RSS 1.0Tuyển tập Nghiên Cứu Biển – Collection of Marine Research Works
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Zooplankton assemblages in De ghi lagoon, Binh Dinh provinceCollection of Marine Research WorksThis paper presents the results of zooplankton surveys in De Gi lagoon 2009, 2010, and 2020. Change of zooplankton communities was analyzed based on species richness, diversity, abundance, and species composition over the three sampling time points. In De Gi lagoon, the copepod group (subclass Hexanauplia) dominated with 61 in 85 zooplankton identified species, followed by Hydrozoa and Malacostraca with seven and five species, respectively. The remaining groups (Polychaeta, Branchiopoda, Ostracoda, Sagittoidea, Appendicularia, Thaliacea, Tentaculata, and Gastropoda) had low species richness, varied from 1 to 2 species. The Copepod assemblages compose mainly small species and have good adaptation in high salinity variabilities, such as Paracalanus and Acartia. In the lagoon, species richness and diversity increased from the upper lagoon to the lagoon's mouth over the years, but most pronounced in 2020. The average zooplankton density this year was low, 9.136 inds.m-3, much lower than in 2009 with 54.022 inds.m-3. Cluster analysis demonstrated the complexity of the zooplankton structure in the lagoon when the similarity in species composition between seasons and years is ca. 27%. Seasonal changes in zooplankton assemblages presented 58-73% dissimilarity, with the dry season having higher diversity, biomass, and calanoid copepodites and larvae. After ten years, since 2010, the zooplankton assemblages differed by 60-72% with higher diversity and lower abundance but remained similar ratios between dominant Calanoida and other orders in the copepod assemblages. Invertebrate larval abundance in De Gi lagoon should be considered as an important resource for their dominance and variation between seasons and distribution. This research provides basic scientific data on the zooplankton communities of De Gi lagoon, which has not been published before, contributing the baseline to any further studies the South-Central Viet Nam.
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Composition and distribution seaweeds in Thuyen Chai island (Truong Sa islands-Vietnam)Collection of Marine Research WorksThuyen Chai Island, located in the South of the Spratly Archipelago (Vietnam), features a seagrass bed, coral reef ecosystem, and a tidal zone. All of these causes contribute to the expansion of seaweed diversity. This report gives the first findings of the seaweed flora in the rainy season. The results of the survey revealed 82 species of seaweed belong to 4 phyla. Among them, there are 42 species of Rhodophytes (comprising 51% of total species), 14 Chlorophytes (17%), 21 Ochrophytes (26%) and 5 Cyanobacteriophytes (6%). The findings show that the composition of seaweed species on Thuyen Chai island varies depending on the habitats of coral reefs and seagrass beds.
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Species composition and density free-living marine Nematoda in coastal tidal areas of Khanh Hoa provinceCollection of Marine Research WorksThe paper presents species composition and density of free-living nematodes marine in coastal tidal areas of Nha Trang, Khanh Hoa. 27 species was found, belonging to 11 families, 25 genera and three orders. The family Oxystominidae has the highest number of individuals (25.35%). The diversity index of the Nematode community is H'=1.83 on average, and the average density of nematodes is 75±26,23 (individuals/10cm²). The highest density of nematodes is located in the subtidal zone infralittoral fringe Hon Chong HC_3 (253 individuals/10cm). Initially, the results indicate bottom sediment significantly affects the density of individuals and the diversity of species composition of free-living marine nematodes in coastal tidal areas of Khanh Hoa province.
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A study of dispersal patterns of reef corals in Vietnam under the influence of current regime of Bien DongCollection of Marine Research WorksRecognizing the flow regime in the breeding season is the dominant factor for the marine biota, a flow diagram of the Bien Dong (East Vietnam Sea) in the transitional season has been established to examine the relationship between the current and its distribution and diversity of reef-forming coral in the sea of Vietnam. The data source for modeling the current regime is updated from the Climate Forecast System Reanalysis of the National Center for Environmental Prediction (NCEP CFSR) and exploited from the HYCOM + NCODA Global 1/12.5 database for the period 1993-2012 and of HYCOM + NCODA Global 1/12o Analysis for the period from 2013 to 2020. Along with that, the finite element method (FEM) was used to build a 3D hydrodynamic model. Based on the constructed flow diagram, the dispersal capacity of coral larvae in each sea area is assessed to compare with previous observations on the species diversity of reef-forming corals. The finding includes: (1) the Gulf of Tonkin and Gulf of Thailand exhibit poor exchange and lower diversity than the continental shelf and coastal waters of Vietnam; (2) Cape Varella is a vital boundary dividing the East Vietnam Sea, forming the most diverse areas in good exchange conditions of water bodies in the south of the 13°N parallel, including the Truong Sa (Spratly) Islands. This system can be considered as part of the Coral Triangle in the Bien Dong.
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Status and temporal changes in reef fish communities in Hon Cau marine protected area, Binh Thuan provinceCollection of Marine Research WorksA study on the status and temporal changes in communities of coral reef fishes in Hon Cau Marine Protected Area was carried out at 12 reef sites in August 2020 in combination with the data from previous studies. A total of 351 species belonging to 128 genera and 45 families of coral reef fish were recorded. The average density in 2020 was 237.3 ± 82.8 individuals/100m2, mainly occupied with small-sized fishes (accounting for 86.8% of total density) and ornamental fish, with the dominant families of damselfishes, wrasses, and cardinalfishes, while the the large-sized fish accounts for a very low rate. Target fishes were found in very low density and dominated by herbivorous feeders (especially rabbitfishes). The area around Hon Cau Island have species diversity (accounting for 94.4% of total species recorded in 2020) and a density of reef fish compared to the Breda shoal and coastal areas. The analysis results show that there were three distinguished assemblages of reef fishes, in which the reef fish communities around Hon Cau Island are different from the shoal and coastal areas. After nearly ten years of establishing Hon Cau MPA, coral reef fish density is maintained relatively stable in the area around Hon Cau Island and significantly decreased in Breda shoal and the coastal areas. There is an increase in the density of herbivorous fishes, while the large-sized and inextricably linked to the coral reef (groupers, snappers, sweetlips, butterflyfishes) with very low or reduced densities over time.
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Common diseases in clownfish: a reviewCollection of Marine Research WorksIron is a trace element involved in many physiological and biochemical processes of aquatic animals and is necessary for the production and normal functioning of hemoglobin, myoglobin, cytochromes, and many other enzyme systems, maintains the structural integrity of the epithelium and thus suppresses pathogens, iron deficiency induces microcytic anemia in certain fish species, iron-free content in mucus membranes and in other tissues that are one of the first glands to protect the host against infection, iron deficiency can decrease host resistance so that iron supplementation increases host resistance disease. This report not only reviews the iron requirement in fish and crustaceans farming but also its effect on the health status.
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Effect efficiency of the fragmentation method to asexual reproduction of Stichodactyla haddoniCollection of Marine Research WorksThis study examines the effect of half and quarter separation methods by fragmentation for culture sea anemone Stichodactyla haddoni (with mouth diameter 28.97±1.37 cm, foot diameter 9.39±0.44 cm, weight 1466.78 ± 192.13g) after 90 days in recirculating aquaculture systems. Research using a completely randomized design with three treatments: control, 1 to 2 individuals and 1 to 4 individuals. Each treatment repeated three replications. The results show that the survival was high, with 88.89±11.111% in control and 88.89 ±5.556% in the anemones cut in half, and 72.22±2,778 % cut in quarters (p>0.05). There was a difference in growth in mouth diameter (p<0.05) but no difference in growth in foot diameter and wet weight (p>0.05). Anemones were cut in half larger, less stressed, and grow faster than the quartered individuals, but the number of anemones from the quaternary separation method was higher. Experiments show that both fragmentation methods are highly effective and can be used to breed Stichodactyla haddoni anemone.
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Effects of different microalgal diets on intensive cultuvation of Cyclopoida copepod Apocyclops sp.Collection of Marine Research WorksEffects of different microalgal diets include Nannochloropsis oculata, Isochrysis sp. and Chaetoceros muelleri on mass culture of copepod Apocyclops sp. was conducted under five treatments (3 replicates) and the experiment lasted 25 days, treatment 1 (N. oculata), treatment 2 (N. oculata and Isochrysis sp., 1:1), treatment 3 (N. oculata : Ch. muelleri, 1:1), treatment 4 (Isochrysis sp. and C. muelleri, 1:1), treatment 5 (N. oculata, Isochrysis sp. and C. muelleri, 1:1:1). The results investigated that copepod fed mixing microalgal diets had better population growth than copepod fed N. oculata only. The highest density of copepod was detected in treatment 3 and 5 with 194.44 ± 101.84 and 194.44 ± 67.36 individuals/ L, respectively, these number were significantly higher than the density of copepod in treatment 1 with 67.67 ± 47.14 inds/ L (P<0.05) but no significantly different with the density of copepod in treatment 2 (105.56 ± 16.67 inds/ L) and treatment 4 (155.56 ± 67.36 inds/ L) (P>0.05).The highest population growth was in cultivation period from 15 to 20 days after that the copepod densities will be reduced. The results of fatty acid analysis showed that the highest DHA and EPA content was in treatment 3 with 32.15 and 16.34%, respectively. The lowest DHA content was in treatment 2 with 27.97% and the lowest EPA was in treatment 1 with 11.84%. The highest and lowest ratio of DHA/EPA was found in treatment 1 with 2.41 and treatment 2 with 1.93, respectively. The highest ratio of EPA/ARA was in treatment 4 with 2.21 and lowest in treatment 5 with 1.95. Based on the results of this study, N. oculata, and C. muelleri is recommended for intensive cultivation of Apocyclops sp.
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An overview of the use of the iron in aquacultureCollection of Marine Research WorksIron is a trace element involved in many physiological and biochemical processes of aquatic animals and is necessary for the production and normal functioning of hemoglobin, myoglobin, cytochromes, and many other enzyme systems, maintains the structural integrity of the epithelium and thus suppresses pathogens, iron deficiency induces microcytic anemia in certain fish species, iron-free content in mucus membranes and in other tissues that are one of the first glands to protect the host against infection, iron deficiency can decrease host resistance so that iron supplementation increases host resistance disease. This report not only reviews the iron requirement in fish and crustaceans farming but also its effect on the health status.
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Environmental assessment of coastal water of Can Gio district - Ho Chi Minh city by sea water quality indexCollection of Marine Research WorksAssessment of water quality plays an essential role in controlling and monitoring environmental quality for economic development. Based on the monitoring results in 2018-2019, the paper aims to classify the water quality based on SQWI in the coastal waters of Can Gio district, Ho Chi Minh City. Although the SQWI value increased from 35 (in 2018) to 82 (in 2019), the water environment was not considered polluted. However, the results also warn of the pollution level due to high SQWI coliform in Cau Den and Long Hoa in the rainy season.
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Pollution of total petroleum hydrocarbon in coastal zone Ca Na, Ninh Thuan provinceCollection of Marine Research WorksThe paper presents the analysis results of total petroleum hydrocarbon (TPH) in the water and sediments of two surveys at 12 stations in the Ca Na sea area in Ninh Thuan province in April 2018 and December 2019. Water samples were extracted by liquid-liquid method with dichloromethane solvent, sediment samples extracted by Soxhlet method, and Dichlorometal. Analysis by gas chromatography with FID detector (GC-FID). The total hydrocarbon content is calculated from the carbon range C9 to C36. The results showed that the concentration of TPH in the water ranged from 1.2 to 32.3µg/l with an average of 11.9±6.2µg/l, nearshore stations in the north (Mui Dinh) have higher concentrations than in the south (Ca Na), the concentration in December 2019 was higher than in April 2018 at most stations. In the sediments, the average TPH content is 4.3µg/gdry, ranging from 1.7-11.0 µg/gdry, showing that the sediment here has not been contaminated with TPH.
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Composition and antioxidant activity of crude extract from squid Uroteuthis chinensisCollection of Marine Research WorksThe antioxidant activities against DPPH free radical of crude extracts using ethyl acetatee and methanol from Uroteuthis Chinensis were studied muscles of, ranged from 13.43% to 41.13%. TLC and FT-IR analysis of several fractions methanol extracts showed the presence of amino acids, peptides, and proteins. SDS-PAGE result of some fractions of methanol extracts described the presence of proteins with a molecular weight of 19-220 kDa. The antioxidant activities of different segments of the Uroteuthis Chinensis were various.
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Preparation of nanohydroxyapatite from skipjack tuna bone (Katsuwonus pelamis) by alkaline hydrolysis and thermal calcination methodsCollection of Marine Research WorksAs the main component of bones and teeth, hydroxyapatite (HAp) is considered a vital biomaterial in many fields. Meanwhile, fishbone by-products are abundant sources of HAp. Therefore, this study was conducted to prepare nano HAp from skipjack tuna bone (Katsuwonus pelamis) using alkaline hydrolysis and thermal calcination methods. After pre-treatment of fish bones for removing organic impurities, the bone powders were under alkaline hydrolysis in 1 M NaOH solution at 250o C for 1 hour. This method allows to obtain HAp nanopowders with an average particle size of only 22 nm; whereas, when heating at 600o C for four hours, the calcium formed was on average larger (40 nm) in size than the alkaline hydrolysis product. The HAp nanopowders formed by alkaline hydrolysis had a molar ratio of Ca/P 1.929, higher than that of the calcinated sample (1.848). These Ca/P molar ratios prove that the nano-HAp powders are B-type biological hydroxyapatites confirmed by the FTIR spectrum. In addition, the heavy metal contents of calcium powders are detected within safety limits of regulatory requirements of Vietnam regulations on dietary supplements and functional foods.
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Hydroxyapatite: physicochemical properties, biological role and marine originCollection of Marine Research WorksBiomedical materials research aims to find new forms of materials and medical devices, which can able to adapt to the bio-physiological mechanism of the human body, avoid the elimination, therefore helping improve the quality of human life. Hydroxyapatite (HAp) is one of the stable calcium phosphate (CaP) with loBiomedical materials research aims to find new forms of materials and medical devices, which can able to adapt to the bio-physiological mechanism of the human body, avoid the elimination, therefore helping improve the quality of human life. Hydroxyapatite (HAp) is one of the stable calcium phosphate (CaP) with low solubility and Ca/P ratio similar to the Ca/P ratio in bones and teeth (Ca/P = 1.67). These properties allow HAp to be served as bone-regenerating materials or as a drug carrier. Nowadays, most HAp applied materials are products of synthesis processes, but they are still not enough for widespread applications. Therefore, several chemical methods have been developed to obtain natural HAp from marine organisms such as corals, cuttle-bones, seashells, fish scales, fish bones and algae. w solubility and Ca/P ratio similar to the Ca/P ratio in bones and teeth (Ca/P = 1.67). These properties allow HAp to be served as bone-regenerating materials or as a drug carrier. Nowadays, most HAp applied materials are products of synthesis processes, but they are still not enough for widespread applications. Therefore, several chemical methods have been developed to obtain natural HAp from marine organisms such as corals, cuttle-bones, seashells, fish scales, fish bones and algae.
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Microplastics in three sandy beaches in Khanh Hoa provinceCollection of Marine Research WorksMicroplastics (MPs) are small plastic debris (< 5 mm) which pose negative impacts to marine ecosystems. This paper investigated microplastic abundance in 0–5 cm and 5–10 cm layers of three sandy beaches in Khanh Hoa province. The results showed that fiber was the most abundant microplastics in the samples, comprising 85% of the total microplastics. Fragment and film were reported with smaller percentages, over 10% and 2%, respectively. In addition, the effect of grain sizes on microplastic abundance in two sediment layers was also observed. At Doc Let and Cam Lam, sediments were mainly of fine grain sizes, microplastic concentrations decreased, when the sample depths increased. On the other hand, at Bach Dang, sediment sizes ranged from medium to coarse sizes, the difference of microplastic levels in two layers was not significant.
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Estimation of water transport exchange between the East Vietnam Sea and the neighboring seas using a 3D hydrodynamic modelCollection of Marine Research WorksThe East Vietnam Sea connects the Pacific and Indian Oceans through several interocean straits (SCSTF). A high resolution (4 km) simulation is performed with the three-dimensional regional ocean model SYMPHONIE to provide consistent estimates of the climatological averages and the interannual variability of the water transport exchanged between the East Vietnam Sea and the neighboring seas. The East Sea receives an annual average water transport of 4.45±1.35 Sv, mainly from the Luzon Strait (95%). Less than 5% of the water input comes from the atmosphere, rivers and the Balabac Strait. The East Vietnam Sea laterally releases the total amount of water input, mainly to the Sulu Sea through the Mindoro strait (49%), to the East China Sea via the Taiwan strait (28%) and to the Java Sea through the Karimata strait (22%). The interannual variability of total exchanged water volume is driven by water transport at Luzon and Mindoro straits. ENSO has a significant impact on water transport at Luzon and Mindoro straits.
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Characteristics of the wind regime in Hon Yen island (Phu Yen province) from analysis of NCEP CFSR dataset (1979-2020)Collection of Marine Research WorksThe wind data set of 10 m on the sea surface is provided by meteorological data NCEP CFRS corresponding to 42 years (1979–2020), with hourly frequency. The purpose of this paper is to find the most effective numerical method for the Weibull distribution function for the wind regime in Hon Yen waters based on analyzing and comparing the efficiency of 10 (ten) numerical methods, namely, the empirical method of Justus (EMJ), the empirical method of Lysen (EML), the method of moments (MoM), the graphical method (GM), the Mabchour’s method (MMab), the energy pattern factor method (EPFM), the maximum likelihood method (MLM), the modified maximum likelihood method (MMLM), the equivalent energy method (EEM), and the alternative maximum likelihood method (AMLM). According to the analysis results, the EPFM method is best suited for the wind regimes of January, July and December; MLM method is best suited for February, June, August and September wind regimes; The EML method is best suited for the wind regime in March and October and the EMJ method is best suited for November. The AMLM method often results in inaccurate results in forecasting the wind regime in the Hon Yen area.
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Research on Synop eddy currents (large size) in the East Vietnam SeaCollection of Marine Research WorksThe field survey to determine the size, location, morphology and time of appearance of Synop vortexes in the East Vietnam Sea is not feasible in the current conditions of our country. The East Vietnam Sea stretches over 25 degrees latitude, with the main climate and weather conditions of the tropics, with monsoon and equator, so the possibility of the appearance of Synop vortexes is entirely possible. Indirectly studying the Synopic vortexes of the East Vietnam Sea, using the research model, has also obtained certain results. Recently, a number of ocean circulation models have developed strongly of three-dimensional modeling problems, the models have applied effective calculations on the seas and world oceans of Synopic processes without also describes oceanic spectra ranging from small to global in size, ranging in duration from a few seconds to thousands of years. Using the calculated ROMS (Regional Ocean Modeling System) model, the current field in the East Vietnam Sea appears many different large-sized vortex shapes. There exists a large vortex pattern covering several small internal vortices. The vortex may appear only in the western part of the East Vietnam Sea, or only in the eastern part of the East Vietnam Sea. There exist contiguous double vortices, this double vortex is usually two reversible vortices, the belt of eddies flows continuously in opposite directions from west to east or from east to west. Comparing the research results with other research results published by foreign authors shows that there is a concordance.
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Antibiotics resistance in pathogenic bacteria isolated from water and sediment around the floating fish farms in the Nha Trang bayCollection of Marine Research WorksTo assess the impact of antibiotic use in aquaculture in Nha Trang bay, we conducted this study with the aim of assessing antibiotic resistance of opportunistic pathogenic bacteria isolated from water and sediment around shrimp/fish cages in the Nha Trang bay. 109 strains of Vibrio, Salmonella-Shigella and Aeromonas groups were isolated in the surrounding environment of farming areas in Dam Bay and Hon Mieu. Antimicrobial resistance test of these 109 strains showed that in the water environment in Dam Bay, TET (96.6%) and NIT (92.5%) were the two antibiotics with the highest rates of resistant bacteria while no bacteria were resistant to RIF. All 5 types of antibiotics had a statistically insignificant percentage of antibiotic-resistant bacteria in water samples at Hon Mieu, ranging from 33.3% to 68.9%. Also in the water environment, the rate of antibiotic-resistant bacteria in Dam Bay was not influenced by the distance to the cages (42.5–66.6%). Meanwhile, in Hon Mieu, the highest rate of resistant bacteria was observed at the distance of 200 m (100%) away from cages and the lowest rate at the distance of 100 m (20%). In the sediment environment around the cages, both the Dam Bay and Hon Mieu farming areas showed the highest rates of antibiotic-resistant bacteria against TET, NIF and RIF had the lowest rate of resistant bacteria. Among the total of 109 strains tested for antibiotic resistance, 2 strains labeled TCBS_HM200 m and SS_HM200 m were found to be resistant to all 5 tested antibiotics. These two strains were respectively identified as Vibrio harveyi and Oceanimonas sp.
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Antioxidant activity of extract from some squid species in Khanh HoaCollection of Marine Research WorksThe antioxidant activities against DPPH free radical of crude extracts using ethyl acetate and methanol from ink sac, muscles, and bones of 5 squid species (Uroteuthis chinensis, Uroteuthis sibogae, Uroteuthis duvaucelii, Sepia esculenta, Sepioteuthis lessoniana) collected in Khanh Hoa waters were investigated. These activities ranged from 4.21% (ethyl acetate extract from ink of U. chinensis) to 54.51% (methanol extract from muscle of S. esculenta.). The functional group analysis by infrared adsorption spectrum (FTIR) in these crude extracts revealed the absorption peaks of melanin in ink, polysaccharide in bone and protein in muscle extracts. In addition, the SDS-PAGE result of some methanol extracts showed the presence of proteins with a molecular weight of 30-150 kDa.
