Taxonomic composition of bacteria associated with cultivated mollusks <Emphasis Type="Italic">Crassostrea lugubris</Emphasis> and <Emphasis Type="Italic">Perna viridis</Emphasis> and with the water of the Gulf of Nha Trang lagoon,Vietnam

One hundred and four strains of heterotrophic bacteria have been isolated and characterized from two species of bivalve mollusks cultivated in the Gulf of Nha Trang (Vietnam) and from the water of a mariculture farm. The isolates have been identified on the basis of morphological, physiological, biochemical, and chemotaxonomic properties, as well as by the content of G+C bases in DNA. In the microflora of mollusks, Vibrio alginolyticus was predominant; the pathogenic species V. harveyi and V. splendidus were found as well. Staphylococci and bacilli occupied the second place in abundance after vibrios. In addition, coryneforms and enterobacteria, as well as Pseudomonas spp. and Pseudoalteromonas spp., were revealed. The composition of the water microflora was more diverse as compared with the microflora of mollusks. In the water, Bacillus spp., Vibrio spp., and Pseudomonas spp. were predominant. Brevibacterium spp. and other coryneform bacteria, as well as enterobacteria, occurred in significant amounts. In addition, Pseudoalteromonas spp., Marinococcus sp., Halobacillus sp., Shewanella sp., Sulfitobacter sp., and bacteria of the CFB cluster were noticed. The presence of pathogenic and conditionally pathogenic bacterial species in the water and mollusks is probably the reason for the high death rate of cultivated animals at the mariculture farm.     

Characterization of communities of heterotrophic bacteria associated with healthy and diseased corals in Nha Trang Bay (Vietnam)

A comparative investigation of the heterotrophic microflora of 11 species of healthy corals and of white-band-diseased and yellow-band-diseased corals inhabiting the reefs of Nha Trang Bay (Vietnam), which has been exposed to anthropogenic impact, was performed. Fifty-nine strains of heterotrophic bacteria isolated on Y/K and Endo media were investigated and characterized. All the isolates were identified at the genus level by consideration of the results of analysis of their phenotypic properties, determination of the molar percent of G+C bases in their DNA, and the composition of fatty acids of their lipids. In the composition of the microflora of tissues of healthy corals, gamma-proteobacteria prevailed, with halomonads being dominant among them. In addition, the gram-negative bacteria included Pseudomonas and Vibrio spp., members of the Cytophaga-Flavobacterium-Bacteroides (CFB) phylogenetic cluster, and Moraxella sp. The gram-positive bacteria revealed included Bacillus, Staphylococcus, Halococcus, and Micrococcus spp., and coryneform bacteria. In the composition of the microflora of the tissues of affected corals, bacteria of the family Enterobacteriaceae and of the genera Planococcus and Arthrobacter, which were not revealed in healthy hydrobionts, were found. The anthropogenic impact is not the sole factor determining the infection of corals.     

Additions to the Gobioidei Fauna of Nha Trang and Phan Thiet Bays (South China Sea,Vietnam)

Journal of Ichthyology - Information is provided on new specimens of the recently described Amblyeleotris memnonia species (Gobiidae), previously known only by its holotype. The absence of...     

Characterization of Communities of Heterotrophic Bacteria Associated with Healthy and Diseased Corals in Nha Trang Bay (Vietnam)

A comparative investigation of the heterotrophic microflora of 11 species of healthy corals and of white-band-diseased and yellow-band-diseased corals inhabiting the reefs of Nha Trang Bay (Vietnam), which has been exposed to anthropogenic impact, was performed. Fifty-nine strains of heterotrophic bacteria isolated on Y/K and Endo media were investigated and characterized. All the isolates were identified at the genus level by consideration of the results of analysis of their phenotypic properties, determination of the molar percent of G+C bases in their DNA, and the composition of the fatty acids of lipids. In the composition of the microflora of tissues of healthy corals, γ-proteobacteria prevailed, with halomonads being dominant among them. In addition, the gram-negative bacteria included Pseudomonas and Vibrio spp., members of the Cyto-phaga-Fla-vobacterium-Bacteroides (CFB) phylogenetic cluster, and Moraxella sp. The gram-positive bacteria revealed included Bacillus, Staphylococcus, Halococcus, and Micrococcus spp., and coryneform bacteria. In the composition of the microflora of the tissues of affected corals, bacteria of the family Enterobacteriaceae and of the genera Planococcus and Arthrobacter, which were not revealed in healthy hydrobionts, were found. The anthropogenic impact is not the sole factor determining the infection of corals.     

Evidence for influenza and RSV interaction from 10 years of enhanced surveillance in Nha Trang,Vietnam, a modelling study

Influenza and Respiratory Syncytial Virus (RSV) interact within their host posing the concern for impacts on heterologous viruses following vaccination. We aimed to estimate the population level impact of their interaction. We developed a dynamic age-stratified two-pathogen mathematical model that includes pathogen interaction through competition for infection and enhanced severity of dual infections. We used parallel tempering to fit its parameters to 11 years of enhanced hospital-based surveillance for acute respiratory illnesses (ARI) in children under 5 years old in Nha Trang, Vietnam. The data supported either a 41% (95%CrI: 36–54) reduction in susceptibility following infection and for 10.0 days (95%CrI 7.1–12.8) thereafter, or no change in susceptibility following infection. We estimate that co-infection increased the probability for an infection in <2y old children to be reported 7.2 fold (95%CrI 5.0–11.4); or 16.6 fold (95%CrI 14.5–18.4) in the moderate or low interaction scenarios. Absence of either pathogen was not to the detriment of the other. We find stronger evidence for severity enhancing than for acquisition limiting interaction. In this setting vaccination against either pathogen is unlikely to have a major detrimental effect on the burden of disease caused by the other.     

Gurnards of the Genus Pterygotrigla (Triglidae) of Nha Trang Bay and Adjacent Waters (Vietnam,South China Sea)

Journal of Ichthyology - An overview of the species of gurnards of the genus Pterygotrigla, found in Nha Trang Bay and the adjacent water area of the South China Sea (south of Central Vietnam) has...     

Distribution and factors influencing on structure of reef fish communities in Nha Trang Bay Marine Protected Area, South-Central Vietnam

Visual censuses of coral reef fishes in Nha Trang Bay Marine Protected Area (MPA) were conducted during September–October 2005. Nha Trang Bay MPA is relatively rich in reef fishes compared to other areas in Vietnam and the Pacific Ocean outside the ‘Coral Triangle,’ consistent with its biogeographic location in the western South China Sea. A total of 266 species of 40 families of coral reef fishes formed five distinct assemblages. Spatial variations in distribution and structure of the assemblages were associated with eight significant biological and physical variables which were cover of living hard corals, encrusting corals, branching corals, Acropora, Millepora, Montipora, depth and distance from the coast of the mainland. The six factors in front are likely related to provision of shelter and nutrition, while the distance factor is likely to represent a gradient in disturbance and impacts from various mainland sources including sedimentation and pollution discharge from nearby rivers. Local species richness ranged from 35 to 70 species 500 m⁻² (mean: 51 ± 2 SE) for reef flat stations and from 23 to 68 species 500 m⁻² (mean: 48 ± 4 SE) for reef slope stations. Total species richness at each site averaged 76 species (±4 SE), ranging from 56 to 110 species, dominated by wrasses, damselfishes, butterflyfishes, parrotfishes, surgeonfishes, groupers and goatfishes. Density of total fishes at each station ranged from 348 to 1,444 individuals 500 m⁻² (mean: 722 ± 302 SE) for the reef flat stations and from 252 to 929 individuals 500 m⁻² (mean: 536 ± 215.7 SE) for the reef slope stations. Overall mean density at each site averaged 628.9 (±238.4 SE) individuals 500 m⁻². The highly protected sites supported higher mean density of fishes per site (ranged: 904.5–1,213 individuals 500 m⁻² for Hon Mun and 1,167.5 individuals 500 m⁻² for Hon Cau) compared to other sites (<800 individuals 500 m⁻²). Of the families included in the census, densities were dominated throughout the MPA by damselfishes and wrasses. Many target species, particularly groupers, snappers and emperors, were rare or absent and the low abundance of big fishes was consistent with over-harvesting. Similarly a low density of butterfly fishes and angelfishes is likely related to the supply for marine aquaria in Vietnam and overseas. This study provides an important baseline against which the success of present and future MPA management initiatives may be assessed.     

Changes in the composition and structure of coral communities of Mju and Moon islands, Nha Trang Bay, South China Sea

In October 2003 and January 2005, comparative observations were made on the reefs of Mju and Moon islands near the city and port of Nha Trang, which we first investigated in 1981. Appreciable changes due to anthropogenic impact have occurred on the reefs that are the nearest to the city. There was a reduction in substrate cover by reef-building corals, a substitution of dominant scleractinian species, and a decrease in the numbers and diversity of common species of corallobionts. The index of species diversity for scleractinians also decreased. The seaweeds Chnoospora and Halimeda spread into all zones of the reefs. Changes in coral communities on more distant and protected reefs were not so marked.     

Association of pneumococcal carriage in infants with the risk of carriage among their contacts in Nha Trang,Vietnam: A nested cross-sectional survey

BackgroundInfants are at highest risk of pneumococcal disease. Their added protection through herd effects is a key part in the considerations on optimal pneumococcal vaccination strategies. Yet, little is currently known about the main transmission pathways to this vulnerable age group. Hence, this study investigates pneumococcal transmission routes to infants in the coastal city of Nha Trang, Vietnam.Methods and findingsIn October 2018, we conducted a nested cross-sectional contact and pneumococcal carriage survey in randomly selected 4- to 11-month-old infants across all 27 communes of Nha Trang. Bayesian logistic regression models were used to estimate age specific carriage prevalence in the population, a proxy for the probability that a contact of a given age could lead to pneumococcal exposure for the infant. We used another Bayesian logistic regression model to estimate the correlation between infant carriage and the probability that at least one of their reported contacts carried pneumococci, controlling for age and locality. In total, 1,583 infants between 4 and 13 months old participated, with 7,428 contacts reported. Few infants (5%, or 86 infants) attended day care, and carriage prevalence was 22% (353 infants). Most infants (61%, or 966 infants) had less than a 25% probability to have had close contact with a pneumococcal carrier on the surveyed day. Pneumococcal infection risk and contact behaviour were highly correlated: If adjusted for age and locality, the odds of an infant’s carriage increased by 22% (95% confidence interval (CI): 15 to 29) per 10 percentage points increase in the probability to have had close contact with at least 1 pneumococcal carrier. Moreover, 2- to 6-year-old children contributed 51% (95% CI: 39 to 63) to the total direct pneumococcal exposure risks to infants in this setting. The main limitation of this study is that exposure risk was assessed indirectly by the age-dependent propensity for carriage of a contact and not by assessing carriage of such contacts directly.ConclusionsIn this study, we observed that cross-sectional contact and infection studies could help identify pneumococcal transmission routes and that preschool-age children may be the largest reservoir for pneumococcal transmission to infants in Nha Trang, Vietnam.     

Gobies (Gobioidei) of soft bottoms from Nha Trang and Van Phong bays (South China Sea,Vietnam)

Gobioid fishes collected in Nha Trang and Van Phong bays (Vietnam) represented by 44 species, including 30 species continuously associated with soft bottoms in the open parts of the bays with normal marine conditions are reviewed. A new species, Navigobius khanhoa sp. n., is described. This species differs from other species of the genus in much higher number of rays in the second dorsal fin (26), smaller size of the mouth, teeth on the jaws arranged in a single row, and other characters. Four species from the genera Acentrogobius, Eviota, Favonigobius, and Gnatholepis have not been identified to the species, and, most likely, some of them are new for science. Nine species are recorded in the fauna of Vietnam for the first time: Aulopareia unicolor, Bathygobius hongkongensis, Egglestonichthys bombylios, Glossogobius circumspectus, Oplopomops diacanthus, Oxyurichthys auchenolepis, Tomiyamichthys ex gr. russus, Tryssogobius porosus, and Valenciennea immaculata. An occurrence of Glossogobius olivaceus in the fauna of Vietnam is confirmed. Three species, G. olivaceus, Oligolepis acutipennis, and Periophthalmus kalolo, are recorded in the Cai River delta for the first time. A new synonymy is established: Eviota gurjanovae (Prokofiev, 2007) = E. prasina (Klunzinger, 1871). The current state of knowledge of Gobiidae fauna of Vietnam is discussed, and the updating of the species composition of Gobiodontini of Nha Trang Bay is presented in addition to the species list published earlier (Prokofiev, 2007).     

Impact of recent coastal development and human activities on Nha Trang Bay, Vietnam: evidence from a Porites lutea geochemical record

Nha Trang Bay (NTB) is located on the Central Vietnam coast, western South China Sea. Recent coastal development of Nha Trang City has raised public concern over an increasing level of pollution within the bay and degradation of nearby coral reefs. In this study, multiple proxies (e.g., trace metals, rare earth elements (REEs), and Y/Ho) recorded in a massive Porites lutea coral colony were used to reconstruct changes in seawater conditions in the NTB from 1995 to 2009. A 14-year record of REEs and other trace metals revealed that the concentrations of terrestrial trace metals have increased dramatically in response to an increase in coastal development projects such as road, port, and resort constructions, port and river dredging, and dumping activities since 2000. The effects of such developmental processes are also evident in changes in REE patterns and Y/Ho ratios through time, suggesting that both parameters are critical proxies for marine pollution.     

Spatial and Temporal Genetic Variation of Green Mussel, Perna viridis in the Gulf of Thailand and Implication for Aquaculture

The culture of green mussel (Perna viridis) in the Gulf of Thailand depends on natural spat which are believed to come from spawning grounds adjacent to major river mouths. In the present paper, genetic diversity of spatial and temporal populations of green mussel in the Gulf of Thailand was investigated using five microsatellite loci. The results showed moderate genetic variation of all 11 populations (averaged number of alleles per locus, A = 10.4–12.2; effective number of alleles per locus, A _e = 5.36–6.59; mean allelic richness, A _r = 10.23–12.06; observed heterozygosity, H _o = 0.52–0.63, and expected heterozygosity, H _e = 0.66–0.73) without significant differences among populations. No sign of bottleneck or genetic disequilibrium was observed. Genetic differentiation among spatial populations was low (F _ST = 0.0046, CI_0.95 = 0.0020–0.0083 for the samples collected in January, 2007, and F _ST = 0.0088, CI_0.95 = 0.0010–0.0162 for the samples collected in July, 2007) while temporal variation was significant as revealed by the analysis of molecular variance. Multidimensional scaling separated temporal population groups with minor exception. The assignment test revealed that most of the recruits were from other populations.     

Annotated checklist of species of the family pomacanthidae (Actinopterygii,Perciformes) from the Nha Trang Bay (South China Sea,Central Vietnam)

Angelfishes (Fam. Pomacanthidae) of the Nha Trang Bay (Central Vietnam) are reviewed. Fourteen species of pomacanthids belonging to six genera (Apolemichthys, Centropyge, Chaetodontoplus, Genicanthus, Pomacanthus, and Pygoplites) are recorded in the bay. All species are identified on preserved material. Two new species for the bay are found: Centropyge bispinosa and C. heraldi. C. herald is new species for coastal waters of Continental Vietnam and of adjacent areas. For all pomacanthid species of the bay, areas are described, brief diagnostic characteristics are supplied, and distribution by biotopes and depths is indicated based on data of underwater observations.     

Present-Day State of Coral Reefs of Nha Trang Bay (Southern Vietnam) and Possible Reasons for the Disturbance of Habitats of Scleractinian Corals

Our investigations were conducted from 1990 to 2002. Sampling of bottom sediments and biological objects, as well as photo and video shooting, were performed during scuba diving. The state of the environment and coral reef communities was assessed using the chemical–analytical, fluorometric, and luminometric methods, as well as the Ames test and the transect technique. The research results suggest that the spectrum and distribution pattern of persistent congeners of PCDD/Fs (dioxins) in bottom sediments are similar to those of the defoliant Agent Orange and that the bottom sediments are toxic and display photo inhibition and a mutagenic effect. The bottom of the bay is heavily silted throughout its depth. Many large dead colonies of corals without mechanical damage were observed everywhere. The total coverage by live corals in all sites investigated does not exceed 30%. Although, without a doubt, many factors contributed much to the disturbance of the bay ecosystems, the actual trigger for the degradation of the coral reefs seems to be the input of dioxin-containing chemicals used as defoliants during the American–Vietnamese war (Vietnam War).     

Anomalous Behavior of Free-Swimming Echeneis naucrates (Echeneidae) in the Aquaculture Areas of Nha Trang Bay (South China Sea,Southern Central Vietnam)

Journal of Ichthyology - The results of observations of the behavior of free-swimming sharksuckers Echeneis naucrates in a prosperous ecosystem (Maldives, Indian Ocean) and in the areas exposed to...     

Attenuation of oil pollutants in the Arabian Gulf water by bacteria naturally associated with live fish

This paper describes the potential of oil-utilizing bacteria associated with live fish from the Arabian Gulf for hydrocarbon attenuation in seawater polluted with oil. Maintaining local live fish (grey mullet and tilapia) in seawater artificially polluted with crude oil or individual hydrocarbons for 3 w led to dramatic attenuation of those compounds. The same result was obtained when instead of live fish, the bacterial consortia scraped off from the fish surfaces were used. Almost similar hydrocarbon attenuation results were obtained irrespective of whether the system was fertilized with NH₄NO₃ or not. Parallel counting of oil-utilizing bacteria associated with fish on a nitrogen-containing and a nitrogen free-medium gave almost similar numbers, indicating that most of the hydrocarbon-utilizing bacteria could fix atmospheric nitrogen. The predominant hydrocarbon-utilizing bacteria isolated from fish grew well in nitrogen-free medium and gave positive nitrogenase test as revealed by their potential for acetylene reduction to ethylene. Molecular fingerprinting showed that crude oil-polluted seawater samples incubated for 3 w contained two new 16S rDNA bands probably corresponding to hydrocarbon-utilizing bacteria. It was concluded that fish individuals accommodate rich bacterial consortia with the combined potential for hydrocarbon-utilization and nitrogen-fixation, which makes them efficient in cleaning hydrocarbon pollutants in water without need for nitrogen fertilization.