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  • 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.
  • Characteristics of sediment distribution and prospects of marine placers in shallow costal waters of Binh Dinh province

    Trinh, The Hieu; Nguyen, Dinh Dan (2018)
    This paper presents characteristics of distribution of sediment types in shallow coastal waters (0–50 m water) in Binh Dinh province. The results show that sediments of the surface layer of the studied area have a rather complicated distribution, reflecting many sedimentation periods, in which the sandy sediment type is predominant. They consist of eight types of sediment and are divided into five major zones of sediment from the shore to the corresponding depths: From shore to 5 m, 6–24 m, 31–33 m, 35–47 m, and from 47 m or more. The paper also outlines the heavy mineral prospects contained in the sediments, including: Ilmenite, rutile, zircon, anatase, monazite, magnetite. Heavy minerals are concentrated mainly in the grain size from 0.125–0.25 mm, among which ilmenite is predominant with content in the heavy range of 65.5–83.43% and is mainly distributed in the type of fine sand deposits at depths from 5 m to 24 m. Based on that, it is possible to delineate five prospective areas within the study area.
  • Distribution features of measured wave characteristics in coastal waters of Ninh Thuan province, Viet Nam

    Le, Dinh Mau; Nguyen, Van Tuan (2018)
    This paper presents the distribution features of wave characteristics based on the continued measurement wave data with interval of 1 hour from January to December 2013 in coastal waters of Ninh Thuan province. The study results show that the dominant wave directions were in East-North-East (ENE), East (E), South-South-East (SSE) and South-East (SE) with occurrence frequency of 36.7%, 20.5%, 18.2% and 11.6% respectively. During North-East (NE) monsoon the dominant wave directions were in ENE and E. During South-West (SW) monsoon the dominant wave directions were in SSE and SE. The remaining directions were rare. The maximum values of wave height (Hmax) was 4.84 m (11/2013), wave period (T) was 10.9 s (11/2013). The occurrence frequency of Hs ≤ 0.5 m was 43.9%, Hs ≈ 0.5–1.0m was 21.9%, Hs ≈ 0.5–1.0 m was 21.9%, Hs ≈ 1.0–2.0 m was 27.3%, Hs > 2.0 m was 6.8% and calm wave condition (Hs ≤ 0.25 m) was 8.1%. The duration and intensity of wave action were dominant in NE monsoon period.
  • Some study results on the characteristics and variability of water masses in the South Central Vietnam

    To, Duy Thai; Bui, Hong Long; Nguyen, Van Tuan; Nguyen, Chi Cong; Phan, Thanh Bac; Nguyen, Truong Thanh Hoi; Nguyen, Duc Thinh; Nguyen, Thi Thuy Dung (2018)
    Study on the characteristics and variability of water masses has great practical significance in determining the original of water bodies for the most general view of the hydrodynamics in that area. This also helps in comprehensive research and water partition according to the set of natural conditions to serve the rational exploitation of marine resources and environmental protection. The study on the water masses in the South Central Vietnam has been carried out by many scientists and has quite detailed results in the characteristic of water mass in this area, but the results are mainly based on measured data of salinity-temperature up to 2006. Although the distribution of data is relatively good, but the systemization and synchronization are limited. In this paper, based on updating the newly observed data from many projects in recent years such as Vietnam-Russia (2011), Vietnam-USA (2013, 2015), and basic projects in the Institute of Oceanography (2016, 2017), the results have identified the origin of surface water masses in the study area from the East Vietnam Sea, the Western Pacific Ocean and the Java Sea. In addition, we have also seen changes in the number of water masses and the structure of the water mass changes in characteristics such as temperature, salinity, and depth of their existence during ENSO.
  • The initial study on circulation at North-Western Pacific by numerical model

    Pham, Xuan Duong (2015)
    This paper shows the results of the initial study on circulation at North-West Pacific by numerical model (ROMS). Using OpeNDAP (Open-source Project for a Network Data Access Protocol) access to global data obtained in the study area as input to the model. The first results showed that there were strong currents flowing continuously near the west coast of the East Sea and the east coast of the Philippines. The velocity of circulation at the east coast of Philippines was often greater than that at the west coast of Vietnam. In the North-Western Pacific, there was more turbulence appeared in the different regions with diameter of 50 kilometers to hundreds of kilometers. Calculation on the circulation in the West of East Sea compared with the documents of the Naval Command in 1985 showed that the direction of movement of floating objects was similar.
  • Topographical and sedimentological characteristics of Van Phong bay, Khanh Hoa province

    Pham, Ba Trung; Nguyen, Dinh Dan; Tran, Van Binh; Trinh, Minh Cuong (2014)
    The coastline of Van Phong bay is alternation between rocky coast, rocky headlands and sandy beaches. Four main types of terrain can be distinguished such as: bedrock, accumulation, abrasion - erosion, and ancient accumulation coasts. In addition, the coastline of Van Phong bay is gathered a lot of marine accumulative terrace. Bottom topography of Van Phong bay could be divided into two parts: Ben Goi bay (inside part) is characterized by the shallow depth (less than 20m) with the main axis is laid in Northeast-Southwestern direction. Bottom topography is relatively simple with gentle slope. Van Phong bay (outer part) is characterized by deeper depth (from 20 to 30m) with the main axis is laid in Northwest-Southeastern direction. The bottom topography is relatively flat. Besides, the embayment of Co Co – Cua Be area, with average depth of 20 - 23m, which is connected to the open sea through Cua Be channel. Cua Be channel is characterized by average depth of more than 30m and width of about 1.2km, which is an ideal natural area for marine transportation and harbor activities. Depending on the source of supplied materials and hydro-litho-dynamic processes the surface layer of bottom sediment in Van Phong bay is dominated by medium sand, silt and clay. In there, the silt and clay cover the largest area.
  • Geomorphological characteristics of Nha Trang bay and adjacent area

    Tran, Van Binh; Nguyen, Dinh Dan; Pham, Ba Trung (2015)
    The bottom topography of Nha Trang bay and adjacent area is very diverse and complex, especially in architecture of terrain morphology. It was partitioned by a system of many large and small islands in Nha Trang bay, and created many features of the terrain types on the surface of the seabed such as: deep creek, valley trough mix between the islands that was favorable condition for the marine transportation. The sediment types were differentiated quite clearly on the surface of the seabed topography from the coarse grain of gravelly sand to mud-clay. Therefore, the geomorphology was also varied. By the traditional research method, the geomorphology was divided into 9 geomorphological units and was shown on an overall picture through three different dynamic zones: two geomorphological units for surf wave zone; five geomorphological units for wave zone of destruction and deformation, and two geomorphological units for offshore wave zone.
  • The experimental study on current fronts during the southwest monsoon in the coastal waters of Khanh Hoa province

    Pham, Sy Hoan; Nguyen, Ba Xuan; Bui, Hong Long (2015)
    Calculation of current fronts plays the important role in oceanographic research. It will be the key for calculating other fronts in oceanography as temperature, salinity… However, up to now calculation of current fronts in the coastal areas has not been interested specially, because it may be not enough samples. Some characteristics of gradient of the current components and their fronts were defined depending on newly observed data in July and August 2010. Values of gradient of longitudinal current component were higher and more variant than latitudinal current component. Values of gradient module of longitudinal and latitudinal current components varied from 0.03 to 9.76 cm/s/km and from 0.04 to 6.94 cm/s/km respectively. Average values of gradient of these components were very small, from 0.74 to 1.40 cm/s/km (latitudinal component) and from 1.36 to 2.01 cm/s/km (longitudinal component). Gradient module near the surface layers (2 m and 5 m of depth) was higher and more variant than that at deeper layers (25 m and 50 m). The front index, which current components begin forming fronts, was defined by more 2.44 cm/s/km and more 3.94 cm/s/km for longitudinal and latitudinal current component correspondingly depended on statistical gradients.

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