Deep Seawater Research Articles

Adaptation to the shallow sea floor environment of a species of marine worms, Oligobrachia mashikoi, generally inhabiting deep-sea water

Beard worms from the family Siboglinidae, are peculiar animals and are known for their symbiotic relationships with sulfur bacteria. Most Siboglinids inhabit the deep-sea floor, thus making difficult to make any observations in situ. One species, Oligobrachia mashikoi, occurs in the shallow depths (24.5 m) of the Sea of Japan. Taking advantage of its shallow-water habitat, the first ecological survey of O. mashikoi was performed over a course of 7 years, which revealed that its tentacle-expanding behavior was dependent on the temperature and illuminance of the sea water. Furthermore, there were significantly more O. mashikoi with expanding tentacles during the nighttime than during the daytime, and the prevention of light eliminated these differences in the number of expending tentacles. These results confirmed that the tentacle-expanding behavior is controlled by environmental light signals. Consistent with this, we identified a gene encoding a photoreceptor molecule, neuropsin, in O. mashikoi, and the expression thereof is dependent on the time of day. We assume that the described behavioral response of O. mashikoi to light signals represent an adaptation to a shallow-water environment within the predominantly deep-sea taxon.

Characterization of a Newly Available Coastal Marine Dissolved Organic Matter Reference Material (TRM-0522).

Recent methodological advances have greatly increased our ability to characterize aquatic dissolved organic matter (DOM) using high-resolution instrumentation, including nuclear magnetic resonance (NMR) and mass spectrometry (HRMS). Reliable DOM reference materials are required for further method development and data set alignment but do not currently exist for the marine environment. This presents a major limitation for marine biogeochemistry and related fields, including natural product discovery. To fill this resource gap, we have prepared a coastal marine DOM reference material (TRM-0522) from 45 m deep seawater obtained ∼1 km offshore of Sweden's west coast. Over 3000 molecular formulas were assigned by direct infusion HRMS, confirming sample diversity, and the distribution of formulas in van Krevelen space was typical for a marine sample, with the majority of formulas in the region H/C 1-1.5 and O/C 0.3-0.7. The extracted DOM pool was more nitrogen (N)- and sulfur (S)-rich than a typical terrestrial reference material (SRFA). MZmine3 processing of ultrahigh-performance liquid chromatography (UPLC)-HRMS/MS data revealed 494 resolvable features (233 in negative mode; 261 in positive mode) over a wide range of retention times and masses. NMR data indicated low contributions from aromatic protons and, generally speaking, low lignin, humic, and fulvic substances associated with terrestrial samples. Instead, carboxylic-rich aliphatic molecules were the most abundant components, followed by carbohydrates and aliphatic functionalities. This is consistent with a very low specific UV absorbance SUVA254 value of 1.52 L mg C-1 m-1. When combined with comparisons with existing terrestrial reference materials (Suwannee River fulvic acid and Pony Lake fulvic acid), these results suggest that TRM-0522 is a useful and otherwise unavailable reference material for use in marine DOM biogeochemistry.

Assessment of the stiffened panel performance in the OTEC seawater tank design: Parametric study and sensitivity analysis

Ocean thermal energy conversion (OTEC) is a process of generating electricity by exploiting the temperature difference between warm surface seawater and cold deep seawater. Due to the high static and dynamic pressures that are caused by seawater circulation, the stiffened panel that constitutes a seawater tank may undergo a reduction in ultimate strength. The current paper investigates the design of stiffening systems for OTEC seawater tanks by examining the effects of stiffening parameters such as stiffener sizes and span-over-bay ratio for the applied combined loadings of lateral and transverse pressure by fluid motion and axial compression due to global bending moment. The ultimate strength calculation was conducted by using the non-linear finite element method via the commercial software known as ABAQUS. The stress and deformation distribution due to pressure loads was computed in the first step and then brought to the second step, in which the axial compression was applied. The effects of pressure on the ultimate strength of the stiffener were investigated for representative stiffened panels, and the significance of the stiffener parameters was assessed by using the sensitivity analysis method. As a result, the ultimate strength was reduced by approximately 1.5% for the span-over-bay ratio of 3 and by 7% for the span-over-bay ratio of 6.

Application of deconvolution interferometry to receiver ghost reflection in vertical cable seismic survey

AbstractMarine vertical cable seismic is to probe targets near the submarine with use vertical hydrophone array suspending in deep sea water. Despite imaging of primary reflections from vertical cable seismic data can provide seismic profiles with high resolution, its submarine illumination is much narrower than that of conventional towed‐streamer seismic owing to the irregular geometry. In view of the fact that imaging of multiples can provides better subsurface illumination with fine resolution, we present a strategy for imaging of receiver ghost reflections from vertical cable seismic data, based on seismic interferometry by deconvolution. This method can convert first‐order receiver ghosts into virtual primaries from the towed‐streamer data without velocity model and source‐receiver position. We illustrate the deconvolution interferometry for the receiver ghost reflections with the real vertical cable seismic data in Shenhu area, South China Sea and further obtain virtual primary reflections. Finally, we use these virtual primaries to successfully construct a stacked image and obtain a post‐stack migration image with conventional seismic data process method. This stacked and migrated image significantly extends the submarine illumination with higher resolution and it is useful in characteristics recognition of hydrate‐bearing sediments and free gas.

A baseline for the monitoring of Mediterranean upper bathyal biogenic reefs within the marine strategy framework directive objectives

The Marine Strategy Framework Directive (MSFD, 2018) was adopted to achieve a Good Environmental Status (GES) in the EU's marine waters and to protect resources and ecosystem services, including the deep-sea waters and seafloor. The deep sea (below 200 m) is the largest biome on Earth, and its biodiversity plays a key role, despite being strongly threatened by several anthropogenic stressors, potentially affecting some ecosystem functions. Among the main deep-sea structuring species, the habitat-forming cold-water corals (CWCs) are known to form Vulnerable Marine Ecosystems (VMEs). In the Mediterranean Sea, in the last two decades, a significant effort has been devoted to unveiling the distribution, extension and ecological role of scleractinian CWCs (Madrepora oculata and Desmophyllum pertusum), but quantitative data on their conservation status are very limited. Because of their ecological importance and vulnerability, Italy has extended the implementation of the MSFD to the deep sea, carrying out specific monitoring programmes on these scleractinian CWCs. In this regard, this study established, for the first time, an extensive standardized baseline for national monitoring programmes focusing on two recently discovered upper bathyal areas dominated by scleractinian CWCs (Dohrn Canyon and Corsica Channel). The goal was to evaluate the ecological status of the bathyal biogenic reefs using traditional diversity and impact variables as well as the innovative photogrammetry tool. In both areas, the investigations have increased the knowledge about the extent of the habitat and new CWC assemblages in good health conditions were discovered. The pressure extent is limited with respect to the total extent of the CWC habitat, accounting for approximately 32% and 63% of the fishing-related items entangled on structuring species. The photogrammetric approach showed a deviation of about 33% in the measurement of the population size structures. Moreover, the use of a standardised operative protocol has been proposed to obtain reliable, coherent, and comparable data for future monitoring activities. This approach improved scientific knowledge for the two studied areas and it is pivotal in defining long-term monitoring activities useful to assess the effectiveness of specific protection measures, for these VMEs.

Membranihabitans maritimus sp. nov., a marine bacterium isolated from deep seawater.

A Gram-stain-negative, non-motile, rod-shaped bacterial strain, designated C281T, was isolated from seawater sampled at the Marshallese seamount chain. Results of 16S rRNA gene analysis revealed that strain C281T was most closely related to Membranihabitans marinus CZ-AZ5T with 92.7 % sequence similarity. Phylogenetic analysis indicated that the new isolate represented a novel species by forming a distinctive lineage within the family Saprospiraceae. The DNA G+C content of strain C281T was 38.4 mol%. The genome sizes of strain C281T and the reference strain M. marinus CZ-AZ5T were 5 962 917 and 5 395 999 bp, respectively. The average nucleotide identity and in silico DNA-DNA hybridization values between strains C281T and M. marinus CZ-AZ5T were found to be low (69.3 and 17.6 %, respectively). Different functional genes were found in the genome of strain C281T, such as CZC CBA, polysaccharide utilization loci and linear azol(in)e-containing peptide cluster coding genes. The NaCl range for growth was 0.5-15.0 %. Positive results were obtained for hydrolysis of Tween 60 and urease. MK-7 was the sole respiratory quinone. The major fatty acids were C16 : 1 ω6c and/or C16 : 1 ω7c, iso-C15 : 0 and iso-C15 : 1 F. The major polar lipids of strain C281T were phosphatidylethanolamine, phosphatidylglycerol, two unidentified lipids and five unidentified glycolipids. On the basis of its taxonomic characteristics, the isolate represents a novel species of the genus Membranihabitans, for which the name Membranihabitans maritimus sp. nov. (type strain C281T=KCTC 92171T=MCCC M27001T) is proposed.

A Combination of Deep-Sea Water and Fucoidan Alleviates T2DM through Modulation of Gut Microbiota and Metabolic Pathways

Fucoidan and deep-sea water (DSW) are attractive marine resources for treating type 2 diabetes (T2DM). In this study, the regulation and mechanism associated with the co-administration of the two were first studied using T2DM rats, induced by a high fat diet (HFD) and streptozocin (STZ) injection. Results demonstrate that, compared to those with DSW or FPS alone, the orally administered combination of DSW and FPS (CDF), especially the high dose (H-CDF), could preferably inhibit weight loss, decrease levels of fasting blood glucose (FBG) and lipids, and improve hepatopancreatic pathology and the abnormal Akt/GSK-3β signaling pathway. The fecal metabolomics data show that H-CDF could regulate the abnormal levels of metabolites mainly through the regulation of linoleic acid (LA) metabolism, bile acid (BA) metabolism, and other related pathways. Moreover, H-CDF could adjust the diversity and richness of bacterial flora and enrich bacterial groups, such as Lactobacillaceae and Ruminococcaceae UCG-014. In addition, Spearman correlation analysis illustrated that the interaction between the gut microbiota and BAs plays an essential role in the action of H-CDF. In the ileum, H-CDF was verified to inhibit activation of the farnesoid X receptor (FXR)-fibroblast growth factor 15 (FGF15) pathway, which is regulated by the microbiota-BA-axis. In conclusion, H-CDF enriched Lactobacillaceae and Ruminococcaceae UCG-014, thereby changing BA metabolism, linoleic acid metabolism, and other related pathways, as well as enhancing insulin sensitivity and improving glucose and lipid metabolism.

Laboratory investigation of the effect of the pore pressure on argillaceous siltstone permeability

The permeability of argillaceous siltstone is a critical parameter for the sustainable development of natural gas hydrates in the ocean beds. In the laboratory, the pressure pulse method is frequently used to measure permeability. However, the influence of pore pressure on permeability test results of argillaceous siltstone by pulse method is not established, resulting in inconsistencies between permeability test results in the laboratory and those in deep seawater (water depth ≥ 500 m). First, the effect of bound gas content in argillaceous siltstone on the rate of volume change in the test medium is considered, and the computation model of the pressure pulse method is validated. Next, the effect of pore pressure on the permeability of argillaceous siltstone is investigated while keeping the effective stress of the sample constant. The experimental results show that as pore pressure increases, the permeability of argillaceous siltstone increases gradually. The permeability measured in a 6 MPa pressure environment is two orders of magnitude greater than that measured in a 1 MPa pressure environment and the increased range is piecewise linear. The reasons for the increased permeability are investigated using the hydrophilicity of the argillaceous siltstone materials. Under high pressure, the hydrophobic properties of montmorillonite, quartz and kaolinite reduce the seepage resistance of argillaceous siltstone. The experimental results will serve as a foundation for future research, improving the accuracy of argillaceous siltstone permeability estimates.

Unveiling the Role of In Situ Sulfidation and H2O Excess on H2S Decomposition to Carbon-Free H2 over Cobalt/Ceria Catalysts

The emerging energy and environmental concerns nowadays are highlighting the need to turn to clean fuels, such as hydrogen. In this regard, hydrogen sulfide (H2S), an abundant chemical compound found in several natural sources and industrial streams, can be considered a potential carbon-free H2 source through its decomposition. In the present work, the H2S decomposition performance of Co3O4/CeO2 mixed oxide catalysts toward hydrogen production is investigated under excess H2O conditions (1 v/v% H2S, 90 v/v% H2O, Ar as diluent), simulating the concentrated H2S-H2O inflow by the Black Sea deep waters. The effect of key operational parameters such as feed composition, temperature (550–850 °C), and cobalt loading (0–100 wt.%) on the catalytic performance of Co3O4/CeO2 catalysts was systematically explored. In order to gain insight into potential structure-performance relationships, various characterization studies involving BET, XRD, SEM/EDX, and sulfur elemental analysis were performed over the fresh and spent samples. The experimental results showed that the 30 wt.% Co/CeO2 catalyst demonstrated the optimum catalytic performance over the entire temperature range with a H2 production rate of ca. 2.1 μmol H2∙g−1·s−1 at 850 °C and a stable behavior after 10 h on stream, ascribed mainly to the in-situ formation of highly active and stable cobalt sulfided phases.

Drainage integration of small endorheic basins at the Pleistocene-Holocene transition: An example from southern Italy

The drainage integration of three Late Pleistocene intramontane basins located in the southern Italian Apennines was reconstructed by integrating information derived from geomorphic, structural, and stratigraphic analyses. The Santaloja (SLJ), Lago (LG), and Pantani (PN) basins are located in the axial zone of the Apennines fold-and-thrust belt where they mainly comprise Mesozoic to Cenozoic deep-sea water siliceous and calcareous rocks. The Quaternary development of these intramontane basins draining the Basento River catchment provides an example of drainage evolution within collisional mountain belts and its tectonic and climatic controlling mechanisms. Tectonically, sets of NW-SE- and NE-SW-trending faults formed a large trough with ensuing river valley development configured to synclinal folds. The ongoing interplay of these active and passive tectonic controls lead to compartmentalisation into three endorheic basins. Uncalibrated radiocarbon dating of peat layers from boreholes reveals that lacustrine facies conditions prevailed during the Late Pleistocene, spanning 34,785 to 41,325 ka during Marine Isotope Stage 3. Morphometric analysis suggests that these endorheic lacustrine basins subsequently became integrated via overspill from 13.25 kyr calBC onwards linked to Late Pleistocene climatic changes creating the Basento River. Within the axial zone of the southern Apennines, tectonically driven headwards erosion is commonly attributed to lengthening of major rivers like the Basento River. However, this study demonstrates a more complex interplay between tectonics and climate change for intramontane basin development and its drainage evolution.

Direct Production of Bio-Recalcitrant Carboxyl-Rich Alicyclic Molecules Evidenced in a Bacterium-Induced Steroid Degradation Experiment.

Carboxyl-rich alicyclic molecules (CRAM) are highly unsaturated compounds extensively distributed throughout aquatic environments and sediments. This molecular group is widely referred to as a major proxy of recalcitrant organic materials, but its direct biosynthesis remains unclear. Steroids are a typical anthropogenic contaminant and have been previously suggested to be precursors of CRAM; however, experimental evidence to support this hypothesis is lacking. Here, a steroid-degrading bacterium, Comamonas testosteroni ATCC 11996, was incubated in a liquid medium supplemented with testosterone (a typical steroid) as the sole carbon source for 90 days. Testosterone-induced metabolites (TIM) were extracted for molecular characterization and to examine the bioavailability during an additional 90-day incubation after inoculation with a natural coastal microbial assemblage. The results showed that 1,775 molecular formulas (MFs) were assigned to TIM using ultrahigh-resolution mass spectrometry, with 66.99% categorized as CRAM-like constituents. A large fraction of TIM was respired or transformed during the additional 90-day seawater incubation; nevertheless, 638 MFs of the TIM persisted or increased during incubation. Among the 638 MFs, 394 were commonly assigned in natural deep seawater samples (depths of 500 to 2,000 m) from the South China Sea. Compared to the catabolites of the well-established testosterone degradation pathway, we compiled a list of bio-refractory MFs and potential chemical structures, some of which shared structural homology with CRAM. These results demonstrated direct microbial production of bio-refractory CRAM from steroid hormones and indicated that some of the biogenic CRAM resisted microbial decomposition, potentially contributing to the aquatic refractory dissolved organic matter (DOM) pool. IMPORTANCE CRAM are an operationally defined DOM group comprising a complex mixture of carboxylated and fused alicyclic structures. This DOM group is majorly characterized as refractory DOM in the marine environment. However, the origins of the complex CRAM remain unclear. In this study, we demonstrated that testosterone (a typical steroid) could be transformed into bio-refractory CRAM by a single bacterial strain and observed that some of the CRAM highly resisted microbial degradation. Through molecular comparison and screening, potential chemical structures of steroid-induced CRAM were suggested. This study established the biological connection between steroids and bio-refractory CRAM, and it provides a novel perspective explaining the fate of terrestrial contaminants in aquatic environments.

Re-appearance of precipitated aragonite crystal fans as evidence for expansion of oceanic dissolved inorganic carbon reservoir in the aftermath of the Lomagundi-Jatuli Event

The initial accumulation of atmospheric oxygen is marked by the unprecedented positive δ13Ccarb excursions of the Lomagundi-Jatuli Event (LJE) and records an interval of abnormal O2 production through elevated rates of organic carbon burial. Emerging evidence suggests that the post-LJE atmosphere-ocean system might have suffered a significant deoxygenation. These dynamic perturbations in the oceanic redox state and biogeochemical cycles would have led to fundamental changes in carbonate precipitation dynamics. Here, we report the discovery of centimeter-sized crystal fans in the post-LJE Huaiyincun Formation, Hutuo Supergroup in the North China Craton. The hexagonal cross-sections and square terminations suggest that these fan-like dolomitic structures were originally aragonite crystal fans (ACF). Variations of stromatolite morphology and frequent occurrences of storm-related deposits in the Huaiyincun Formation point to repeated cycles of sea level changes. The bedding-parallel distribution of the ACF and the homogeneous δ13C values of the ACF-bearing dolostones are consistent with a primary depositional origin for the ACF. An updated compilation of published records of ACF throughout geological history highlights a clear absence of ACF from the initiation of the Paleoproterozoic Great Oxidation Event until the end of the LJE, and a global reappearance of ACF in the post-LJE late Paleoproterozoic. We propose that the reappearance of ACF is in agreement with the expansion of the oceanic dissolved inorganic carbon reservoir. At the same time, consumption of dissolved oxygen during the oxidation of organic matter might have been stimulated by ferruginous deep seawater, facilitating the formation of Huiayincun ACF.

Reproductive biology of the two main reef-building cold-water coral species (Desmophyllum pertusum and Madrepora oculata) in the Mediterranean Sea

Although cold-water coral (CWC) biology, physiology, and connectivity, have been extensively studied, few studies have so far focused on their reproductive biology. The reproductive biology of colonies of the reef-building Lophelia pertusa (Linnaeus 1758), now synonymised as Desmophyllum pertusum, and Madrepora oculata (Linnaeus 1758) from the Mediterranean Sea, an area particularly exposed to the effects of anthropogenic pressures, was investigated for the first time using histological techniques. Samples were collected from the Lacaze-Duthiers canyon in the Gulf of Lion, northwestern Mediterranean Sea, where the corals are living at 13 °C, close to their upper limit of thermal tolerance. The gametogenic cycle suggests a seasonal spawning of D. pertusum in autumn to early winter, similarly to population from the Gulf of Mexico. This period corresponds to the formation of storm-induced deep-sea water plumes, likely acting as a time giver for coral spawning and facilitates larval dispersal. Madrepora oculata shows continuous reproduction as already identified in eastern and western North Atlantic, with reproductive features of a species less opportunistic than D. pertusum, consistent with its other biological characteristics. This difference between the two species is of paramount importance to define strategies of conservation.

Hydrodynamic Analysis of Rigid-Flexible Composite Structure of Large Aquaculture Platform Subjected to Waves

Deep-sea aquaculture cages have an important role in the marine fishery development process. With the increase of the sea depth, the sea conditions will be worse, as waves ups and downs, the stability performance of the cages decreases obviously. As the deep sea water is far away from the land, the environment is complex and changeable and the poor mobility of the system, all these factors can bring great economic losses to the aquaculture practitioners. Compared to the traditional cage system, the large aquaculture platform is more prominent. The aquaculture platform is composed of flexible bodies and slender rigid components. As the flexible bodies and the slender rigid components are coupled with each other, the response of the whole system is very complicated. For such a complex ocean system structure, the numerical simulation in the initial design stage can greatly speed up the design process and save many experimental resources. The aquaculture platform has been discretized into a lumped mass model based on the unique properties of a particular sea state and an aquaculture platform, and OrcaFlex has developed a dynamic simulation approach based on those parameters. With the change of the wave direction, the real-time response of the 6.8 thousand tons aquaculture platform under different wave directions has been realized. The dynamic response of the mooring system under different wave directions is obtained. The findings offer a theoretical foundation for the optimal aquaculture platform design.

A performance study of R717 and R22 as the working fluid for OTEC plant

The purpose of this paper is to compare the thermal efficiency of an ocean thermal energy conversion (OTEC) cycle using R717 and R22 working fluids. An OTEC system typically operates at the temperature difference between the average warm surface seawater of 30 °C and the cold deep seawater of 8 °C. The temperature difference will then power a turbine to produce electricity. R22 and R717 are two potential working fluids to be used in the OTEC cycle to absorb heat due to their saturation temperature. However, R22 is associated with higher global warming potential and the global warming potential (GWP) of 1,760, compared to R717 with zero GWP. The study shows that the thermal efficiency of R22 is 0.211% higher than R717. Moreover, the thermal power required by the water circuit to cool/heat the OTEC circuit for R717 is 13% higher than R22. However, the required working fluid flow rate of the R717 system is 81.5% lower than R22, making the former significantly smaller in size.

Optimization of environmental DNA analysis using pumped deep-sea water for the monitoring of fish biodiversity

Deep-sea ecosystems present difficulties in surveying and continuous monitoring of the biodiversity of deep-sea ecosystems because of the logistical constraints, high cost, and limited opportunities for sampling. Environmental DNA (eDNA) metabarcoding analysis provides a useful method for estimating the biodiversity in aquatic ecosystems but has rarely been applied to the study of deep-sea fish communities. In this study, we utilized pumped deep-sea water for the continuous monitoring of deep-sea fish communities by eDNA metabarcoding. In order to develop an optimum method for continuous monitoring of deep-sea fish biodiversity by eDNA metabarcoding, we determined the appropriate amount of pumped deep-sea water to be filtered and the practical number of filtered sample replicates required for biodiversity monitoring of deep-sea fish communities. Pumped deep-sea water samples were filtered in various volumes (5–53 L) at two sites (Akazawa: pumping depth 800 m, and Yaizu: pumping depth 400 m, Shizuoka, Japan) of deep-sea water pumping facilities. Based on the result of evaluations of filtration time, efficiency of PCR amplification, and number of detected fish reads, the filtration of 20 L of pumped deep-sea water from Akazawa and filtration of 10 L from Yaizu were demonstrated to be suitable filtration volumes for the present study. Fish biodiversity obtained by the eDNA metabarcoding analyses showed a clear difference between the Akazawa and Yaizu samples. We also evaluated the effect of the number of filter replicates on the species richness detected by eDNA metabarcoding from the pumped deep-sea water. At both sites, more than 10 sample replicates were required for the detection of commonly occurring fish species. Our optimized method using pumped deep-sea water and eDNA metabarcoding can be applied to eDNA-based continuous biodiversity monitoring of deep-sea fish to better understand the effects of climate change on deep-sea ecosystems.

Performance Evaluation of Control Compatibility for an OTEC Pump Shutdown Condition

South Korea is currently in the preparatory stage of commercializing an ocean thermal energy conversion (OTEC) system, as the demonstration of a 1 MW scale OTEC system has been accomplished. However, the commercialization of OTEC requires the establishment of a control system for various environmental changes. Therefore, pre-emptive identification of the system’s risk factors and the process of analyzing the impact of the system, building control items, and optimizing control are necessary. This study aims to establish and analyze an optimized control system for MW-scale OTEC risk factors, such as the shutdown of seawater or refrigerant pumps. The selected OTEC system was designed for 1070 kW class facilities, with a 36.6% portion of total electricity usage by the seawater pump and refrigerant pump. As a result, an on/off control system was adopted in order to eliminate the risk factors. By adjusting this option, dry operation of the refrigerant pump, water hammering, and liquid inflow into the turbine were successfully prevented. To be more specific, the initial system was to be shut down due to a sharp decrease in power at the point where the deep seawater flow rate was 538 kg/s (35.7% of max flow rate) and the surface seawater flow rate was 715 kg/s (38.4% of max flow rate). This situation was improved by adopting parallel operation of seawater pumps and on/off control, thereby leading to a more stabilized operation by maintaining a flow rate of over 1864 kg/s for surface seawater and 1507 kg/s for deep seawater. Moreover, it was confirmed that the flow rate of the pump was reduced by 1.89 kg/s per second in the process of pump shutdown during a single operation mode of the refrigerant pump. Parallel operation made it possible to maintain 60.2% of the output by increasing the power of the second pump’s flow rate in the event of the first pump shutting down. The final seawater temperature differential power generation model derived from this study consists of two refrigerant pumps and two surface seawater and deep seawater pumps in order to prevent system shutdown caused by a single pump failure. The final design was reflected in the final delivery to Kiribati, which is located near the equator.

Presence, Sources and Transport of Polycyclic Aromatic Hydrocarbons in the Arctic Ocean

AbstractPolycyclic aromatic hydrocarbons (PAHs) are continuously released from multiple sources and are prone to long‐range transport. Little is known regarding their presence, transport and fate in remote and deep oceans. Polyethylene passive samplers were hence deployed at deep moorings and surface seawater in the Fram Strait and Canadian Archipelago, as well as in air and surface water of the lower Great Lakes, a potential high‐emission region, to understand the transport of PAHs to the Arctic. Dissolved PAHs showed significantly higher concentrations in the lower Great Lakes than those in the high Arctic. Concentrations of dissolved PAHs (Σ19PAHs) ranged from 33 to 300 pg/L in the Fram Strait; the vertical profiles generally exhibited a decreasing trend toward deep waters, which was potentially influenced by hydrological and biogeochemical processes. PAHs were exported from the Arctic Ocean to the North Atlantic through the Fram Strait and the Davis Strait.

Deep Sea Water Inhibited Pancreatic β-Cell Apoptosis and Regulated Glucose Homeostasis by Affecting Lipid Metabolism in Db/Db Mice

Deep sea water (DSW) is a natural resource rich in minerals, which participates in biological processes such as energy metabolism, regulates serum glucose and lipids levels, and has a certain protective effect on endocrine and metabolism-related diseases. Studies have shown that the improvement of glucose tolerance in diabetic mice by DSW may be associated with the protective effect on the structure and function of pancreatic islets, and the specific mechanism is still unclear. Other studies have shown that long-term exposure to high concentrations of fatty acids can lead to apoptosis and dysfunction of pancreatic β-cell, increasing the risk of type 2 diabetes mellitus (T2DM). Down-regulation of plasma fatty acid levels may reduce pancreatic β-cell dysfunction, thereby improving glucose homeostasis. Understanding the specific mechanism of DSW regulating blood glucose is of great significance for its clinical application. In the present study we used db/db mice as a T2DM model and treated mice with deep ocean mineral concentration (DOMC, a commercial product of DSW) for 4 and 12 weeks. Basic information, serum biochemical indicators, and pathological tissues were gathered for exploration. The db/db mice treated with 4 weeks' DOMC (db/db+DOMC) showed decreased plasma cholesterol and triglyceride levels. Tests implied that in adipose tissues, the db/db+DOMC group's lipolysis process was inhibited, and the β-fatty acid oxidation process was promoted. Besides, DOMC reduced lipogenesis and encouraged β-oxidation in the liver, as a result, improved fatty liver in db/db mice. Further measurements showed DOMC improved glucose homeostasis slightly in db/db animals after a 12-week treatment by preventing pancreatic β-cell apoptosis. DOMC inhibited pancreatic β-cell apoptosis and regulated glucose homeostasis in db/db mice by lowering the lipid levels via regulation of fatty acid β-oxidation, lipolysis, and lipogenesis processes.

Comparison of electrochemical corrosion performance of eutectic Al-Si automotive alloy in deep seawater and 3.5% NaCl solution

The corrosion of aluminium silicon alloys is of vital importance, as they are frequently exposed to corrosive environments. The alloy is often exposed to seawater in marine applications, and despite having NaCl, the seawater contains some other ions. The purpose of this study is to compare the electrochemical corrosion performance of eutectic Al-Si alloys in seawater with 3.5% NaCl in order to understand the effects of those additional components, and an alloy with trace silicon is also considered for comparison. Electrochemical impedance spectroscopy (EIS) and Tafel polarization methods were implemented for the corrosion analysis. The results of these methods imply that the eutectic alloy is more resistant to corrosion in seawater than in NaCl solution. Some additional elements in seawater produce protective layers on the alloy surface, shielding the alloy from corrosion in seawater. The open circuit potential is shifted towards the nobler direction for the eutectic alloy than in the trace Si-added alloy. The eutectic alloy's corrosion rate and current (Icorr) are higher. Mg2Si precipitates in the eutectic alloy, forming oxide films of MgO and SiO2, protect the alloy from further corrosion. The alloys' surface morphologies were analyzed not only by optical microscope but also by scanning electron microscope. The photos depict reduced damage on the surfaces corroded in the seawater environment compared to the NaCl solution environment. The Si phases are discernable in these images. Additional demolishment and pit formations are identified on the surfaces of the eutectic alloy from SEM inspection. Fewer pits and damages are observed in the case of seawater environments. The EDS analysis shows a higher amount of oxygen for the alloy corroded in NaCl solution, supporting the phenomenon of more damage than in seawater.