DSpace Community: Tất cả chứa ở đây

Heavy metal bioaccumulation and health risk assessment from cultured fishes in Khanh Hoa Province, Viet Nam

2026-03-12T00:00:00Z

Title: Heavy metal bioaccumulation and health risk assessment from cultured fishes in Khanh Hoa Province, Viet Nam Authors: Nguyen, Xuan Vy; Nguyen, Nhat Nhu Thuy; Le, Trong Dung; Nguyen, Xuan Thuy; Nguyen, Ngoc Tung; Nguyen, Thi My Ngan; Dao, Viet Ha Abstract: This study investigated the bioaccumulation of heavy metals in 87 seafood samples from five species of marine organisms along the coast of Khanh Hoa Province, Viet Nam, in order to assess associated health risks. The results showed that heavy metal levels in the muscle tissues of the cultured species were generally below the maximum legislative limits of Viet Nam. However, Cd and Pb levels in some cultured species were higher than the maximum limits set by the European Commission. Estimated daily intake of the metals was below the provisional limits. The target hazard quotient for all analysed metals was below 1. Only for cockle, the hazard index exceeded 1. Target cancer risk values of Cd, Cr, and Pb ranged between 10−4 and 10−6. The results of the health risk assessment suggested there is no significant non-carcinogenic health risk from individual metals in these seafood species for local residents.

Improvement of reproductive performance of clown anemonefish, Amphirion ocellaris (Cuvier, 1830), with vitamin C

2026-03-12T00:00:00Z

Title: Improvement of reproductive performance of clown anemonefish, Amphirion ocellaris (Cuvier, 1830), with vitamin C Authors: Ho, Son Lam; Nguyen, Thi Nguyet Hue; Dao, Thi Hong Ngoc; Dang, Tran Tu Tram; Do, Hai Dang; Nguyen, Truong Tan Tai; Hoang, Xuan Ben; Dao, Viet Ha; Pham, Thi Khanh; Nguyen, Thi My Ngan Abstract: An enhancement in broodstock nutrition can significantly influence the reproductive success of fish species. This study investigated the impact of vitamin C supplementation in broodfish diets on the reproductive performance, egg quality, and larvae parameters of clown anemonefish (Amphiprion ocellaris). Five diet treatments with varying levels of vitamin C in form of L-Ascorbyl-2-Polyphosphate (0.0, 200, 400, 600, and 800 mg kg-1 diet) were implemented over a 12-month period. Results indicated positive effects of vitamin C supplementation on fecundity, egg quality, hatching rate, larvae survival, and malformation rate (p<0.05). The treatment with 600 mg kg-1 diet exhibited the highest hatching rate (94.61%), lowest egg loss rate (12.86%), and lowest malformation rate (0.519%). Egg diameter and larval size did not significantly differ among treatments (p>0.05). Although vitamin C supplementation reduced re-maturation time and increased spawning frequency, the differences were not statistically significant (p>0.05). Overall, a dietary supplementation of 600 mg kg-1 vitamin C is recommended to improve reproductive performance in clownfish broodstock.

Low phylogeographic diversity in the calcified green macroalga Halimeda macroloba (Bryopsidales) in Southeast Asia

2026-03-12T00:00:00Z

Title: Low phylogeographic diversity in the calcified green macroalga Halimeda macroloba (Bryopsidales) in Southeast Asia Authors: Draisma, Stefano G. A.; Hu, Zi-Min; Wang, Qi-Qi; Nguyen, Xuan Vy Abstract: Southeast Asia is an important marine biodiversity hotspot. Revealing the spatial patterns and environmental drivers related to population genetic structure in this region is a prerequisite for conservation biogeography and genetics. In this study, we applied two chloroplast markers (tufA and rpl2–rpl16) to evaluate population genetic variation and phylogeographic structure of the green macroalga Halimeda macroloba (12 populations, 275 individuals) in Southeast Asia. Both markers showed extremely low genetic variation and haplotype diversity in H. macroloba, with no clear phylogeographic separation between both sides of the Thai-Malay Peninsula (TMP). A postglacial founder effect and predominant asexual reproduction by fragmentation in H. macroloba, together with monsoon-driven ocean currents driving stepping-stone dispersal, may account for the observed remarkable phylogeographic homogeneity around the TMP. However, the tufA and rpl2-rpl16 markers congruently detected a phylogeographic break between the TMP and the eastern South China Sea, despite no obvious observable barrier to gene flow. These results raise the importance to take in situ actions to conserve the indicator species Halimeda in an era of ocean acidification and warming.

Occurrence of multidrug-resistant Enterobacteriaceae and antibiotic-resistant genes in the anthropogenic impacted bay of Nha Trang, Viet Nam

2026-03-12T00:00:00Z

Title: Occurrence of multidrug-resistant Enterobacteriaceae and antibiotic-resistant genes in the anthropogenic impacted bay of Nha Trang, Viet Nam Authors: Nguyen, Quang Huy; Tran, Hoang Son; Vu, Dinh Quang; Nguyen, Dang Quang; Bui, Duc Thinh; Do, Thu Uyen; Le, Thi Thu Hang; Tran, Thi Thanh Tam; Pham, Hoang Nam; Hoang, Trung Du Abstract: Antimicrobial resistance (AMR) has increased significantly due to the widespread transmission of multidrugresistant (MDR) bacteria and antibiotic-resistance genes (ARGs) within and between animals, environments, and humans. Unfortunately, the AMR situation in the coastal areas is little known. In this study, we investigated the occurrence and distribution of MDR Enterobacteriaceae from water and sediment samples collected in Nha Trang Bay, Viet Nam. Overall, 48/107 (45.8 %) identified and isolated bacteria belong to risk group 2 pathogens. More than 57 % of Enterobacteriaceae isolates exhibited MDR phenotypes, in which Escherichia coli, Klebsiella pneumoniae, and Citrobacter freundii were the most prevalent species. In addition, eight ARGs including sul1, sul2, sul3, tetQ, tetB, mecA, blaVIM and blaKPC were detected with high abundance in most of water and sediment samples. Notably, class 1 integron-integrase gene intI1 was widely distributed (95.8 %) in all samples with a total absolute abundance of 2.9 × 105 copies/ml water and 9.7 × 107 copies/g sediment. We also identified significant relationships between sul3, tetB, blaVIM, blaKPC and intI1 with bacterial density, chlorophyll A, phosphorus and temperature. These observations suggest that intI1 gene and nutrients could promote the emergence and propagation of antibiotic-resistance bacteria (ARB) and ARGs in the Nha Trang Bay.

Surface circulation characterization along the middle-south coastal region of Vietnam from high-frequency radar and numerical modelling

2025-01-01T00:00:00Z

Title: Surface circulation characterization along the middle-south coastal region of Vietnam from high-frequency radar and numerical modelling Authors: Tran, Thanh Huyen; Sentchev, Alexei; To, Duy Thai; Herrmann, Marine; Ouillon, Sylvain; Nguyen, Kim Cuong Abstract: Coastal water dynamics along the Vietnamese middle southern coast (VMSC) region, part of the South China Sea, are highly complex with large spatiotemporal variability whose drivers are not yet well understood. For the first time, high-resolution surface current data from high-frequency radar (HFR) measurements were obtained in this region during the early (transition) phase of the Asian summer monsoon. The data were used for comparison with simulation results from a circulation model, SYMPHONIE, and ultimately to optimize the wind forcing in the model. Both modeling and HFR were able to show the spatial and temporal evolution of the surface circulation, but some discrepancies were found between model and HFR data on some days, coinciding with the evolution of the wind. Two methods were used to optimize the wind forcing, namely the ensemble perturbation smoother (EnPS) and the wind correction method using wind-driven surface currents (EkW). Both methods achieved a significant reduction (∼ 36 %–40 %) in the error of the surface current velocity fields compared to the measured data. Optimized winds obtained from the two methods were compared with satellite wind data for validation. The results show that both optimization methods performed better in the far field, where topography no longer affects the coastal surface circulation. The optimization results revealed that the surface circulation is driven not only by winds but also by other factors such as intrinsic ocean variability, which is not entirely controlled by boundary conditions. This indicates the potential usefulness of large velocity datasets and other data fusion methods to effectively improve modeling results.