Recent Submissions

  • Tracing sediment transport and bed regime in Nha Trang Bay

    Nguyen, Tac An; Vo, D. S.; Phan, M. T.; Nguyen, H. H.; Ittekott, V. (2000)
    Three spatial structure groups of radionuclides in U and Th series, 210Pb-excess and 137Cs, and 40K were found based on analyzing temporal and spatial datum of their content by factor analysis with oblique rotation in Nhatrang bay.U and Th spatial structure with their contours decreased toward the offshore, ran longshore and divided seawater of bay into two parts with strong gradient on both sides. Inside part located from center of Nhatrang bay toward the seashore with three main deposit centers of their contents higher than 23 Bq/kg.dry for 238U and 40 Bq/kg.dry for 232Th, indicated unstability of shoreline. Almost sediments coming from river extended toward the offshore, were stopped and transported toward southeastern. The outside part was less than abovementioned content. The boundary line between two parts superposed with the constantly limit line of turbid plume in the rainy season. Direct influence of the continental runoff was limited by the 9 Bq/kg.dry contour of 238U, 19 Bq/kg.dry contour of 232Th. Longshore current was a predominant process whereas lateral transport as sifting and winnowing process of finer grains in sediments of Nhatrang bay. Areas that had very low content of 137Cs and 210Pb-excess adjoining shoreline showed areas being eroded. Accumulation of 137Cs and 210 Pbexcess nearby river mouth characterized for fine compositions of sediments controlled by seasonal plumes and sites further toward the south indicated finer materials transported from river and accumulated in lack of hydrodynamic process. Near shore accumulation of 40K revealed the sediments there originated from bed erosion.
  • Heavy metal concentration in South Vietnam waters

    Le, Thi Vinh; Pham, V. T.; Duong, T. K.; Nguyen, H. T.; Pham, H. T. (2000)
    Data obtained from investigations which had been carried out during 1998-1999 in the waters of South Vietnam indicate that concentrations of Fe and Zn were usually higher than permissible limits. In the East South Vietnam waters, Fe concentration varied from 77 to 4450g/l (mean 1045g/l) and Zn concentration varied from 7.24 to 74.1g/l (mean 26.7g/l), Pollution coefficients of the two metals were 10.4 and 2.7 respectively. In the Gulf of Thailand, variation range of Fe was 133-850g/l (mean 318g/l) and of Zn was 4.8-167.8g/l (mean 23.46g/l); corresponding pollution coefficients were 3.2 and 2.3. Mn, Cu, As had mean concentrations lower than permissible limits. In the East South Vietnam waters, variation range for Mn was 9.0-444.6g/l (mean 57.0g/l), for Cu was 1.0-20.3g/l (mean 3.1g/l) and for As was 1.0-10.5 g/l (mean 3.7 g/l). In the Gulf ofThailand, Mn concentration varied from 1.2 to 410.5g/l (mean 19.1g/l), Cu concentration varied from 1.2 to 14.7g/l (mean 3.7g/l), variation range of As concentration was 1.0-13.3g/l with the mean value was 3.6g/l. Scarce data relating to Hg, Cd, Pb showed that their concentrations in the East South Vietnam waters were negligible (usually < 1.0g/l).
  • Some behaviours of strongest short-term coastal change induced by cross-shore wave energy flow and corresponding theoretical consideration

    Le, Phuoc Trinh (2000)
    There is a number of famous theoretical and experimental works that oriented themselves to solve actual problem of coastal change, including the change of coastline, under versatile influence of oceanic wind waves. In this paper the author would like to give supplementally a few new behaviours of that phenomena observed along the coasts of Vietnam, such as coastal collapse & primitive on-the-spot accumulation, material hurl, etc. Most simple theoretical explanation of them grounding on the Newton's second law has been presentedand as results of that there appeared such notion as indicator and criterion which could be used for demarcation of different behaviours in initial stage of general coastal changing processes.
  • Status of the shore area from Tiengiang to Camau: causes of accumulation and erosion

    Trinh, The Hieu; Do, Minh Tiep; Pham, Ba Trung; Nguyen, Huu Suu (2000)
    The paper presents some results of the research programs which had been performed during 1996-1999 (“Studying of river-sea interaction in the mouth of Tien river” and KHCN.06.08). Based on these results the morphological schemes of the shore areas from Tiengiang to Camau were compiled; causes and mechanics of accumulation and erosion were also determined. These results may be used as scientific basis for forecasting the development of the shoreline, it will contribute to the management, protection and reasonable exploitation the shore areas.
  • The software for oceanographic data management: VODC for PC 2.0

    Phan, Quang; Vu, V. T.; Ngo, M. T.; Lau, V. K.; Dang, N. T. (2000)
    To manage and process a large amount of oceanographic data, users must have powerful tools that simplify these tasks. The VODC for PC is software designed to assist in managing oceanographic data. It based on 32 bits Windows operation system and used Microsoft Access database management system. With VODC for PC users can update data simply, convert to some international data formats, combine some VODC databases to one, calculate average, min, max fields for some types of data, check for valid data…
  • Features of wave field, its effect to erosion - deposition processes in the Cua Dai (Hoi An), Cai river mouth (Nha Trang) and Phan Thiet Bay in typical local wind conditions

    Bui, Hong Long; Le, Dinh Mau (2000)
    Based on the hydrodynamic model and Shore Protection Manual (CERC - USA) we have calculated wave field characteristics in the typical wind conditions (wind velocity equal to 13m/s in the high frequency direction of the wind regime). Comparison between measured and calculated wave parameters was presented and these results were corresponded to each other. The following main wave characteristics were calculated:-Pattern of the refraction wave field.-Average wave height field.-Longshore current velocity field in surf zone.From distribution features of wave field characteristics in research areas, it could be summarized as following:- The formation of wave fields in the research areas was unequal because of their local difference of hydrometeorological conditions, river discharge, bottom relief…- At Cuadai (Dai mouth, Hoian) area in the N direction of incident wave field, wave has caused serious variation of the coastline. The coastline in the whole region, especially, at the south of the mouth was eroded and the foreland in the north of the mouth was deposited.- At Cai river mouth (Nhatrang) area in the E direction of incident wave field, wave has effected strongly and directly to the inshore and channel structure.- At Phanthiet bay area in the SW direction of incident wave field, wave has effected strongly to the whole shoreline from Da point to Ne point and caused serious erosion.
  • The characteristics of distribution and change of the seawater temperature and salinity of Cai river estuary and Northern Part of Nha Trang bay in the dry and rainy season

    Nguyen, Ba Xuan; Tong, Phuoc Hoang Son (2000)
    In this paper, some results of analyzing the hydrographic characteristics of theseawater temperature and salinity are presented. The received results showed that: in dry season, the influence of the Cai river water has is limited in Cai river estuary with the approximate transferable distance from the river mouth to the open sea of about 1 km. The isohaline 32%o could be defined as the separate boundary of the Cai river water; In rainy season, due to the river water discharges are high, the influence of Cai river water could be transferred to the open sea and island areas. The immerge of the Cai river water in the open sea areas in rainy season has changed the vertical structure of salinity and temperature in the northern part of Nhatrang bay. In both seasons, the Cai river water have influenced in the surface water layers 0 - 2m and the water layers deeper than 2m are influenced by the sea waters with the salinity of higher than 32%o.
  • Structural features of geostrophic circulation in open region of the South China Sea

    Vo, Van Lanh; Tong, Phuoc Hoang Son (2000)
    On the basis of observation data of water temperature and salinity the mean seasonal geostrophic circulation in open region of the South China Sea (SCS) was computed by the dynamic method relative to the 800 decibar reference surface. The results of computation let go to following notices:In both main monsoons (winter and summer) there are two main geostrophic eddies: the anticlockwise eddy in the northern and northwestern part, and the clockwise eddy in the southern part of the SCS with corresponding divergent and convergent zones. The main frontal zones go along the middle latitudes of the sea from the southern continental shelf of Vietnam to the area west of Luzon Island. The strength and stability of the current in winter are higher than in summer. The Kuroshio has an enough strong branch intruding into the SCS through Bashi Strait in winter creating in the sea the water structure similar to that of the Northwest Pacific subtropical and tropical regions. In summer the Kuroshio water can intrude directly only into the area southwest of Taiwan.
  • Effects of sand and live rock bottom on water quality in aquarium tank

    Do, Huu Hoang; Dang, Tran Tu Tram; Nguyen, Thi Nguyet Hue; Do, Hai Dang (2018)
    Marine ornamental aquarium is more and more popular. Nowadays, biofiltration system can convert nitrogen from toxic forms (NH4+/NH3, NO2-) into a less toxic form (NO3-), which creates a better water quality for the development of ornamental fishes in aquarium tank. This experiment was carried out to evaluate the efficiency of environmental quality by supplementation of sand and live rock in aquarium tank. There were two treatments with rock and sand supplement to the bottom of the tanks (NT1) and tanks without rock and sand added (NT2). There were 3 replicates for each treatment and the experiments were carried out in ten weeks. Results showed that sand and live rock could improve water quality and play as good place for fish and other creature hiding and reduce the water used. Water temperatures were 28.69oC (NT1) and 28.80oC (NT2), pH was about 8.13, salinity ranged from 34‰ to 35‰ in both treatments. NH4+was 0.035 ± 0.003 mgN/ml in the two treatments. After 2 weeks of putting fish in the experimental tanks NO2- values were 0.023 mgN/l (in treatment NT2) and 0.018 mgN/l (in treatment NT1). The average values of NO2- for whole experimental period in the NT1 and NT2 were 0.008 ± 0.001 mgN/l and 0.010 ± 0.002 mgN/l, respectively (P = 0.061). NO3- values were not significantly different between the two treatments (P > 0.05). However, the ratio of NO2-/NO3- in NT1 was lower compared to this value in NT2 (NT1: 0.15 ± 0.03% and NT2: 0.39 ± 0.09%, P = 0.018). This paper provides an important reference to help aquarists to design and control their ornamental aquarium tank suitably.
  • Effect of dietary vitamin E on reproductive performance, egg quality and larvae of clownfish Amphiprion ocellaris (Cuvier, 1830)

    Dao, Thi Hong Ngoc; Nguyen, Thi Nguyet Hue; Dang, Tran Tu Tram; Huynh, Duc Lu; Ho, Son Lam; Huynh, Minh Sang; Doan, Van Than; Do, Hai Dang (2018)
    This study was carried out to determine the effects of vitamin E (a-tocopherol) in five levels (0, 125, 250, 375 and 500 mg vitamin E/kg feed) in broodfish diets on reproductive, egg and larval quality parameters of clownfish (Amphirion ocellaris). Each treatment was repeated in triplicate and the supplemental feeding trial was arranged for 13 months. The result showed that there were no significant differences in re-maturation and spawning periods, spawning frequency, fecundity, egg diameter and larval size of Nemo fish observed between the treatments. However, diets supplemented with vitamin E positively influenced the rate of egg loss, hatching rate of egg and survival rate of the 3 days post hatch. The overall result of this experiment indicated that the optimum vitamin E requirement of clownfish for reproductive performance was 375 mg vitamin E/kg feed.
  • Certain properties of calcium hydroxyapatite from skipjack tuna bone, Katsuwonus pelamis

    Le, Ho Khanh Hy; Pham, Xuan Ky; Dao, Viet Ha; Nguyen, Thu Hong; Phan, Bao Vy; Doan, Thi Thiet; Nguyen, Phuong Anh (2018)
    This paper is concerned with certain properties of calcium hydroxyapatite from skipjack tuna bone (Katsuwonus pelamis) which are by-products of fish export industry. Hydroxyapatite Ca10(PO4)6(OH)2 and β-tricalcium phosphate Ca3(PO4)2, the high-value compounds, have been successfully extracted from skipjack tuna bones. The bones were heated at different temperatures of 600oC, 900oC, 1200oC. While at 600oC hydroxyapatites were obtained with Ca/P ratio of 1.658, comparable to the value of 1.67 found in human bone; the hydroxyapatite crystals of average size of 0.25 µm were formed with the same size distribution. In case of heated bone samples at 900°C and 1200°C, the calcium formed were biphasic calcium phosphate composed of hydroxyapatite and β-tricalcium phosphate; the Ca/P ratio was between 1.660–1.665; the calcium crystals of more than 1 µm were highly porous and connected to each other in priority orientation of tube direction.
  • Investigation of protein patterns and antioxidant activity of collagen hydrolysates from skin of Fan-bellied leatherjacket Monacanthus chinensis by various enzymes

    Pham, Xuan Ky; Phan, Bao Vy; Dao, Viet Ha; Le, Ho Khanh Hy; Nguyen, Thu Hong; Doan, Thi Thiet; Nguyen, Phuong Anh (2018)
    Collagen extracted from the skin of fan-bellied leatherjacket was hydrolyzed and tested for antioxidant activity. The yields of acid soluble collagen (ASC) and pepsin soluble collagen (PSC) were 14.8% and 19.6%, respectively, based on the wet weight of skin. The SDS-PAGE results showed that collagen from the skin of this fish consists of α1 and α2 chains with molecular weight (MW) approximately 100 kDa, identified as type I collagen. Hydrolysis of collagen by the other enzymes, such as papain, bromelain, pepsin and alcalase could produce the peptides with MW less than 28 kDa. Hydrolyzed collagen possessed the antioxidant activity with different levels and greater than that of normal collagen.
  • Initial application of nonlinear regression models to assess biological self-purification capacity in Vung Ro Bay (Phu Yen)

    Nguyen, Huu Huan; Nguyen, Trinh Duc Hieu (2018)
    The self-purification of waters is a complex process, including physical, biological and chemical processes. Based on experimental data in May 2014 and December 2014 in Vung Ro bay (Phu Yen), this paper assesses biological self-purification capicity through the biodegradation of organic matter and nutrient assimilation. The capacity of biodegradation of organic matter is represented by nonlinear regression models of the relationship between BOD and decay time: model of Streeter - Phelps, Young and Clark (1965); Mason et al., (2006). The capacity of nutrient assimilation is represented by the nonlinear regression models of the relationship between photosynthesis and irradiance: Model of Webb et al., (1974); Platt et al., (1980); Eilers and Peeters (1988). Using the least squares method on the nonlinear regression model, the parameters characterizing the self purification process in Vung Ro waters were identified. The study results indicated that the rate of organic biodegradation in Vung Ro waters was 0.1073 ± 0.0781 days-1 (with RMSE = 0.0663 ± 0.0386); the half-time of decay was about 6 days. The maximum intensity of photosynthesis in Vung Ro waters was 57.6881 ± 25.2211 mgC (mgChal)-1h-1 (with RMSE = 3.5900 ± 2.2170); maximum nutrient assimilation of phytoplankton was 9.1719 ± 3.5962 mgN/m3/h and 1.2693 ± 0.4977 mgP/m3/h.
  • Status of exploitation of marine resources in the world biosphere reserve of Cu Lao Cham - Hoi An

    Nguyen, Van Long; Mai, Xuan Dat (2018)
    Assessments of commercial and seed resources of target species in the waters of the World Biosphere Reserve of Cu Lao Cham - Hoi An were conducted through 11 consultations at 11 local communes/wards surrounding the Reserve in November-December 2015 in combination with analysis of 150 samples collected from fishing boats using various fishing gears and landing sites in the rainy (November 2015) and dry (June 2016) seasons. Assessments of spawning and nursery grounds of target resources were conducted in three main periods (December 2015, June and August 2016). Results from this study show that there were 29 fishing gears catching more than 208 species of fishes, molluscs, crustaceans, echinoderms and polychaetes, in which 36 species are considered as target resources. The total catch of commercial and seed resources was about 12,796.4 tons and 7,405,800 individuals (7,020,400 seeds equivalent to 780 kg of seeds of orange-spotted spinefoot and 385,400 seeds of mangrove red snapper, orange-spotted grouper, malabar grouper, spotted scat and mud crab), giving a revenue of 210 billion VND (about 9.5 million USD) harvested in 2015, in which fishes are the most important resources. The waters surrounding the coral reefs and estuary supported a total catch of about 10.8 and 22.2 times higher than that in the Thu Bon estuary and the coral reefs in Cu Lao Cham islands respectively. The area surrounding the mud flats (Go Hi) in Cam Thanh commune where nypa palms and seagrasses grew is the most important nursery ground for seeds of target species.
  • Diversity of grouper fish (Serranidae) in coastal zone waters from Da Nang to Binh Thuan

    Vo, Van Quang (2018)
    Based on surveys in 2014 and 2015, the species composition of groupers (Serranidae) caught in coastal areas from Da Nang to Binh Thuan is quite diverse with 38 species belonging to 7 genera. A collection of published works and these surveys (2014–2015) have showed that this sea area has 58 species belonging to 11 genera of family Serranidae; genus Epinephelus has been the most diverse one with 35 species. In which Khanh Hoa waters have the highest number of species of grouper with 45 species, followed by Binh Thuan with 25 species. The species of grouper from Da Nang to Binh Thuan coastal waters occupy 80.6% compared to the component species of grouper in Vietnam’s waters (72 species) and 46% of species of grouper in the Bien Dong (126 species). Groupers of Khanh Hoa waters are also more diverse compared with those in coral reef of Vietnam and coastal zone of North Central areas. The species composition of groupers (Serranidae) from Da Nang to Binh Thuan coastal zones has the association with six areas, including Andaman Sea (Thailand), coral reef of Vietnam, coral reef of Truong Sa archipelago, Quang Ninh - Thua Thien-Hue provinces, Hong Kong and Taiwan waters. In which similarity coefficient is highest with Hong Kong and Quang Ninh - Thua Thien-Hue provinces. However, it is lowest with coral reef of Truong Sa archipelago.
  • Assessment of the survival and growth rate of some hard coral species rehabilitated in Ly Son MPA Quang Ngai province

    Hoang, Xuan Ben; Thai, Minh Quang; Phan, Kim Hoang; Mai, Xuan Dat; Hua, Thai Tuyen; Nguyen, An Khang (2018)
    The total 3,630 foliose corals belonging to Pachyseris speciosa, Merulina scabriculata, Montipora verucosa and Echinopora lamellosa species were translated to restoration in Ly Son MPA. Translated hard corals to restoration were successfully and effectively rehabilitated by using techniques to attach fragment on dead coral substratum and concrete sink (reef balls). Mean survival rate of coral fragments ranged from 96.9% (± 2.7 SD) to 98.5% (± 1.3 SD) on the concrete sink and dead coral substratum, respectively. The growth rate of three species Echinopora lamellosa, Merulina scabriculata and Montipora verucosa ranged between 1.5–2.1 mm/month and did not differ between concrete sink, dead coral substratum and control (P > 0.05). Meanwhile Pachyseris speciosa showed a low growth rate of 0.9–1.5 mm/month which was significantly different between translated fragments and control (P < 0.05). The rehabilitation and protection activities of coral reefs in Ly Son should be continued and expanded, contributing to the protection of biodivesity and marine resource for sustainable economic development.
  • Species composition and distribution of Mollusca and Echinodermata on coral reefs in survey on Akademik Oparin RC in 2016-2017

    Thai, Minh Quang; Hua, Thai Tuyen; Nguyen, An Khang (2018)
    A study on the species composition and distribution of Mollusca and Echinodermata on coral reefs from Quang Tri to Binh Thuan was conducted during the field survey between Vietnam and Russia on the AKADEMIK OPARIN RC vessel in 2016 and 2017 at 39 reef stations. 150 species were identified belonging to 100 genera, 50 families, 22 orders, 7 classes distributed on coral reefs. The species composition of mollusca and echinodermata was different between study areas.
  • An assessment on the effectiveness of coral reef management by tourism sector in Nha Trang bay, Viet Nam

    Vo, Si Tuan; Hua, Thai Tuyen; Nguyen, Van Long; Phan, Kim Hoang; Hoang, Xuan Ben; Mai, Xuan Dat (2018)
    The models of coral reef management for the development of ecological tourism were conducted under the coordination among the 3 businesses (Khanh Hoa Salanganes Nest Company, Vinpearl Nha Trang and Tri Nguyen Tourism), Institute of Oceanography and Khanh Hoa Department of Natural Resources & Environment. The analysis of trends of coral cover, density of reef fishes and big size invertebrates at 3 sites allowed assessing effectiveness of 3 years’ management. The stability of hard coral cover, except the decline at southern Hon Tam due to impacts of the typhoon in Nov., 2017 indicated no increased damage to corals from human activities. However, the dominance of small size fish (< 10 cm in length), the decline of density of larger size fish and the poorness of large size invertebrate showed continuous overexploitation at these managed areas.
  • Biodiversity of zooplankton community in coastal area of Son Tra peninsula, Da Nang

    Truong, Si Hai Trinh; Nguyen, Tam Vinh (2018)
    Zooplankton samples were collected at 16 stations in the coastal waters of Son Tra peninsula, Da Nang city in dry season (7/2016). At each station, zooplankton samples were collected by using Juday net (mouth diameter: 37 cm, mesh-zise: 200 µm) from 1 m above bottom to surface. 112 species belonging to 11 zooplankton groups were identified. Copepod was a dominant group with 67 species, followed by Tunicate (13) and Gastropod (7). The Northeast and Northwest areas of Son Tra peninsula have a higher biodiversity than the South and Southeast based on number of species, species richness value. An average density of zooplankton was 7.768 ins.m-3 and was decided by copepod density (3.759 inds.m-3 on average). Station 4 had the highest number of individual and station 18 had the lowest zooplankton density. Oikopleura fusiformis was dominant in most of stations in the north area (22.16%) and in the northwest (15.97%), while copepod species Paracalanus crassirostris was dominant in the northwest (16.51%) and in the south (24.57%) of Son Tra based on SIMPER analysis (90%).
  • Phytoplankton in coastal waters of Da Nang province

    Tran, Thi Le Van; Doan, Nhu Hai; Phan, Tan Luom; Nguyen, Thi Mai Anh; Tran, Thi Minh Hue; Huynh, Thi Ngoc Duyen (2018)
    Phytoplankton, especially community characteristics, in coastal waters of Da Nang have not been well studied. This present study analyzed data of phytoplankton for diversity and abundance from surveys from 2002 to 2016 at 44 stations in the coastal Da Nang waters. A total of 316 taxa from 9 classes were identified: Dinophyceae (134 taxa), Mediophyceae (77 taxa), Coscinodiscophyceae (44 taxa), Bacillariophyceae (36 taxa), Cyanophyceae (3 taxa), Dictyochophyceae (2 taxa), Bacillariophyta classis incertae sedis (1 taxon), Conjugatophyceae (1 taxon) and Thecofilosea (1 taxon). A list of 36 species of potentially harmful microalgae was recorded in coastal waters of Da Nang. In which, Pseudo-nitzschia spp. often had higher cell densities in some locations during the northeast monsoon. Analyzing diversity indices in different locations showed that there were significance differences of Margalef and Shannon indices, low in estuarine area (CS) and higher in the south of Son Tra peninsula (NST). Meanwhile no strong differences of Pielou and Simpson indices were found among the locations. However, there were strong differences of Margalef, Simpson and Pielou indices, which were found over the three studied years (2004, 2005, and 2006), mainly in NST, the northeast of Son Tra peninsula (DBST) and Da Nang bay (VDN). Analysis of species accumulation curves indicated that only 56–95% of species was found compared to maximal expected species richness in all studied locations. DMS analysis showed that there was year-based similarity among the years (ca. 50% of similarity) of phytoplankton communities. Among the studied years, average phytoplankton cell densities in Da Nang bay and the northeast of Son Tra were higher than those in other years and locations. This present study on species richness, expected species richness and variation in phytoplankton abundance suggested that there is a need of increasing sampling efforts, especially in riverine area and DBST for better understanding of characteristics of phytoplankton communities in coastal Da Nang waters.

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