Marine Environmental Conditions Research Articles

Multi-source and multi-scale data integration for the assessment of the marine environmental status of the Basque Coast (SE Bay of Biscay)

In the context of the European Marine Strategy Framework Directive (MSFD, 2008/56/EC), Member States are required to assess the environmental status of marine waters. With the aim to support practitioners in this effort, and guide them in the identification of management solutions, a team of researchers has brought together available information for the Basque coastal zone (SE Bay of Biscay), and assessed the marine environmental status of these waters. To undertake the study, the area was divided into Marine Reporting Units (MRUs), following the MSFD terminology, which had specific areas assigned. The information used for the assessment was obtained from a variety of open sources (i.e., in-situ long-term monitoring data, biological data from annual/triannual surveys, multibeam echosounder data, satellite data, and had been collected at different spatial scales, from the coastline to offshore, covering the whole Exclusive Economic Zone. A total of 67 indicators were used, covering some ecosystem components: physico-chemistry of sediments and waters, phytoplankton, benthic fauna and flora, fish, birds, mammals, and alien species. The associated data, for 2010 to 2019, were then collated and integrated to assess the environmental status in a holistic way, using NEAT (Nested Environmental status Assessment Tool). The analyses included spatial scenarios (coastline to offshore), as well as filtering by different MSFD descriptors (i.e., biodiversity, alien species, eutrophication, seafloor integrity and contamination). Overall, the Basque coast is in good status, with no clear spatial gradient. But when focusing on specific ecosystem components (e.g., seabirds, mammals, some commercial fish species), it is possible to identify some components in bad status, with scope for improvement through the implementation of management measures. The integrated assessment approach presented and the outputs that are obtained can be used to guide European practitioners in their efforts to prioritize management measures. Furthermore, results are comparable to those reported in official MSFD assessments, confirming the power of the NEAT software.

Comparative study of TLP and ETLP performance in Caspian Sea environment using numerical method

This paper presents a numerical analysis to compare a Conventional TLP (CTLP) and an Extended TLP (ETLP) performance in marine environmental conditions. Both platforms have 12 tethers installed in a water depth of 700 m located in the Caspian Sea under irregular JONSWAP waves, wind and current loads. A coupled BEM-FEM numerical time and frequency domain analysis was performed to estimate motions and mooring line cumulative fatigue damage of two kinds of tension leg platforms. Besides, power spectra density (PSD) of heave motion, which is the most important displacement in the vertical plane for TLPs, under different wave periods at a wave angle of 30 deg was investigated. Finally, to have an in-detailed overlook, surge, heave and pitch RAO of platforms in critical wave periods under wave angles from 0 to 45 deg were studied. Model results showed that the CTLP demonstrate larger mooring fatigue damage and therefore less safety against wave, wind and current loads. However, perturbed waves induce more perturbance around the ETLP than the CTLP which in turn needs a proper control system to damp it. In addition, the obtained results show that in the Caspian Sea condition, mainly the ETLP demonstrates a smaller heave, surge and pitch motions than those of the CTLP under various wave periods. Altogether these results show that using a control system ETLP with respect to the CTLP demonstrates more efficient performance.

Simulation and Analysis of Multiphase Flow in a Novel Deepwater Closed-Cycle Riserless Drilling Method With a Subsea pump+gas Combined Lift

Recently, deepwater resource exploration has grown rapidly. Because the conditions of marine environment and seabed geology are more complex, deepwater drilling needs to numerous confront challenges, such as more complicated wellbore situations, low drilling efficiency, and high cost. Advanced novel drilling methods serve as significant impetus to facilitate the rapid advancement in deepwater oil-and-gas exploration and development. However, adopting riserless drilling methods may pollute marine environment and yield poor wall protective effects, while drilling methods with risers may suffer from relatively high cost and risk. Based on these dilemmas, in this study, a novel deepwater closed-cycle riserless drilling method with a subsea pump + gas combined lift is proposed. The proposed novel closed-cycle method has also established a multiphase flow drilling model and analyzed the effects of drilling fluid displacement, gas injection displacement, gas injection site and seawater depth on the multiphase flow in the wellbore. The simulation results revealed the following: As the gas migrates upward along the pipeline, its flow velocity first increases slowly and then rapidly owing to the volume expansion of gas. Larger displacement of drilling fluid demands greater working power of the subsea lifting pump, which is characterized by a nonlinear relationship. The gas injection displacement can effectively mitigate the load-bearing capacity of the pump, and increasing gas injection displacement leads to a decreased subsea lifting pump working power requirement; the decreasing effect on pump power load is more significant in the case of low gas injection displacement. Increasing the depth of gas injection sites reduces the subsea pump working with a decreasing slope with respect to the power descent. Finally, the subsea pump lifting power demand increases approximately linearly with an increasing seawater depth. Subsequently, an optimization method of hydraulic parameters for deepwater closed-cycle riserless drilling was proposed, which provides a theoretical foundation for the selection of subsea pumping power as well as the optimization of gas injection sites and displacement.

Surf smelt accelerate usage of endogenous energy reserves under climate change.

Surf smelt (Hypomesus pretiosus) are ecologically critical forage fish in the North Pacific ecosystem. As obligate beach spawners, surf smelt embryos are exposed to wide-ranging marine and terrestrial environmental conditions. Despite this fact, very few studies have assessed surf smelt tolerance to climate stressors. The purpose of this study was to examine the interactive effects of climate co-stressors ocean warming and acidification on the energy demands of embryonic and larval surf smelt. Surf smelt embryos and larvae were collected from spawning beaches and placed into treatment basins under three temperature treatments (13°C, 15°C, and 18°C) and two pCO2 treatments (i.e. ocean acidification) of approximately 900 and 1900 μatm. Increased temperature significantly decreased yolk size in surf smelt embryos and larvae. Embryo yolk sacs in high temperature treatments were on average 7.3% smaller than embryo yolk sacs from ambient temperature water. Larval yolk and oil globules mirrored this trend. Larval yolk sacs in the high temperature treatment were 45.8% smaller and oil globules 31.9% smaller compared to larvae in ambient temperature. There was also a significant positive effect of acidification on embryo yolk size, indicating embryos used less maternally-provisioned energy under acidification scenarios. There was no significant effect of either temperature or acidification on embryo heartrates. These results indicate that near-future climate change scenarios may impact the energy demands of developing surf smelt, leading to potential effects on surf smelt fitness and contributing to variability in adult recruitment.

Investigating terrestrial and oceanic environmental conditions to identify possible factors influencing seaweed bed distribution in Tsushima Islands, Japan

A decrease in seaweed beds has been a serious problem in the coastal areas of the Tsushima Islands, and other areas in Japan and worldwide. In the Tsushima Islands, certain coastal areas in the northeastern (NE) area contain seaweed beds, while their depletion is of serious concern in other areas. The influence of terrestrial and oceanic waters, and their relationship with seaweed bed distribution in the Tsushima Islands, Japan was examined to understand the marine environmental conditions. We conducted comprehensive investigations based on water sampling and their analyses in this study. Water qualities including total iron, dissolved iron, nitrate nitrogen, nitrite nitrogen and phosphate-phosphorus, and carbon stable isotope ratios of particulate organic matter (POM) in seawaters and river waters in the NE and southwestern (SW) areas of the Tsushima Islands were seasonally monitored. The seawater quality results showed no distinct differences between the NE and SW areas. This observation indicates that the materials, including iron supplied from terrestrial areas, were not the primary factors characterizing the seaweed bed distribution, despite the seaweed bed distribution in the NE area being larger than that in the SW area. Meanwhile, the seasonal variations in the δ13C values of POM in the NE area were more evident than those in the SW area. This implies the significant contribution of oceanic POM in the NE area, possibly due to the existence of island-induced current and cyclonic eddies, and its influence on the coastal water qualities. These environmental properties have been suggested to potentially influence the characteristics of seaweed bed distribution in the Tsushima Islands.

The effects of environmental information provision on plastic bag use and marine environment status in the context of the environmental levy in Greece.

The focus of this study is to examine the level of awareness, as well as the impacts of environmental information provision, regarding plastic bag consumption in Greece, taking into consideration the effects of plastic pollution in the marine environment within the framework of the environmental levy. This study was conducted through the use of two structured questionnaires as web-based surveys. The aim of both questionnaires was to explore citizen attitudes towards the marine environment in addition to their preferences with regard to the implementation of a program aimed at marine conservation and the reduction of plastic bag use. Data on plastic bag consumption at a national level were also incorporated. This research was carried out according to the contingent valuation method aimed at estimating citizen willingness-to-pay (WTP) on both structured questionnaires. The first questionnaire utilized the minimal legal WTP (ML-WTP) model resulting in 834 responses in total, while the second questionnaire applied a double-bounded dichotomous choice method and amassed 713 responses in aggregate. Based on the results of the first questionnaire, pre-existing environmentally friendly behaviour was further enhanced by the introduction of the environmental levy on plastic bags. The second questionnaire revealed that marine conservation is based both on collective as well as individual responsibility. This study provides evidence that the utilization of both economic and non-economic measures may be very effective in considerably reducing plastic bag consumption and its detrimental impact on the marine environment.

해양로봇 성능평가에 관한 동향 분석 및 객관적 시험절차 구축에 관한 연구

Recently, the research on marine IoT (Internet of Things) has been diversified. The demand for marine robots capable of responding to advanced missions has been increasing. However, it is difficult to objectively evaluate the performance of marine robots. This is mainly because several problems hinder this evaluation, such as high-weight and large-scale marine robots, uncertainty in marine environmental conditions, and performance evaluation costs. Thus, KIOST(Korea Institute of Ocean Science and Technology) is building the Jang Yeongsil as a ship that can professionally conduct field tests and evaluations at sea. Additionally, they are conducting research activities to evaluate the objective performance of marine robots. Therefore, in this paper, performance evaluation trends of land/marine robots are analyzed, and evaluation items for test evaluation of marine robots are presented based on this analysis. Using depth keeping, the results were verified through a third-party witness verification. The third-party witness test results demonstrate the test procedure’s reasonableness.

Rare Earth Element Geochemistry of Late Cenozoic Island Carbonates in the South China Sea

Marine carbonates, precipitating from seawater through inorganic geochemical and biogeochemical processes, are considered to have recorded the seawater geochemical signatures reflecting the marine environmental conditions during their formation. However, they are susceptible to post-depositional diagenetic alteration. The redox conditions and chemical composition of the diagenetic fluid may be different from those of the overlying seawater. Therefore, assessing whether carbonate rocks that have experienced variable diagenesis could still preserve primary seawater geochemistry is a prerequisite before inferring ancient marine environments using geochemical tracers such as the cerium anomaly (Ce/Ce*). Here, we investigate rare earth elements plus yttrium (REY) geochemical features of reefal carbonates from the XK-1 core in the Xisha Islands of the South China Sea. We aim to evaluate whether island carbonates have the potential to preserve reliable primary seawater REY geochemical characteristics after experiencing meteoric diagenesis, marine burial diagenesis, or dolomitization. The results show that even after variable diagenetic alteration, all carbonate samples exhibit seawater-like REY patterns, which are characterized by negative Ce anomalies (Ce/Ce* < 1), distinctively high Y/Ho ratios (>44), and uniform depletion of light rare earth elements (LREE) relative to heavy rare earth elements (HREE) ((Pr/Yb)N < 1). This suggests that the original seawater REY signatures are retained, regardless of varying degrees of changes in the mineralogical composition, diagenetic fluid composition, and redox state. The unmodifiable REY characteristics in carbonates during diagenesis can be attributed to three aspects: (1) during meteoric diagenesis, the low REY content of meteoric fluids and the short-term reactions between fluids and carbonates make it difficult to significantly alter the REY composition of carbonates; (2) during marine burial diagenesis, the ubiquitous cementation creates a relatively closed environment that facilitates the inheritance of REY signatures from primary carbonates; (3) during dolomitization, the dolomitizing fluids derived from penecontemporaneous seawater would not destroy but rather promote the preservation of the original seawater REY signatures in dolostones. The Ce/Ce* variations indicate that the Xisha carbonates have been deposited under constantly oxic conditions since the Neogene, consistent with paleontological and redox-sensitive element geochemical evidence.

Environmental inferences based on benthic foraminifera in surface sediments from the Beagle Channel (Argentina): A multiproxy approach

Micropaleontological analysis was performed on 22 samples of recent marine sediments from the Beagle Channel (Tierra del Fuego, Argentina) between 10 and 100 m of depth. The most important foraminifera found in the channel were Cibicidoides dispars (d'Orbigny), Buccella peruviana (d'Orbigny), Cibicides aknerianus (d'Orbigny), Cibicides fletcheri Galloway and Wissler, and Neoeponides bradyi (Le Calvez), which inhabit in clayey–sandy marine sediments. The observed variations in diversity and abundance revealed shallow marine conditions, low-energy, and low to moderate salinity, in the west sector and a deeper environment with normal marine conditions, high-energy, highly‑oxygenated and cold seawater in the east sector of the channel. The study area is a complex scenario with numerous landforms that lead to the formation of micro-environments in which patchy distribution of foraminifera was recognized. This study based on foraminifera and the sedimentological analysis supports the previous palynological information from the channel, which also shows an increase in number and diversity of dinocyst species reflecting the eastward changes of the marine environmental conditions due to the influence of the Atlantic.

Statistical tolerance–cost–service life optimization of blade bearing of controllable pitch propeller considering the marine environment conditions through meta-heuristic algorithm

Abstract Blade bearing is the key mechanism of the controllable pitch propellers (CPPs) to adjust the pitch to change the thrust. In the marine environment, wear and deformation of the contact surface of the blade bearing are quite large, which may result in leakage to reduce the service life of CPP. However, most studies on tolerance optimization of blade bearing disregard deformations and wear, and it could result in unreasonable tolerances and impair the CPP’s service life. In this paper, to establish the statistical tolerance–cost–service life optimization model of the blade bearing of the CPP considering the marine environment effects in propellers, a prediction model about the relationship between the thrust and rotation speed of the CPP considering environment conditions of wind, wave, and ocean currents is constructed. Based on this, the wear and deformation are simulated according to the predicted rotation speed in the marine environment. Considering the deformation and wear in the marine environment, a tolerance analysis model of the assembly deviations of the blade bearing is introduced, and the assembly characteristics and functional requirements are established and converted into probability constraints to establish the service-life model based on statistical tolerance analysis and Monte Carlo simulation methods. Afterward, a statistical tolerance–cost–service life optimization model is established and transformed into a single-objective optimization problem through the normalization method and the weighted sum method, and solved by a meta-heuristic algorithm named cuckoo search. Finally, the application of the proposed model is demonstrated through a case involving the blade bearing of a CPP, and the optimized results show that the manufacturing cost of the blade bearing is reduced and its service life is extended.

Assessment of the ecological quality of soft-bottom benthic communities in the Syrian coast, Eastern Mediterranean

The present study was aimed to evaluate several benthic biological indices to assess the ecological quality status of marine environments in Syria. Samples were obtained from four different areas of Syrian coast (Al-Bassit, Banias, Tartous and Al-Hamidia) on a monthly scale from March 2007 to December 2007. Results showed that the percentage of benthic species are increased significantly in the stations with healthy ecological status. The cluster analysis and the MDS have shown that the studied stations are subjected to environmental disturbance. Some species have been found to be more sensitive (high values of Hurlbert Index) than others such as the Rhinoclavis kochi, which belonged to the Gastropodes taxa and Notomastus latericeus belonged to the polychaetes taxa. The ecological quality of the Syrian coast was assessed using three biotic indices (H′, AMBI and BQI). The Shannon–Wiener index H′ was ranged from 2.88 to 5.39. Thus, the ecological status varied between moderate and high. The values of AZTI Marine Biotic Index (AMBI) and Benthic Quality Index (BQI) classified the ecological state between high and good (slight disturbance).

Natural attenuation of sulfometuron-methyl in seawater: Kinetics, intermediates, toxicity change and ecological risk assessment

This research aims to evaluate the environmental feasibility of sulfometuron-methyl (SM) as a growth inhibitor for restricting the growth of Spartina alterniflora. To achieve this purpose, the natural attenuation characteristics, ecological risk, degradation pathway, and comprehensive toxicity changes of SM in seawater were investigated under the simulated marine environmental conditions of Jiaozhou Bay, China. The natural attenuation of SM in seawater followed first-order reaction kinetics with a rate constant (K) of 0.0694 d−1 and a half-life of 9.99 days. When photolysis, hydrolysis, and biodegradation pathways act alone, the rate constants K of SM were 0.0167, 0.0143, and 0.0099 d−1 respectively, indicating that their contributions to the total removal of SM decreased in turn. The calculation results of risk quotient (RQ) showed that the seawater containing 10 mg/L of SM demonstrated a very high risk to marine diatom Skeletonema costatum before and after 21 days of attenuation with RQ values of 24.46 and 6.32, respectively, however, the risk to other marine organisms (fish, crustaceans, and bivalves) decreased from moderate (RQ < 1) to low (RQ < 0.01). Four attenuation products of SM were identified and two degradation pathways of SM in seawater were proposed. Based on the rate of inhibition of bioluminescence, SM in seawater was not harmful to Photobacterium phosphoreum T3, whereas the toxicity of seawater containing SM increased with the extension of attenuation time, suggesting the formation of intermediate products with high aquatic toxicity. According to the toxicity values predicted by ECOSAR, the toxicity of one identified attenuation product was higher than that of SM. To the best of our knowledge, this is the first report on the attenuation characteristics and toxicity changes of SM in seawater. The results indicated that the toxicity of both SM and its degradation products to non-target marine organisms should be considered in evaluating the feasibility of SM in controlling coastal Spartina alterniflora.

Ultimate Limit State Scour Risk Assessment of a Pentapod Suction Bucket Support Structure for Offshore Wind Turbine

Scour risk assessment considering reaction force at foundation was proposed and applied to newly developed pentapod suction bucket support structures for a 5.5 MW offshore wind turbine under ultimate limit state environmental load. Scour hazard was obtained according to scour depth by using an empirical formula, which is the function of marine environmental conditions such as significant wave height, significant period, and current velocity. Fragility of the pentapod support structure was evaluated using the bearing capacity limit state criterion under ultimate limit state load case. Scour risk was assessed by combining the scour hazard and the fragility. Finally, scour risk of the developed pentapod suction bucket support structure under ultimate limit state has been assessed.

An In Situ Experiment to Evaluate the Aging and Degradation Phenomena Induced by Marine Environment Conditions on Commercial Plastic Granules.

In this paper, we present two novel experimental setups specifically designed to perform in situ long-term monitoring of the aging behaviour of commercial plastic granules (HDPE, PP, PLA and PBAT). The results of the first six months of a three year monitoring campaign are presented. The two experimental setups consist of: (i) special cages positioned close to the sea floor at a depth of about 10 m, and (ii) a box containing sand exposed to atmospheric agents to simulate the surface of a beach. Starting from March 2020, plastic granules were put into the cages and plunged in seawater and in a sandboxe. Chemical spectroscopic and thermal analyses (GPC, SEM, FTIR-ATR, DSC, TGA) were performed on the granules before and after exposure to natural elements for six months, in order to identify the physical-chemical modifications occurring in marine environmental conditions (both in seawater and in sandy coastal conditions). Changes in colour, surface morphology, chemical composition, thermal properties, molecular weight and polydispersity, showed the different influences of the environmental conditions. Photooxidative reaction pathways were prevalent in the sandbox. Abrasive phenomena acted specially in the sea environment. PLA and PBAT did not show significant degradation after six months, making the possible reduction of marine pollution due to this process negligible.

Effect of Co addition on the microstructure, thermal stability and anti-corrosion properties of AlNiZrYCox high-entropy metallic glass ribbons

In this current research, the effect of Co addition on the microstructure and anti-corrosion properties of equiatomic AlNiZrY high-entropy metallic glass (abbreviated to HE-MG) ribbons were investigated. Also, the thermal stability and crystallization activation energy of these HE-MG ribbons have been studied. Ribbons of composition (Al1/4Ni1/4Zr1/4Y1/4)100-xCox (x= 0, 5, 8, 12) were synthesized via arc-melting method and melt-spinning technique. By increasing the content of Co, we found that the melt-spun equiatomic AlNiZrY and Co-containing AlNiZrY HE-MG ribbons could still remain amorphous state. The thermal stability of ribbons were conducted by means of a differential scanning calorimeter (DSC), which suggested that the thermal stability of four kinds of HE-MG ribbons is higher than common Al-Ni-based amorphous alloys. The maximum apparent activation energy of crystallization through thermodynamic analysis at different heating rates can reach ∼630 kJ/mol for (Al1/4Ni1/4Zr1/4Y1/4)92Co8 HE-MG ribbons. The microstructure characterization of each HE-MG ribbon before and after one-day corrosion immersion was done by scanning electron microscopy (SEM). In order to evaluate the microhardness and corrosion resistance of the as-received HE-MG ribbons with and without the addition of Co, the microhardness measurements and the electrochemical corrosion tests in 3.5 wt.% NaCl solution were carried out. The results revealed that the average microhardness value of HE-MG ribbons are all above 470 HV0.1, regardless of whether the ribbons immersed in corrosive media for one-day immersion or not. The corrosion current density of (Al1/4Ni1/4Zr1/4Y1/4)88Co12 HE-MG ribbons is around 0.46 μA/cm2, which possesses the sterling anti-corrosion property and opens vital possibilities for the development of high-performance metal coatings under the condition of harsh marine environment.

Geochemical Characteristics and Their Marine Environmental and Organic Source Implications for the Lower Cambrian Shales in Guizhou Province, South China

Abstract In this study, we conducted systematic analysis of total organic carbon (TOC) content, lipid biomarkers, carbon isotopes of kerogen (δ13Ckerogen), and mineral composition in Niu-ti-tang (Є1n) and Pa-lang (Є1p) shales from Guizhou Province in order to provide a better understanding of the organic sources and marine environmental condition during deposition of the Lower Cambrian shales of South China. The results show that a broad variety of lipid biomarkers, such as n-alkanes, pristane, phytane, terpanes, hopanes, and steranes, are in these shales, which suggests a significant contribution of various paleobios with bacterial microorganisms and algae thriving under a low-salinity and stable anoxic environment. The negative δ13Ckerogen value (minimum −36.4‰) and occurrence of pyrite (1–7.5%) and carbonates (2.4–57.3%) indicate that bacterial sulfate reduction prevailed under anoxic conditions during deposition of the Lower Cambrian shales. Moreover, the difference in mineral and δ13Ckerogen composition between Є1n and Є1p shales might imply significant changes in primary production and paleoocean environments due to sea-level rise, as shown by the higher average TOC content in Є1p shales (2.52%) compared to that in Є1n shales (1.79%). The covariances of TOC content and mineral and δ13Ckerogen composition suggest that the Є1p shales might have been deposited under a higher sea level associated with high primary productivity, compared to Є1n shales. Thus, high primary productivity driven by sea-level rise is suggested to be the main controlling factor on organic matter enrichment in Є1p shales under stable anoxic conditions.

Comparative study of mineral element content in fishes from the south and north seas of java island using neutron activation analysis

Fish is an environmental bioindicator and a contributor to the daily intake of mineral elements. The content of mineral elements in fish is influenced by what it eats and its environment. Moreover, based on location, around the north coast of Java there are denser residential and industrial areas compared to around the south coast of Java. In this study, we analyzed the mineral content of fish of the same species originating from the southern and northern seas of Java using neutron activation analysis. Fish samples of the same 11 species were each collected from fish auctions in Pemalang and Garut districts. The samples were washed, and then the meat was taken and dried by the freeze-drying method. The samples were irradiated in the G.A. Siwabessy multi-purpose reactor through the rabbit system then counted using gamma spectrometry. The results obtained as many as 17 mineral elements in fish: Na, K, Mg, Cl, Ca, Br, Fe, Zn, Sr, Al, Cr, Se, Rb, Mn, Co, Hg, and Cs. Statistical test results show that there are various differences (positive covariance on 14 elements, negative covariance on 3 elements) for each element between fish from the South Java Sea and North Sea, which indicates that marine environmental conditions have contributed significantly to changes in mineral content on fish.

Joint parameter-input estimation for virtual sensing on an offshore platform using output-only measurements

This paper presents a recursive Bayesian inference framework for joint parameter-input identification, and virtual sensing for strain time history prediction of an offshore platform using sparse output-only measurements. The studied offshore platform, known as FINO3, is in the North Sea and is instrumented with a variety of sensors, including accelerometers and strain gauges. Offshore platforms are fatigue critical structures due to harsh marine environmental conditions and continuous cyclic wind and wave loads. Therefore, continuous monitoring of strain time histories at hotspot locations of offshore structures is important for reducing maintenance cost and avoiding unexpected failures. A windowed unscented Kalman filter (UKF) is employed to estimate an uncertain modeling parameter (foundation stiffness) and unknown input load time histories using output-only acceleration and strain measurements. The input loads are divided into overlapping windows, and windowed inputs and model parameters are combined as an augmented state vector in the UKF framework. Then strain time histories at critical locations are estimated through a virtual sensing strategy using the estimated input loads and model parameter. A traditional modal expansion approach combined with model updating is also implemented for the purpose of verification and comparison. The proposed method is first demonstrated through a numerical study using a finite element model of FINO3, where accurate model parameter and input estimations are obtained. Then the approach is further investigated using the actual measurements on FINO3. More accurate strain predictions are provided by the UKF than the modal expansion approach, which recommends the proposed UKF method for fatigue monitoring and input estimation.

Palaeoenvironmental changes based on foraminifera during the late Holocene at the Beagle Channel, Argentina.

A foraminiferal faunal study was carried out in a Holocene marine section from Arroyo Baliza, located on the northwest coast of the Beagle Channel, to contribute to the knowledge of the palaeoenvironmental conditions during the marine Holocene event. Foraminiferal assemblage was represented by 32 species distributed among 21 genera. The assemblage was dominated by Elphidium macellum (Fichtel & Moll) Elphidium alvarezianum (d'Orbigny), Cribroelphidium excavatum (Terquem) and Buccella peruviana (d'Orbigny), accompanied by Cibicides fletcheri Galloway & Wissler and Cibicidoides dispars (d'Orbigny) in low proportion. The predominance of Peridiniales dinocysts in the marine palynomorphs assemblage, suggested inner neritic conditions with cooler and more nutrient-rich waters. The distribution of the foraminiferal species was variable throughout the section indicating palaeoenvironmental changes in Arroyo Baliza between 3499-2595 cal yr BP. A gradual passage from high energy, cold and well-oxygenated marine waters towards a shallower environment with low energy and low to moderate salinity of the waters were linked to the regressive phase. This study complements and supports the previous palynological data from this section, which reflects an increase in number and diversity of dinocyst species indicating marine environmental conditions during the late Holocene as it exists today in the Beagle Channel.

Geochemical characteristics and organic matter enrichment mechanism of Permian black mudstone in the South Yellow Sea Basin, China

The middle Permian organic matter-rich mudstone in the South Yellow Sea Basin has been considered the most important source rock for Paleozoic reservoirs in the basin. However, information on the variation in depositional environment within the Qixia Formation to lower Longtan Formation interval is lacking, and the formation mechanism of these organic matter-rich mudstones is unclear. Based on a series of geochemical analyses of borehole CSDP-2, the paleoclimatic conditions, nature of the watermass, paleoproductivity and terrestrial detrital influx of the different intervals in the middle Permian of the South Yellow Sea Basin were assessed to determine the main factors controlling organic matter enrichment. All three intervals (from the Qixia Formation to the lower Longtan Formation) were deposited under a relatively warm and humid paleoclimate with moderate terrestrial detrital input. The Qixia Formation was deposited under oxic paleoredox conditions in a normal marine environment. During deposition of the Gufeng Formation, the paleoredox conditions changed to suboxic with intermittent anoxia associated with paleoproductivity higher than that in the other studied intervals. The lower Longtan Formation was characterized by a brackish watermass, suboxic paleoredox conditions and low paleoproductivity. The covariant relationships among paleoproductivity, paleoredox conditions, watermass salinity indicators and TOC content indicate that paleoproductivity was the critical factor controlling organic matter abundance. High primary productivity not only provided organic matter but also enhanced organic matter preservation by consuming oxygen in the watermass, which resulted in the formation of the organic matter-rich source rock in the Gufeng Formation. • The Gufeng Formation exhibits higher paleoproductivity than other two intervals. • Higher paleoproductivity resulted in relative reducing redox condition. • Paleoproductivity level controls the deposition of OM-rich source rock.