-scale geographic characterization of the bacterial communities present in beach sands. While previous studies have evaluated how environmental factors influence bacterial community composition, few have evaluated bacterial communities in freshwater sands. Furthermore, the use of a consistent methodology to characterize bacterial communities here allowed a novel comparison of communities across geographic regions. We reveal that while the community composition in sands at individual beaches is distinct, beach sands within the same region harbor similar assemblages of bacteria and these assemblages differ greatly between regions. In addition, moisture, associated with distance from the shoreline, strongly influences the bacteria present in sands and more strongly influences the bacteria present than sample depth does. Thus, the data presented here offer an important basis for a broader characterization of the ecology of bacteria in sands, which may also be relevant to public health and resource management initiatives.
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Yang, Hengyi, Hao Wang, Yong Ma et Minyi Xu. « Prediction of Wave Energy Flux in the Bohai Sea through Automated Machine Learning ». Journal of Marine Science and Engineering 10, no 8 (26 juillet 2022) : 1025. http://dx.doi.org/10.3390/jmse10081025.
Texte intégralRésumé :
The rational assessment of regional energy distribution provides a scientific basis for the selection and siting of power generation units. This study, which focused on the Bohai Sea, set 31 research coordinate points in the Bohai sea for assessing the potential/trends of wave energy flux (WEF). We applied a point-to-point time series prediction method which modelled the different geographical coordinate points separately. Subsequently, we evaluated the performance of three traditional machine learning methods and three automated machine learning methods. To estimate WEF, the best model was applied to each research coordinate points, respectively. Then, the WEF was calculated and predicted based on the data of MWP, SWH, and water depth. The results indicate that, for all coordinates in the Bohai Sea, the H2O-AutoML algorithm is superior to the other five algorithms. Gradient boosting machine (GBM), extreme gradient boosting (XGBoost), and stacked ensemble models yielded the best performance out of the H2O algorithms. The significant wave height (SWH), the mean wave period (MWP), and the WEF in the Bohai Sea tended to be concentrated in the center of the sea and dispersed in the nearshore areas. In the year 2000, 2010, 2020, and 2030, the maximum annual average WEF at each research coordinate in the Bohai Sea is around 1.5 kW/m, with a higher flux in autumn and winter. In summary, the results provide ocean parameter characterization for the design and deployment of wave energy harvesting devices. Moreover, the automated machine learning introduced herein has potential for use in more applications in ocean engineering.
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Ajanaf, T., D. Gómez Grás, A. Navarro, J. D. Martín-Martín, J. R. Rosell et A. Maate. « The building stone of the Roman city of Lixus (NW Morocco) : provenance, petrography and petrophysical characterization ». Geologica Acta 18 (31 août 2020) : 1–16. http://dx.doi.org/10.1344/geologicaacta2020.18.13.
Texte intégralRésumé :
The characterization of building materials is a key tool to assess deterioration processes and improve potential restoration works of archaeological sites. The aim of this paper is to identify and characterize the most important building stones used in the construction of the Roman city of Lixus (Larache, Morocco) by means of petrographic and petrophysical techniques. Based on the visual analysis of the monuments, three major building stones (i.e. lithotypes) have been identified: i) Oligocene sandstones, ii) Quaternary sandstones and iii) Quaternary conglomerates. Based on the analysis of the regional geology and exploitation marks, these three lithotypes have been recognised to crop out in the surroundings of Lixus and the quarries, presumably Roman in origin, recognized. The Oligocene sandstone is the primary building stone in Lixus as it forms and crops out extensively in the Tchemmis hill, at the top of which the city is settled. The Quaternary sandstones and conglomerates, which represent nearshore deposits and eolianites, crop out along the Atlantic coast where they form part of the cliffs next to Larache. Petrographic results indicate that lithotypes differ notably in grain size, ratio of detrital to allochemical components, and the configuration of their porous system. Mechanical analysis shows that the Oligocene sandstones are more resistant to compression than the Quaternary sandstones and conglomerates, the latter exhibiting relatively low compressive strength. The Oligocene sandstones, which display scarce porosity and permeability, show a hydric behaviour characterized by a very low degree of absorption and desorption water, likely resulting from a poor connectivity of the pore network. Contrary to the latter lithotype, the Quaternary sandstones, which exhibit very high porosity and permeability, display a hydric behaviour characterized by high degree of both absorption and desorption of water. This is attributed to the low degree of cementation compared to porosity of this lithotype and the excellent connectivity of the porous network. Finally, Oligocene and Quaternary sandstones do not show a significant weight loss after the accelerated artificial aging test, indicating that both are slightly affected by salt crystallization and presumably ice formation. Results indicate that the relatively fine state of conservation of the building rocks of Lixus is linked to intrinsic factors such as mineralogy and petrophysical characteristics together with the favourable effect of the climatic condition of the study area.
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Suriamin, Fnu, et Matthew J. Pranter. « Lithofacies, depositional, and diagenetic controls on the reservoir quality of the Mississippian mixed siliciclastic-carbonate system, eastern Anadarko Basin, Oklahoma, USA ». Interpretation 9, no 3 (27 juillet 2021) : T881—T910. http://dx.doi.org/10.1190/int-2020-0165.1.
Texte intégralRésumé :
In the eastern Anadarko Basin of central Oklahoma, the variability of Mississippian lithofacies, diagenetic products, and reservoir quality is critical for reservoir development. We have investigated lithofacies variability based on sedimentological characteristics and diagenetic alteration through integration of core and thin sections by using optical microscope, scanning electron microscope, energy dispersive X-ray diffraction spectroscope, and electron probe microanalyzer-cathodoluminescence analyses. Based on detailed descriptions of five cores (approximately 260 m [approximately 850 ft]) and analysis of 34 thin sections, we concluded that the Mississippian strata consists of eight lithofacies that represent wave-influenced nearshore with restricted embayment (lagoon) and channel or lobe deposits. We observed diagenetic alteration including calcite cementation, mechanical compaction, albitization, quartz cementation, silicification, dolomitization, Fe-dolomite cementation, pyritization, and dissolution. A paragenesis scheme suggests that quartz cementation occurred earlier compared to albitization and Fe-dolomite cementation. The Fe-dolomite is the latest authigenic mineral formed, whereas the quartz and calcite cement can be attributed to earlier diagenesis. The calcite, quartz, and Fe-dolomite cementation might have potentially increased the brittleness index and frackability of the rocks. The reservoir quality is relatively good in the channel or lobe deposits and is generally poor in the upper shoreface to upper offshore environments. The reservoir quality is significantly reduced by clays, calcite cement, and mechanical compaction. However, the dissolution of calcite cement and detrital grains tends to improve reservoir quality by forming secondary pores. We prove that understanding the characteristic of lithofacies variation, depositional environments, and diagenetic alterations of the Mississippian strata is crucial for optimal development of the Mississippian reservoirs in the eastern Anadarko Basin. We develop a predictive framework that aids in reservoir characterization.
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Gershelis, Elena, Andrey Grinko, Irina Oberemok, Elizaveta Klevantseva, Natalina Poltavskaya, Alexey Ruban, Denis Chernykh, Andrey Leonov, Natalia Guseva et Igor Semiletov. « Composition of Sedimentary Organic Matter across the Laptev Sea Shelf : Evidences from Rock-Eval Parameters and Molecular Indicators ». Water 12, no 12 (14 décembre 2020) : 3511. http://dx.doi.org/10.3390/w12123511.
Texte intégralRésumé :
Global warming in high latitudes causes destabilization of vulnerable permafrost deposits followed by massive thaw-release of organic carbon. Permafrost-derived carbon may be buried in the nearshore sediments, transported towards the deeper basins or degraded into the greenhouse gases, potentially initiating a positive feedback to climate change. In the present study, we aim to identify the sources, distribution and degradation state of organic matter (OM) stored in the surface sediments of the Laptev Sea (LS), which receives a large input of terrestrial carbon from both Lena River discharge and intense coastal erosion. We applied a suite of geochemical indicators including the Rock Eval parameters, traditionally used for the matured OM characterization, and terrestrial lipid biomarkers. In addition, we analyzed a comprehensive grain size data in order to assess hydrodynamic sedimentation regime across the LS shelf. Rock-Eval (RE) data characterize LS sedimentary OM with generally low hydrogen index (100–200 mg HC/g TOC) and oxygen index (200 and 300 CO2/g TOC) both increasing off to the continental slope. According to Tpeak values, there is a clear regional distinction between two groups (369–401 °C for the inner and mid shelf; 451–464 °C for the outer shelf). We suggest that permafrost-derived OM is traced across the shallow and mid depths with high Tpeak and slightly elevated HI values if compared to other Arctic continental margins. Molecular-based degradation indicators show a trend to more degraded terrestrial OC with increasing distance from the coast corroborating with RE results. However, we observed much less variation of the degradation markers down to the deeper sampling horizons, which supports the notion that the most active OM degradation in LS land-shelf system takes part during the cross-shelf transport, not while getting buried deeper.
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Bentamy, Abderrahim, Semyon A. Grodsky, Gildas Cambon, Pierre Tandeo, Xavier Capet, Claude Roy, Steven Herbette et Antoine Grouazel. « Twenty-Seven Years of Scatterometer Surface Wind Analysis over Eastern Boundary Upwelling Systems ». Remote Sensing 13, no 5 (3 mars 2021) : 940. http://dx.doi.org/10.3390/rs13050940.
Texte intégralRésumé :
More than twelve satellite scatterometers have operated since 1992 through the present, providing the main source of surface wind vector observations over global oceans. In this study, these scatterometer winds are used in combination with radiometers and synthetic aperture radars (SAR) for the better determination and characterization of high spatial and temporal resolution of regional surface wind parameters, including wind speed and direction, wind stress components, wind stress curl, and divergence. In this paper, a 27-year-long (1992–2018) 6-h satellite wind analysis with a spatial resolution of 0.125° in latitude and longitude is calculated using spatial structure functions derived from high-resolution SAR data. The main objective is to improve regional winds over three major upwelling regions (the Canary, Benguela, and California regions) through the use of accurate and homogenized wind observations and region-specific spatial and temporal wind variation structure functions derived from buoy and SAR data. The long time series of satellite wind analysis over the California upwelling, where a significant number of moorings is available, are used for assessing the accuracy of the analysis. The latter is close to scatterometer wind retrieval accuracy. This assessment shows that the root mean square difference between collocated 6-h satellite wind analysis and buoys is lower than 1.50 and 1.80 m s−1 for offshore and nearshore locations, respectively. The temporal correlation between buoy and satellite analysis winds exceeds 0.90. The analysis accuracy is lower for 1992–1999 when satellite winds were mostly retrieved from ERS-1 and/or ERS-2 scatterometers. To further assess the improvement brought by this new wind analysis, its data and data from three independent products (ERA5, CMEMS, and CCMP) are compared with purely scatterometer winds over the Canary and Benguela regions. Even though the four products are generally similar, the new satellite analysis shows significant improvements, particularly in the upwelling areas.
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Niroumand-Jadidi, Milad, Nima Pahlevan et Alfonso Vitti. « Mapping Substrate Types and Compositions in Shallow Streams ». Remote Sensing 11, no 3 (29 janvier 2019) : 262. http://dx.doi.org/10.3390/rs11030262.
Texte intégralRésumé :
Remote sensing of riverbed compositions could enable advances in hydro-morphological and habitat modeling. Substrate mapping in fluvial systems has not received as much attention as in nearshore, optically shallow inland, and coastal waters. As finer spatial-resolution image data become more available, a need emerges to expand research on the remote sensing of riverbed composition. For instance, research to date has primarily been based on spectral reflectance data from above the water surface without accounting for attenuation by the water-column. This study analyzes the impacts of water-column correction for substrate mapping in shallow fluvial systems (depth < 1 m). To do so, we performed three different experiments: (a) analyzing spectroscopic measurements in a hydraulic laboratory setting, (b) simulating water-leaving radiances under various optical scenarios, and (c) evaluating the potential to map bottom composition from a WorldView-3 (WV3) image of a river in Northern Italy. Following the retrieval of depth and diffuse attenuation coefficient ( K d ), bottom reflectances were estimated using a water-column correction method. The results indicated significant enhancements in streambed maps based on bottom reflectances relative to maps produced from above-water spectra. Accounting for deep-water reflectance, embedded in the water-column correction, was demonstrated to have the greatest impact on the retrieval of bottom reflectance in NIR bands, when the water column is relatively thick (>0.5 m) and/or when the water is turbid. We also found that the WV3’s red-edge band (i.e., 724 nm) considerably improved the characterization of submerged aquatic vegetation (SAV) densities from either above-water or retrieved bottom spectra. This study further demonstrated the feasibility of mapping SAV density classes from a WV3 image of the Sarca River in Italy by retrieving the bottom reflectances.
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Mitsopoulos, Panagiotis, et Malaquias Peña. « Characterizing Coastal Wind Speed and Significant Wave Height Using Satellite Altimetry and Buoy Data ». Remote Sensing 15, no 4 (10 février 2023) : 987. http://dx.doi.org/10.3390/rs15040987.
Texte intégralRésumé :
Wind speed and significant wave height are the most relevant metocean variables that support a wide range of engineering and economic activities. Their characterization through remote sensing estimations is required to compensate for the shortage of in situ observations. This study demonstrates the value of satellite altimetry to identify typical spatial patterns of wind speed and significant wave height in the northeastern region of the United States. Data from five altimetry satellite missions were evaluated against the available in situ observations with a 10 km sampling radius and a 30 min time window. An objective analysis of the collective altimeter dataset was performed to create aggregated composite maps of the wind speed and significant wave height. This asynchronous compositing of multi-mission altimeter data is introduced to compile a sufficient sampling of overpasses over the area of interest. The results of this approach allow for quantifying spatial patterns for the wind speed and significant wave height in the summer and winter seasons. The quality of altimeter estimations was assessed regarding the distance from the coast and the topography. It was found that while the altimeter data are highly accurate for the two variables, bias increases near the coast. The average minimum and maximum wind speed values detected in buoy stations less than 40 km from the coast were not matched by the aggregated altimeter time series. The method exposes the spatial and time gaps to be filled using data from future missions. The challenges of the objective analysis near the coast, especially in semi-enclosed areas, and the implications of the altimeter estimations due to the land contamination are explained. The results indicate that the combination of altimetry data from multiple satellite missions provides a significant complementary information resource for nearshore and coastal wind and wave regime estimations.