Search Results (164)

Coastal marine ecosystems are facing serious ecological risks from metals pollution, threatening biodiversity and human health. The main objective of this study is to evaluate the spatial distributions and ecological risks of dissolved cadmium (Cd), lead (Pb), and copper (Cu) in the Shandong Peninsula coastal areas, China. Two sampling campaigns were conducted at 21 sites in early spring 2025 to measure the concentrations of the three trace metals in the study area using an electrochemical detection system. The results revealed higher metals concentrations in nearshore areas (e.g., port entrances, aquaculture zones, and estuaries). Specifically, the Cd, Pb, and Cu concentrations in the study area ranged from 0 to 0.079 µg L⁻¹, 0.30 to 0.84 µg L⁻¹, and 2.19 to 4.79 µg L⁻¹, with average concentrations of 0.033, 0.55, and 3.18 µg L⁻¹, respectively. The contamination factors (C_f) of the three metals were below 1, indicating low pollution levels and thus meeting China’s Class I seawater quality standard. However, the ecological risk assessment, employing complementary methods, revealed varying interpretations: the risk quotient (RQ), based on species sensitivity distribution and predicted no-effect concentrations (PNECs), indicated low risks associated with Cd and Pb (RQ < 0.1) but a high risk for Cu (RQ > 1) at all sites, attributable to the exceedance of Cu’s protective threshold (0.46 µg L⁻¹), despite its low C_f. These findings highlight the need for continuous monitoring of Cu due to its high ecological impacts. In contrast, the Hakanson potential ecological risk index (ERI), which incorporates toxicity coefficients, suggested overall low risks (ERI < 150) for the combined metals; however, Cd contributed approximately 70% to the ERI due to its high toxicity coefficient, warranting attention despite the low individual Erⁱ values for Cd across the study area. This study provides valuable recent data on metals pollution dynamics in the Shandong Peninsula coastal areas, offering a scientific basis for developing marine pollution control policies and sustainable marine resource management. Full article

Nile tilapia (Oreochromis niloticus) is a key species due to its rapid growth, high nutritional value, and adaptability to diverse environments. However, changes in water salinity pose significant challenges to tilapia farming. Elucidating the adaptive strategies of tilapia to fluctuating salinity environments is crucial for improving aquaculture efficiency. This study investigated the transcriptional signature of growth-hormone-releasing hormone, somatostatin, growth hormone, and insulin-like growth factor (grhr-sst-gh-igf) axis in Nile tilapia under different salinity conditions (0 g/L, 16 g/L, and 30 g/L). The results showed that in brackish or seawater, Nile tilapia rapidly upregulate brain igfbp5 paralogues and their regulators (sst5, sstr2) to sustain growth-active IGF-1 signaling, while in the liver and gut, they downregulate sstr2b, igfbp1/7, and ghrh to reallocate energy toward osmoregulation. Physiological regulation, such as the use of ligand analogs, or genetic enhancement targeting these genes might hold promise for improving salt acclimation, which would enable profitable farming in brackish or coastal ponds and offer a simple tool for more resilient and efficient tilapia production. Full article

A perforated aquaculture vessel represents an environmentally sustainable approach to fish farming, leveraging seawater circulation to optimize water quality and enhance fish health and growth. The perforations on the side of the fish tank significantly influence its hydrodynamic characteristics. This study investigated the influence of pore parameters on the perforated fishing tank with various pore designs, such as the asymmetric distribution of the opening in depth, windward, and leeward directions. A numerical study was conducted using STAR-CCM+ to analyze the perforated tank under beam wave conditions. This study aimed to analyze the effects of pore location, opening ratio, and asymmetric distribution on the hydrodynamic performance and flow characteristics within aquaculture tanks. The results demonstrated that an asymmetric pore distribution on the windward and leeward sides of the vessel had a notable impact on the roll motion and the flow velocity in the vicinity of the pores. The findings also indicated that the effects of pore distribution were more significant than those of opening ratio, especially regarding asymmetry. The results revealed that higher flow velocities occurred under a smaller opening ratio. Modifying pore structure parameters on the windward and leeward sides can alter the local flow field. Full article

The Sanniang Bay (SNB) and Dafeng River Estuary (DFR) in the Northern Beibu Gulf, China, are critical habitats for the Indo-Pacific humpback dolphin (Sousa chinensis). However, whether and how the decreased dissolved oxygen (DO) has happened in bottom seawater remains poorly understood. This study investigated DO depletion and microbial community responses using a multidisciplinary approach. High-resolution spatiotemporal sampling (16 stations across four seasons) was combined with functional annotation of prokaryotic taxa (FAPROTAX) to characterize anaerobic metabolic pathways and quantitative PCR (qPCR) targeting dsrA and dsrB genes to quantify sulfate-reducing bacteria. Partial least-squares path modeling (PLS-PM) was employed to statistically link environmental variables (seawater properties and nutrients) to microbial community structure. Results revealed pronounced bottom DO declining to 5.44 and 7.09 mg L⁻¹, a level approaching sub-optimal state (4.0–4.8 mg L⁻¹) in September. Elevated chlorophyll-a (Chl-a) near the SDH coincided with anaerobic microbial enrichment, including sulfate reducers (dsrA/dsrB abundance: SNB > DFR). PLS-PM identified seawater properties (turbidity, DO, pH) and nitrogen as key drivers of anaerobic taxa distribution. Co-occurrence network analysis further demonstrated distinct microbial modules in SNB (phytoplankton-associated denitrifiers) and DFR (autotrophic sulfur oxidizers, nitrogen fixation, and denitrification). These findings highlight how environmental factors drive decreased DO, reshaping microbial networks and threatening coastal ecosystems. This work underscores the need for regulating aquaculture/agricultural runoff to limit eutrophication-driven hypoxia and temporarily restrict human activities in SNB during peak hypoxia (September–October). Full article

This study examined the effects of calcium, magnesium, and potassium ion concentrations on Strongylocentrotus intermedius through seven experimental rearing groups: two calcium ion levels (550 mg/L and 733 mg/L), two magnesium ion levels (1727 mg/L and 2302 mg/L), two potassium ion levels (533 mg/L and 710 mg/L), and a control. After 45 days of cultivation, 733 mg/L of calcium ions significantly reduced the S. intermedius survival rate, while 550 mg/L of calcium ions had no significant adverse effects on survival, growth (SGR), the feed conversion ratio (FCR), gonad colour, or immune enzyme activity, and it significantly increased the gonad index (GI). Meanwhile, 2302 mg/L of magnesium ions caused 100% mortality within 2 days, and 1727 mg/L of magnesium ions significantly reduced the survival rate and SGR while increasing the FCR. Additionally, 710 mg/L of potassium ions had no significant impact on the survival rate but significantly reduced SGR, the GI, and gonad colour while increasing the FCR, whereas 533 mg/L of potassium ions showed no significant adverse effects on survival, SGR, the FCR, gonad colour, digestive enzyme activity, or immune enzyme activity. The study results indicate that when formulating artificial seawater using source water with elevated calcium, magnesium, and potassium ion concentrations for S. intermedius aquaculture, calcium ions under 550 mg/L and potassium ions under 533 mg/L are biologically acceptable. However, magnesium ions require adjustment to a narrow optimal range to ensure survival and physiological performance. Full article

Alexandrium spp. blooms and paralytic shellfish poisoning pose serious economic threats to coastal communities and aquaculture. This study evaluated the removal efficiency of two Alexandrium minutum strains using natural kaolinite clay (KNAC) and kaolinite with polyaluminum chloride (KPAC) at three concentrations (0.1, 0.25, and 0.3 g L⁻¹), two pH levels (7 and 8), and two cell densities (1.0 and 2.0 × 10⁷ cells L⁻¹) in seawater. PAC significantly enhanced removal, achieving up to 100% efficiency within two hours. Zeta potential analysis showed that PAC imparted positive surface charges to the clay, promoting electrostatic interactions with negatively charged algal cells and enhancing flocculation through Van der Waals attractions. In addition, the study conducted a cost estimate analysis and found that treating one hectare at 0.1 g L⁻¹ would cost approximately USD 31.75. The low KPAC application rate also suggests minimal environmental impact on benthic habitats. Full article

Aeromonas salmonicida is an age-old fish pathogen widely distributed in seawater and freshwater environments that causes significant economic losses to the global aquaculture industry. Genetic mutations and the emergence of thermophilic strains are factors in the continuous expansion of A. salmonicida’s host range. Beyond infecting fish, A. salmonicida poses a potential threat to mammalian and human health. This review synthesizes recent global research advances concerning A. salmonicida, encompassing strain characteristics, genomic features, virulence factors, and pathogenic mechanisms, as well as the clinical manifestations in infected fish and mammals, and discusses prevention and treatment methods. Particular emphasis is placed on evaluating the potential prophylactic roles of Chinese herbs and bacteriophages against A. salmonicida infection. Furthermore, the review provides perspectives on future research directions, diagnostics, and disease management, informed by contemporary domestic and international studies on this pathogen. Full article

Low seawater temperatures are expected to depress fish growth in aquaculture. However, recent evidence suggests diet composition may offer mitigation for some species. This study evaluated the impact of different diets on juvenile meagre (Argyrosomus regius) in cage farming at low seawater temperatures (average 15.19 °C), conditions known to typically suppress meagre growth. Three replicated groups of fish (initial weight ≈ 107 g) were fed for six months either sardines (group A) or commercial pellets (groups B/C, with group C moisturized). The results demonstrate that the nutritional profile of sardines effectively mitigates cold-induced growth reduction in meagre. While pellet-fed meagre experienced expected growth depression, sardine-fed meagre exhibited a doubled temperature growth coefficient (TGC) and an 80% higher final average weight than the pellet groups (A: 346.13 g, B: 194.44 g, C: 188.93 g). Full article

This study addresses the challenge of solid pollutant collection in seawater pond recirculating aquaculture by designing a novel funnel-shaped sewage collection device and evaluating its performance through Computational Fluid Dynamics (CFD) simulations and experimental validation. The results reveal that the device forms a rotating flow field, effectively concentrating solid particles in a central low-velocity zone with a diameter of approximately 2 m when the sewage pump is inactive. The optimal bottom dip angle for efficient sewage discharge is determined to be 21 degrees, with flow velocities near the outlet ranging between 0.031 and 0.062 m per second, sufficient to mobilize particles smaller than 5 mm. Prototype testing demonstrates a solid pollutant collection efficiency of 75.7 percent, confirming the device’s practical effectiveness in improving water quality and operational performance. This research offers a validated and efficient solution for solid waste management in aquaculture systems. Full article

The recirculating aquaculture system (RAS) has been rapidly adopted worldwide in recent years due to its high productivity, good stability, and good environmental controllability (and therefore friendliness to environment and ecology). Nevertheless, the effluent from seawater RAS contains a high level of ammonia nitrogen which is toxic to fish, so it is necessary to overcome the salinity conditions to achieve rapid and efficient nitrification for recycling. The moving bed biofilm reactor (MBBR) has been widely applied often by using PE fillers for efficient wastewater treatment. However, the start-up of MBBR in seawater environments has remained a challenge due to salinity stress and harsh inoculation conditions. This study investigated a new PE-filler surface modification method towards the enhanced start-up of mariculture MBBR by combining liquid-phase oxidation and maifanstone powder. The aim was to obtain a higher porous surface and roughness and a strong adsorption and alkalinity adjustment for the MBBR PE filler. The hydrophilic properties, surface morphology, and chemical structure of a raw polyethylene filler (an unmodified PE filler), liquid-phase oxidation modified filler (LO-PE), and liquid-phase oxidation combined with a coating of a maifanstone-powder-surface-modified filler (LO-SCPE) were first investigated and compared. The results showed that the contact angle was reduced to 45.5° after the optimal liquid-phase oxidation modification for LO-PE, 49.8% lower than that before modification, while SEM showed increased roughness and surface area by modification. Moreover, EDS presented the relative content of carbon (22.75%) and oxygen (42.36%) on the LO-SCPE surface with an O/C ratio of 186.10%, which is 177.7% higher than that of the unmodified filler. The start-up experiment on MBBRs treating simulated marine RAS wastewater (HRT = 24 h) showed that the start-up period was shortened by 10 days for LO-SCPE compared to the PE reactor, with better ammonia nitrogen removal observed for LO-SCPE (95.8%) than the PE reactor (91.7%). Meanwhile, the bacterial community composition showed that the LO-SCPE reactor had a more diverse and abundant AOB and NOB. The Nitrospira has a more significant impact on nitrification because it would directly oxidize NH₄⁺-N to NO₃⁻-N (comammox pathway) as mediated by AOB and NOB. Further, the LO-SCPE reactor showed a higher NH₄⁺-N removal rate (>99%), less NO₂⁻-N accumulation, and a shorter adaption period than the PE reactor. Eventually, the NH₄⁺-N concentrations of the three reactors (R1, R2, and R3) reached <0.1 mg/L within 3 days, and their NH₄⁺-N removal efficiencies achieved 99.53%, 99.61%, and 99.69%, respectively, under ammonia shock load. Hence, the LO-SCPE media have a higher marine wastewater treatment efficiency. Full article

Extreme weather events such as heavy rainfall significantly reduce surface salinity in coastal waters, presenting considerable challenges to the aquaculture of Japanese scallops (Mizuhopecten yessoensis) in shallow cage systems. This study investigated the effects of chronic low-salinity stress on the growth performance, antioxidant capacity, and gene expression profile of M. yessoensis using a 60-day salinity gradient experiment. S33 represents the control treatment with normal seawater salinity (33‰), while S30, S28, and S26 represent experimental groups with progressively lower salinities of 30‰, 28‰, and 26‰, respectively. A decline in salinity was accompanied by an increase in oxygen consumption. The S26 group exhibited a higher ammonia excretion rate (2.73 μg/g·h) than other groups, indicating intensified nitrogen metabolism. Growth was inhibited under low-salinity conditions. The S33 group exhibited greater weight gain (16.7%) and shell growth (8.4%) compared to the S26 group (11.6% and 6%), which also showed a substantially higher mortality rate (46%) compared to the control (13%). At 28‰, antioxidant enzyme activities (T-AOC, SOD, CAT, POD) were elevated, indicating a moderate level of stress. However, at the lowest salinity (26‰), these indicators decreased, reflecting the exhaustion of the antioxidant systems and indicating that the mollusks’ adaptive capacity had been exceeded, leading to a state of stress fatigue. NAD-MDH activity was elevated in the S26 group, reflecting enhanced aerobic metabolism under stress. Transcriptome analysis revealed 564 differentially expressed genes (DEGs) between the S33 and S26 groups. Functional enrichment analysis indicated that these DEGs were mainly associated with immune and stress response pathways, including NF-κB, TNF, apoptosis, and Toll/Imd signaling. These genes are involved in key metabolic processes, such as alanine, aspartate, and glutamate metabolism. Genes such as GADD45, ATF4, TRAF3, and XBP1 were upregulated, contributing to stress repair and antioxidant responses. Conversely, the expressions of CASP3, IKBKA, BIRC2/3, and LBP were downregulated, potentially mitigating apoptosis and inflammatory responses. These findings suggest that M. yessoensis adapts to chronic low-salinity stress through the activation of antioxidant systems, modulation of immune responses, and suppression of excessive apoptosis. This study provides new insights into the molecular mechanisms underlying salinity adaptation in bivalves and offers valuable references for scallop aquaculture and selective breeding programs. Full article

Melanosis, or melanized focal changes (MFCs), is a significant issue in the Atlantic salmon (Salmo salar) farming industry, causing economic losses due to fillet downgrading. Nevertheless, molecular mechanisms underlying melanosis remain poorly understood, particularly in Chilean aquaculture. This study aimed to characterize transcriptional regulation associated with melanogenesis and inflammation in salmon muscle tissues exhibiting melanosis. Samples were collected from fish at three productive stages, all with MFCs in muscle in common: freshwater at two different origins and accumulated thermal units “ATUs” (300 ATUs post-antibiotic overdose, “Security”; 600 ATUs post-vaccination, “Vaccination”) and seawater harvest (“Harvest”). Gene expression analysis by qPCR targeted melanogenesis-related genes (mitf, tyr, and dct) and immune markers (arg2, inos2, and il-1β). Results revealed significant transcriptional modulation in freshwater samples, including downregulation of mitf, upregulation of dct, and changes in immune-related genes (arg2 and inos2). In contrast, seawater (“Harvest”) samples showed significant upregulation of tyr and dct, but no significant immune gene modulation. These findings indicate distinct molecular responses depending on the MFCs’ development stage, emphasizing early stages as critical points for intervention. Unlike recent studies, which have predominantly focused on samples from the harvest stage, this work uniquely integrates results from both the freshwater phase and the harvest stage. Full article

Malachite green (MG) is a highly toxic dye commonly used in industries and aquaculture, leading to significant environmental contamination and health hazards. Therefore, sensitive and selective detection of MG in real samples is urgently needed. This study presents the development of a molecularly imprinted surface-enhanced Raman spectroscopy (MI-SERS) plasmonic sensor for the rapid and sensitive detection of MG. The sensor consists of a gold nanostar (Au NS) layer as the SERS substrate and an imprinted polydopamine layer containing specific recognition sites for MG. Taking full advantage of the plasmonic effect of SERS and selective recognition capability of imprinted materials, under optimized conditions, the sensor demonstrated high sensitivity, with a detection limit of 3.5 × 10⁻³ mg/L, excellent selectivity against interference from other organic dyes, and robust performance with recoveries of 90.2–114.2% in real seawater samples. The MI-SERS sensor also exhibited good reproducibility, stability, and reusability. These findings suggest that the MI-SERS sensor is a promising tool for real-time monitoring of MG contamination in complicated samples. Full article

The microalgal strains Picochlorum costavermella VAS2.5, Picochlorum oklahomense SAG4.4, Picochlorum oklahomense PAT3.2B, Microchloropsis gaditana VON5.3, and Nephroselmis pyriformis PAT2.7 were cultured in a Stirred Tank Reactor at 25 °C or 20 °C in modified artificial seawater and their biotechnological potential was assessed. VAS2.5, VON5.3, and PAT2.7 were high in biomass production at both temperatures (i.e., 438.8–671.3 mg/L and 418.4–546.7 mg/L at 25 °C and 20 °C, respectively), though P. oklahomense strains grew only at 25 °C. The highest lipid percentage was recorded for the cultures of VAS2.5 (19.3 ± 0.7%) and VON5.3 (16.4 ± 1.5%) at 25 °C, notably rich in ^{Δ5,8,11,14,17}C20:5, while PAT2.7 proved a major producer of ^Δ9C16:1. The predominant lipid fraction was glycolipids and sphingolipids (41.3–57.4%) for VAS2.5, PAT2.7 at 25 °C and VON5.3 at 20 °C and neutral lipids (55.6–63.5%) in the other cultures, indicating the different effect of temperature on lipid synthesis of the various microalgae. Additionally, almost all strains stood out for their high protein content, exceeding 50% in the culture of PAT3.2B, but polysaccharide and pigment content were not high. The biochemical profiles of the isolates showcased their suitability for use primarily as feed additives in the aquaculture sector. Full article

The yellowfin seabream Acanthopagrus latus (Houttuyn, 1782) belongs to the order Spariformes and family Sparidae and is tender, rich in fat, and nutritious, making it a high-value seafood variety along the China coast. The fry can be used for large-scale aquaculture in both seawater and freshwater. Due to environmental pollution and excessive fishing, natural A. latus populations have declined significantly in recent years, which severely depletes genetic diversity. Here, we analyzed the genetic structure of four wild A. latus populations in the South China Sea to provide insights into the genetic resources. In particular, we analyzed 40 samples from four sampling sites through whole-genome resequencing, yielding 515 Gb of raw data and 132,505,081 single nucleotide polymorphisms. Population structure, phylogenetic, and principal component analyses revealed that the four populations were homogeneous and did not show clustering based on geographical origin, indicating extensive admixture. This could be attributed to recent enhancement and release activities in the South China Sea. This information may help to protect and utilize A. latus germplasm resources. Full article