Shallow Sites Research Articles

Organic matter sulfurization and organic carbon burial in the Mesoproterozoic

Throughout the Proterozoic Era, sedimentary organic carbon burial helped set the pace of global oxygenation and acted as a major modulator of atmospheric CO2 and climate. Although Proterozoic rocks generally contain low concentrations of organic matter (OM), there are key exceptions to this rule, including the relatively OM-rich Arctic Bay shales from Baffin Island, Canada (Bylot Supergroup, Borden Basin, ∼1.05 Ga). The mechanisms driving elevated OM concentrations in these and other Proterozoic shales remain poorly understood. In the Mesozoic and Cenozoic, organic matter sulfurization can be a major driver of enhanced OM burial across a range of redox conditions comparable to those inferred for many Proterozoic environments. Therefore, in this study, we evaluate the role of sulfurization in driving OM preservation in the Mesoproterozoic Borden Basin and discuss its relevance to Proterozoic systems in general. We present the first evidence for syngenetic-to-early-diagenetic OM sulfurization in a Proterozoic basin, which begins to fill a several-billion-year gap in our record of organic S across Earth history. We find that OM sulfurization was particularly extensive in shales from a relatively shallow-water section (Alpha River) but less extensive in shales deposited in deeper water (Shale Valley), which is consistent with models that infer sulfidic ‘wedges’ or O2-minimum-zone-type structures on shelf margins at least intermittently at this time. At the shallower site, organic S and pyrite are similarly 34S-depleted and thus likely formed at roughly the same time near the sediment–water interface under conditions previously interpreted to have been ferruginous to intermittently sulfidic. In contrast, at the deeper-water site, large S-isotope differences between pyrite and organic S along with low apparent OM sulfurization intensities indicate that pyrite formation was favored over OM sulfurization during early sedimentation under variable but primarily ferruginous conditions. Although Mesoproterozoic biomass can be substantially sulfurized, indicators of sulfurization intensity are not correlated with OM concentrations, and therefore sulfurization does not appear to have been the primary driver of enhanced OM concentrations in Arctic Bay Formation shales. The link between sulfurization and total OM preservation may have been modulated during the deposition of Arctic Bay Formation shales by differences in iron availability, nutrient cycling, and particle dynamics in the Mesoproterozoic.

Understanding Subsurface Fracture Evolution Dynamics Using Time‐Lapse Full Waveform Inversion of Continuous Active‐Source Seismic Monitoring Data

AbstractPredicting the behavior, geometry, and flow properties of subsurface fractures remains a challenging problem. Seismic models that can characterize fractures usually suffer from low spatiotemporal resolution. Here, we develop a correlative double‐difference time‐lapse full waveform inversion of continuous active source seismic monitoring data for determining high‐spatiotemporal‐resolution time‐lapse Vp models of in‐situ fracture evolution at a shallow contamination site in Wyoming, USA. Assisted by rock physics modeling, we find that (a) rapidly increasing pore pressure initializes and grows the fracture, increasing the porosity slightly (from ∼13.7% to ∼14.6%) in the tight clay formation, thus decreasing Vp (∼50 m/s); (b) the fluid injection continues decreasing Vp, likely through the introduction of gas bubbles in the injectate; and (c) final Vp reductions reach over ∼150 m/s due to a posited ∼4.5% gas saturation. Our results demonstrate that high‐resolution Vp changes are indicative of mechanical and fluid changes within the fracture zone during hydrofracturing.

Microbial Communities of Peaty Permafrost Tundra Soils along the Gradient of Environmental Conditions and Anthropogenic Disturbance in Pechora River Delta in the Eastern European Arctic

Microbial communities play crucial roles in the global carbon cycle, particularly in peatland and tundra ecosystems experiencing climate change. The latest IPCC assessments highlight the anthropogenic changes in the Arctic peatlands and their consequences due to global climate change. These disturbances could trigger permafrost degradation and intensification of the biogeochemical processes resulting in greenhouse gas formation. In this study, we describe the variation in diversity and composition of soil microbial communities from shallow peat tundra sites with different anthropogenic loads and applied restoration interventions in the landscape of remnant fragments of terraces in the Pechora River delta, the Russian Arctic, Nenets Autonomous Okrug. The molecular approaches, including quantitative real-time PCR and high-throughput Illumina sequencing of 16S RNA and ITS, were applied to examine the bacterial and fungal communities in the soil samples. Anthropogenic disturbance leads to a significant decrease in the representation of Acidobacteria and Verrucomicrobia, while the proportion and diversity of Proteobacteria increase. Fungal communities in undisturbed sites may be characterized as monodominant, and anthropogenic impact increases the fungal diversity. Only the verrucomicrobial methanotrophs Methyloacifiphilaceae were found in the undisturbed sites, but proteobacterial methanotrophs Methylobacterium-Methylorubrum, as well as different methylotrophs affiliated with Methylophilaceae, and Beijerinckiaceae (Methylorosula), were detected in disturbed sites.

Antarctic Bioconstructional Bryozoans from Terra Nova Bay (Ross Sea): Morphology, Skeletal Structures and Biomineralization

Among Antarctic bryozoans, some species are able to develop calcitic bioconstructions promoting habitat complexity, but the processes leading to biomineral formation are mostly unknown. The present work investigated three Antarctic bryozoans, from morphological to skeletal features, including the organic matrix associated with the skeleton (SOM). Cellarinella nutti Rogick, 1956 and Reteporella frigida Waters, 1904 were collected in November 2018 from a shallow site (25 m) and Cellarinella njegovanae Rogick, 1956 from a deep site (110 m) at Terra Nova Bay (Ross Sea, Antarctica). Both Cellarinella species showed 5–6 “growth check lines” (gcl) on their laminae. The morphometrical characterization conducted on the growth bands (gb) and zooids, within the band across bands, revealed a variability in length with time (C. nutti: from 4099 µm for gb1 to 1449 µm for gb6; C. njegovanae: from 1974 µm for gb 3 to 7127 µm for gb2). Zooid length varied within gb, from the proximal to the distal part of the bands, but differences also occurred across bands. The shortest zooids (~625 µm) were found at the proximal part and the longest (~ 1190 µm) in the middle part of the gb in C. nutti, whereas in C. njegovanae the shortest zooids (~ 660 µm) were found in the distal part and the longest (~1190 µm) in the proximal part of the gb. Micro-CT analyses indicated the ratio of basal zooidal walls (RbwT gcl/gb) ranged from 3.0 to 4.9 in C. nutti and from 2.3 to 5.9 in C. njegovanae, whereas Reteporella frigida did not form any gcl on either side of the colony. Preliminary characterizations of the SOM for the three species evidenced a mixture of proteins and polysaccharides with properties similar to those of better-known biominerals, in terms of quantity and electrophoretic behavior. In addition, a “lectin fingerprint” has been established for the first time in bryozoans, displaying the presence of chitin or chitin-related saccharides. Understanding the complexity of the processes regulating skeleton formation is a key aspect in comprehending the adaptation of bioconstructional ecosystems and the survival of the associated biodiversity under the future ocean.

Crystal structure and biochemical analysis of acetylesterase (LgEstI) from Lactococcus garvieae.

Esterase, a member of the serine hydrolase family, catalyzes the cleavage and formation of ester bonds with high regio- and stereospecificity, making them attractive biocatalysts for the synthesis of optically pure molecules. In this study, we performed an in-depth biochemical and structural characterization of a novel microbial acetylesterase, LgEstI, from the bacterial fish pathogen Lactococcus garvieae. The dimeric LgEstI displayed substrate preference for the short acyl chain of p-nitrophenyl esters and exhibited increased activity with F207A mutation. Comparative analysis with other esterases indicated that LgEstI has a narrow and shallow active site that may exhibit substrate specificity to short acyl chains. Unlike other esterases, LgEstI contains bulky residues such as Trp89, Phe194, and Trp217, which block the acyl chain channel. Furthermore, immobilized LgEstI retained approximately 90% of its initial activity, indicating its potential in industrial applications. This study expands our understanding of LgEstI and proposes novel ideas for improving its catalytic efficiency and substrate specificity for various applications.

Cruise report CAGE15-3

The cruise had two main objectives: Deployment of the two CAGE ocean floor observatories (OS1 and OS2) at shallow PKF site and deeper PKF site; CAGE ocean floor observatories were designed and build as collaborative work of CAGE scientists with Kongsberg engineers. Observatories have identical set up except that only one of them have side looking multibeam. The set up is: Seabed Platform/seabed lander/mooring frame (x2) – OS1 has black mooring frame, OS2 has grey mooring frame, CTD (x2), Oxygen sensor (x2), CH4 sensor (x2), CO2 sensor (x2), pH sensor (x1), Fluorometer (x2), ADCP (x2), Current profiler (x1), Multibeam echosounder (x1) – grey lander, OS2, Broadband Hydrophone (x2), Flowmeter (x2) For specific description of each lander, please refer to ‘taking over’ documents (WP4 team leader). Landers and sensors arrived to Tromsø with a track from Hamburg, A. Silyakova was a reference person to receive goods and shipping documents. Time period between 24 and 26 of June was the assemblage of observatories and tests of telemetry/communication/camera on a launcher. Pär Jeanson (PhD student WP4) and Reidar Kaasa (substitute engineer instead of Anoop in WP4) from CAGE were assigned to receive training on observatory assemblage/communication. 26 of June – taking over procedure. Sites for the deployment were discussed during preparatory phase. Water depth at the sites could not exceed 500 meters due to restrictions in relation to the recovery rope, which is only 500 meters long. Photographs from the tow cam used during CAGE 15-2 cruise (chief scientist on the cruise G. Panieri) revealed sites with bacterial mats on the ocean floor. Prior each deployment we did echosounder and multibeam survey to know where flares are highly concentrated. Information from the survey was mapped instantly. Target spots for both observatories were chosen based on all this combined information. Oceanographic survey in the area of shallow PKF methane flares; From the “Testing seep fertilization hypothesis” proposal:‘ During cruise CAGE 14-1 the USGS-GAS system detected elevated methane fluxes near the coast and over the shelf seep site in ca. 90m water depth. Methane fluxes above the 240 and 400m site are much less, although slightly elevated with respect to the open ocean (e.g. Vestnesa). Unexpectedly, high methane concentrations (up to 20nM) are often accompanied by low CO2 concentrations. Initial estimates of the total CO2 budget show that under those conditions seep areas are CO2 sinks. What are the biological, geochemical and hydrographic conditions that made these seeps a CO2 sink? Are the observations from CAGE 14-1 repeatable? And ultimately, what are the processes causing the strong CO2 consumption.’It was decided to test seep fertilization hypothesis during CAGE 15-3 cruise by conducting comprehensive water sampling for biogeochemical environment in the entire water column above the area of methane flares. At the same time, USGS-GAS system was onboard allowing to simultaneously measuring surface water/lower atmosphere gas concentrations. This potentially allows calculating vertical gas flux from one realm to another. Depending on available time, collaborators equipment and human resources, water from 64 CTD stations was samples for following parameters: CH4 concentration; discrete sampling to introduce into CDRS system – 13C CH4, CO2; pH; DIC and 13C DIC; DOC; MOx; FISH; DNA; DMSP; CDOM; Nutrients (nitrate, silicate, phosphate). The cruise may be known as: CAGE15_3

CAGE14-1 Cruise Report: CAGE research school in Arctic Marine Geology and Geophysics

Cruise CAGE 14-1 is one of several cruises in 2014 that will be carried out to collect cross-disciplinary data for addressing the objectives of the Norwegian Centre for Arctic Gas Hydrate, Environment and Climate, CAGE. The Norwegian Research Council funds CAGE for a period of 10 years to addressee main scientific questions about gas hydrate environments in Arctic regions. Cruise CAGE 14-1 was also hosting this year’s AMGG research school cruise with 14 PhD students participating, most of them from CAGE. The cruise focused on acquisition of seismic, oceanographic, atmospheric, geochemical and sediment and benthic fauna sampling data from three target areas: the shallow shelf and shelf edge methane seepage sites at Prins Karls Forelanda sediment drift on the western flank of the Knipovich Ridgethe Vestnesa Ridge Research objectives were planned long the goals of CAGE and its individual work packages, and the teaching would be organized along these goals. Scientific problems that are to be addressed in these two key target areas include the periodicity of seepage (i.e. time scales of active, inactive and reactivated systems), quantification of methane concentrations in surface sediments, water column and above the sea surface, gas and hydrates, the nature of gas sources, and the benthic communities occurring at the seep sites. Specific objectives of cruise CAGE 14-1 were as follows: Hydro-acoustic mapping of methane bubble plumes above shallow and deep-water vent fields.Seismic surveying and multibeam mapping across the contours of the Svyatogor Rise.Sediment sampling using gravity, box and multi-corer for sediment and pore-water geochemical analysesSampling of benthic fauna at several seep sites and reference stations in all three target areas.Acquisition of oceanographic data for measuring oceanographic conditions and methane concentrations in the water column, particularly at the shallow shelf sites. The cruise may be known as: CAGE14_1

Shallow Landslide Site Characterization using Electrical Resistivity Technique (ERT) at Balukhali Rohingya Refugee Camps of Ukhiya, Cox's Bazar, Bangladesh

As the geotechnical investigation is a challenging task due to natural heterogeneity and the limited data so the cheap surface geoelectric resistivity method is widely applied to know the complex subsurface information. To produce the electrical images for a site located at Balukhali Rohingya Refugee Camps area in Ukhiya-Teknaf, Cox’s Bazar, Bangladesh, a field data acquisition technique along with RES2DINV software has been performed. Two Wenner soundings on the 25 m and 50 m image lines at every 1 m and 2 m electrode spacing respectively reveal the shallow subsurface lithological variations. On the other hand, 34 samples were collected from two boreholes at different depths and tested under field and laboratory conditions to measure some basic geotechnical properties such as moisture content, grain size distribution, liquid limit, plastic limit, plasticity index, and specific gravity. These geotechnical parameters were compared with the constructed electrical images and confirmed the significance of the electrical resistivity values. Therefore, the geoelectrical resistivity method can be applied as an additional tool to support and enhance conventional geotechnical interpretation purposes as well as shallow landslide site characterization in Bangladesh.

Macroalgal cover on coral reefs: Spatial and environmental predictors, and decadal trends in the Great Barrier Reef.

Macroalgae are an important component of coral reef ecosystems. We identified spatial patterns, environmental drivers and long-term trends of total cover of upright fleshy and calcareous coral reef inhabiting macroalgae in the Great Barrier Reef. The spatial study comprised of one-off surveys of 1257 sites (latitude 11-24°S, coastal to offshore, 0-18 m depth), while the temporal trends analysis was based on 26 years of long-term monitoring data from 93 reefs. Environmental predictors were obtained from in situ data and from the coupled hydrodynamic-biochemical model eReefs. Macroalgae dominated the benthos (≥50% cover) on at least one site of 40.4% of surveyed inshore reefs. Spatially, macroalgal cover increased steeply towards the coast, with latitude away from the equator, and towards shallow (≤3 m) depth. Environmental conditions associated with macroalgal dominance were: high tidal range, wave exposure and irradiance, and low aragonite saturation state, Secchi depth, total alkalinity and temperature. Evidence of space competition between macroalgal cover and hard coral cover was restricted to shallow inshore sites. Temporally, macroalgal cover on inshore and mid-shelf reefs showed some fluctuations, but unlike hard corals they showed no systematic trends. Our extensive empirical data may serve to parameterize ecosystem models, and to refine reef condition indices based on macroalgal data for Pacific coral reefs.

Microfaunal Recording of Recent Environmental Changes in the Herschel Basin, Western Arctic Ocean

ABSTRACTMicrofaunal assemblages of benthic foraminifera, ostracods, and tintinnids from two marine sediment cores retrieved from the Herschel Basin of the Canadian Beaufort Sea shelf document relationships with environmental parameters such as salinity, sea-ice cover, and turbulence. Cores YC18-HB-GC01 and PG2303-1 were collected at 18 and 32 m water depth, respectively. At these sites, sediment accumulation rates range between 0.6 and 1.7 cm yr–1 allowing a near-annual temporal resolution over the last 50 years. Multivariate analyses indicate that benthic foraminiferal assemblages respond primarily to food supply. Dissimilarities between the microfaunal assemblages of the two cores are mainly the result of bottom water salinity levels linked to water depth. High abundance of the benthic foraminiferal species Elphidium clavatum and occurrences of Elphidium bartletti point to varying, but relatively low, salinities at the shallow core site YC18-HB-GC01, which may be affected by variations in the summer halocline depth. Higher species diversity and more abundant Cassidulina reniforme and Stainforthia feylingi characterize the deeper core PG2303-1, which might reflect more stable conditions and higher bottom-water salinities throughout the studied time interval. The most important microfaunal shift of the last 50 years, observed in the shallower longer core YC18-HB-GC01, occurred at the turn of the 21st century. Prior to ∼2000 CE, the presence of Islandiella norcrossi indicates more stable and saline conditions. Since ∼2000 CE, increased abundances of Haynesina nivea and of the ciliate Tintinnopsis fimbriata suggest decreased salinity and increased turbidity. An increased abundance of Eoeponidella pulchella after ∼2000 CE suggests a concurrent increase in productivity in the last two decades. This shift is nearly synchronous with a decrease in mean summer sea-ice concentration, which can play an important role in bottom water stability on the shelf. Easterly winds can induce a reduction in the sea-ice cover, but also foster a westward spreading of the Mackenzie River plume and the upwelling of nutrient-rich Pacific waters onto the shelf. Both factors would explain the increased freshening and productivity of the Herschel Basin. The last two decades were also marked by a decrease in ostracod abundance that may relate to higher water turbidity. This study shows that combining information from benthic foraminifera, ostracods, and tintinnids provides a comprehensive insight into recent hydrographic/climatic changes in nearshore Arctic habitats, where productivity is critical for the food security of local communities.

Investigating beaked whale’s regional habitat division and local density trends near the Deepwater Horizon oil spill site through acoustics

Pre-spill and post-spill passive acoustic data collected by multiple fixed acoustic sensors monitoring about 2400 km2area to the west of the Deepwater Horizon oil spill in the northern Gulf of Mexico (GoM) were analyzed to understand long term local density trends and habitat use by different species of beaked whales. The data were collected in the Mississippi Valley/Canyon area between 2007 and 2017. A multistage algorithm based on unsupervised machine learning was developed to detect and classify different species of beaked whales and to derive species- and site-specific densities in different years before and after the oil spill. The results suggest that beaked whales continued to occupy and feed in these areas following the Deepwater Horizon oil spill thus raising concerns about (1) potential long-term effects of the spill on these species and (2) the habitat conditions after the spill. The average estimated local density of Cuvier’s beaked whales at the closest site, about 16 km away from the spill location showed statistically significant increase from July 2007 to September 2010, and then from September 2010 to 2015. This is the first acoustic study showing that Gervais’ beaked whales are predominantly present at the shallow site and that Cuvier’s species dominate at two deeper sites, supporting the habitat division (ecological niche) hypothesis. The findings call for continuing high-spatial-resolution long-term observations to fully characterize baseline beaked whale population and habitat use, to understand the causes of regional migrations, and to monitor the long-term impact of the spill.

Fortnightly variability of Chl a in the Indonesian seas

Abstract. Twenty years of daily MODIS-Aqua ocean color observations (2002–2022) are used to identify periodic variability of near-surface chlorophyll (Chl a) in the Indonesian seas. The frequency spectrum of Chl a is dominated by the mean and low-frequency monsoonal variability; however, a prominent peak around the fortnightly tidal period, MSf, is present. Harmonic analysis is used to quantify and map the fortnightly Chl a signal, which is discovered to be significant along the continental shelves of NW Australia and at several sites associated with narrow passages between the Lesser Sunda Islands, within the Sulu Archipelago, and at a few other sites in the Philippines Archipelago. Fortnightly variability at the shallow coastal sites is attributed to the spring–neap cycle of barotropic ocean currents, while we hypothesize that the variability in deeper water near the island passages is due to the modulation of vertical nutrient fluxes by baroclinic tidal mixing. The results document the significance of tidal mixing and highlight the heterogeneous character of biophysical processes within the Indonesian seas.

Site amplification prediction model of shallow bedrock sites based on machine learning models

Prediction of the site amplification is of primary importance for a site-specific seismic hazard assessment. A large suite of both empirical and simulation-based site amplification models has been proposed. Because they are conditioned on a few simplified site proxies including time-averaged shear wave velocity up to a depth of 30 m (VS30) and site period (TG), they only provide approximate estimates of the site amplification. In this study, site amplification prediction models are developed using two machine learning algorithms, which are random forest (RF) and deep neural network (DNN). A comprehensive database of site response analysis outputs obtained from simulations performed on shallow bedrock profiles is used. Instead of simplified site proxies and ground motion intensity measures, matrix data which include the response spectrum of the input ground motion and shear wave velocity profile. Both machine learning based models provide exceptional prediction accuracies of both the linear and nonlinear amplifications compared with the regression-based model, producing accurate predictions of both binned mean and standard deviation of the site amplification. Among two machine learning techniques, DNN-based model is revealed to produce better predictions.

Imaging near-surface S-wave velocity and attenuation models by full-waveform inversion with distributed acoustic sensing-recorded surface waves

Distributed acoustic sensing (DAS) technology is, increasingly, the seismic acquisition mode of choice for its high spatial sampling rate, low cost, and nonintrusive deployability. It is being widely evaluated as an enabler of seismic monitoring for [Formula: see text] sequestration in building subsurface time-lapse images and in characterizing near-surface environments. To advance this evaluation, field seismic surveys with optical fibers have been conducted at the Containment and Monitoring Institute’s Field Research Station (CaMI.FRS) in Newell County, Alberta, Canada. In comparison to the standard geophones, optical fibers deployed in surface trenches at CaMI.FRS have recorded high-quality surface waves, rich in low frequencies and exhibiting limited spatial aliasing. These benefits have motivated us to apply the full-waveform inversion (FWI) approach to image the S-wave velocity ([Formula: see text]) and attenuation (quality factor [Formula: see text]) models at shallow site using the surface waves recorded by optical fibers. Compared to the conventional surface-wave dispersion approach, FWI can intrinsically incorporate fundamental and high-order modes and produce [Formula: see text] model with high spatial resolution that resolves horizontal variations. The low-frequency components below 10 Hz measured in the DAS recordings are helpful to overcome the cycle-skipping problem of FWI. Following the adjoint-state method, [Formula: see text] sensitivity kernel can be calculated efficiently with memory strain variables. The [Formula: see text] model is iteratively estimated with a new misfit function measuring root-mean-square amplitude differences, which helps to reduce the trade-off artifacts. The synthetic data obtained from the inverted models are consistent with the observed data in amplitude and phase. The inversion results provide valuable information to characterize the near-surface environments at CaMI.FRS and are expected to support seismic imaging in deeper [Formula: see text] injection zones.

Discovery of Potential RAGE inhibitors using Receptor-Based Pharmacophore Modeling, High Throughput Virtual Screening and Docking Studies.

Receptor for Advanced Glycation End products (RAGE) is a transmembrane receptor that can bind to various endogenous and exogenous ligands and initiate the inflammatory downstream signaling pathways. So far RAGE has been involved in various disorders including cardiovascular and neurodegenerative diseases, cancer, and diabetes. Blocking the interactions between RAGE and its ligands is a therapeutic approach to treat these conditions. In this context, we effectively utilized the receptor-based-pharmacophore modeling to discover structurally diverse molecular compounds having potential to effectively bind with RAGE. Two pharmacophore models were developed on V-domain of RAGE using Phase application of Schrodinger suite. The developed pharmacophoric features were used for screening of 1.8 million drug-like molecules downloaded from ChEMBL database. The molecules were scrutinized according to their molecular weight as well as clogP values. Phase screening was performed to find out the molecules that matched the developed pharmacophoric features that were further selected to analyze their binding modes using high-throughput virtual screening, extra precision docking studies and MM-GBSA ΔG binding calculations. These analyses provided ten hit RAGE inhibitory molecules that can bind to two different shallow binding sites on the V-domain of RAGE. Among the obtained compounds two compounds ChEMBL501494 and ChEMBL4081874 were found with best binding free energies that proved their receptor-ligand complex stability within their respective binding cavity on RAGE. Therefore, these molecules could be utilized for further designing and optimizing the future class of potential RAGE inhibitors.

Multistage Triaxial Behavior of Shallow Landslide Hazard Site Soil of Rangamati Sadar Area, Bangladesh

Multistage Triaxial Behavior of Shallow Landslide Hazard Site Soil of Rangamati Sadar Area, Bangladesh

Performance of blue mussel culture in nearshore and offshore environments

Bivalve aquaculture in nearshore sites has expanded worldwide. Mussel farming productivity is commonly assumed to depend on survival and growth performance, which can be highly variable among spat stocks originating from different sites, even at a microgeographical scale. Using a traditional two-year production cycle, we monitored the productivity of neighbouring blue mussel (Mytilus edulis) spat stocks that had been cultivated in such contrasted environments that are shallow lagoons and open sea sites. We demonstrated that mussels collected in the nearshore, Bassin du Havre-Aubert (BHA) lagoon, exhibited the best survival rate (≥ 90%) in both nearshore and offshore sites, while other stocks experienced mortality as high as 60% under the same conditions. At spat recovery, the BHA spat stock showed higher gene expression levels for catalase and heat shock protein 70 (HSP70), which are involved in antioxidant defenses and the cellular stress response, respectively. Offshore conditions clearly enhanced overall growth performance independently of stock origin, as shown by the higher condition indexes, higher energy lipids (triacylglycerol), and generally higher glycogen content in mussels at the end of the production cycle. These observations of improved performance at the more favourable open-water conditions, particularly during summer, confirmed the importance of site-related environmental factors for productivity. The observed survival (+ 23%) and growth (+ 27%) trends support the hypothesis that offshore cultivation represents a valuable strategy for mussel aquaculture development. Considering current social, environmental, economic, and resource constraints, offshore mussel cultivation may be a viable alternative strategy for aquaculture development.

Shallow- and deep-ocean Fe cycling and redox evolution across the Pliensbachian–Toarcian boundary and Toarcian Oceanic Anoxic Event in Panthalassa

The late Pliensbachian to early Toarcian was characterized by major climatic and environmental changes, encompassing the early Toarcian Oceanic Anoxic Event (T-OAE, or Jenkyns Event, ∼183 Ma) and the preceding Pliensbachian–Toarcian boundary event (Pl/To). Information on seawater redox conditions through this time interval has thus far come mainly from European sections deposited in hydrographically restricted basins, and hence our understanding of the redox evolution of the open ocean (and in particular Panthalassa – the largest ocean to have existed) is limited. Here, we present high-resolution Fe-speciation and redox-sensitive trace metal data from two Panthalassic Ocean sections across the Pl/To and the T-OAE intervals, one deposited in deep water (paleo-water depth >∼2.7 km) and the other on a shallow margin (paleo-water depth likely <∼50 m). Data from the deep-water open-ocean site indicate anoxic-ferruginous conditions from the late Pliensbachian to the onset of the T-OAE, with a rather fluctuating redox state alternating between oxic and anoxic/euxinic conditions across the Pl/To boundary. At least intermittent bottom-water euxinia characterized the T-OAE, followed by a subsequent transition toward more oxygenated conditions. By contrast, trace metal data from the shallow margin site indicate that oxygenated to possibly suboxic conditions prevailed. However, elevated highly reactive iron contents, dominated by Fe (oxyhydr)oxides, characterize this shallow-water site. These observations suggest that upwelling, driven in part by increased sea level and prevailing winds from the open ocean, brought anoxic-ferruginous waters onto the shelf, whereupon Fe2+ oxidation was initiated in oxic shallow waters.

Diporeia site preference in Lake Superior: Food or physical factors?

Vital to the Lake Superior food web, the amphipod Diporeia remains the dominant macroinvertebrate in Lake Superior despite drastic population declines throughout the rest of the Laurentian Great Lakes. Diporeia is most abundant in the slope region of the lake at water depths between 30 and 125 m. It has been hypothesized that this depth range is preferred because of elevated primary production and deposition within this zone. This hypothesis of food driving habitat preference has not been directly tested. Here we used 120-hour preference-avoidance trials to record Diporeia choice of sediments from different water depths, seasons, and other treatments. Most preferences were weak to absent; however, Diporeia strongly preferred sediment from 30- and 60-m water depths over deeper or shallower sites. Contrary to the hypothesis about food driving habitat choice, chemical characteristics did not explain this strong preference. Grain size variation was the only measured variable that was consistent between the sites preferred by Diporeia and different from unpreferred sites. Both the 30- and 60-meter sites contained predominantly medium silt but had a wider range in grain sizes. These results indicate that physical habitat characteristics may have a stronger bearing on Diporeia habitat preference than food availability and may account for their distribution in the lake. The results also may imply that the role of dreissenid mussels as ecosystem engineers altering sediment physical characteristics may be important where they are abundant.

Modelling site response at regional scale for the 2020 European Seismic Risk Model (ESRM20)

Quantitative estimation of seismic risk over a region requires both an underlying probabilistic seismic hazard model and a means to characterise shallow site response over a large scale. The 2020 European Seismic Risk Model (ESRM20) builds on the 2020 European Seismic Hazard Model (ESHM20), requiring additional information to firstly parameterise the local site condition across all of Europe, and subsequently determine its influence on the prediction of seismic ground motion. Initially, a harmonised digital geological database for Europe is compiled, alongside a model of topographic/bathymetric elevation and a database of 30 m averaged shearwave velocity measurements (V_{S30}), in order to produce separate 30 arc-second maps of inferred V_{S30} based on topography and on geology. We then capitalise on a large database of seismic recording stations in Europe for which site-to-site ground motion residuals (delta S2S_{S}) have been determined with respect to the shallow crustal ground motion model used in the ESHM20. These residuals allow us to incorporate site amplification functions into the European GMM calibrated upon either observed or inferred V_{S30}, or on the European geology and topography models. We present the resulting pan-European seismic site amplification model and assess its impact on seismic hazard and risk compared against other approaches. The new site amplification model fulfils the requirements of the ESRM20 and, providing uncertainty is fully propagated, yields estimates of seismic hazard and risk at a large space scale that may be comparable to other methods often applied at local/urban scale where better-constrained site information is available.