Shell (Norway)

The importance of restoring filter-feeders, such as the Eastern oyster Crassostrea virginica, to mitigate the effects of eutrophication (e.g. in Chesapeake Bay) is currently under debate. The argument that bivalve molluscs alone cannot control phytoplankton blooms and reduce hypoxia oversimplifies a more complex issue, namely that ecosystem engineering species make manifold contributions to ecosystem services. Although further discussion and research leading to a more complete understanding is required, oysters and other molluscs (e.g. mussels) in estuarine ecosystems provide services far beyond the mere top-down control of phytoplankton blooms, such as (1) seston filtration, (2) benthic–pelagic coupling, (3) creation of refugia from predation, (4) creation of feeding habitat for juveniles and adults of mobile species, and for sessile stages of species that attach to molluscan shells, and (5) provision of nesting habitat.

Reconstructing the genomes of bilaterian ancestors is central to our understanding of animal evolution, where knowledge from ancient and/or slow-evolving bilaterian lineages is critical. Here we report a high-quality, chromosome-anchored reference genome for the scallop Patinopecten yessoensis, a bivalve mollusc that has a slow-evolving genome with many ancestral features. Chromosome-based macrosynteny analysis reveals a striking correspondence between the 19 scallop chromosomes and the 17 presumed ancestral bilaterian linkage groups at a level of conservation previously unseen, suggesting that the scallop may have a karyotype close to that of the bilaterian ancestor. Scallop Hox gene expression follows a new mode of subcluster temporal co-linearity that is possibly ancestral and may provide great potential in supporting diverse bilaterian body plans. Transcriptome analysis of scallop mantle eyes finds unexpected diversity in phototransduction cascades and a potentially ancient Pax2/5/8-dependent pathway for noncephalic eyes. The outstanding preservation of ancestral karyotype and developmental control makes the scallop genome a valuable resource for understanding early bilaterian evolution and biology.

Women are still a minority in the economics profession. By the mid-2000s, just under 35 percent of PhD students and 30 percent of assistant professors were female, and these numbers have remained roughly constant ever since. Over the past two decades, women’s progress in academic economics has slowed, with virtually no improvement in the female share of junior faculty or graduate students in decades. Little consensus has emerged as to why, though there has been a renewal of widespread interest in the status and future of women in economics and of the barriers they face to professional success. In this paper, we first document trends in the gender composition of academic economists over the past 25 years, the extent to which these trends encompass the most elite departments, and how women’s representation across fields of study within economics has changed. We then review the recent literature on other dimensions of women’s relative position in the discipline, including research productivity and income, and assess evidence on the barriers that female economists face in publishing, promotion, and tenure. While differences in preferences and constraints may directly affect the relative productivity of men and women, productivity gaps do not fully explain the gender disparity in promotion rates in economics. Furthermore, the progress of women has stalled relative to that in other disciplines in the past two decades. We propose that differential assessment of men and women is one important factor in explaining this stalled progress, reflected in gendered institutional policies and apparent implicit bias in promotion and tenure processes.

BACKGROUND: The Pacific oyster (Crassostrea gigas) is a bivalve mollusc with vital roles in coastal ecosystems and aquaculture globally. While extensive genomic tools are available for C. gigas, highly contiguous reference genomes are required to support both fundamental and applied research. Herein we report the creation and annotation of a chromosome-level assembly for C. gigas. FINDINGS: High-coverage long- and short-read sequence data generated on Pacific Biosciences and Illumina platforms were used to generate an initial assembly, which was then scaffolded into 10 pseudo-chromosomes using both Hi-C sequencing and a high-density linkage map. The assembly has a scaffold N50 of 58.4 Mb and a contig N50 of 1.8 Mb, representing a step advance on the previously published C. gigas assembly. Annotation based on Pacific Biosciences Iso-Seq and Illumina RNA-Seq resulted in identification of ∼30,000 putative protein-coding genes. Annotation of putative repeat elements highlighted an enrichment of Helitron rolling-circle transposable elements, suggesting their potential role in shaping the evolution of the C. gigas genome. CONCLUSIONS: This new chromosome-level assembly will be an enabling resource for genetics and genomics studies to support fundamental insight into bivalve biology, as well as for selective breeding of C. gigas in aquaculture.

Restoration of degraded ecosystems is an important societal goal, yet inadequate monitoring and the absence of clear performance metrics are common criticisms of many habitat restoration projects. Funding limitations can prevent adequate monitoring, but we suggest that the lack of accepted metrics to address the diversity of restoration objectives also presents a serious challenge to the monitoring of restoration projects. A working group with experience in designing and monitoring oyster reef projects was used to develop standardized monitoring metrics, units, and performance criteria that would allow for comparison among restoration sites and projects of various construction types. A set of four universal metrics (reef areal dimensions, reef height, oyster density, and oyster size–frequency distribution) and a set of three universal environmental variables (water temperature, salinity, and dissolved oxygen) are recommended to be monitored for all oyster habitat restoration projects regardless of their goal(s). In addition, restoration goal‐based metrics specific to four commonly cited ecosystem service‐based restoration goals are recommended, along with an optional set of seven supplemental ancillary metrics that could provide information useful to the interpretation of prerestoration and postrestoration monitoring data. Widespread adoption of a common set of metrics with standardized techniques and units to assess well‐defined goals not only allows practitioners to gauge the performance of their own projects but also allows for comparison among projects, which is both essential to the advancement of the field of oyster restoration and can provide new knowledge about the structure and ecological function of oyster reef ecosystems.

ABSTRACT We considered the importance of low frequencies in seismic reflection data for enhanced resolution, better penetration, and waveform and impedance inversion. We reviewed various theoretical arguments underlining why adding low frequencies may be beneficial and provided experimental evidence for the improvements by several case studies with recently acquired broadband data. We discussed where research and development efforts in the industry with respect to low frequencies should be focusing.

ABSTRACT Permian aeolian sediments on the island of Arran are divisible into dune (including draa) and interdune deposits. Both types display a distinctive and unusually wide variation in grain size. The dominant features of the dune deposits are grainfall lamination, sandflow lamination, and inverse graded lamination associated with ripple‐form lamination and normal graded lamination. The flat‐lying aeolian interdune deposits are characterised by granule and sand ripples, horizontal lamination in coarse sand and granules, plane bed lamination and inverse graded lamination. Associated structures include ripple‐form lamination and deflation lags. Three types of trace fossil associated with completely bioturbated horizons occur in some low‐angle dune and interdune deposits. The aeolian facies interfinger with alluvial fan deposits giving rise to three recognizable facies belts. Marginal aeolian deposits are associated with fluvial conglomerates and are dominated by interdune deposits and occasionally very thin barchan deposits (set height 3‐37 cm). Intermediate aeolian deposits are characterized by interbedded crescentic dune, small draa (dune set height 5 cm‐4.5 m) and interdune deposits, and rare fluvial and lake sediments. Basinal aeolian deposits are dominated by draa deposits (dune set height 0.2‐28 m) associated with rare interdune sediments. Transverse dunes and draas were moved by north‐eastern palaeowinds towards the foot of the alluvial fans. The aeolian sediments were deposited in a fault‐bounded desert basin.

Abstract Oyster reef living shorelines have been proposed as an effective alternative to traditional coastal defence structures (e.g. bulkheads, breakwaters), with the benefit that they may keep pace with sea‐level rise and provide co‐benefits, such as habitat provision. However, there remains uncertainty about the effectiveness of shoreline protection provided by oyster reefs, which limits their broader application. We draw evidence from studies along the east and gulf coasts of the United States, where much research and implementation of oyster reef restoration has occurred, to better define the existing gaps in our understanding of the use of restored oyster reefs for shoreline protection. We find potential disconnects between ecological and engineering functions of reefs. In response, we outline how engineering and ecological principles are used in the design of oyster reef living shorelines and highlight knowledge gaps where an integration of these disciplines will lead to their more effective application. Synthesis and applications. This work highlights the necessary steps to advance the application of oyster reef living shorelines. Importantly, future research should focus on appropriate designs and conditions needed for these structures to effectively protect our coasts from erosion, while supporting a sustainable oyster population, thereby providing actionable nature‐based alternatives for coastal defence to diverse end‐users.

One of the paramount goals of oyster reef living shorelines is to achieve sustained and adaptive coastal protection, which requires meeting ecological (i.e., develop a self-sustaining oyster population) and engineering (i.e., provide coastal defense) targets. In a large-scale comparison along the Atlantic and Gulf coasts of the United States, the efficacy of various designs of oyster reef living shorelines at providing wave attenuation was evaluated accounting for the ecological limitations of oysters with regard to inundation duration. A critical threshold for intertidal oyster reef establishment is 50% inundation duration. Living shorelines that spent less than one-half of the time (<50%) inundated were not considered suitable habitat for oysters, however, were effective at wave attenuation (68% reduction in wave height). Reefs that experienced >50% inundation were considered suitable habitat for oysters, but wave attenuation was similar to controls (no reef; ~5% reduction in wave height). Many of the oyster reef living shoreline approaches therefore failed to optimize the ecological and engineering goals. In both inundation regimes, wave transmission decreased with an increasing freeboard (difference between reef crest elevation and water level), supporting its importance in the wave attenuation capacity of oyster reef living shorelines. However, given that the reef crest elevation (and thus freeboard) should be determined by the inundation duration requirements of oysters, research needs to be refocused on understanding the implications of other reef parameters (e.g., width) for optimizing wave attenuation. A broader understanding of the reef characteristics and seascape contexts that result in effective coastal defense by oyster reefs is needed to inform appropriate design and implementation of oyster-based living shorelines globally.

Microbial metabolism is the engine that drives global biogeochemical cycles, yet many key transformations are carried out by microbial consortia over short spatiotemporal scales that elude detection by traditional analytical approaches. We investigate syntrophic sulfur cycling in the 'pink berry' consortia of the Sippewissett Salt Marsh through an integrative study at the microbial scale. The pink berries are macroscopic, photosynthetic microbial aggregates composed primarily of two closely associated species: sulfide-oxidizing purple sulfur bacteria (PB-PSB1) and sulfate-reducing bacteria (PB-SRB1). Using metagenomic sequencing and (34) S-enriched sulfate stable isotope probing coupled with nanoSIMS, we demonstrate interspecies transfer of reduced sulfur metabolites from PB-SRB1 to PB-PSB1. The pink berries catalyse net sulfide oxidation and maintain internal sulfide concentrations of 0-500 μm. Sulfide within the berries, captured on silver wires and analysed using secondary ion mass spectrometer, increased in abundance towards the berry interior, while δ(34) S-sulfide decreased from 6‰ to -31‰ from the exterior to interior of the berry. These values correspond to sulfate-sulfide isotopic fractionations (15-53‰) consistent with either sulfate reduction or a mixture of reductive and oxidative metabolisms. Together this combined metagenomic and high-resolution isotopic analysis demonstrates active sulfur cycling at the microscale within well-structured macroscopic consortia consisting of sulfide-oxidizing anoxygenic phototrophs and sulfate-reducing bacteria.

Abstract Prospect delineation in volcanic basins is commonly hampered by poor sub-basalt imaging. Recent seismic advances focusing on low frequencies have significantly enhanced structural imaging, but not the seismic resolution. Currently, the sub-basalt play is mainly a structural play. On the North Atlantic margin, success has been booked with the discovery of the sub-basalt anticlinal Corrib gas field, offshore Ireland. However, not all sub-basalt anticlines observed on seismic data are valid prospects because some of them are located directly above large igneous complexes, displaying highly overmature and overcompacted sedimentary sections with little porosity. Use of filtered gravity and magnetic data and potentially seismic velocity analysis can easily delineate and subsequently de-risk these prospects. Sill intrusion can generate subtle anticlinal traps that might be valid prospects because the thermal effect of sills is relatively limited. Thus, there is less chance of generating an overmature prospect, unless the sills occur in high numbers. Filtered gravity and magnetic data sets, in combination with local geology, can be used in the early stages of sub-basalt exploration to low-grade regions with a high amount of large intrusives. This approach is highlighted for the North Atlantic volcanic province and offshore western India. Potentially, the most prospective regions of volcanic basins are where flood basalts simply blanket sedimentary basins without intrusives in the direct subsurface. In this case, basalt thickness estimation and associated burial depth become an important parameter to estimate prospectivity. Seismic modeling suggests that it might be difficult to constrain basalt thickness from seismic sections without reliable calibration. Although an increase in volcanism in sedimentary basins generally tends to increase risks, proper integration of geophysical and geological data should be able to better evaluate volcanic basins.

In a time-lapse 3-D seismic (TL3D) project, a “monitor” seismic survey is compared to a “base” survey. Ideally, the base survey is a 3-D data set acquired before production from the field started. Normally, the monitor survey is acquired after several years of production. The observed differences between the base and the monitor survey can be interpreted in terms of changes in fluid saturation and pressure.

Abstract Two end-member classes of sediment distribution systems on topographically complex slopes are distinguished here: (a) cascades of silled sub-basins , and (b) connected tortuous corridors . In the first scenario a process of filling and spilling of successive silled sub-basins down a slope occurs. For each sub-basin a sill tends to hinder further downslope flow of at least the basal sandy portions of sediment gravity flows until deposition reduces the relief sufficiently to allow spill down-slope. Spill is associated with incision in the sill. In the connected tortuous corridors scenario, flows avoid bathymetric obstacles, but follow a (laterally confined) continuous tortuous path down the slope. Without complete three-dimensional imaging of slope architecture it can be possible to incorrectly infer from two-dimensional profiles a cascade of silled sub-basins model. Thus flow paths in adjacent apparent subbasins can be connected out of the plane of section. Convergent thinning and convergent baselap stratal patterns occur in both scenarios, but only in the silled sub-basin case do such patterns occur against closing frontal slopes. For a given complex slope morphology, dominant controls on fill patterns and reservoir architecture are (a) the history of sediment supply character, and (b) rates of structure growth relative to rates of smoothing of topography by erosional and depositional processes. Two particularly important aspects of sediment supply are (i) flow volumes relative to scales of receiving spaces, and (ii) flow properties (in particular, transported grain size distribution, flow thickness and flow concentration), these controlling depositional gradients and the equilibrium profiles to which slopes tend to grade.

Abstract Existing facies models of tide‐dominated deltas largely omit fine‐grained, mud‐rich successions. Sedimentary facies and sequence stratigraphic analysis of the exceptionally well‐preserved Late Eocene Dir Abu Lifa Member (Western Desert, Egypt) aims to bridge this gap. The succession was deposited in a structurally controlled, shallow, macrotidal embayment and deposition was supplemented by fluvial processes but lacked wave influence. The succession contains two stacked, progradational parasequence sets bounded by regionally extensive flooding surfaces. Within this succession two main genetic elements are identified: non‐channelized tidal bars and tidal channels. Non‐channelized tidal bars comprise coarsening‐upward sandbodies, including large, downcurrent‐dipping accretion surfaces, sometimes capped by palaeosols indicating emergence. Tidal channels are preserved as single‐storey and multilateral bodies filled by: (i) laterally migrating, elongate tidal bars (inclined heterolithic strata, 5 to 25 m thick); (ii) forward‐facing lobate bars (sigmoidal heterolithic strata, up to 10 m thick); (iii) side bars displaying oblique to vertical accretion (4 to 7 m thick); or (iv) vertically‐accreting mud (1 to 4 m thick). Palaeocurrent data show that channels were swept by bidirectional tidal currents and typically were mutually evasive. Along‐strike variability defines a similar large‐scale architecture in both parasequence sets: a deeply scoured channel belt characterized by widespread inclined heterolithic strata is eroded from the parasequence‐set top, and flanked by stacked, non‐channelized tidal bars and smaller channelized bodies. The tide‐dominated delta is characterized by: (i) the regressive stratigraphic context; (ii) net‐progradational stratigraphic architecture within the succession; (iii) the absence of upward deepening trends and tidal ravinement surfaces; and (iv) architectural relations that demonstrate contemporaneous tidal distributary channel infill and tidal bar accretion at the delta front. The detailed facies analysis of this fine‐grained, tide‐dominated deltaic succession expands the range of depositional models available for the evaluation of ancient tidal successions, which are currently biased towards transgressive, valley‐confined estuarine and coarser grained deltaic depositional systems.

Analysis of 2D and 3D seismic records from the continental shelf off western Norway, in combination with chronological constraints from 14C dates, has led to a model for the glacial development in these shelf areas between c. 15 and 13 14C ka BP. On the shallow Måløy Plateau adjacent to the Norwegian Channel, iceberg scours are preserved below a prominent moraine ridge, which by correlation to the Norwegian Channel indicate ice retreat at c. 15 14C ka BP. Subsequently, the ice advanced across the scoured surface and deposited a till sheet before stabilizing to deposit a prominent moraine, termed the Bremanger Moraine. Based on location on the shelf, seismic stratigraphy, morphology and C dates the Bremanger Moraine is correlated with a significant moraine on the continental shelf off Trøndelag. We suggest that these features are products of a regional glacial event, the Bremanger Event, dated to <15–13.3 14C ka BP. The Bremanger Event is probably a result of the deteriorating climatic conditions in the NE Atlantic during Heinrich event 1.

Field examples from the Pliocene to Pleistocene succession of the Crotone Basin document the variability of stratal architecture in syntectonic units deposited in normal fault-bounded basins. Relatively thick trangressive intervals are common within these successions, as shown in the Zinga 2, Zinga 3 and Strongoli stratal units. Transgressive packages are formed by lagoonal mudstones that are abruptly overlain by shoreface sandstones. Aggradational highstand shallow-marine packages are typical of the lower Pliocene succession in half-graben basins. These deposits resulted from balanced conditions between the rate of sediment supply and the rate of creation of accommodation. Relatively thick forced regressive deposits are common within basins during phases where the accommodation–supply ratio is low (e.g. the middle Pleistocene San Mauro Sandstone). These deposits, influenced by growth faulting and folding, recorded base-level lowering linked to glacio-eustasy. A complex stratal architecture may be the consequence of the alternation between tectonic subsidence and uplift (e.g. the Serra Piani stratal unit). Such variations are thought to be related to the onset of an earliest mid-Pliocene transpressional tectonic phase. The studied deposits, therefore, show a marked tectonic control that strongly influenced their stratal architecture. These examples represent interesting cases of sequence-stratigraphic analysis in growth-faulted contexts.

Abstract Post-depositional remobilization and injection of sand can significantly change the geometry of deepwater clastic reservoirs. Features associated with these processes are particularly well developed in the lower Paleogene of the South Viking Graben of the UK and Norwegian North Sea. Seismic scale sandstone intrusions can be grouped in two classes. Class 1 comprises low-angle (20-40 degrees) tabular sandstone intrusions emanating from steep-sided in situ sand bodies within the Balder Formation. The intrusions may be 5-30+m thick and crosscut 120-250+m of compacted stratigraphic section. They terminate at an unconformity at the top of the Frigg interval where they may have extruded onto the palaeo-seafloor. Class 2 comprises conical sandstone intrusions that emanate some 50-300+m upward from distinct apexes located 400-700+m above the nearest depositional sand body. The conical intrusions may have been sourced from underlying sand bodies by clastic blow out pipes. Both types of intrusions seem to adopt their particular geometry independently of (but occasionally exploiting) polygonal faults within the encasing mudstones. Sandstone intrusions may be highly porous and permeable and are thus important both as reservoirs and as plumbing within thick mudstone sequences.

Spatial variations in nekton use are often attributed to differences in the configuration and composition of habitat. We predicted that differences in nekton use among intertidal creeks were related to certain geomorphological characteristics. We measured or derived 28 features at 8 intertidal creeks in the high salinity North Inlet Estuary, South Carolina, USA. Nekton were collected simultaneously from all creeks once each season for 2 yr. Spatial variations in total abundance and biomass were greater than seasonal variations. Differences of 3- to 30-fold in resident and transient taxa densities occurred among creeks on the same date. Relative use (ranks) was similar among seasons and years. In canonical correlation analyses, depth, steepness, flow, and location were primary factors for total nekton and many taxa. Creeks that were shallow, broad, and filled and emptied slowly supported the greatest use. Total nekton use was not related to creek size, amount of edge, or oyster bottom. Grass shrimp Palaemonetes spp., numerically dominant in 83% of the collections, responded most to creek shape. Mummichog Fundulus heteroclitus favored shallow creeks with low flow and low proportions of submerged bottom at low tide. Juvenile spot Leiostomus xanthurus and pinfish Lagodon rhomboides were associated with the same features throughout their seasonal periods of occurrence. Persistent differences in nekton use of adjacent intertidal creeks might be explained by behavioral selection for preferred conditions and reoccupation of selected creeks. Geomorphological variations are significant among sites and must be considered when assessing factors affecting nekton use along salinity and other environmental gradients.

ABSTRACT This paper describes part of a comprehensive joint-industry project on upheaval buckling. It develops a semi empirical simplified design method and detailed design methods based on a new numerical analysis, and illustrates their application by examples. It assesses alternative design strategies, and the implications of strain-based design. INTRODUCTION When a pipeline is operated at a temperature and pressure higher than ambient, it will try to expand. If the line is not free to expand, the pipe will develop an axial compressive force. I£ the force exerted by the pipe on the soil exceeds the vertical restraint against uplift movement created by the pipe's submerged weight, its bending stiffness, and the resistance of the soil cover, the pipe will tend to move upward, and considerable vertical displacements may occur. The pipeline response might then be unacceptable because of excessive vertical displacement or excessive plastic yield deformation. Upheaval buckling is hence a failure mode that has to be taken into account in the design of trenched and buried pipelines. The possibility of upheaval buckling is of increasing concern to the operators of flow lines in the North Sea and elsewhere. Their concern has been heightened by upheaval buckling incidents in the Danish and Norwegian sectors, and by the cost of protective measures such as rock dumping. Shell International Petroleum Maatschappij (SIPM) initiated a comprehensive upheaval buckling research program in 1987. In its final form, the research program included six phases:review of available models;comparative analysis;cover response, testing and modeling;numerical upheaval buckling model;analysis of alternative concepts;development of an upheaval buckling guideline. The present paper is one of a series describing the results of the programmer. It concentrates on phases 5 and 6, which were subcontracted by SIPM to a joint venture of three UK engineering companies r Andrew Palmer and Associates r Advanced Mechanics and Engineering, and Lloyds Register. The paper is primarily concerned with the design aspects of upward buckling of buried pipelines. Unburied pipelines can buckle in a related but different mode, in which they snake sideways across the seabed. This mode too is important in practice and can play a major part in relieving the effects of axial force, but it is outside the scope of the present paper. The paper first briefly describes the phenomenon, and puts forward a simplified method for preliminary design. It goes on to describe a conceptual design method based on the application of the UPBUCK program, and applies the methods to a design example. The paper then considers alternative strategies to resolve upheaval problems, and examines in more detail one of these strategies, a reduction in wall thickness made possible by the replacement of stress criteria on longitudinal stress with strain-based design criteria.

Quantitative and qualitative aspects of reproduction in the giant scallop Placopecten magellanicus (Gmelin) were compared between populations in the Damariscotta River (13 to 20 m depth) and the Gulf of Maine (170 to 180m depth).Gonad weight (p < 0.005) and gonad index (p < 0.01) were significantly greater in the shallow-water population dunng the period of gametogenesis.Oocytes of scallops in the shallow-water population developed gradually and spawning occurred in the fall.In spite of reduced gonadal production, scallops at the deep-water site completed gametogenesis.Oogenesis in the deep-water population was characterized by a greater initial rate of oocyte growth, resorption and a possible minor spring spawning, a period of redevelopment with continued resorption, and a later, more abrupt fall spawning.Gametogenesis was generally less synchronous among individuals in the deep-water population and oocytes were less dense withn gonadal tissue.The reduction in gonad production at the deep-water site was manifested as a reduced fecundity (number of eggs), rather than reduced egg size, as mean oocyte bameters were similar for both populations.In spite of apparent energehc hmitations, scallops at 180 m produce and spawn apparently viable ova, but in considerably lower numbers than those from shallower depths.