Southern Shelf Research Articles

The Rare Trilobites Exallaspis (Odontopleuridae) and Kosovoproetus? (Tropidocoryphidae) in the Homerian (Silurian) Of The Prague Basin, Bohemian Massif

Abstract The deep-water Aulacopleura koninckii Assemblage in the lower Homerian (T. testis Sub-Biozone) “Aulacopleura shales“ strata at the classical ‘Barrande’s pits’ locality on the Černidla hillside at Loděnice in the Prague Basin is supplemented by the addition of two new trilobite taxa, viz. Exallaspis? perunicana sp. n. and Kosovoproetus? aff. praecursor (Přibyl & Vaněk 1987). The palaeogeographic distribution of Exallapis Ramsköld & Chatterton, 1991 is extended by the occurrence of Exallaspis? perunicana sp. n. and the younger Exallaspis sp. in the upper Homerian (the P. parvus – G. nassa Biozone) of the Prague Basin, reflecting the faunal migration between the southern shelf of the Baltica palaeocontinent and the Perunica microcontinent accross the Rheic Ocean. The small dimensions of the K.? aff. praecursor exoskeletons compared to those of K.? praecursor in the bordering shallow-water Liolalax–Sphaerexochus– Cheirurus Assemblage represent another example of adaptive nanism in trilobites of the Aulacopleura-Raphiophorus Biofacies.

Influence of ocean dynamics on the route of argonauts in the Southeastern Brazil Bight

Argonauts (Cephalopoda: Argonautidae), also known as ‘paper nautilus’, are epipelagic octopuses that are believed inhabit the open ocean despite being rarely encountered alive. Previous studies on the early-life stages of cephalopods have reported unexpectedly high abundances of argonauts in continental shelf areas of the Southeastern Brazilian Bight (SBB). Based on this finding, we explored the potential ocean dynamics driving both seasonal and interannual argonaut paralarvae occurrence in the SBB shelf. A historical archive ofplankton samples (n = 884) collected during 22 survey cruises between 1974 and 2010 covering the northern portion of the SBB was used. Spatiotemporal analysis combining environmental variables and horizontal and vertical abundance maps indicated that high frequency of argonaut paralarvae mostly occurred during summer with a high interannual variability. Horizontal and vertical maps revealed that they were mainly transported from the open ocean into the shelf by the onshore intrusion of water masses promoted by meanders and eddies of the offshore Brazil Current. Furthermore, argonaut occurrence in the southern shelf areas was remarkably influenced by the coastal jet originating from upwelling in the northern SBB. These results suggest that argonauts may be used as indicators of mesoscale processes. The present study provides a novel hypothesis for the route of argonauts from the pelagic realm to the continental shelf.

Negative δ13Ccarb values at the Jurassic-Cretaceous boundary – Vaca Muerta Formation, Neuquén Basin, Argentina

The stable carbon isotopic compositions of carbonate sediments (δ13Ccarb) have been widely used to reconstruct the global carbon cycle and as a stratigraphic correlation tool. This work investigates a δ13Ccarb record of marine organic-rich, mixed siliciclastic‐carbonate mudstones accumulated from the Tithonian (late Jurassic) to the early Valanginian (early Cretaceous) in a retro-arc basin connected to the Proto-Pacific Ocean (Neuquén Basin, Argentina). The high-resolution record of δ13Ccarb values of these strata from outcrops at various locations in the basin differ from those in the coeval pelagic strata of the Tethys. The δ13Ccarb profile in the Puerta Curaco area shows an overall increasing trend from average values of −7‰ (early Tithonian) to approximately 0‰ (early Valanginian). The negative δ13Ccarb values occur in a ~ 400 m thick TOC-rich succession (TOC > 2%) and are arranged in 3 large-scale increasing-decreasing cycles. Although absolute values are offset, main trends are similar in other outcrops and in subsurface wells. The co-occurrence of the highest U/Th (>1.4) and the most negative δ13Ccarb values suggests that the major trends in the δ13Ccarb profile might be modulated by oscillations in oxygen content within the basin probably driven by sea-level changes. Clastic-dominated transgressive hemicycles have higher TOC and more negative δ13Ccarb values while the opposite occurs in carbonate-rich regressive hemicycles. A trend from “normal” Tithonian surface-water values (avg. +2‰) in the southern shelf to increasingly negative δ13Ccarb values towards the basin center indicates a mixing between platform-derived carbonate material unaffected by diagenesis and carbonate precipitated or altered in a dysoxic/anoxic basin. The δ13Ccarb profile in the Tethyan realm does not record this episode of high burial of organic carbon occurred in the Neuquén basin during the Tithonian and Berriasian but display a slightly decreasing trend between +2.5 and +1.5‰.

Gasgeochemical features in the western part of the East Vietnam Sea (Bien Dong Sea)

During the joint Russian-Vietnamese studies in the East Vietnam Sea (known as Bien Dong or the South China Sea), manifestations of new hydrocarbon-accumulating zones were discovered; evidences of the presence of mineral indicators for solid minerals in shelf deposits were obtained; a unique zone, where accumulations of ferromanganese crusts and nodules have been formed, was revealed for the first time; evidence of unique properties of deep-water fine-dispersed carbonate sediments (which makes it possible to attribute them to an independent type of mineral resources of the East Vietnam Sea) were obtained; the ikaite mineral (that serves as an indicator of methane migration zones and cold marine paleo-conditions) was discovered in the Phu Khanh basin; heavy concentrates with indicators of rare forms of ore mineralization were collected; features of methane and mercury fluxes into the atmosphere, cultures of methane-oxidizing, oil-oxidizing and sulfate-reducing bacteria were registered for the first time within the study areas. New data on gravity and magnetic field anomalies along the shelf and slope of Vietnam have been obtained. The article presents the results of coastal geophysical and gasgeochemical research obtained in 2010–2020 within the Joint Russian-Vietnamese Laboratory for Marine Geosciences (POI FEB RAS - IMGG VAST). For the first time, anomalous methane fields (comparable to anomalies on the oil- and gas-bearing shelf and the gas hydrate-bearing slope of Sakhalin Island) were registered in the water column. The gravimagnetic survey was carried out on the central and southern shelf and the continental slope of Vietnam; the executed works supplemented the geophysical data, which had been obtained in the 80s–90s of the preceding century. The paper contributes to the Russia-Vietnamese program within the UN Decade of Ocean Sciences for Sustainable Development framework.

Post-500 ka and Holocene activity on distributed faults of the North Anatolian Fault system along the southern shelf of Marmara Sea, Turkey

Geodetic monitoring and patterns of seismicity indicate that the Northern Branch of the North Anatolian Fault (NAF) absorbs the majority of the relative motion between the Eurasia and Anatolia plates along the northern Marmara Sea. Nonetheless, historical seismicity documents that the Central Branch of NAF is also hazardous, with earthquakes diffusely occurring in the southern Marmara Sea. In order to better assess the seismic hazards facing large cities along the southern coast, we recently collected geophysical data across the adjacent shelf. These data include closely spaced high-resolution multichannel seismic profiles, sparker seismic profiles, CHIRP sub-bottom profiles, and multibeam bathymetric data. The stratigraphic and structural analyses of this new dataset and prior datasets highlight the geometry of three long faults and many shorter, discontinuous faults. The three longer faults are interpreted as primarily strike-slip fault zones. All the mapped faults are Late Quaternary active and, in fact, many fault segments are Holocene active. Smaller discontinuous faults are present in Gemlik and Erdek bays, some of them clearly active during Holocene time. This pattern of Late Quaternary active faults can account for the well-documented dispersed seismicity on the southern shelf. Based on the lengths of the various fault segments, we estimate that earthquakes with moment magnitude as high as 7.4 may occur along the southern shelf of the Marmara Sea. Therefore, the system of distributed faults that constitutes the Central Branch of the NAF in that area represents a significant seismic hazard for the southern coastal cities.

In the shadow of a giant reef: Palaeoecology of mesophotic coral communities from the Givetian of Anti-Atlas (Morocco)

One of the keys to the success of modern and ancient reef ecosystems is the phenomenon of photosymbiosis. Photosymbiotic corals can thrive down to the limits of the photic zone, and the coral communities living in the lower part of the photic zone are known as mesophotic coral reef ecosystems (MCE). Recent studies have shown that MCEs were already present in the middle Palaeozoic. The reefs of that time reached the peak of their distribution during the Givetian, when they were present even as far as 50°S. One of the southernmost Givetian reefs is the Aferdou el Mrakib reef, exposed in the eastern Anti-Atlas (Morocco). At the base of this reef, numerous small carbonate bioherms are exposed. These structures formed low-relief banks that developed probably at moderate water depths of several tens of meters. In the present contribution, we analyse the paleoecology of these peculiar communities. The assemblage is dominated by platy and encrusting coenitid (Roseoporella) and alveolitid (Alveolites) tabulate corals, as well as abundant platy stromatoporoids and solitary cystyphillid rugose corals. The platy morphology of corals is widely considered as an adaptation related to photosymbiosis, and is especially common in MCEs. In combination with palaeobathymetric and sedimentological data, this characteristic suggests that the studied banks developed at the bottom of the euphotic zone. The MCEs of the Aferdou el Mrakib reef share major taxonomic and ecological similarities with the previously described MCEs from the southern shelf of Laurussia and a reef community from southern China, emphasizing a high degree of cosmopolitanism of the Middle Devonian mesophotic ecosystems. Communities studied here are also the most poleward MCEs described to date.

Longitudinal Study of DNA Methylation and Epigenetic Clocks Prior to and Following Test-Confirmed COVID-19 and mRNA Vaccination.

The host epigenetic landscape rapidly changes during SARS-CoV-2 infection, and evidence suggest that severe COVID-19 is associated with durable scars to the epigenome. Specifically, aberrant DNA methylation changes in immune cells and alterations to epigenetic clocks in blood relate to severe COVID-19. However, a longitudinal assessment of DNA methylation states and epigenetic clocks in blood from healthy individuals prior to and following test-confirmed non-hospitalized COVID-19 has not been performed. Moreover, the impact of mRNA COVID-19 vaccines upon the host epigenome remains understudied. Here, we first examined DNA methylation states in the blood of 21 participants prior to and following test-confirmed COVID-19 diagnosis at a median time frame of 8.35 weeks; 756 CpGs were identified as differentially methylated following COVID-19 diagnosis in blood at an FDR adjusted p-value < 0.05. These CpGs were enriched in the gene body, and the northern and southern shelf regions of genes involved in metabolic pathways. Integrative analysis revealed overlap among genes identified in transcriptional SARS-CoV-2 infection datasets. Principal component-based epigenetic clock estimates of PhenoAge and GrimAge significantly increased in people over 50 following infection by an average of 2.1 and 0.84 years. In contrast, PCPhenoAge significantly decreased in people fewer than 50 following infection by an average of 2.06 years. This observed divergence in epigenetic clocks following COVID-19 was related to age and immune cell-type compositional changes in CD4+ T cells, B cells, granulocytes, plasmablasts, exhausted T cells, and naïve T cells. Complementary longitudinal epigenetic clock analyses of 36 participants prior to and following Pfizer and Moderna mRNA-based COVID-19 vaccination revealed that vaccination significantly reduced principal component-based Horvath epigenetic clock estimates in people over 50 by an average of 3.91 years for those who received Moderna. This reduction in epigenetic clock estimates was significantly related to chronological age and immune cell-type compositional changes in B cells and plasmablasts pre- and post-vaccination. These findings suggest the potential utility of epigenetic clocks as a biomarker of COVID-19 vaccine responses. Future research will need to unravel the significance and durability of short-term changes in epigenetic age related to COVID-19 exposure and mRNA vaccination.

Kuroshio Intrusion and Its Impact on Swordtip Squid (Uroteuthis edulis) Abundance in the Southern East China Sea

Swordtip squid (Uroteuthis edulis) is a primary target species of the commercial fishery in the southern East China Sea (ECS), and they normally migrate to a quasi-permanent upwelling zone (called a cold dome) off northeastern Taiwan for spawning and growth during spring (March–May) and fall (October–December) in a year. We examined the connection of the variability in its standardized annual catch per unit effort (CPUE) during 2009–2017 in regard to the physical processes on the southern shelf of the ECS using temperature and wind observations from an isle north of Taiwan (Peng-jia-yu) as well as satellite sea surface temperature and absolute geostrophic velocity. The annual CPUE is positively correlated with the daily temperature anomaly at Peng-jia-yu in the cold dome in October of the previous year and April of the year. A warmer environment favors the recruitment and consequently the catch of the swordtip squid. During the spawning periods of the 9 years, the warm water carried by the Kuroshio frequently intruded atop the cold dome, which benefited the growth of the larvae and consequently helped maintain a certain value of the standardized annual CPUE. The anomalously low CPUE in 2012 and 2016 is attributed to the blocking of the Kuroshio intrusion due to cold and less salty China Coastal Water atop the cold dome in the spring spawning of 2012 and 2016. Based on the velocity strength in the cold dome and in a specified shelf region together with the daily temperature anomaly at Peng-jia-yu, an occupation intensity factor is used to evaluate the dominance of warm Kuroshio water and cold shelf water in the cold dome, which could help predict annual catches.

Paleo Isobaths in 3D Seismic Exploration Data Uncover Submerged Shorelines From Glacial Lowstands: A Case Study From the Levant Basin

Modern petroleum exploration extracts 3D volumes of seismic data where certain curves can be drawn delimiting stratigraphic horizons. Such curves hold a promise as piercings for identifying tectonic offsets in 3D. Pinchout points on vertical sections connect with adjacent sections to form contours in 3D. Such a contour, showing quasi-uniform depth, may be considered a paleo-isobath. Here we focus on pinchout paleo-isobaths in the western shores of the Levant that might record ∼120 m drop in sea level at the peak of late Quaternary glacials. We identified a pinchout isobath, ∼15 km offshore, ∼140 m below sea level. Water depth averages ∼90 m, and sediment cover averages ∼45 m. Allowing for isostatic adjustment, this is compatible with eustatic levels of the last two glacial maxima. We hypothesize that the contour mapped is closely related to the shoreline of one of the last glacial maxima. The pinchout pattern is continuous for ∼25 km in the southern reaches of the survey area, at depths of 137 ± 2.5 m, an isobath within the observational uncertainty. The isobath is lost for ∼10 km in the central portion of the survey, north of which a slightly deeper isobath reappears for 7 km, until it disappears approaching a bathymetric trough. The deeper pinchout isobath reappears in the northernmost section of the survey, where it deepens by an average of 5–6 m relative to the southern part (from 137 m to 142 m). The deepening of the pinchout contour is consistent with massive sliding underlying the trough. Sliding here has been attributed to sediment load or salt tectonics, and has been recently associated with a local tsunami dating 9.6 ± 0.3 ka. Recent work relocated the deepest earthquakes on the Levant southern shelf (depths circa 30 km) to the trough, with epicenters coinciding with the boundary faults. This may indicate an active deep-seated tectonic feature. Expressions of the contour outside the survey area will offer tests to our paleo-shoreline hypothesis. Additional pinchout isobaths and pinchout contours associated with earlier lowstands will help constrain tectonic rates as well as glacial eustatic levels and hydro-isostatic effects, with potential regional and global applications.

Significance of nutrients in oxygen-depleted bottom waters via various origins on the mid-outer shelf of the East China Sea during summer

East China Sea (ECS) is considered one of the largest dissolved oxygen (DO) depleted areas in the world's oceans. To assess the relative importance of water sources and biological processes to modulate low DO water over the ECS shelf, we conducted 7 cruises in the summers between 2004 and 2015. To cover a broad study area, observations were taken by both Chinese and Japanese research vessels in 2013, the consistent DO values were obtained in the intercalibration station from China and Japan. The subsurface/bottom water DO depletion was observed over both the inner and mid-outer shelves. In 2009 and 2013, the low DO (3–4.2 mg L−1) area covered ca. 4 × 104 km2 on the mid-outer shelf, comparable with the reported area of summer hypoxia off the Changjiang estuary. On the basis of a seven endmember mixing model using heavy rare earth elements, temperature and salinity data collected in 2013 and 2015, we determined that on the southern shelf the low DO water mainly originated from Kuroshio Subsurface Water (28–72%). Both the DO level in the dominant source water and organic matter (OM) remineralization modulated the formation and expansion of low DO waters. Oxygen-depleted bottom waters featured with high nutrients were both transported from the water's source regions and produced by OM remineralization on the mid-outer shelf. The estimated regenerated nutrient fluxes derived from OM respiration in the bottom water of the mid-outer shelf were equivalent to 18–37% of the nitrate and nitrite, and 2 to 5-fold the phosphorus, delivered from the Changjiang River in summer. The large quantity of regenerated nutrients from oxygen-depleted bottom waters on the mid-outer shelf could be utilized and support primary production in the adjacent oceans. Our findings provide valuable observation for simulation models of nutrient cycles and budgets in the ECS and adjacent oceans.

Coastal trapped waves in the southern Caspian Sea

Previous studies reported coastal trapped waves (CTWs) in the Caspian Sea (CS). This study deals with the generation mechanisms, the temporal and spatial variability of CTWs in this area, and their transformations during propagation from the origin to the destination using recent measurements and high-resolution numerical simulations. CTWs are observed at all stations with periods of 2–6 days after northerly storms. The Absheron Peninsula, old Sefidrud delta, and Nur coasts were identified as the CTWs prone regions. The generation of CTWs in these locations was confirmed using numerical experiments. The propagation away from the generating location of CTWs was analyzed using a representative real wind storm. In the west part of the CS, the generation mechanism of CTWs is mainly similar to the barotropic Kelvin waves; in contrast, it is similar to the continental shelf waves in the southern shelves. The results can be used to study the contribution of generated CTWs to the transport of sediment and biological materials in all large lakes.

Morpho-stratigraphic characterization of the southern shelf of Porto Santo Island (Madeira Archipelago): Insights for small-scale instability processes and post-LGM sedimentary architecture

Shelves surrounding volcanic islands represent only a small portion of the entire submarine edifice that can extend to a few thousand meters below sea level. Despite their small areas, shelves show a significant morphologic imprint made by the erosional, depositional, tectonic and volcanic processes when compared to those left on slopes or the submarine bases of islands. Therefore, shelf morphology can be used to improve our knowledge about the island evolution, especially the more recent events. In this study, we use multibeam bathymetry, side scan sonar and seismic reflection profiles of the southern shelf of Porto Santo Island in Madeira Archipelago to map its seabed morphology and seismic stratigraphy from the nearshore to the shelf edge. Based on morphological and seismo-stratigraphic differences, the study area has been divided in three sectors (Western, Central and Eastern). In general, the shelf consists of an erosive rocky surface mostly covered by sediments, and locally outcropping on the seafloor, especially on the Western and Eastern sectors. On these sectors two sets of submerged erosional terraces have been mapped at different depths (35–45 m, 50–75 m). The depth range of the terraces and their absence in the Central sector suggests that these were formed/modified at least by the Marine Isotope Stages (MIS) 5a-5d stillstands or even by older relative sea-level stillstands. Dykes, which are more resistant to erosion than the surrounding outcrops, have orientations that are similar to the volcanic and structural features present on the island (NNE-SSW and NW-SE). The sedimentary cover on the shelf is highly varied both in thickness and internal architecture, mainly due to different onshore sediment supply and available accommodation space. Two main seismic units have been recognized: the lower one (U1) is interpreted as a transgressive deposit, formed during the sea level rise after the Last Glacial Maximum (LGM); the upper one (U2) is interpreted as a modern highstand deposit. The Western sector is practically sediment-starved, except for a local thin sedimentary cover of U2 on the inner and outer shelf. The Central sector shows U2 as a sigmoidal-oblique progradational clinoform characterized by inner prograding geometry on top of U1. The Eastern sector shows U2 as sigmoidal clinoform extending over a large area and having a more aggradational component. The shelf edge shows an overall arcuate shape that strongly matches the coastline configuration, suggesting the occurrence of an old large-scale landslide event (LS1) prior to the shelf formation. Further incisions in the shelf edge of the Central sector are interpreted as resulting from mass-movements, classified as LS2 and LS3. LS2 is at least older than seismic unit U1 and LS3 formed during the late Holocene. The volume of the LS2 event (0.6 km3) suggests that it might have caused a hazardous tsunami if it failed as a single event. The recent LS3 events, due to their small magnitude were probably not hazardous. These observations provided a more comprehensive understanding of the recent evolution of Porto Santo insular shelf in terms of mass-movement processes and post-LGM sedimentary architecture.

Holocene morpho-stratigraphic evolution of a compound submarine deltaic system in front of the shelf-incising Almanzora and Garrucha Canyons (Palomares margin, southeastern Iberia)

The Holocene morpho-stratigraphic evolution of a compound submarine deltaic system linked with the Antas and Almanzora Rivers on the narrow (< 5 km) shelf along the Palomares margin (southeastern Iberia) has been reconstructed from the integrated analysis of geomorphology, seismo-stratigraphy and sedimentology. The shelf morphology is characterized by a 3–4 km wide deltaic body off the Almanzora River, where seafloor undulations and gullies are present. Larger and more incised gullies, crescent-shaped bedforms and pockmarks are recognizable at or close to the head of shelf-indenting canyons associated with the Almanzora-Garrucha canyon system.The seismo-stratigraphy displays a strong and irregular basal reflector overlain by a sedimentary wedge, showing variable thicknesses (1–25 m) and seismic characteristics along and across the shelf. The main depocenter of this wedge is not located off the Almanzora River mouth (i.e., the main sedimentary input in the study area) but along the southern shelf encompassing the Almanzora and Antas Rivers. Grain-size and sand compositional analyses show that silty sand with high terrigenous content (mostly quartz and mica) is mainly found on the submarine deltaic body. In contrast, sandy silt with variable ratios between terrigenous and biogenic contents is retrieved from the canyon head and associated gullies as well as from the surrounding mid-outer shelf.The evolution of the Antas-Almanzora compound delta has been divided into three evolutionary stages, mainly driven by the interplay between paleo-topography and riverine and marine processes and modulated by sea level changes during the Holocene. The origin of the present-day morphological features is also discussed, again highlighting a complex interaction between sedimentary gravity flows (mainly flash flood-generated hyperpycnal flows), storm-waves and shelf currents, fluid seepage and retrogressive slope failures.

Field classification of fractured reservoirs of crystalline basement

Development of oil and gas deposits in fractured reservoirs entails certain risks due to peculiarities of geological structure. Classification and identification of fractures in reservoirs is of high-priority importance and makes it possible to assess the impact of both fractured systems and matrix blocks on field development parameters. This article presents the results of statistical and qualitative analysis of the influence of fracture systems and fracture heterogeneity to classify reservoirs in crystalline basement granitoids using the example of the White Tiger (Bach Ho) and Dragon (Rong) fields located on the southern shelf of the South China Sea (Viet Nam). Field classification of fractured reservoirs is based on a well-marked difference in parameters between wells within a field, due to fracture heterogeneity. In order to solve the tasks set, construction and analysis of graphs of well performance parameters distribution (productivity, flow rates, accumulated indicators, etc.) as well as Lorenz curves were carried out. According to the results, all the objects under study are characterized by asymmetrical shape of distribution curves, which indicates a significant influence of fracturing. Based on the calculated values of the fracture influence coefficient, it is found that fractured reservoirs in crystalline basement, as a first approximation, belong to type 2. This fact is inconsistent with the earlier works on crystalline basement, in which rocks are classified as reservoirs of type 1. Such contradiction is explained by the fact that the microfracture systems and the blocky low-permeability part exhibit matrix properties, but are not fully matrix. This part of the reservoir is proposed to be called a “pseudo-matrix”. If macrocracks dominate in the section, the basement rocks are identified as type 1 fractured reservoirs, but if microfracture systems (“pseudo-matrix”) dominate in some parts of the void space, they may show the properties of type 2 reservoirs forming a mixed type of fractured reservoirs.

Environmental impacts of physical and dynamical characteristics of the southern coastal waters of the Caspian Sea

ABSTRACTThis research evaluated the variability of current characteristics and seawater properties in the middle part of the southern shelf of the Caspian Sea. The effect of the coastal flow on marine debris dispreading was assessed in the southern Caspian Sea for the first time. The findings showed the existence of thermal stratification containing seasonal thermocline with thickness of about 40 m in the water column. Maximum monthly along-shore current velocities around 1.3 m s−1 were observed in November and December. Monthly variations were clearly found in both flow velocity and local wind components. However, no significant levels of correlation between wind and current speeds were observed during the study in the region. In some cases, the mean monthly cross-shore component velocities were measured at about 29 cm s−1 in November. The findings indicated that there was no upwelling phenomenon associated to the regional wind in the study area. In situ current measurements indicated dominant east and north-northeast directions, presumably related to the effect of general circulation in the southern basin. Current profiles in the water column displayed similarity in directions at 10, 15 and 20 m depths over the continental shelf. The field samples and analysis revealed that the soft and smaller-scale seawater litters can be carried long distances by the current along the coast. Most coastal based and marine litters originated from the tourist activities (in the middle and western parts of the shores) and waste emanated from the river (Tonekabon-Nowshahr).

Zooplankton functional group responses to environmental drivers off the west coast of Vancouver Island, Canada

Zooplankton diversity and biomass are integral to marine ecosystem functioning. Functional trait-based approaches enable an examination of ecosystem dynamics in which species groups are defined by their functional roles (i.e. functional groups) within the ecosystem, rather their taxonomic identity. Changes in the relative and absolute biomass of zooplankton functional groups may affect the productivity of higher trophic levels via change in secondary production rates and the efficiency of energy transfer. Traits from 55 mesozooplankton species were assembled from the literature and applied to a 35-year time series (1980–2016) for the southern shelf area off the west coast of Vancouver Island, Canada. Eight functional groups were identified by clustering species on the basis of functional trait similarity. A time series of biomass anomalies was calculated for each functional group, after which links between functional group biomass anomalies and several environmental variables were examined. Generalized additive modeling (GAM) identified local sea surface temperature as the most important driver of biomass anomaly patterns for three groups: Doliolids, Omnivore-Herbivores, and the Active Ambush Omnivores. The Southern Oscillation Index (SOI) was also a main driver for three groups: Egg-Brooding Carnivores, Broadcast Carnivores, and Cruise Carnivores-A. The Ocean Niño Index (ONI) was significant for Active Ambush Omnivores and Egg-Brooding Carnivores, whereas the Pacific Decadal Oscillation (PDO) was a driver of Broadcast Carnivores and Cruise Carnivores-A. The Doliolids group also varied with surface salinity, and Cruise Carnivores-B with the North Pacific Gyre Oscillation (NPGO). The relative contribution of several zooplankton functional groups to the overall biomass showed no temporal trends but some groups had increased or decreased abundance contributions. This suggests functional redundancy within groups, as smaller or larger species may dominate based on environmental conditions. Our analysis demonstrates that functional group biomass anomalies vary with environmental variables, where conditions may favor certain functional groups, therefore dictating how the ecosystem is functioning.

Ecological response to changes in the structure of water masses in the pelagic of the Canary Current Marine Ecosystem

Based on the results of sea expeditions, interannual changes in structure of the ichthyocenosis in the pelagic zone of the southern shelf of Morocco in the Atlantic Ocean were studied in connection with changes in the habitat. Mass pelagic fish were selected as reference biological species: European and West African horse mackerel, European sardine, Eastern mackerel, sea bream, sea snipe, myctophids, as well as non-commercial fish species. Field data were obtained during the implementation of complex oceanographic surveys in the fall seasons (October-November) 2015–2018. The results of control trawls were used, in which any species amounted to at least 70 % of the catch. The analysis of the species composition of the control trawls, data of hydroacoustic tracking of trawls, thermohaline water characteristics is carried out. Data pairing was carried out by phased extraction and transformation using standard computer programs for processing various types of data (acoustic, hydrological, ichthyological), as well as specially designed programs that allow you to create a single database. It has been established that recent changes in the number of commercial and by-catch species observed in the ARZ of Morocco in recent years are associated with the presence or absence of so-called “settlement windows”, which appear in the T, S‑diagram field by regions of different configurations, which indicates changes in the ratios of water masses. Based on the identified relationships between changes in the ratio of water masses and changes in the species composition of the control trawls of accounting replenishment surveys, estimates of the expected changes in the biomass of mass pelagic fish in the coming years are made.

Seismic amplitude and attribute data from Mesozoic strata in the Skagerrak (Danish-Norwegian North Sea): Indicators for fluid migration and seal bypass systems

The Skagerrak builds the transition from the exposed Palaeozoic basement of South Norway to thick Mesozoic to Cenozoic sediments covering Danish Jutland. It states the southern Norwegian Trench, and comprises from W to E the Mesozoic Farsund Basin, the northernmost sector of the Sorgenfrei-Tornquist Zone and the Palaeozoic Skagerrak Graben. Over the past decades, fluid escape structures at the southern Skagerrak Shelf and in the central Norwegian Trench were investigated and layer-parallel fluid migration from Mesozoic rocks was suggested. However, a fluid source or a corresponding migration system of the fluids has not been proposed yet. In this study, a joint interpretation of seismic imagery and seismic attributes reveals fluid indications and migration systems in the Farsund Basin and the central Skagerrak. We propose that source rocks of the Lower Jurassic Fjerritslev Formation generated thermogenic fluids in the Farsund Basin as well as in the Fjerritslev Trough. For the central Skagerrak, a time-structure map of the base of the F-III member of the Fjerritslev Formation shows that these fluids could migrate upward forced by buoyancy and partially bypassed by faults, and seep out in the Norwegian Trench. Furthermore, we propose that fluid escape structures on the southern shelf were likely caused by seepage of biogenic fluids under bottom current action.

Middle Jurassic (Bajocian) planktonic foraminifera from the northwest Australian margin

Abstract. The aim of this paper is to document three well-preserved morphotypes of Middle Jurassic (Bajocian) planktonic foraminifera from the continental margin of northwestern Australia. This location is on the southern shelf of the Middle Jurassic Tethys Ocean, and these occurrences of planktonic or meroplanktonic species are the first to be reported from the Jurassic of the Southern Hemisphere. The morphotypes include a new subspecies of Globuligerina bathoniana (Pazdrowa): Globuligerina bathoniana australiana n. ssp. Two other taxa are also described: Globuligerina altissapertura n. sp. and Mermaidogerina loopae n. gen. n. sp. The microstructure of the wall is shown in scanning electron microscope images. The change from chamber to chamber in the formation of the surface ornament by secondary lamination, and its subsequent burial within the wall, is demonstrated in detail.

Stokes Drift in Topographic Waves over an Enclosed Basin Shelf

AbstractThe effect of the continental shelf wave on the flow field over the southern shelf of the Caspian Sea (CS) as the largest enclosed basin of the world, is investigated. Considerable currents with subinertial time scales are observed over the continental shelf in the southern CS. For variations in the surface layer with typical periods of 1 day, local episodic wind events appear to be the driving force. For longer time scales, it is suggested that the observed currents are due to passing continental shelf waves. Measurements over the continental shelf and shelf slope, showing periods of 2–6 days, indicate the presence of such waves. Combined with theory and numerical modeling, the amplitude of the continental shelf wave modes at the coast is assessed from current meter observations. It is demonstrated that the mean drift velocity (the Stokes drift) for long continental shelf waves is determined entirely by the shelf geometry. For the actual shelf mode, it is shown that the associated Stokes drift constitute a nonnegligible mean current along the shelf. This current should be taken into account when assessing the transport of biological material and neutral tracers along the southern coast of the CS.