http://tvhdh.vnio.org.vn:8080/dspace/handle/123456789/19538 2026-08-25T06:36:38Z http://tvhdh.vnio.org.vn:8080/dspace/handle/123456789/21820 Title: Effect of temperature and light intensity on the growth of Eucheuma denticulatum seaweed branches from Van Phong Bay under laboratory conditions. Authors: Vu, Thi Mo; Le, Trong Nghia; Tran, Mai Duc; Le, Truong Trung Lien; Ho, Son Lam; Anuraj, Anirudhan Abstract: Establishing an initial source of tissue culture material is the first and most important step in the propagation process. To prepare for this stage, seaweed must be acclimatized in vitro for 4 to 8 weeks before sterilization. In this study, Eucheuma denticulatum seaweed branches were collected from seaweed farms operated by local households in Van Phong Bay, Dai Lanh commune, Khanh Hoa province, brought to the laboratory, and acclimatized in a controlled environment. Healthy branches with a glossy brown color were carefully selected, cut into 10–15 cm lengths, and fresh-weight 13–15 grams samples were tied to mesh frames and placed in glass tanks measuring 35 × 40 × 60 cm. Environmental factors such as temperature (22–30oC) and light intensity (40–200 µmol photons·m-2·s-1) were tested. The results showed that after six weeks of acclimation, E. denticulatum branches thrived best at 26oC, achieving a high survival rate of 73.33%, a fresh weight of 21.38 g, the highest cumulative growth rate of 1.12 %·day-1, and the lowest ice-ice disease prevalence at 1.11%. Similarly, after six weeks of acclimation, the branches showed optimal growth under specific light intensity conditions of 120 µmol photon·m-2·s-1, with a high survival rate of 77.78%, a fresh weight of 28.82 g, the highest cumulative growth rate of 1.77 %·day-1, and no occurrence of ice-ice disease. The E. denticulatum branches cultivated under optimal conditions are poised to serve as ideal raw materials for propagation through tissue culture techniques, paving the way for efficient production and the replacement of natural seaweed stocks. 2026-01-01T00:00:00Z http://tvhdh.vnio.org.vn:8080/dspace/handle/123456789/21819 Title: Intercomparison of statistical and machine-learning methods for sea-level trend estimation at the Hon Dau tide gauge (1960–2024). Authors: Vu, Duy Vinh; Sylvain, Ouillon; Dao, Dinh Cham; Nguyen, Thi Thu; Nguyen, Minh Hai; Trinh, Hoai Thu Abstract: This paper presents an intercomparison of statistical, machine-learning, and signal decomposition methods for estimating sea-level trends using the long-term tide-gauge record at Hon Dau tide gauge (northern Vietnam) during 1960–2024. Classical statistical approaches (Mann–Kendall, Ordinary Least Squares), machine-learning models (Random Forest, Support Vector Regression, Artificial Neural Network, Long Short-Term Memory), and signal decomposition techniques (Empirical Mode Decomposition, and Complete Ensemble Empirical Mode Decomposition with Adaptive Noise) were employed to assess linear, nonlinear, and multi-scale sea-level variations. The results indicate a stable diurnal tidal regime with pronounced seasonal modulation, with lowest water levels occurring in March (182.1 cm) and highest levels in October (208.9 cm). All methods consistently detect a statistically significant long-term rise in mean sea level of approximately 3.7–3.9 mm.yr⁻¹ (equivalent to about 25–27 cm over six decades). A higher rate of sea-level rise, on the order of 7–9 mm.yr⁻¹, is identified for the more recent period 2005–2024. Machine-learning and decomposition-based approaches provide complementary insights into nonlinear behavior and multi-scale oscillations associated with ENSO and monsoon variability, while classical statistical methods offer transparent baseline estimates of long-term change. Seasonal analyses further reveal stronger and more stable increases during the dry season and weaker, more variable trends during the wet monsoon. Overall, the consistency of trend estimates across multiple methods highlights the robustness of the observed sea-level rise and underscores the value of a multi-method framework for sea-level monitoring and climate adaptation studies in Vietnam. 2026-01-01T00:00:00Z http://tvhdh.vnio.org.vn:8080/dspace/handle/123456789/21814 Title: Numerical simulation of seasonal currents in the Mekong Coastal Area: a case in 2019 Authors: Nguyen, Thanh Duong; Vu, Duy Vinh; Nguyen, Minh Hai Abstract: This study, employing the Delft3D numerical model, investigated the Mekong Delta’s seasonal current dynamics by simulating its hydrodynamic regime in 2019. Using Nash-Sutcliffe Efficiency and Root Mean Square Error metrics, the model’s accuracy in replicating measured water levels (cm) and currents at various stations was validated, achieving acceptable simulation results. This allowed for a reliable analysis of the delta’s current patterns. The study revealed that while the overall direction and peak velocity of current remain relatively consistent throughout the year, their spatial distribution undergoes significant shifts, particularly during the transitional periods between seasons. Monthly flow velocities reflect this seasonality, with strong (up to 1 m/s) and consistent northeast-southwest surface flows during the low flow season (minimal stratification), driven by northeasterly winds. Conversely, the flood season exhibits greater regional variability in velocity and direction due to strong freshwater input and fluctuating winds, with surface velocities reaching 1 m/s in the Mekong estuary in October but decreasing sharply with depth (strong stratification), and flow directions shifting dynamically throughout the season. 2025-01-01T00:00:00Z http://tvhdh.vnio.org.vn:8080/dspace/handle/123456789/21813 Title: The reproductive biology of mangrove crab (Neosarmatium smithi) in Xuan Thuy National Park, Nam Dinh, Vietnam Authors: Lai, Duy Phuong; Do, Manh Dung; Luu, Xuan Hoa; Nguyen, Xuan Thanh Abstract: The results of the analysis of 458 samples of mangrove crab (Neosarmatium smithi) collected in areas where mangrove crab is distributed in the tidal zone with mangrove forests in Xuan Thuy Nam Dinh National Park from October 2022 to September 2023 showed that the spawning season of mangrove crab is from mid - April to early September, and is concentrated from early June to early August. In all months, the ratio of females to males is always dominant. The female/male ratio in the mangrove crab population averages 1.36 and ranges from 1.25–1.46. The onset of sexual maturity occurs when the carapace width (CW) of females exceeds 21 mm and that of males exceeds 24 mm. Absolute fecundity (Fa) ranged from 17,580–25,733 eggs/individual, averaging 21,571 eggs/individual. The larvae of the mangrove crab develop from zoea larvae with 5 sub - stages, and megalop larvae with 3 sub - stages. Our findings contribute information to the planning of the artificial seed production, conservation and sustainable development of the mangrove crab native resource. 2025-01-01T00:00:00Z http://tvhdh.vnio.org.vn:8080/dspace/handle/123456789/21812 Title: Assessing the vulnerability of marine ecosystems in the Gulf of Tonkin to human impacts and climate change - natural disasters Authors: Tran, Duc Thanh; Dang, Hoai Nhon; Bui, Van Vuong; Duong, Thanh Nghi; Nguyen, Dang Ngai; Cao, Thi Thu Trang; Vu, Duy Vinh Abstract: The Gulf of Tonkin (Vietnam part) comprises 12 typical marine ecosystems distributed across 7 ecological regions. Human activities impacting the marine ecosystems are classified into three groups: strong impacts (fishing, aquaculture, navigation - ports, and marine infilling); medium impacts (dredging - dumping, mining, tourism - services); and weak impacts (security - defense). Climate change and natural disasters affecting marine ecosystems are categorized into three impact groups. The strong impact group includes water temperature, typhoons, waves, and rising sea levels. The medium impact group consists of turbidization, local freshening, salinization, and erosion. The low-impact group comprises circulation disturbances and sedimentation. The vulnerability of marine ecosystems, influenced by human activities, climate change, and natural disasters, varies and is classified into three levels. Highly vulnerable areas include lagoons, estuarine areas, tidal flats, seagrass beds, and coral reefs. The medium vulnerability encompasses ecosystems such as beaches, mangrove forests, and permanent wetlands. Low vulnerability encompasses ecosystems such as the seafloor, marine lakes, rocky coasts, and upwelling areas. Ecological zones with a high vulnerability levels include the coastal marine zones of Mong Cai - Do Son (Z.1) and Mui Roon - Hai Van (Z.4). The zones with medium vulnerability levels include the coastal marine zones of Do Son - Lach Truong (Z.2) and Lach Truong - Mui Roon (Z.3). In contrast zones with a low vulnerability levels include the northern marine zones of the Gulf (Z.5), the middle marine zone of the Gulf (Z.6), and the southern marine zone of the Gulf (Z.7). 2025-01-01T00:00:00Z