Sea Environment Research Articles

The complete mitogenome of Argentina brasiliensis Kobyliansky, 2004 and a phylogenetic analyses of the order Argentiniformes.

The deep sea environment is the largest environment and host some of the most extreme ecosystems on Earth, therefore, possessing a large and unique fish diversity that encompasses about 15% of all known species. Our knowledge about these fishes is still very limited in many biological fields basically due to the complexity to obtain specimens for research. In the present study, we describe the complete mitochondrial genome of Argentina brasiliensis, aiming a species characterization and the study of the phylogenetic relationships in the order Argentiniformes. The mitogenome is composed by 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, and a control region (D-loop), as found in other vertebrates. The phylogenetic results show that the order Argentiniformes is composed by two family groups the first formed by Argentinidae and Opisthoproctidae and the second formed by Bathylagidae and Microstomatidae. Additionally, we found that the genus Argentina is not monophyletic, and we suggest additional studies in the family Argentinidae to better investigate this question.

Decline in Size-at-Maturity of European Hake in Relation to Environmental Regimes: A Case in the Eastern Ionian Sea.

European hake, Merluccius merluccius L. 1758, is a highly valuable demersal fish species exploited in both the east Atlantic and the Mediterranean Sea. Changes in the size-at-maturity of this species have been reported in various geographic areas. Size-at-maturity is a key parameter in fishery management. Our main goal was to study the trend of the size-at-maturity of European hake in the eastern Ionian Sea (Central Mediterranean) over the last five decades. Utilizing a multi-decadal series of data for various environmental variables, we employed multivariate analyses and non-additive modeling in an attempt to identify shifts in the climatic environment of the eastern Ionian Sea and whether the maturation of the hake population could be affected by these changes. The analyses used suggest a plausible environmental regime shift in the study area in the late 1990s/early 2000s. The decrease in size-at-maturity that was detected in the last two decades may, thus, be associated with environmental changes. However, as many fish stocks already experience fishery-induced evolution, further investigation is necessary to determine whether this environmental effect is an additional stressor on a possibly already fishery-impacted population. The outcomes of this study highlight the importance of investigating the relationship between fish reproductive traits and altered environmental conditions, as the latter are generally ignored during assessments, affecting the robustness of fishery management.

Antioxidant Activity and Isolation of Bioactive Compounds from Seaweed of Silpau (Dyctyosphaeria sp)

Seaweed is the key to developing habitat in deep sea, coastal, and estuarine environments. Seaweed, humans, and animals have been interrelated since the beginning, especially as a food source of fiber, protein, vitamins, antioxidants, and bioactive compounds. Natural antioxidants are seen as a superior and safe method of fighting free radicals. Sources of antioxidants usually come from land plants and rarely from seaweed. Silpau is a seaweed and a local food ingredient in Maluku Province, Indonesia, and has the potential as an antioxidant. Antioxidant and bioactive compounds are needed by humans and animals as antibodies to fight various negative influences from the environment. This research aimed to isolate and characterize active antioxidant compounds and the toxicity of silpau extracts. The extraction of the active compound begins with a single maceration method for 3 x 24 hours with methanol solvent, processing with the partition extraction method for subfraction separation using column chromatography with the silica gel stationary phase and the mobile phase solvent n-hexane: ethyl acetate with a ratio (50: 1 ~ 1: 1) gradient. The sample toxicity was tested using the Brine Shrimp Lethality Test method. The trial activity used the Free Radical Reduction method with 2,2-diphenyl-1-pikrilhidrazil as a reagent. This research succeeded in isolating one bioactive compound from the glare green macroalgae. Based on the phytochemical analysis and FT-IR spectrophotometer, sub-fraction IV was identified as a triterpenoid class of compounds that has an IC50 value of 126,582 μg / ml and is considered an antioxidant.

Studies on the Prevalence Rate of Neoplastic Growth in Fish Johniuss Dussumieri (Valenciennes, 1833) of Karachi Coast Due to Polluted Sea Environment

Background: With the growing concern over the impacts of environmental pollution on marine life, this study addresses the critical issue of neoplastic growth in fish populations. The increasing prevalence of tumors in fish due to contaminated marine environments has raised alarms about ecosystem health and public health implications. Objective: The primary objective of this research was to assess the prevalence and seasonal variation of neoplastic growth in fish populations, particularly focusing on the impact of environmental pollution. Methods: Fish specimens were collected from various markets and examined for neoplastic growth. The study employed observational techniques, statistical analyses including ANOVA and Duncan's Multiple Range Test, and assessed seasonal variations from January 2019 to December 2022. Results: A total of 2,373 fish were examined, with 193 cases of neoplastic growth identified, indicating a substantial prevalence of tumors. The statistical analysis revealed significant variations in tumor prevalence, with a notable correlation to environmental factors. Conclusion: The study concludes that environmental pollution significantly impacts the prevalence of neoplastic growth in fish populations. This has profound implications for marine ecology and public health, emphasizing the need for effective environmental management and pollution control measures.

Early corrosion behavior of 35CrMo steel for high-strength bolt in simulated shallow and deep sea environments

Early corrosion behavior of 35CrMo low-alloy steel for high-strength bolt in the simulated shallow seawater and deep-sea environment was studied using mass loss measurement, electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), Raman spectrometer, X-ray photoelectron spectrometer (XPS) and 3D microscope. The results show that the corrosion of 35CrMo steel initiates mainly at the steel matrix around the inclusions of CaO–MgO–Al2O3, (Ca, Mn)S and their mixed composite. The corrosion rate in the simulated deep-sea environment is lower than that in the shallow seawater, which is declined with immersion time. The corrosion products formed in the two environments are composed of γ-FeOOH, α-FeOOH, Fe3O4 and little Cr(III) oxide or/and hydroxide, but the rust layer produced in the deep-sea environment is thin and uniform. The steel has pits in a shallow dish shape and tends to develop uniform corrosion in the deep-sea environment.

Maritime Search Path Planning Method of an Unmanned Surface Vehicle Based on an Improved Bug Algorithm

Due to the complicated and changing circumstances of the sea environment, path planning technology is essential for unmanned surface vehicles (USVs) to fulfill search tasks. In most cases, the location of the underwater target is unknown, so it is necessary to completely cover the search area. In this paper, the global static path is planned using a parallel line scan search. When encountering unknown obstacles, the improved Bug algorithm is used for local dynamic path planning according to the sensor detection information. This paper first sets up the safe expansion area to ensure the safety of the USV during the obstacle avoidance process and optimizes the movement direction considering the operation and behavior characteristics of the USV. To meet the requirement of USV steering, the Bezier curve is used to smooth the path points, which greatly improves the smoothness of the path. In this paper, the multi-mode switching strategy of the Bug algorithm based on obstacle boundary width obtained by the sensor is proposed, which ensures no area omissions and meets the requirement of search area coverage during the process of bypassing obstacles. The simulation results show that the improved Bug algorithm can maintain a safe distance along the obstacle boundary to bypass the obstacle. Moreover, the improved Bug algorithm effectively improves the path oscillation phenomenon of traditional Bug and shortens the path length and operating time. Finally, through the global search path planning simulation and comparison experiments, the effectiveness of the proposed method is verified.

Ranking the main risks that can lead to the pollution of the marine environment in the Black Sea

The aim of the paper is to present the way in which the main risks that can lead to the pollution of the marine environment of the Black Sea can be ranked using multicriteria analysis, based on the AHP process (Analytic Hierarchy Process). This analysis represents a solid basis for the decision-making process. Based on this hierarchy, the decision-makers in the maritime field can easily visualize both the risk assessment criteria and the risks that must be taken into account. The analyzed risks (oil spills, shipwrecks, ship collision, fire explosion) in relation to the considered criteria (bad weather conditions, high-density traffic, human errors, ship age) have been ranked as follows: "ship collision" risk with overall priority = 0.366 is the one that must be considered the most dangerous in relation to the considered criteria, followed in descending order by the risk of "oil spills" with overall priority = 0.303, the risk of "shipwrecks" with overall priority = 0.181 and finally the risk of "fire explosion" with overall priority = 0.150.

Fluid-structure interaction of spherical pressure hull implosion in deep-sea pressure: Experimental and numerical investigation

Implosion may occur when a hollow pressure structure with geometric imperfections works in deep-sea environments. Therefore, the implosion phenomenon and failure mechanisms of a titanium alloy spherical pressure hull are investigated by experiments and developed numerical methods in ultra-high-pressure water conditions. Firstly, the experiments were conducted using a full-ocean-depth sea environment simulator. Then the validity of the numerical analysis were demonstrated by comparing the shock wave of fluid and destroyed fragments of structure. Finally, the characteristics of underwater implosion were examined under different hydrostatic pressures, including the propagation of shock waves, high-speed motion of the compressible flow, nonlinear deformation of the spherical pressure hull, and energy balance and evolution. The results showed that the vertical impact effect occurs during the underwater implosion of a metallic sphere. Moreover, the shock wave emerges earlier and the cracks break into smaller fragments with the increase of hydrostatic pressure. Besides, the smaller volume of the air cavity is compressed and the larger amplitude of potential energy is dropped when the hydrostatic pressure is larger. Meanwhile, the internal energy of air and structure increases, while the internal and kinetic energy of air oscillates slightly due to the pulsation characteristics of the air cavity.

Foraminifera in the Holocene sediments at the shallow sea from Phu Loc (Thua Thien Hue) to Hoi An (Quang Nam) (0÷60 m of water depth)

The shallow sea (0÷60 m of water depth) from Phu Loc (Thua Thien Hue) to Hoi An (Quang Nam) belongs to the internal shelf in Central Vietnam. This is quite a good geological structure for the land-sea interaction study, especially during the Holocene. Therefore, it is necessary to study the geological history of the area during the Holocene period. Foraminifera is the subject of geological studies to solve the environmental problems of sedimentary, stratigraphic, and paleogeography. However, at present, the research documents on Foraminifera in the sediments in Vietnam in general as well as in the research area in particular are still very modest. This paper presents research results of Foraminifera fauna in Holocene sediments from Phu Loc (Thua Thien Hue) to Hoi An (Quang Nam) (0÷60 m of water depth). 93 species, belonging to 48 genera, 28 families and 5 suborders Foraminifera have been identified based on the analysis of 59 available samples. Miliolina Delage et Hérouard, 1896 has 06 families, 18 genera and 40 species; Rotaliina Delage et Hérouard, 1896 has 12 families, 15 genera and 29 species; Textulariina Delage et Hérouard, 1896 has 03 families, 05 genera and 07 species; Lagenina Delage et Hérouard, 1896 has 03 families, 04 genera and 07 species; Globigerinina Delage et Hérouard, 1896 has 04 families, 06 genera and 10 species. The quality of the benthonic Foraminifers is dominant, clearly showing the geological environment of the shallow sea near shore, where the hydrodynamic regime is high and the salt concentration is not stable.

Utilization of Cement and Concrete for Deep Sea Infrastructure

AbstractThe use of cementitious materials in deep sea environments, focusing on the durability challenges of low‐temperature seawater and hydraulic pressure, are presented in this paper. The authors conducted laboratory and deep‐sea field experiments, thermodynamic calculation, and evaluated the performance of different types of binders in deep sea conditions. Durability of rebar in cementitious materials was investigated. In situ construction methods using cementitious materials was demonstrated on the deep‐sea field. Testing results revealed that deep sea conditions, especially low‐temperature seawater, can accelerate the disintegration of cement hydrates, and the use of pozzolanic admixture and calcium aluminate cement can improve its resistance. Our study provides valuable insights and applicability of cementitious materials to deep sea infrastructure construction.

Hydrogen Embrittlement Susceptibility of Ti-6Al-4V Alloys Fabricated by Electron Beam Melting in Simulated Deep-Sea Environment

The hydrogen embrittlement susceptibility of electron beam melted Ti-6Al-4V alloy (ET) was compared with that of conventional wrought alloy (WT). Hydrogen permeation, electrochemical, and slow strain rate tensile tests as well as surface observation were conducted under a simulated sea environment. The results show that the hydrogen embrittlement susceptibility of ET is lower than that of WT, which can be attributed to the intense texture of ET with a smaller specific surface area of grain boundary, preventing hydrogen permeation. Moreover, with increasing depth of the ocean, the hydrogen embrittlement susceptibility of both ET and WT TC4 alloys increases considerably. This reduced hydrogen embrittlement resistance can be attributed to the degradation of the passivation film, accelerating the permeation flux of hydrogen.

Seasickness susceptibility and the vestibular time constant: a prospective study.

Human passive motion during boat, car or airplane travel may trigger motion sickness. Seasickness is the most provoking manifestation of motion sickness. It imposes major constraints on quality of life and human performance. Based on seasickness susceptibility the population is usually categorized into susceptible (S) and non-susceptible (NS). During repeated exposure some susceptible individuals undergo habituation and obtain symptoms relief, reflecting a third group of habituating (H) individuals. Recently, accumulative evidence suggests that the vestibular time constant (Tc) is associated with motion sickness susceptibility and attenuation of symptoms. These studies demonstrated that repeated passive motion stimuli lead to temporary short-term (days) changes in Tc, whereas sea sickness habituation process lasts 3 to 6months. Therefore, the goal of the present study was to examine the behavior of Tc during the entire span of the seasickness habituation process between the H, S and NS groups to find an objective test for seasickness severity prediction. Tc of 30 subjects was prospectively evaluated pre, 3 and 6months post exposure to sea environment using a computerized rotatory chair system protocol. Seasickness severity was evaluated by Wiker questionnaire. Significantly shorter Tc was found in the S group compared with the NS and H groups. Further analysis revealed lower maximal Slow Phase Velocity (mSPV) and nystagmus frequency (total number of beats/second) in the S group. Our results suggest that Tc, mSPV and nystagmus frequency might serve as a prediction for seasickness severity. This study was retrospectively registered on December 7th 2022 and assigned the identifier number NCT05640258.

Study on suppression of violent sloshing in a multiple tuned liquid column damper by porous media layers

Multiple tuned liquid multi-column damper (MTLCD) is a passive damping device that is used to suppress the motion of semisubmersible floating offshore wind turbine (FOWT). However, the violent sloshing within the MTLCD under extreme sea environments reduces the anti-pitch motion effect. Thus, this study employed an innovative MTLCD with porous media layers, which can increase the flow energy dissipation, suppress the violent sloshing and enhance the damping moment (Mdamping). The OpenFOAM is used to simulate the hydrodynamic force in MTLCD, where the numerical method is validated by the decay test of a scaled model. The numerical natural period of the MTLCD shows good agreement with the experimental and analytical results. The sloshing characteristics, including pressure, damping moment impulse and work of the MTLCD without porous media, are analyzed firstly under simple harmonic rotation amplitudes (θ0) of 2°–20°. Subsequently, porous media layers are installed in the MTLCD with different heights (hp), including immersion and suspension, in order to improve the MTLCD's damping moment. Wavelet transform and wavelet-based bicoherence are utilized to analyze the nonlinear behaviors of the damping moment under violent sloshing. The breaking, surging and converging in the MTLCD are captured by the numerical method. The analyses show that the porous layers can suppress the violent sloshing by dissipating the fluid kinetic energy, and the damping moment work can be significantly improved when θ0 >6°. The liquid surging with bubbles leads to the nonlinear behaviors in the MTLCD, the sloshing energy transfer to the frequency doubling by three-wave interaction.

Study on corrosion behavior of typical carbon steel and low alloy steel in deep sea of different sea areas

Abstract In order to meet the development needs of deep-sea oil and gas resources, deep-sea corrosion coupon tests were carried out in the South China Sea, the Western Pacific Ocean, and the Indian Ocean, which can provide a strong guarantee for the rationality of material selection of oil and gas pipelines, platforms and other facilities. In-depth studies were conducted on the environmental adaptability of typical carbon steel and low alloy steel materials after exposure for one year in the deep-sea environment of different sea areas. The main environmental factors affecting deep-sea corrosion behavior were also collected and analyzed. The results showed that the corrosion morphology of carbon steel and low alloy steel in deep sea environment was more uniform than that in the shallow seawater. With the increase of seawater depth, the evolution law of their corrosion rates in different sea areas was similar, with an obvious decline of corrosion rate in the beginning. The gray correlation results indicated that it was mainly controlled by temperature and dissolved oxygen. The high hydrostatic pressure had limited effect on accelerating the deep sea corrosion rate of carbon steel and low alloy steel, but it promoted the formation of more uniform corrosion morphology.

Experimental investigation on dynamic shear modulus of undisturbed marine soils in the east coast of China

The dynamic shear modulus G is one of the vital parameters for the dynamic properties of marine soils and is crucial for marine geotechnical engineering design. In order to investigate the G characteristics of various marine soils, a series of resonant column tests were performed on undisturbed marine soils with various depths taken from Bohai Bay, Yangtze River estuary, and Jintang Strait, respectively. In addition, the maximum dynamic shear modulus Gmax and strain-compatible G of the tested marine soils were compared with the marine and terrestrial soils from the published literature. A remarkable finding is that, compared with terrestrial soils, the marine soils in different sea area present the stronger nonlinear behavior with lower shear modulus due to the special depositional environment. With the increasing of H, G in each strain range increase, and the dynamic characteristics of the marine soils gradually transition from nonlinear to linear, the Gmax and reference shear strain γ0 value of marine soils in different sea areas increases linearly with the increasing H, but the Gmax and γ0 growth rate varied with the sea environment and soil type. Based on the quantitative prediction equation of the Gmax and G attenuation relationship (G/Gmax ∼ γ) of various marine soils, a new prediction equation can be also established to predict G value in different depth and strain levels of various marine soils. The proposed equation are validated by independent experimental data of marine and terrestrial soils from the literature. In this regard, the proposed procedure provides a significant advantage in the evaluation of dynamic properties of marine soils in practice.

Preparation of Cold Sprayed Titanium TA2 Coating by Irregular Powder and Evaluation of Its Corrosion Resistance

Titanium coating on a steel substrate by surface technology can improve the corrosion resistance of steel. In this paper, the titanium TA2 coating was deposited on X80 steel by cold spraying equipment with a low-cost irregular powder. The effects of the carrier gas temperature on the microstructure, microhardness, wear resistance, adhesion and corrosion resistance of titanium coatings, especially in a deep sea environment, were studied by methods of porosity analysis, thermal field emission scanning analysis, energy spectrum analysis, Vickers hardness tests, bonding strength tests, friction and wear tests and electrochemical tests. The results showed that as the carrier gas temperature increased from 300 °C to 900 °C, the porosity of the coating decreased to 0.93%, and the hardness and bonding strength of the coating increased to 247 HV0.5 and 46.7 MPa, respectively. With the increase in hydrostatic pressure from 0.1 MPa to 40 MPa, the dimensional blunt current density of the titanium coating with 0.93% porosity was still in the order of 10−7 A·cm−2 with the cast titanium TA2.

Impact of dust deposition on the growth of marine autotrophic and heterotrophic microorganisms: Evidence from the South China Sea

Aeolian dust can provide nutrients for the ocean and affect the growth of phytoplankton. However, the impacts of dust deposition on autotrophic and heterotrophic microorganisms have rarely been studied. In this study, we conducted two microcosm experiments in the low-nutrient and low-chlorophyll environment of the South China Sea and found that dust did not stimulate the abundance of autotrophic and heterotrophic microorganisms. Our results show that dust contains most of the unreacted iron-bearing minerals, and thus provides limited bioavailable iron and nitrogen for bacterioplankton and phytoplankton growth. These results elucidate the overlooked impacts of the properties of the iron-bearing minerals in aeolian dust on microbial communities, which may play an important role in marine ecosystems and climate change.

Interfacial Bond Properties of Underwater Concrete Coated with Bisphenol A Epoxy Resins.

This study investigated changes in the interfacial properties of epoxy-coated concrete exposed to various conditions, regarding the epoxy type, coating equipment, and exposure environment and period. The measured coating thickness and pull-off bond strength exhibited diverse trends, depending on the exposure period and conditions. In the real sea (RS) environment, the average bond strengths for bisphenol A (BPA) (E1), BPA with zinc powder (E2), and BPA with cresyl glycidyl ether (E3) were 1.26, 1.93, and 1.92 MPa, respectively. The coating method did not significantly affect the measured coating thickness and strength values. The conventional roller (D1) exhibited the highest thickness variation, with a value of 214.45 μm. The RS condition significantly increased the coating thickness (34% to 158%) compared to the tap water (TW) condition. The exposure conditions had little impact on bond strength except for E3, which showed an increased strength (2.71 MPa) over 7-91 days, especially under RS conditions, while E2 remained constant at approximately 1.82 MPa. This study offers insights into factors influencing marine concrete coating performance and discusses limitations and future work.

A comprehensive study of the estuary sea environment in the Bay of Bengal, near the Mahanadi River confluence

This study focuses on the environmental conditions of the Mahanadi Estuary near Paradeep Harbor and the adjacent sea. Data collected from May 2013 to April 2020 from 32 GPS fixed stations was analyzed to assess the water quality in different zones (estuarine, mixed zone, mixed zone south, and mixed zone north) of study area. Parameters such as pH, SST, TSS, nitrite, phosphate, silicate, TOC, chlorophyll, fecal coliform, and heavy metals were used to estimate the Water Quality Index (WQI) for each zone. The study found a deterioration (> 30%) in the overall water quality of the Mahanadi Estuary from 2013 to 2020, potentially attributed to river inflows, port activities, and industrial outflows in to the coastal ecosystem. Seasonal variations in temperature, salinity, turbidity, nitrite, nitrate, and ammonia were observed. The water quality showed a deteriorating trend in estuarine, mixed zone, mixed zone south, and mixed zone north. Based on the water quality indices, the ecosystem shows moderate levels of stress. The degraded water quality highlights the need for a targeted mitigation plan to reduce external pressures and enhance the overall ecosystem quality.Graphical

Investigating the efficiency of a novel offshore pumped hydro energy storage system: Experimental study on a scale prototype

We introduce a novel offshore pumped hydro energy storage system, the Ocean Battery, which can be integrated with variable renewable energy sources to provide bulk energy storage. Its working principle is based on that of conventional pumped hydro storage with notable differences: the Ocean Battery is installed on the seabed, is powered by the hydrostatic pressure at the depth of deployment, and uses conditioned water as a working fluid within a closed hydraulic system to minimize the effects of corrosion and biofouling on the internal system. Herein we focus on the novel aspects of the Ocean Battery to investigate their effects on performance relative to that of conventional pumped hydro storage. Specifically, we present an analytical model that accounts for energy losses in the hydraulic system to predict pressures and flow velocities under different operating conditions and validate model predictions with measurements performed on an experimental small-scale prototype deployed in a relevant sea environment. Following validation, we use the model to estimate the round-trip efficiency of a scaled-up hydraulic system connected to pumps and turbines working at peak efficiencies, with the latter adopted from literature. The round-trip efficiency of such a scaled-up system is shown to be comparable to that of conventional pumped hydro storage.