• 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.
    • Application of toxicity testing technique: determination of LC50 of arsenic on some marine organisms

      Le, Lan Huong (2000)
      Results obtained from toxicity testing experiments on Artemia (1998), Tiger prawn (Penaeus monodon) (1998-1999) and Seabass (Lates carcarifer) (1998-1999) led to determine the LC50 values of Arsenic on them with 24-h, 48-h, 72-h, and 96-h exposure. LC50-s tended to decrease by the exposure duration. In the same exposure duration, LC50 value of Seabass showed smaller than that of Tiger prawn and both values were smaller than that of Artemia. It means that the sensitivity to lethal toxic effect of Arsenic showed decreasing by following order: Seabass > Tiger prawn > Artemia.
    • 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.
    • 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.
    • Assessment on environmental status and consideration for the impact of cage aquaculture on sediment quality in Vung Ro bay, Phu Yen province.

      Hoang, Trung Du; Nguyen, Huu Huan; Vo, Hai Thi; Le, Trong Dung; Le, Tran Dung; Nguyen, Huu Hai (2015)
      The results of investigated and analyzed sediment samples were collected during May, 2014 in Vung Ro bay showed that the distribution of particles sizes in the sediment samples had almost type of muddy and muddy – clay sediments (the average particle sizes ranged from 0.063 - 0.004 mm, with the proportion > 40%). Content of TOM in surface sediments slightly changed among areas) with the average value of 71.04 ± 7.52 mg/g (ranged from 52.92 to 75.56 mg/g). The profile distribution of TOM, TOC and total P contents in the depth of the sediment cores at inside and outside of farming areas were not highly fluctuated among sediment layers. The differences of the total N content in sediment layers showed that there was the gradually increasing trend from the lower sediment layers upwards (higher from 6 cm to 0 cm depths) in both of sediment cores. Heavy metal contents slightly ranged among the investigated points and were relatively low: Cu ranged from 6.19 to 7.90 mg/kg; Pb ranged from 22.53 to 25.76 mg/kg; Zn ranged from 41.48 to 59.58 mg/kg; Cd ranged from 0.14 to 0.31 mg/kg and As ranged from 2.80 to 8.10 mg/kg. The results of petroleum hydrocarbon also showed very low content with the average value was 4.4 ± 1.7mg/kg. Total Vibrio spp. showed high density in most points, and average value was 132,249 ± 69,948 cfu/100g. The contents of heavy metals in the bay did not exceed the critical values in QCVN 43: 2012/BTNMT.
    • 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%).
    • Biological characters of Lutianus erythopterus (Bloch, 1790) on the southeastern region of Vietnam

      Le, Trong Phan; Ho, Ba Dinh; Dinh, Hong Thanh; Vo, Van Quang (2000)
      Lutianus erythropterus (Grimson snapper) is one of the most common snappers in the southeastern region of Vietnam. The Grimson snapper fishery in this region is a very important source of food and revenue for Vietnam, but knowledge of the biology of the species is rare. This work presents first results on age and length, growth-rate, length - weight relationship, periods of spawning, feeding intensity and food composition of this species.
    • 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.
    • The calculated results of current field and its effects on the process of sediment transport at Dong Bo river mouth (Cua Be), Nha Trang

      Vu, Tuan Anh (2002)
      In dry season, the calculated results for a tidal phase (from 11h/28/4 - 11h/29/4/01) showed that the maximum velocity of the currents was 37 cm/s in ebb-tide phase and 28 cm/s in flood-tide phase. The movement of bottom materials was not considerable, about 1 m3 of bottom materials run out from the study region. In rainy season, in the tidal period (from 23h/4/11 – 23h/5/11/01), the current field was stronger than that in dry season with maximum values of velocities of 100 cm/s and 27 cm/s, in ebb-tide and flood-tide phases, respectively. There was about 10 m3 of bottom materials running out from the region. The maximum erosion rate was 380.10-4 m per 24 hours (tidal period) and the maximum deposition rate was 210.10-4 m per 24 hours.
    • 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.
    • 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.
    • 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.
    • 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.