Seawater Research Articles

Antifouling activity of PEGylated chitosan coatings: Impacts of the side chain length and encapsulated ZnO/Ag nanoparticles

PEGylation is regarded as a common antifouling strategy and the effect is normally linked with surface hydrophilicity of the coatings. Herein, the biopolymer chitosan (CS) was grafted by polyethylene glycol (PEG) of different chain lengths (molecular weight 200, 4 k and 100 k Da) to verify if the hydrophilicity of CS-PEG coatings is crucial in determining antifouling activities and if PEG chain length influences biofouling in marine environment. Properties of copolymers such as melting points and crystallinity are affected by grafting PEG. The water contact angle (WCA) of CS-PEG coatings increases with the chain length of grafted PEG, from 27° to 58°. Photocatalyst of zinc oxide-silver (ZnO/Ag) was also studied and its embedment (2 % to CS-PEG) renders the surface of CS-PEG coatings more hydrophobic with WCA increased from 52° to 86°. Antibacterial, anti-diatom, and anti-biofilm activities of the coatings were evaluated in natural sea water. The bacterial density on CS-PEG coatings was dramatically reduced to 4 × 104 compared to the control of 7 × 104 ind/mm2, and further to 2 × 104 for CS-PEG-ZnO/Ag coatings. CS-PEG coatings also strongly inhibit diatoms (120–200 ind/mm2), but the inclusion of ZnO/Ag did not obviously enhance such effect (50–150 ind/mm2). The findings provide useful insights for designing polymer-based antifouling coatings.

Characterizing and Implementing the Hamamatsu C12880MA Mini-Spectrometer for Near-Surface Reflectance Measurements of Inland Waters.

In recent decades, inland water remote sensing has seen growing interest and very strong development. This includes improved spatial resolution, increased revisiting times, advanced multispectral sensors and recently even hyperspectral sensors. However, inland waters are more challenging than oceanic waters due to their higher complexity of optically active constituents and stronger adjacency effects due to their small size and nearby vegetation and built structures. Thus, bio-optical modeling of inland waters requires higher ground-truthing efforts. Large-scale ground-based sensor networks that are robust, self-sufficient, non-maintenance-intensive and low-cost could assist this otherwise labor-intensive task. Furthermore, most existing sensor systems are rather expensive, precluding their employability. Recently, low-cost mini-spectrometers have become widely available, which could potentially solve this issue. In this study, we analyze the characteristics of such a mini-spectrometer, the Hamamatsu C12880MA, and test it regarding its application in measuring water-leaving radiance near the surface. Overall, the measurements performed in the laboratory and in the field show that the system is very suitable for the targeted application.

Tribological characteristics of graphene nanoplatelets-filled PTFE under dry sliding and sea water environmental conditions

This study focuses on enhancing the tribological performance of polytetrafluoroethylene (PTFE) composites by incorporating graphene nanoplatelets (GNPs) through compression moulding technique. The main aim of the research was to investigate how varying weight percentages of GNP (1 wt %, 3 wt % and 5 wt %) influence the friction and wear properties of PTFE composites under both dry sliding and saline water environment. A significant reduction in the coefficient of friction (COF) and wear rate was observed with the addition of GNP, particularly in seawater. Specifically, the reduction of COF in sea water reached up to 58.765% with 3% of GNP compared to dry sliding. For wear reduction, a reduction of up to 90.247% was observed with 5% GNP in sea water condition. These findings reveal the potential of GNP-filled PTFE composites in applications requiring enhanced tribological properties in both dry and aqueous environments. The originality of this work lies in the comprehensive analysis of the environmental influence on GNP-filled PTFE composites, providing understandings of their applicability in marine environments.

Environmental salinity differentiates responses to acute hypothermal stress in milkfish

Global warming has led to an increase in the frequency of cold extremes, causing significant economic losses in aquaculture, particularly in subtropical regions. Milkfish (Chanos chanos) holds significant importance in aquaculture within subtropical Asian regions. Despite milkfish's ability to tolerate varying salinity levels, frequent cold snaps associated with extreme weather events have caused substantial mortality. Understanding the molecular and cellular mechanisms underlying cold stress-induced cell death is crucial for developing effective strategies to mitigate such losses. Given the pivotal role of the liver in fish physiology, we established a primary milkfish hepatocyte culture demonstrating robust proliferation and expressing a unique marker leptin A. The molecular characterization of cold-treated hepatocytes at 18 °C showed that the mRNA levels of superoxide dismutase (sod1) and catalase (cat), responsible for neutralizing reactive oxygen species (ROS), were downregulated in freshwater (FW) conditions, while cat expression was upregulated in seawater (SW) conditions. This differential modulation of ROS signaling implies distinct responses in FW and SW, leading to higher ROS levels and increased cell death in FW condition compared to those in SW. Transcriptomic analysis of liver tissues from milkfish reared in FW or SW, with or without cold stress, revealed distinct gene expression patterns. Although cold stress affected a common set of genes in both FW and SW conditions, SW-specific cold responsive genes are associated with metabolic pathways while FW-specific genes were linked to cell proliferation pathways. Notably, gene set enrichment analysis highlighted the downregulation of cytochrome-related genes, a major source of ROS production, in response to cold stress in SW. In summary, our study unveils an insightful mechanism whereby the salinity of SW counteracts cold stress-induced ROS signaling, emphasizing the feasibility and practicality of preconditioning fish in SW as a preventive measure against cold stress-induced mortality.

Photocatalytic removal of aldrin and dieldrin using graphene oxide and TiO2‐doped CuFe2O4

AbstractBACKGROUNDConventional treatment processes and existing photocatalysts have proven insufficient in efficiently removing aldrin and dieldrin. Consequently, this study aimed to investigate the removal of aldrin and dieldrin from surface water using a titanium dioxide/graphene oxide/copper ferrite (TiO₂/GO/CuFe₂O₄) nanocomposite.RESULTSThe highest photodegradation efficiencies for aldrin (100%) and dieldrin (99%) were achieved with a TiO₂/GO/CuFe₂O₄ nanocomposite dosage of 1.3 mg L−1, at a sunlight intensity of 9 W m−2 and an optimal photodegradation time of 25 min. The maximum UV absorption wavelength of the TiO₂/GO/CuFe₂O₄ nanocomposite was observed at 365 nm. The quantum yield of the nanocomposite was recorded as 2.69 × 102 mol einstein−1, and its bandgap energy was determined to be 3.31 eV. The first‐order kinetic rate constants for aldrin and dieldrin were calculated as 0.05 and 0.047 min−1, respectively. X‐ray diffraction analysis confirmed the crystal structure of CuFe₂O₄/TiO₂, while Fourier transform infrared spectroscopy detected carboxylic, epoxy, carbonyl and other oxygenated groups within the TiO₂/GO/CuFe₂O₄ nanocomposite. Scanning electron microscopy and transmission electron microscopy images revealed that CuFe₂O₄ was situated on the outer layer of GO. Energy‐dispersive X‐ray analysis identified the elemental composition of the TiO₂/GO/CuFe₂O₄ nanocomposite as comprising GO, C, Cu, Fe, Ti and O. A reusability study demonstrated that the nanocomposite maintained excellent performance, achieving 99% removal efficiency after 79 cycles and 97% after 100 cycles.CONCLUSIONSThe TiO₂/GO/CuFe₂O₄ nanocomposite effectively removed aldrin and dieldrin from surface water. This nanocomposite holds promise for the remediation of other aquatic ecosystems, such as bays, rivers and ocean waters. © 2024 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

You can bring plankton to fecal indicator organisms, but you cannot make the plankton graze: particle contribution to E. coli and MS2 inactivation in surface waters.

Organisms that are associated with feces ("fecal indicator organisms") are monitored to assess the potential for fecal contamination of surface water bodies in the United States. However, the effect of the complex mixtures of chemicals and the natural microbial community within surface water ("particles") on fecal indicator organism persistence is not well characterized. We aimed to better understand how particles, including biological (e.g., potential grazers) and inert (e.g., minerals) types, affect the fecal indicator organisms Escherichia coli K-12 ("E. coli") and bacteriophage MS2 in surface waters. A gradient of particles captured by a 0.2-µm-pore-size filter ("large particles") was generated, and the additional particles and dissolved constituents that passed through the filter were deemed "small particles." We measured the ratio of MS2 and E. coli that survived over a 24-h incubation period for each condition (0%-1,000% large-particle concentration in raw water) and completed a linear regression that included large- and small-particle coefficients. Particles were characterized by quantifying plankton, total bacterial cells, and total solids. E. coli and MS2 persistence was not significantly affected by large particles, but small particles had an effect in most waters. Small particles in higher-salinity waters had the largest, negative effect on E. coli and MS2 survival ratios: Significant small-particle coefficients ranged from -1.7 to -5.5 day-1 in the marine waters and -0.89 to -3.2 day-1 in the fresh and estuarine waters. This work will inform remediation efforts for impaired surface water bodies.IMPORTANCEMany surface water bodies in the United States have organisms associated with fecal contamination that exceed regulatory standards and prevent safe recreation. The process to remediate impaired water bodies is complicated because these fecal indicator organisms are affected by the local environmental conditions. For example, the effect of particles in surface water on fecal indicator concentrations are difficult to quantify in a way that is comparable between studies and water bodies. We applied a method that overcomes this limitation to assess the effects of large particles, including natural plankton that could consume the seeded fecal indicator organisms. Even in environmental water samples with diverse communities of plankton present, no effect of large particles on fecal indicator concentrations was observed. These findings have implications for the interpretation and design of future studies, including that particle characterization of surface water may be necessary to assess the fate of fecal indicators.

Chaos analysis and traveling wave solutions for fractional (3+1)-dimensional Wazwaz Kaur Boussinesq equation with beta derivative

Wazwaz Kaur Boussinesq (WKB) equation can effectively simulate the behavior of water waves in shallow water, including the nonlinear effect and dispersion phenomenon of waves, which is of great significance for understanding the dynamic process of ocean, river and other water bodies. To enrich the wave equation theory, the (3+1)-dimensional integer order derivative of WKB equation is changed to the fractional one with beta derivative. The current work deals with the fractional (3+1)-dimensional WKB equation for discussing its chaotic behavior and establishing some new analytic solutions. The chaotic properties of the equation are verified by the trend of evolution along with time, Lyapunov exponents and initial sensitivity analysis. And then complete discrimination system for polynomial method is applied to derive some trigonometric, hyperbolic, Jacobi elliptic and other solutions. The graphical demonstrations are provided for part of these solutions. From these visualized graphs, the solitary, periodic and quasi-periodic wave are shown and the effect of fractional derivatives on the equation can be seen intuitively.

Enhancing compressive behaviour of seawater sea sand concrete filled hybrid carbon-glass FRP tubes exposed to seawater: Effect of thickness

This study presents a novel investigation into the impact of tube thickness on the residual compressive strength of sea water sea sand concrete (SWSSC) filled filament wound hybrid fibre-reinforced polymer (HFRP) tubes, positioning them as innovative alternatives to traditional concrete-filled steel tubes in corrosive marine environments. The research explores tube thicknesses of 2 mm, 3 mm, and 4 mm, employing a unique hybrid configuration of 50 % carbon fibre reinforced polymer (CFRP) internal layers and 50 % glass fibre reinforced polymer (GFRP) external layers. This study examines the effect of these configurations on compressive mechanical properties, microstructural characteristics, and damage progression under alkaline and seawater conditions. Additionally, the research evaluates cross-ply and hoop orientations as variables in filament winding fibre orientation. A comprehensive set of 108 hybrid tubes were filled with an alkaline solution to simulate the SWSSC environment and exposed to seawater at varying temperatures and durations. Accelerated aging experiments were conducted in the laboratory to assess the long-term compressive performance of SWSSC-filled HFRP tubes exposed to seawater. Long-term compressive strength predictions were made using the Arrhenius theory, based on short-term accelerated aging data. The accelerated test data revealed maximum compressive strength reductions of 33 %, 15 %, and 17 % for 2 mm, 3 mm, and 4 mm cross-ply HFRP tubes, respectively, after 150 days of exposure at 60 °C. For hoop HFRP tubes, the corresponding reductions were 19 %, 18 %, and 17 %. Thicker tubes (3 mm and 4 mm) with sufficient internal CFRP layers protect external GFRP layers from alkaline damage, akin to pure CFRP tubes. Thinner tubes (2 mm) exhibit similar performance to GFRP tubes as alkaline damage spreads from their less substantial internal CFRP layers to the outer GFRP layers. For cross-ply tubes, the recommended strength reduction factors are 0.6 for 2 mm, 0.8 for 3 mm, and 0.8 for 4 mm thicknesses. For hoop tubes, the suggested factors are 0.7 for 2 mm, 0.7 for 3 mm, and 0.8 for 4 mm thicknesses. This study shows the innovative potential of tailored hybrid HFRP tubes in enhancing the durability and performance of marine infrastructure.

Gaps in legislation and communication identified as stakeholders reflect on 30×30 policy in Icelandic waters

Other Effective Conservation Measures (OECMs) recognize that various forms of management actions can contribute to biodiversity conservation. OECMs have been criticized for ambiguity, lack of criteria for evaluation and, thereby, inconsistent implementation. Nevertheless, many coastal states aim to evaluate current management actions as candidates for OECMs and count them toward numerical biodiversity conservation goals. Successful implementation requires careful examination of biodiversity benefits and estimation of the social impacts of such actions. There are numerous fisheries restricted areas within the Icelandic Exclusive Economic Zone, some with designated biodiversity conservation goals, whereas the Icelandic Act of Nature Conservation (60/2913) has rarely been used in marine waters. In the current study, complementary methods are used to broadly examine stakeholder views on the efficiency of current legislation, and future policy, to achieve numerical goals on biodiversity conservation. Despite documenting broad willingness of stakeholders to protect ocean space, gaps in legislation and communication are identified both through survey responses and in interviews with key informants. As a first study to document stakeholder perceptions on using fisheries legislation for the purpose of biodiversity conservation, the results have relevance for future policy on reporting fisheries legislation as OECMs, understanding stakeholder perceptions on different actions and, finally, to inform policy on stakeholder involvement, and outreach campaigns, as governments move forward to meet marine conservation goals.

The enhanced performance of NaFe2PO4(SO4)2/C electrode materials in the desalination of brackish water by capacitive deionization

In this study partial substitution of phosphates in Na3Fe2(PO4)3/C (NFP/C) by sulphates to prepare Na2Fe2(PO4)2SO4 (NFP2S/C) and NaFe2PO4(SO4)2/C (NFPS/C) was carried out by dissolution-evaporation method. The idea is to adjust the properties of NFP/C owing to the differences in the inductive effect and sizes of sulphates and phosphates which results the obtained NFPS/C to record excellent electrochemical and desalination performance. Several characterization techniques used to analyse the synthesized materials confirm the successful doping and structure integrity. Electrochemical study reveals NFPS/C to exhibit the highest capacitance of 127.4 F/g when scanned at 10 mV/s. The results show that when the potential of 1.2 V is applied to desalinate 500 mg/L salt solution the salt removal of about 17.3 mg/g is achieved by NFPS/C while NFP/C attaining 9.8 mg/g. The NFPS/C was then tested in the desalination of real Ocean water and promising results obtained. The salt removal performance presented makes the developed materials promising for application in brackish water desalination by capacitive deionization.

Microbial source tracking and identification of fecal contamination patterns in saltwater estuaries between base- and storm-flow events using dual genome-based approaches

Fecal contamination from natural and anthropogenic sources poses significant threats to saltwater estuaries, particularly after storms or heavy rainfall. Monitoring fecal contamination is essential for protecting these vulnerable ecosystems having important ecological and economic values. In this study, we investigated the abundance, sources, and potential causes of fecal contamination at three marine and seven freshwater stations across Vaughn Bay (WA, USA), a shellfish growing district, during base- and storm-flow events. Additionally, we evaluated the performance of fecal indicator bacteria (FIB) quantification, optical brightener assessment, and qPCR analysis for fecal contamination quantification. We compared the effectiveness of qPCR-based microbial source tracking (MST), which targeted a broad range of hosts including, such as humans, birds, cows, horses, ruminants, dogs, and pigs, with sequencing-based MST in identifying fecal contamination sources. Both MST analysis approaches identified birds and humans as the primary sources of fecal contamination. For marine water stations, freshwater creeks VBU001, VBU002, and VB047, along with drain VB007, were identified as the main sources of human-derived fecal contamination in Vaughn Bay, based on Kendall's tau analysis (τ: 0.58–0.97). This information indicates that the septic systems in the catchment areas of these creeks and drains require further investigation to achieve effective fecal contamination control. Optical brightener, FIB enumeration and qPCR quantification results were generally higher during storm-flow events, although they showed poor correlation with each other (Pearson r < 0.40), likely due to physiological and phylogenetic differences among the target organisms of these methods. However, the sequencing-based method faces challenges in precise quantitative identification of differences in fecal contamination between base- and storm-flow events. Due to its high-throughput and cost-effectiveness, we recommend using sequencing-based analysis for large-scale identification of the primary sources of fecal contamination in water environments, followed by targeted qPCR quantification of MST markers for more precise assessments.

Effects of diluted seawater in drinking water on physiological responses, feeding, drinking patterns, and water balance in crossbred dairy goats

Background and Aim: In tropical regions, the intrusion of saline from seawater (SW) due to global warming and sea level rise in recent years is an important natural factor influencing goat well-being. This study aimed to determine the effects of diluted SW in drinking water on the physiological responses and eating and drinking patterns of crossbred dairy goats under tropical conditions. Materials and Methods: Twenty dairy goats were divided into four groups (five animals each) based on body weight and milk yield. Animals received either fresh drinking water (SW0.0, control) or diluted SW at concentrations of 0.5% (SW0.5, low salinity), 1% (SW1.0, moderate salinity), and 1.5% (SW1.5, high salinity). The experiment was performed for 49 days (1st–7th week). Throughout this period, daily food and water intake were measured every day. In addition, blood collection was performed on day 25. Total urine and feces were collected from days 25 to 29. Meal and drinking patterns were determined on days 31 and 32. Results: Salinity did not influence dry matter intake throughout the experiment (p &gt; 0.05). However, SW had a significant effect on eating patterns. The effect of SW on water intake (WI) was pronounced from the 2nd to 7th weeks of this experiment (p &lt; 0.05). The water balance decreased and plasma antidiuretic hormone levels increased from SW1.5 to SW2.5 compared to the other treatments. Rectal temperature and respiration rate increased from 15:00 to 17:00 in SW1.5 patients. The concentrations of plasma electrolyte, creatinine, and heat shock protein 70 did not differ between treatments (p &gt; 0.05). The urinary excretion of Na+ from SW1.5 and K+ and Cl- from SW1.0 was higher than that from SW0.0 and SW0.5 (p &lt; 0.01). Conclusion: Lactating crossbred goats adapted to low and moderate SW by increasing urine volume and urinary electrolyte excretion (Uex), whereas animals responded to high SW by either increasing Uex or altering drinking patterns to minimize salt stress. Keywords: antidiuretic hormone, dairy goat, kidney, saline water, water balance.

Molecular responses in the intestine of Atlantic salmon (Salmo salar) following light and diet stimulation of smoltification: Potential molecular markers for a seawater-ready smolt

The transfer to seawater (SW) represents a critical stage in the production of Atlantic salmon. The success of the transfer links with the optimal development of hypo-osmoregulatory capacities during smoltification. While various strategies are adopted in aquaculture to stimulate smoltification, considerable fish loss still occurs after transfer to sea cages. Therefore, we investigated the molecular responses in the anterior and posterior intestine of Atlantic salmon, following 1) a photoperiod treatment (24 h light (L):0 h dark (D) → 24 L:0D vs. 7 L:17D → 24 L:0D) and 2) dietary treatment (regular feed or feed enriched with a salt mix/tryptophan), combined with, or without a photoperiodic treatment in freshwater (FW), to evaluate how intestinal osmoregulatory mechanisms are modulated by these treatments, and to identify potential intestinal markers indicative of a SW-ready smolt. Using quantitative real-time PCR (qPCR), we investigated transcript levels of transporters and channels involved in ion movements through the enterocytes, tight junction components, and receptors (i.e., calcium-sensing receptor and prolactin receptor). The two intestinal regions showed different gene profiles and responsiveness towards the experimental treatments. In the anterior intestine, the exposure to short photoperiod (7 L:17D) upregulated Na+/K+ − ATPase subunit alpha 1c (nkaα1c), Na+/K+/2Cl− cotransporter 1 (nkcc1), Na+/K+/2Cl− cotransporter 2 (nkcc2), Cl−/HCO3− exchanger Slc26a6 (slc26a6), and cystic fibrosis transmembrane conductance regulator I (cftrI), in FW and SW. Also, Na+/K+ − ATPase subunit alpha 1b (nkaα1b), occludin (ocln), and prolactin receptor (prlr) were upregulated in FW and claudin 15 (cldn15) in SW groups exposed to this photoperiod. The posterior intestine was less responsive to the experimental treatments, although upregulation of nkcc1, nkcc2, slc26a6, and cftrI was observed in FW in the short photoperiod groups. Hence, our findings show that exposure to a winter signal in FW more effectively activates hypo-osmoregulatory mechanisms in the intestine of Atlantic salmon, where a coordinated and complementary role of the anterior and posterior intestine ensures optimal SW processing. Dietary treatment had a positive but more marginal effect on the regulation of the genes investigated, mainly enhancing the impact of short photoperiod when the two treatments were combined. Overall, we propose the apical Na+/K+/2Cl− cotransporter, nkcc2, and the apical Cl−/HCO3− exchanger, slc26a6, as potential FW molecular markers in the anterior intestine to assess “SW-readiness” in Atlantic salmon smolts.

EXPERIMENTAL INVESTIGATION OF AN INTEGRATED ELECTRO-CATION EXCHANGE REACTOR FOR BETTER CARBON DIOXIDE EXTRACTION AND ENVIRONMENTAL MANAGEMENT

The research focuses on a unique integrated three-compartment electrochemical reactor developed in a laboratory setting. This innovative reactor uses an electrolytic cation exchange technique to extract substantial quantities of carbon dioxide from ocean water as bicarbonate and carbonate while simultaneously producing hydrogen gas for potential hydrocarbon production. The study employs Design Expert Software to evaluate and optimize the implementation of electrochemical carbon dioxide extraction from ocean water. The reactor is divided into three compartments by two cation-exchange membranes: a middle part and two electrode parts for the cathode and anode sides. The membranes possess acidic assets that facilitate cation transport while inhibiting anion movement. The laboratory studies, including 35-minute experimental runs, were conducted to determine the system's feasibility by assessing carbon dioxide extraction under different conditions, such as electrolyte concentration, applied voltage, and pH levels. The reactor achieved a maximum CO₂ extraction rate of 1479.73mg/min, with optimal conditions yielding 1514.6mg/min. The ideal operating parameters were found to be a voltage of 14.8V, an electrolyte concentration of 0.557M, and a pH of 2.26. The results of the optimization study further reveal that carbon dioxide extraction increases with rising pH levels.

Na+ and Cl- adsorption derived enhancement in 4-nitrophenol reduction using Au/Ag nanoparticle: An experimental and theoretical study

4-Nitrophenol (4-NP) is an organic contaminant attached to textiles, pharmaceuticals, and pesticides. Its presence has been increasingly detected in various water bodies such as lakes, rivers, and occasionally in drinking water. The present work shows the reduction of 4-NP using a hybrid catalytic system composed of gold and silver nanoparticles supported onto the biogenic porous silica (AgAu-SiO2). The AgAu nanoparticles were fabricated in situ onto the salinized biogenic silica substrates through a green synthesis. The catalytic reaction was analyzed with NaBH4 and the proposed AgAu-SiO2 catalyst. Mimicking 4-NP reduction reaction in different spiked river/marine water samples revealed superior catalytic activity in marine water. Subsequently, interference studies performed in the presence of different metal salts and pHs (found in the marine water) showed the vital role played by NaCl in the 4-NP reduction as the increase in the NaCl concentration enhances the catalytic activity of the proposed catalyst. Additional reusability of the proposed catalyst demonstrated its efficacy up to 10 cycles. The density functional theory (DFT) results supported the experimental findings, confirming the crucial role of Na+ and Cl- in the catalytic process. Our experimental results, which have significant implications for the field, have been explained by comparing them with DFT calculations. The main reason behind the enhanced catalysis performance in our systems was deduced at the atomic scale. The study included the adsorption energies and electronic density of molecular structures (4-NP and 4-AP) on different surface coverages. In exceptional cases, at the intermediate of 4-NP on Au(111)-NaCl, a displacement of the electronic density is observed, leading to a quinoline-type ring weakening the N-O bond and favoring the catalytic performance.

Growth and biochemical composition of green seaweed Chaetomorpha linum (O.F. Müller) Kützing (1845) cultured in a range of ionic profiles

Seaweed aquaculture in Inland Saline Water (ISW) can utilise degraded land to produce valuable products. ISW is characterized by its different ionic profile to ocean water (OW), particularly the ratios of sodium (Na+) to potassium (K+) ions, and magnesium (Mg2+) to calcium (Ca2+) ions. The feasibility of seaweed cultivation in varying ionic profiles is not yet well understood. This study investigates the growth of Chaetomorpha linum by length (SL) and biomass (TB), cultured in several ionic profiles by mixture of ISW with OW over two 15-day experiments. The first experiment (EXP 1) investigated growth across a broad range of ionic profiles. C. linum was then cultivated across a more specific range of profiles in the second experiment (EXP 2), based on EXP 1 results. Tanks (50 L) were randomly organised outdoors and salinity was maintained at approximately 25 ppt. SL and TB of seaweed was recorded every 3 days. The proximate and mineral composition of harvested seaweed on Day 15 was also analysed. A significant negative correlation (p < 0.001, r = −0.835, N = 13) was observed between non-discrete TB specific growth rate (SGR) and increasing K+ of media in EXP 1. A significant positive correlation (p < 0.001, r = 0.769, N = 28, EXP 1) was observed between potassium (K) in dry matter (mg.g−1) and K+ in media, suggesting lower K+ in media causes increased TB due to higher water flow rate into cells. Calcium (Ca) content (%d.b.) was much higher in K+ deficient media, indicating Ca accumulation occurs in cells to for ion homeostasis when K is not available. Positive SL SGRs across ionic profiles also indicate this species is capable of a high level of internal ion homeostasis. This study provides context for commercial cultivation of C. linum in varying water types, and presents an avenue for salinity-affected dryland farmers to diversify their income through ISW aquaculture.

A systematic review on analytical methods of the neurotoxin β-N-methylamino-L-alanine (BMAA), and its causative microalgae and distribution in the environment

β-N-Methylamino-L-alanine (BMAA), a neurotoxin produced by various microalgal groups, is associated with neurodegenerative diseases and is considered a major environmental factor potentially linked to sporadic amyotrophic lateral sclerosis. This study systematically reviews the analytical methods used to study BMAA in publications from 2019 to the present. It also investigates the causative microalgae of BMAA and its geographical distributions in aquatic ecosystems based on studies conducted since 2003. A comprehensive search using the Web of Science database revealed that hydrolysis for extraction (67%), followed by quantification using LC-MS/MS (LC: 84%; MS/MS: 88%), is the most commonly employed method in BMAA analysis. Among analytical methods, RPLC-MS/MS had the highest percentage (88%) of BMAA-positive results and included a high number of quality control (QC) assessments. Various genera of cyanobacteria and diatoms have been reported to produce BMAA. The widespread geographical distribution of BMAA across diverse ecosystems highlights significant environmental and public health concerns. Notably, BMAA accumulation and biomagnification are likely more potent in marine or brackish water ecosystems than in freshwater ecosystems, potentially amplifying its ecological impacts. Future research should prioritize advanced, sensitive methods, particularly LC-MS/MS with as many QC assessments as possible, and should expand investigations to identify novel microalgal producers and previously uncharted geographical areas, with a special focus on marine or brackish water ecosystems. This effort will enhance our understanding of the environmental distribution and impacts of BMAA.

Stability Analysis of Surface Wellhead Retention in Offshore Exploration Wells

Abstract When offshore exploration wells are carried out, a narrow operating window and prolonged construction period may be encountered, which may lead to the evacuation of the drilling platform. The conductor will be left freestanding in the sea water, posing a great risk to wellhead stability. In this paper, based on finite element simulation of offshore exploratory well freestanding conductors, the stability analysis method is built and evaluation of a well is carried out. It is concluded that in 1 year return period and sea conditions by hanging load return period of 10 years of sea condition, the stability all meet the conditions, but there in 10 years return period of sea state by hanging load and 50 years return period of sea condition did not meet the requirements of stability. In cases where stability requirements are not met, alternative means of retaining the wellhead are recommended. This study has certain guiding significance for the safe and efficient operation of offshore exploration wells.

Effect of inserting a-C layers on anticorrosion behavior of Ni-NiCr-NiCrAlSi composite coating on copper through magnetron sputtering for marine applications

Amorphous carbon film by magnetron sputtering was inserted in the NiCrAlSi layer to form NiCrAlSi/a-C multilayer with modulation period in a range of 131.6 nm to 240.2 nm in the Ni-NiCr-NiCrAlSi coating for a further improvement to copper on corrosion resistance aiming at application as a heat exchanger for mariculture in sea water. After structure characterization, the corrosion behavior of the samples with variant modulation periods of the NiCrAlSi/a-C multilayer keeping the same total thickness(1 μm) was compared using potentiodynamic polarization and electrochemical impedance spectroscopy. The polarization curves show that the corrosion potentials of the coatings with modulation periods of 240.2 nm, 198.4 nm, 158.4 nm and bilayer number 4, 5, 6 for NiCrAlSi/a-C layer are more negative compared to that with modulation period of 131.6nm and bilayer number 7, which indicates that the smallest modulation period results in the highest corrosion resistance. The amorphous a-C sublayer in the multilayer coatings plays an active role in the improvement, for an introduction of the more interfaces between the NiCrAlSi and the a-C sublayers, as well as the compact structure and the chemical inertness to sea water (Cl−). In addition, the NiCrAlSi sublayer can be regarded as an interlayer to release stress in both the a-C sublayer and the NiCrAlSi sublayer, mainly from corrosion products, which also plays an important role for the improved corrosion resistance.

The Palaeozoic assembly of the holocephalan body plan far preceded post-Cretaceous radiations into the ocean depths.

Among cartilaginous fishes, Holocephali represents the species-depauperate, morphologically conservative sister to sharks, rays and skates and the last survivor of a once far greater Palaeozoic and Mesozoic diversity. Currently, holocephalan diversity is concentrated in deep-sea species, suggesting that this lineage might contain relictual diversity that now persists in the ocean depths. However, the relationships of living holocephalans to their extinct relatives and the timescale of their diversification remain unclear. Here, we reconstruct the evolutionary history of holocephalans using comprehensive morphological and DNA sequence datasets. Our results suggest that crown holocephalans entered and diversified in deep (below 1000 m) ocean waters after the Cretaceous-Palaeogene mass extinction, contrasting with the hypothesis that this ecosystem has acted as a refugium of ancient cartilaginous fishes. These invasions were decoupled from the evolution of key features of the holocephalan body plan, including crushing dentition, a single frontal clasper, and holostylic jaw suspension, during the Palaeozoic Era. However, these invasions considerably postdated the appearance of extant holocephalan families 150 million years ago during a major period of biotic turnover in oceans termed the Mesozoic Marine Revolution. These results clarify the origins of living holocephalans as the recent diversification of a single surviving clade among numerous Palaeozoic lineages.