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Recent Submissions

  • Antibiotics resistance in pathogenic bacteria isolated from water and sediment around the floating fish farms in the Nha Trang bay

    Nguyen, Kim Hanh; Nguyen, Trinh Duc Hieu; Nguyen, Minh Hieu; Vo, Hai Thi; Pham, Thi Mien; Hoang, Trung Du; Phan, Minh Thu; Nguyen, Huu Huan (2020)
    To 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.
  • Antioxidant activity of extract from some squid species in Khanh Hoa

    Nguyen, Phuong Anh; Pham, Xuan Ky; Dao, Viet Ha; Le, Ho Khanh Hy; Doan, Thi Thiet; Phan, Bao Vy (2020)
    The 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.
  • Certain properties of nanohydroxyapatite obtained from Lates calcarifer fish bone

    Le, Ho Khanh Hy; Dao, Viet Ha; Pham, Xuan Ky; Nguyen, Phuong Anh; Phan, Bao Vy; Doan, Thi Thiet (2020)
    Fish bone by-products are considered as abundant source of hydroxyapatite (HAp). The preparation of HAp from fish bones not only contributes to improving the value of by-products but also minimizes negative impacts on the environment. In this study, nanohydroxyapatite was successfully obtained from Lates calcarifer fish bone purchased from seafood export company in Khanh Hoa province. Fish bones were under alkali treatment and then heated at 600oC within different time intervals of 1, 2 and 4 hours. Analysis of XRD and SEM showed that the calcium formed was completely single-phase and possessed an average size of 50–64 nm depending on the calcination time. The results of the Ca/P molar ratio from 1.839 to 1.847 prove that the nano-HAp powders are B-type biological hydroxyapatites, which has been confirmed by FTIR spectrum. In addition, the content of heavy metals such as As, Pb, Hg, Cd is detected within safety limits. These properties allow nano-HAp powders to be applied in food and medicine fields.
  • Effect of dietary astaxanthin on reproductive performance, egg quality and larvae of clowfish Amphiprion ocellaris (Cuvier, 1830)

    Nguyen, Thi Nguyet Hue; Ho, Son Lam; Dao, Thi Hong Ngoc; Dang, Tran Tu Tram; Huynh, Minh Sang; Dinh, Truong An; Doan, Van Than; Nguyen, Truong Tan Tai; Do, Hai Dang; Hua, Thai An (2020)
    This study was designed to evaluate the effects of astaxanthin in broodfish diets on reproductive performance, egg quality and larvae quality parameters of clownfish (Amphirion ocellaris). Five treatments were tested with 5 levels of astaxanthin (Carophyll Pink 10% CWS) of 0, 50, 100, 150 and 200 mg/kg added to the feed. Each treatment was repeated in triplicate and the supplemental feeding trials were arranged for 13 months. The results showed that there were significant differences in hatching rate of egg, malformed rate and survival rate of larvae in 3 days post-hatch (p<0.05) among the feeding trials of astaxanthin supplements. The highest hatching rate of egg and survival rate and the lowest malformed rate of larvae were observed in the treatment that was supplemented with astaxanthin 150 mg/kg feed, respectively 92.14 %; 93.57 % and 0.55 %. However, the astaxanthin supplementary diets did not affect the re-maturation and spawning period, spawning frequency, fecundity, egg diameter and larval size of nemo fish among the treatments. The results also suggested that astaxanthin requirement for clownfish broodstock to improve reproductive performance was 150 mg/kg feed.
  • Mollusks in the rocky tidal zone of the Phu Quoc island

    Hua, Thai Tuyen (2020)
    Results of the survey of mollusks in the rocky tidal zones at 22 sites along the Phu Quoc island in April 2019 has identified 42 taxa of Mollusks, belonging to 3 classes: Gastropoda (25 taxa), Bivalvia (16 taxa) and Polyplacophora (1 taxon). Species composition between stations varies from 2 to 9 species. The average density was 21.07 individuals/m2, ranging from 3.67 individuals/m2 in Southeastern Kim Qui to 84.22 individuals/m2 in Hon Dam Ngoai. Density of mollusks was highest in the middle tide zones (42.42 individuals/m2), followed by high tide zones (14.55 individuals/m2) and lowest in the low tide zones. Density dominance belongs to two species Patella sp. and Siphonaria sp. distributed in the middle tide zones.
  • Optimizing conditions for treatment and extraction of collagen from fan-bellied leatherjacket skin Monacanthus chinensis (Osbeck, 1765)

    Doan, Thi Thiet; Pham, Xuan Ky; Phan, Bao Vy; Nguyen, Phuong Anh; Le, Ho Khanh Hy; Dao, Viet Ha; Vu, Ngoc Boi (2020)
    The fan-bellied leatherjacket skin was treated to extract collagen by chemical method. The non-collagenous substances and the pigment in the skin were removed with NaOH and H2O2, respectively. Collagen was extracted with acetic acid. The treatment and extraction conditions were optimized by response surface methodology. The concentrations, skin/solution ratios (g/ml) and times were surveyed. The optimum conditions to remove the non-collagenous substances were as follows: the concentration of NaOH at 0.15M, the ratio (g/ml) at 1/13.9, time at 56.9 hours. Using H2O2 with the concentration at6%, the skin/solution ratio (g/ml) at 1/2, time at 10 minutes were suitable values for skin pigmentation removal. For collagen extraction, the concentration of acetic acid at 0.53M, skin/solution ratio at 1/9.6 g/ml and time in 59.6 hours were optimal.
  • Coral reef fishes in the coastal waters of Ninh Thuan province

    Mai, Xuan Dat; Nguyen, Van Long; Phan, Thi Kim Hong (2020)
    This study was conducted to evaluate the species composition and distribution of coral reef fish communities at 24 sites in three areas Ninh Hai, Phuoc Dinh, and Ca Na in Ninh Thuan province from 2018 to 2019. A total of 301 species belonging to 131 genera and 49 families of coral reef fishes were recorded. Among them, the wrasse (Labridae: 55 species), the damselfish (Pomacentridae: 46 species) and the butterflyfish (Chaetodontidae: 26 species) occupy the three highest proportion. The average density of coral reef fish in coastal waters of Ninh Thuan province is 106.8 ± 23.4 individuals/100 m2, most of them are small sized fish and ornamental fish groups. Ninh Hai has a higher species richness and density than other areas. Meanwhile, Ca Na and Phuoc Dinh have the two highest densities of the large sized fish and food target fish groups. This research also points out the impact of monsoon on the density and distribution of coral reef fish, in which Ninh Hai is most affected.
  • Estimation of the spawning ground of some fish species in the Nha Trang bay

    Vo, Van Quang; Tran, Thi Hong Hoa; Tran, Cong Thinh; Le, Thi Thu Thao (2020)
    The paper presents the results of determining the spawning grounds of some fish species in Nha Trang bay MPA, which were sampled in 9/2018, 11/2018, 5/2019 and 7/2019. The analysis results are based on the distribution of the general density and the developmental stages, analysis of decision trees from egg density, location of stations and months by CHAID (Chi-square Automatic Interaction Detector), allowing a relatively accurate estimate of the spawning ground of the red anchovy (Encrasicholina punctifer Fowler, 1938) and the species of the genus Scarus. As a result, the main spawning grounds for red anchovy were the east of Hon Rua and the northeast of Hon Tam and that of Scarus is the southwest of Hon Mun island.
  • Captive culture of two sea snake species Hydrophis curtus and Hydrophis cyanocinctus

    Nguyen, Trung Kien; Hua, Thai An; Huynh, Minh Sang; Do, Huu Hoang; Cao, Van Nguyen; Ho, Thi Hoa (2020)
    Acclimation culture and trial culture of two sea snake species Hydrophis curtus and H. cyanocinctus in composite tanks were conducted to determine growth, survival rate, predation behavior and prey selection. The results showed that adults of H. curtus and H. cyanocinctus did not capture any prey such as anchovy, eel and shrimp in a period of 30 days of acclimation culture. The body weight of two these species reduced gradually from 783.3 ± 76.4 g and 360.0 ± 60.0 g to 660.0 ± 135.2 g and 315.0 ± 77.8 g, respectively. Survival rate was 100% in H. curtus and 80% in H. cyanocinctus. Meanwhile, the results of acclimation culture of sea snake juvenile revealed that frozen anchovy was preferred prey in both of two species. The body weight of H. curtus increased from 49.8 ± 0.5 g to 70.0 ± 8.2 g and that of H. cyanocinctus was 44.3 ± 3.1 g to 47.1 ± 5.2 g. The prey capture rate of H. curtus and H. cyanocinctus was 100% and 60%, respectively. Survival rate of the juvenile of two species was 100% after 30 days of acclimation culture. In 60 days of trial culture, similar results as acclimation culture were observed in adults of two sea snake species, they still did not capture any prey and the body weight reduced gradually. The result of 60-day culture of sea snake juvenile showed that the prey capture rate was 100% in both of two species. The body weight of H. curtus and H. cyanocinctus increased from 70.0 ± 8.2 g and 57.5 ± 5.8 g to 78.3 ± 15.3 g and 65.0 ± 14.1, respectively. SGR of H. curtus was 0.16 ± 0.32 %/day and that of H. cyanocinctus was 0.52 ± 0.36%/day. The survival rate of H. curtus and H. cyanocinctus was 60% and 40% in period of 60 day trial.
  • Morphology, abundance and the invasiveness of coral-killing sponge Chalinula nematifera (Porifera: Demosponigiae) from Con Dao National Park, Vietnam

    Thai, Minh Quang (2020)
    This is the first study on morphology, abundance and invasion of coral-killing sponge Chalinula nematifera (De Laubenfels, 1954) from offshore waters in Con Dao islands, Vietnam. The results of the study show that the morphology is similar to that in the Western Pacific, but differs in skeletal structure compared to the description in the Eastern Pacific. The density of C. nematifera (average ± standard deviation) is 2.02 ± 5.03 colonies per 100 m2 (present at 12/15 survey stations) with the number of colonization belonging to diameter group 5–20 cm. They invade 30 species belonging to 23 genera of Scleractinia corals (44.7% on foliose/laminar and encrusting coral, 23.86% on massive coral and 21.97% on branching coral). The ability to invade corals of C. nematifera does not limit the host. So, this is considered a potential hazard to the East Vietnam Sea coral reefs in the future.
  • Some species of macro-gastropods in the coastal zone of Khanh Hoa province

    Bui, Quang Nghi; Nguyen, Thi My Ngan; Nguyen, Kha Phu (2020)
    From November 2013 to March 2014, 104 species were collected, belonging to 27 families, 58 genera of Gastropoda in coastal area of Khanh Hoa province. Some families have a large number of species such as Conidae - 15 species; Strombidae - 15 species; Cypraeidae - 10 species; Terebridae - 7 species and Muricidae - 6 species. Many species of economic value are used for food and fine arts. 11 species are listed in Vietnam Red Data Book. Besides, images and information of samples (collecting date, place of sample collection,...) are presented.
  • Species composition and distribution of seaweeds in Phu Yen province

    Nguyen, Thi Thu Hang; Nguyen, Van Tu; Vo, Van Phu; Nguyen, Ngoc Lam (2020)
    Results of four field surveys, conducted from June 2017 to June 2018 found that in the Phu Yen coastal water, a total of 103 seaweed species have been recorded, increasing the total number of seaweed species in Phu Yen province to 133 species, with 81 newly recorded species for Phu Yen geographic area. Among 103 seaweed species, 4 species belong to Cyanobacteria, 38 species belong to Rhdophytes, 24 species belong to Phaeophytes, and 37 species belong to Chlorophytes. The number of species at surveyed sites V1 to V9 varies from 3 species/site (V3) to 83 species/site (V7) and on average 27 species/site. Sørensen’s similarity coefficient varies from 0.05 (between V3 and V7) to 0.86 (V3 and V4) and on average 0.25. 74/103 species were collected in the littoral zone, 67 species in sublittoral zone and most of them are distributed at 0-4 m water depth of subtidal zone. The marine algal flora is represented by mixing of subtropical and tropical characteristics as Cheney index was 3.
  • Assessment of effective coral rehabilitated in Marine Protected Areas of South Vietnam

    Hoang, Xuan Ben; Vo, Si Tuan; Phan, Kim Hoang (2020)
    More than 20,300 fragment corals belonging to 24 species, eight genera and six families were rehabilitated in marine protected areas of south Vietnam. Mean survival rates of coral fragments ranged from 60–97.7%, the average growth rate of the branched corals was 4.8 mm/month meanwhile the foliose coral was 1.9 mm/month. The survival and growth rate of corals are different among areas because each coral species has different biological characteristics, structure colonies and due to differences in natural conditions each area. The results showed that the growth rate of corals will return to normal after 4 months rehabilitation. The factors affected the effective coral rehabilitation including: Coral reef predators, spatial competition among species, environmental conditions change due to human’s activities; and other factors such as hydrodynamic regimes, cutting fragment corals cause its injury damage. The rehabilitation and protection activities of coral reefs in marine protected areas should be continued and expanded, contributing to the protection of biodivesity, marine resource and sustainable coral reefs ecosystem development.
  • Bleaching of coral in Nha Trang, Ninh Thuan, Con Dao and Phu Quoc islands in June–July 2019

    Phan, Kim Hoang; Vo, Si Tuan; Thai, Minh Quang; Dao, Tan Hoc; Hua, Thai Tuyen (2020)
    The studies on coral bleaching were conducted at 21 sites of 4 reef areas in Southern Vietnam, using point transect technique in June–July 2019. Cover of hard corals in the selected sites was quite high with the average values of 65.6 ± 18% % in Con Dao islands, 58.7 ± 26.2% in Ninh Thuan coastal waters, 55.9 ± 17.8% in Phu Quoc island but lower in Nha Trang bay (22.8 ± 15.9%). Soft corals were not abundant with the highest cover in Nha Trang bay (4.73 ± 5.5%) and the lowest in Ninh Thuan (0.16 ± 0.3%). Hard corals were most impacted in Nha Trang bay with 39.5 ± 8.1% bleached, followed by Ninh Thuan reefs (32.9 ± 13.3%), Con Dao Islands (25.0 ± 11.1%) and least affected in Phu Quoc island (7.3 ± 9.05%). For soft corals, ratios of bleached corals were 79.4%, 65.8% and 23.8% in Con Dao islands, Nha Trang bay and Ninh Thuan reefs respectively. No bleached soft coral was recorded in Phu Quoc. At the genus level, Acropora corals were severely affected in Nha Trang bay, Ninh Thuan reefs and Phu Quoc island but not impacted in Con Dao islands. The Porites, Montipora, Millepora genera were quite vulnerable in all sites but no bleaching was observed for Galaxea and Diploastrea genera.
  • Levels of heavy metals in seawater, sediment and in the tissue of Crassostrea belcheri in the Western estuary of Ganh Rai bay

    Le, Hung Phu; Nguyen, Hong Thu; Pham, Hong Ngoc; Le, Trong Dung; Dao, Viet Ha (2020)
    Recent studies have shown that the seawater, sediment and commercial bivalve molluscs in the studied area have been contaminated by some heavy metals Zn, Cu, Pb and Cr. Highly toxic heavy metals like As, Cd, Pb, Hg have tended to accumulate in the tissue of clams. This paper presents the levels of some heavy metals in the seawater, sediment and soft part of oyster (Crassostrea belcheri) samples collected from the western estuaries of Ganh Rai bay in 2015 and 2017. The results also showed that Ha Thanh and Rach Lo sites recorded the highest contents of most studied metals in oyster samples. Levels of metals in oyster were in the order of Zn > Cu > As > Pb > Cr > Cd > Hg and the contents of metals in oyster did not reflect a correlation with those in surrounding environment. Concerning food safety criteria, Pb, Cd and Hg contents were lower than acceptable limit given by the compilation of FAO (1983), whereas As, Cu and Zn contents exceeded the legal limit, especially Zn contents. Cu and Cr contents in sediment samples of Nga Bay and Dong Hoa estuaries were between LEL-SEL values (≥ LEL and < SEL), which may cause biological impacts at moderate level.
  • Zooplankton community in Thi Nai lagoon in the period of 2001-2020

    Nguyen, Tam Vinh; Doan, Nhu Hai (2020)
    This paper presents the results of the surveys on zooplankton in Thi Nai lagoon from 2001 to 2020. There were 179 species found in the lagoon, among which Copepod was the dominant group with 97 species (50.78% of total species), followed by Cladocera with 20 species (10.36%), Hydrozoa with 18 species (9.33%), Tunicata with 11 species (5.7%) and Siphonophora with 10 species (5.18%). Based on Bray-Curtis similarity analysis of zooplankton community and the station position, the sampling stations in the lagoon were grouped into three areas: The upper lagoon (UP), the middle (MI), and the mouth of the lagoon (MO). Among the surveyed years, there was a slight variation in the species number, while the density decreased by time and was especially low in 2020. Zooplankton density was much lower in the rainy season compared to that in the dry season, while the species number was less varied. Analysis of the differences between the areas in the lagoon demonstrated a clear distribution pattern of zooplankton with a decreasing density and an increasing number of species from upper lagoon to the mouth of the lagoon. Zooplankton diversity was less affected by time and only the Pielou index in the MI area between 2004 and 2009 was significantly different. Analysis of the various indices between seasons showed that the MO area was less volatile than the two other regions. The multi-dimensional scaling analysis demonstrated that zooplankton community was less variable by regions (50% similarity) compared to by the years (only 30% of similarity), except in 2009 and 2020 when differences among the areas were significant. Seasonal community change between the dry and rainy seasons was 30%.
  • Variation of phytoplankton community structure in Quang Ngai coastal waters during 2015-2019

    Huynh, Thi Ngoc Duyen; Tran, Thi Minh Hue; Tran, Thi Le Van; Phan, Tan Luom; Nguyen, Ngoc Lam; Doan, Nhu Hai (2020)
    Phytoplankton in coastal waters are important for the evaluation of either biodiversity or environmental impacts because of this highly vulnerable ecosystem. Seasonal and annual changes in the phytoplankton community structure in Quang Ngai waters during the period 2015 to 2019 were analyzed to assess the phytoplankton diversity and reveal possible causes of these changes. A total of 366 phytoplankton taxa belonging to 10 classes were identified throughout this present study. The highest species number was found in 2019 with 295 taxa, followed by those in 2015 (247), 2017 (185), and 2018 (99). The waters of Ly Son transect showed the highest diversity and most stable phytoplankton communities in both dry and rainy seasons, whereas the stations of Quang Ngai coast revealed high variability of the communities. All diversity indices including Margalef, Pielou, Shannon, Simpson did not reflect well differences in average values but a certain degree of variances, indicating possible environmental impacts. During the study time, there were blooms of certain diatom species including Skeletonema spp. in 2015 and Pseudo-nitzschia spp. in 2019. Analysis of a diatoms index, Centric/Pennate ratio, indicated that the waters were in eutrophic status with a decreasing trend from the coast area to Ly Son island in 2015 and 2019. This research built up fundamental data on phytoplankton communities for Quang Ngai province. The Centric/Pennate diatom index and diversity would be used as indicators for environmental changes and their values provided warning of eutrophication in this coastal waters including the water surrounding Ly Son island.
  • Study on distribution characteristics of wind speed field in the sea area of Ly Son island of Quang Ngai province

    Tran, Van Chung; Ngo, Manh Tien; Nguyen, Van Long (2020)
    On the basis of the data source of the 10 m wind field above the sea with the hourly frequency and during the period of 41 years (1979–2019) by the NCEP CFRS, we used the probability distribution functions to study the distribution law of wind speed in the waters of Ly Son island. Specifically, four distribution functions (normal distribution, gamma distribution, Weibull distribution and extreme value distribution) were used to estimate the characteristic parameters of the shape and proportion of the wind distribution in the waters of Ly Son island.
  • Fluctuations of wind and temperature fields in Ninh Thuan-Binh Thuan waters and its possible relationship with coral bleaching

    Van Chung, Tran; Manh Tien, Ngo; Van Nguyen, cao (2020)
    Temperature and wind on the sea surface are factors affecting the development of coral reefs in the seawaters. The research results show that the warming of sea water under the condition of weak wind field is considered a major threat to the bleaching of coral reefs in the sea areas of the Ninh Thuan - Binh Thuan provinces.
  • Observations biologiques sur les Stomatopodes

    Serene, Raoul (Institut Océanographique de Nhatrang (Viet-Nam)Vietnam, 1954)
    The present study deals with a systemic revision of Stomatopods belonging to the collection of the Institut Oceanographique de Nhatrang (Vietnam).

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