Vietnam Journal of Marine Science and Technology

The seahills and seahills ecosystems in the nearshore of Thua Thien-Hue Province (Central Vietnam)

Thu, 22 Feb 2024 00:00:00 +0700

At the seabed in the nearshore, Vietnam has sandbars, shoals, bedrock knobs, rock reefs, and other landforms with elevations a few to several tens of meters higher than the seabed, which is always under the lowest astronomical tide (chart datum) and material structure of diverse compositions such as sands, gravel, boulders, blocks, etc. They have determined and warned on the chart map for the safety of navigation and the navy. These areas are significant fishing grounds due to abundant fish, shrimp, and benthic organisms. However, until now, investigation, research, and knowledge regarding these landforms environment, biomes, and naturals have yet to be explored. This paper presents some initial results of natural features (morphology, genetic terrain, material compositions, and types), environmental features, ecological community features (diversity, major groups of organisms, marine fish resources), and their significance in marine biomes (distribution of organisms, ecological linkage, habitats of endemic species) of a sandbar, bedrock in the nearshore in Thuan An, Tu Hien - Chan May and Lang Co - Hai Van - Son Cha of Thua Thien-Hue province in the framework project of Thua Thien-Hue province and National Independent Project belongs to the National Program 562 with Code Number is ÐTÐLCN.78/22 and Vietnam Academy of Science and Technology Project with Code Number is ÐL0000.01/23–24. Based on these findings, the authors proposed naming this terrain “seahill” and the accompanying ecosystem “seahill ecosystems” in the nearshore of Vietnam while continuing to investigation, survey, and research.

Heavy metals assessment for sustainable management in Estuaries of Ba Ria-Vung Tau Province

Thu, 22 Feb 2024 00:00:00 +0700

Heavy metal concentration in the aquatic environment of estuaries is a significant environmental concern with potential consequences for ecosystems and human health. Heavy metals are naturally occurring elements that can enter aquatic environments through both natural processes and human activities. The interplay between natural processes and human activities, particularly urbanization and industrialization, often exacerbates heavy metal pollution in aquatic ecosystems. Some of the most common heavy metals of concern in estuarine pollution include arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb), zinc (Zn), and iron (Fe). Based on the results of two surveys in rainy and dry seasons, the paper aims to assess the concentrations of heavy metals in the estuarine environment of Ba Ria - Vung Tau Province, Vietnam, to understand the extent of contamination and its potential impacts on the ecosystem and human health. The average concentrations As, Cd, Hg, Pb, Zn, and Fe were 2.01, 0.024, 0.028, 1.63, 4.71, and 492.9 µg/L in water, and 6.70, 0.175, 0.060, 11.78, 41.94, and 3,108.9 mg/kg in sediment, respectively. Heavy metal concentrations in water have an increased trend during the rainy season. In contrast, values in sediment exhibit an opposite pattern, which can be explained by various environmental factors and processes. For water and sediment quality, individual metals, and overall metal contamination levels (the contamination factor - C_f, contamination degree - C_d, and metal pollution index - MPI) may appear to be low, whereas the assessment of the combined effects of multiple metals (Metal quality index - MI > 1) indicates that there is a potential risk to aquatic life in the estuaries. This assessment may underscore the importance of considering not only individual metal concentrations but also their cumulative effects when evaluating water and sediment quality and making decisions regarding protecting aquatic ecosystems. Further investigations and measures may be needed to mitigate potential harm to aquatic organisms and for sustainable management in estuaries.

The fabrication and testing drifting buoys of marine data collection

Le Van Cong, Phan Hong Minh, Nguyen Kieu Hung — Thu, 22 Feb 2024 00:00:00 +0700

This paper presents the primary contents of successfully researching, designing and manufacturing drifting buoys to collect marine data to measure temperature, salinity, and ocean currents in surface layers. The paper presents the basic information about the structure, specifications, the buoys working as the laboratory results, and field tests of drift buoys at sea. The drifting buoy test results at the sea of Van Don - Quang Ninh area met the criteria of water-tightness, buoyancy, and balance; the ability to collect temperature and salinity data of the sensors; the ability to transmit and receive information from drifting buoy at sea to the central computer via a web server; operability of the parachute and the travel of the buoy. The buoy database management software is on the website at http://vnsea.vn. It manages the collected data in real-time, showing the parameters and their variables in space and time, the buoy's tracking on the Google map.

Modern sediment characteristics of Cua Dat Hydroelectric Reservoir based on high-resolution seismic data

Nguyen Van Diep, Duong Quoc Hung, Mai Duc Dong, Bui Viet Dung, Nguyen Quang Dung — Thu, 22 Feb 2024 00:00:00 +0700

The Cua Dat Reservoir is located on the Chu river in Thuong Xuan district, Thanh Hoa Province, Vietnam. It was constructed to serve the Cua Dat hydroelectric power plant with a designed capacity of 97 MW. After ten years of operation (2010–2023), the water accumulation process has formed a modern sediment layer with its own characteristics. High-resolution seismic survey work was carried out using the EdgeTech 3400 Sub-bottom Profiler equipment within the reservoir area of the Cua Dat hydroelectric project, covering over 40 km of survey lines. The processed results and data analysis have revealed fundamental features of the terrain and modern sediment characteristics within the reservoir area. The study indicates that sediment upstream of the dam consist mainly of coarse materials (sand, gravel, etc.) deposited in a medium to weak hydraulic environment with short cycles and very low deposition rates, frequently re-settled due to hydraulic dynamics. The weak cohesion of the sediment materials often causes localized surface slumping phenomena with significant amplitudes, extending up to several meters, disrupting the equilibrium trend of sedimentation and leading to an accumulation of sediment towards the dam intake culvert. These observations provide insights into the dynamics of the reservoir surface sediment environment, while also demonstrating that current reservoir operation and exploitation conditions can ensure longevity and safety as per the design of the Cua Dat hydroelectric project.

Records of species of the snake eels genus \(\textit{Ophichthus}\) (Family Ophichthidae) from Vietnam

Thu, 22 Feb 2024 00:00:00 +0700

In Vietnam, the Ophichthus snake eel genus comprises 14 distinct species. This research aims to document and visually represent three previously undocumented findings and a newly discovered species. The species Ophichthus bicolor and Ophichthus machidai are meticulously described here, their characteristics based on five specimens each, gathered at depths of approximately 100–180 m and 50–100 m, respectively, in the vicinity of Quy Nhon. Additionally, Ophichthus obtusus is comprehensively described using 12 specimens collected from depths ranging from roughly 50 m to 120 m in the Quy Nhon and Nha Trang areas. Two specimens of Ophichthus shaoi were also recovered from Quy Nhon, contributing additional data regarding this species from Vietnamese waters. The identification of most species relied on careful examination of their morphological characters. These findings collectively raised the Ophichthus genus’s representation in Vietnamese waters by introducing three previously undocumented species, raising the total count to 17 compared to prior research. Furthermore, this study provides a comprehensive key to aid in identifying the various Ophichthus species found in Vietnam.

Effects of single or combination of dietary vitamin C and β-glucan supplementation on golden trevally, \(\textit{Gnathanodon speciosus}\) (Carangidae)

Thu, 22 Feb 2024 00:00:00 +0700

This study aims to test the single and combination effects of dietary vitamin C and β-glucan on golden trevally, Gnathanodon speciosus. The basal diet (D0) was added with vitamin C at 200 mg kg^-1 diet (D1), β-glucan at 1.0 g kg^-1 diet (D2), and a combination of vitamin C and β-glucan (200 mg vitamin C and 1 g β-glucan per kilogram diet) (D3). The diets were fed the fish for eight weeks. After eight weeks of diet feeding, the growth rate of the fish enhanced significantly with the presence of vitamin C, β-glucan, and the combination of Vitamin C and β-glucan (p < 0.05). The growth rate was significantly higher in a fish-fed diet combined with vitamin C and β-glucan. Survival rates were not significantly different among diet treatments. Muscle protein of fish ranged from 18.36–21.50% among diet treatments. Fish protein content in fish was not influenced by vitamin C, but the protein was higher in fish fed with the β-glucan-added diet and combination the β-glucan and vitamin C-added diet. The current results suggest that a supplemented combination of vitamin C and β-glucan could boost this golden trevally’s growth and body composition at the juvenile stage.

Molecular identification of \(\textit{Grateloupia}\) and \(\textit{Phyllymenia}\) (Grateloupiaceae) in Vietnam reveals a new record of \(\textit{G. yangjiangensis}\) based on \(\textit{rbc}\)L gene sequences analysis

Thu, 22 Feb 2024 00:00:00 +0700

Worldwide, the marine macroalgae ‘Grateloupia filicina’ showed several lineages. Among them, Grateloupia filicina is limited to the Mediterranean basin. Previously, several cryptic species were identified as ‘Grateloupia filicina’. In this study, numerous Grateloupia spp. collected from coastal Vietnam and voucher specimens were used for morphological observation and phylogenetic analyses. Both analyses for samples collected at Nha Trang reveal a new record of G. yangjiangensis. The phylogenetic trees indicated that the herbarium vouchers labeled ‘G filicina’ and ‘G. livida’ from other locations of Vietnam group to G. yinggehaiensis clade. In addition, the phylogenetic trees also showed that the unknown Grateloupia sp. recently collected from Cat Ba Island is Phyllymenia taiwanensis. Therefore, a new record, G. yangjiangensis, is added to the Vietnamese flora.

Antimicrobial activity assessment of crude broth fermented extracts of marine-derived fungi collected from Bai Tu Long Bay (North Vietnam)

Thu, 22 Feb 2024 00:00:00 +0700

This study aimed to isolate and identify marine fungi from Bai Tu Long Bay and assess their antimicrobial potential. We successfully isolated twenty strains of marine-derived fungi. The crude extracts from these fungi were tested against pathogenic microorganisms. All twenty strains exhibit some degree of growth inhibition against the tested microorganisms. Notably, strains M223, M250, M253, and M256 showed significant antimicrobial activity, with MIC values equal to or lower than the positive control. These results highlight the potential of marine fungi as a rich source of antimicrobial agents, a finding of considerable importance to marine mycology and pharmaceuticals. Further analysis was conducted on four promising isolates. M253 was identified as Hamigera avellanea, while M223, M250, and M256 were found to belong to the Aspergillus genus. These isolates were then analyzed using a phylogenetic tree based on MegaX software.