Study of Marine Sand-Dwelling Dinoflagellate With Four New Records From the Central South Coast of Viet Nam

In this study, marine sand samples were collected from the shallow intertidal zone of Nha Trang bay, Viet Nam. Taxonomic observations were conducted for the sanddwelling dinoflagellates using light, epifluorescent and scanning electron microscopy. Morphology characterizations of the four species namely, Amphidiniopsis hexagona, Thecadinium pseudokofoidii, Amphidinium herdmanii and Fukuyoa ruetzleri have been reported as new records for Vietnamese coastal waters. The genus Amphidiniopsis and Thecadinium are a new addition to the dinoflagellates flora of Viet Nam. Taxomomic descriptions and photographs of these species have been provided. Bangladesh J. Plant Taxon. 28(2): 367-378, 2021 (December)

More about the biodiversity of parasites in Vietnam: a first report of microsporidia (opistosporidia, microsporidia) in coral fish

This is the first report of microsporidia infection in marine fish from Vietnam. Microsporidia (Opistosporidia, Microsporidia) were identified in 4 species of coral fish Cheilinus chlorourus (Labridae), Abudefduf bengalensis (Pomacentridae), Pomacentrus brachialis (Pomacentridae), Atule mate (Carangidae) from Nha Trang Bay (East Sea), Khanh Hoa Province, Vietnam, in 2018 and 2019. Dry smears of blood, intestine and liver were stained using the Giemsa method. Gut and liver were fixed in Bouin’s fluid, processed for routine paraffin infiltration, and sections were stained with Hematoxylin and Eosin. Strong microsporidia infections were the same for all three species revealed in 1 of every 6 fish samples (prevalence 16.7%) of C. chlorourus, A. bengalensis, and P. brachialis. In C. chlorourus there were meronts, sporogonial plasmodia, and sporoblasts found in all layers of intestine (enterocytes, myocytes, mesotheliocytes), pancreas and liver. In A. bengalensis parasites were found in enterocytes of the small intestine and liver. In P. brachialis meronts, sporogonial plasmodia and sporoblasts were in enterocytes of the small intestine. Intracellular parasites are located in parasitophorous vacuoles covered with additional shell, which appeared to be in the process of forming xenoma. Microsporidia infection was revealed in 1 of 31 fish samples of A. mate (prevalence 3 %). Up to 30 of round and oval white xenomas were detected in the gills of fresh samples by microscopy. We tentatively assign the microsporidia to Glugeidae due to host affiliation (fish), localization (digestive system) and xenoma formation. They differ from Pleistophoridae by localization in non-muscular cells.

Physical and Chemical Soil Properties of Mangrove Forests in Vietnam

Recently the area of mangrove (evergreen) forests growing along the coast of Vietnam has been significantly increased by artificial afforestation under the recognition of their ecological role and economic importance. Protection mangrove forests are the largest among all mangrove forests in Vietnam. They act as a belt to prevent coastal roads from erosion and damage due to tides, storms, and tsunamis. However, their role in coastal soil formation is still poorly studied. Soil formation in mangrove forests is influenced by many factors including the following: woody vegetation, tidal saltwater, precipitation, and mountain runoff. The ability of soil to retain water, nutrients, ions, and some other physical and chemical properties is closely related to the soil texture. Long-term monitoring of the soil texture and the content of nutrients in the soil of mangrove forests in the Dam Bay area of the Nha Trang Bay allowed us to distinguish 2 groups of soil phases: typical laterite soil in natural mangrove forests and in rhizophore plantings of 2004 and poorly developed laterite soil in cultural cenoses of 2007 and 2013 and in the littoral zone. These two groups have differences in the soil texture depending on the time of stand formation. The total amount of gravel, aleurite, and silt in the first group of soils is higher than that in the second group. The concentrations of nutrients (phosphorus and nitrogen content) in the soil of mangrove forests is quite high, though it gradually decreases from the soil of natural mangrove forests to the littoral zone. In order to effectively prevent erosion of soils and improve their physical and chemical properties, artificial mangrove forests should continuously be grown along the coast lines of the Nha Trang Bay in the Khanh Hoa province, Vietnam. For citation: Phan T.H., Kovyazin V.F., Zvonareva S.S., Nguyen T.H.T., Nguyen T.L. Physical and Chemical Soil Properties of Mangrove Forests in Vietnam. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 5, pp. 9–21. DOI: 10.37482/0536-1036-2021-5-9-21

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

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.

Estimation of the spawning ground of some fish species in the Nha Trang bay

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.

Bleaching of coral in Nha Trang, Ninh Thuan, Con Dao and Phu Quoc islands in June–July 2019

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.

Cancrion khanhensis sp. nov. (Crustacea: Isopoda: Entoniscidae) infesting Monomia haanii (Stimpson, 1858) (Crustacea: Brachyura: Portunidae) from Nha Trang Bay, Khanh Hoa, Vietnam, with remarks on larval stages of entoniscids and description of a new family, genus and two new species of hyperparasites infesting entoniscids

An undescribed entoniscid isopod was found to parasitize Monomia haani, a common portunid crab in Khanh Hoa province of Vietnam. The new species is the eighth in the genus Cancrion, the second species of Cancrion found parasitizing hosts in the family Portunidae, and the first member of the family Entoniscidae to be described from southeast Asia. The cryptoniscius larva of a species of Cancrion is described for the first time. The new entoniscid infests hosts with a prevalence of 10.1% and intensity of 1 or 2 females per host. A new family, genus and species of cryptoniscoid hyperparasite with novel female and cryptoniscus body morphology is also described; this is the first record of a hyperparasite found infesting an entoniscid isopod. The purported cryptoniscus larva of Tiarinion texopallium Shields & Ward, 1998 is shown to be that of a hyperparasitic cryptoniscoid isopod closely allied to the new Vietnamese hyperparasite and is described as a new species belonging to the new family and genus.

More Than Expected From Old Sponge Samples: A Natural Sampler DNA Metabarcoding Assessment of Marine Fish Diversity in Nha Trang Bay (Vietnam)

Sponges have recently been proposed as ideal candidates to act as natural samplers for environmental DNA due to their efficiency in filtering water. However, validation of the usefulness of DNA recovered from sponges to reveal vertebrate biodiversity patterns in Marine Protected Areas is still needed. Additionally, nothing is known about how different sponge species and morphologies influence the capture of environmental DNA and whether biodiversity patterns obtained from sponges are best described by quantitative or qualitative measures. In this study, we amplified and sequenced a vertebrate specific 12S barcode with a set of universal PCR primers (MiFish) for metabarcoding environmental DNA from fishes, to unveil fine-scale patterns of fish communities from natural-sampler DNA retrieved from 64 sponges (16 species) located in eutrophic and well-preserved coral reefs in Nha Trang Bay (central Vietnam). Ninety tropical fish species were identified from the sponges, corresponding to one third of the total local ichthyofauna reported from previous extensive conventional surveys. Significant differentiation in fish communities between eutrophic and well-preserved environments was observed, albeit eutrophication only explained a modest proportion of the variation between fish communities. Differences in efficiency of capturing fish environmental DNA among sponge species or morphologies were not observed. Overall, the majority of detected fish species corresponded to reef-associated small-sized species, as expected in coral reefs environments. Remarkably, pelagic, migratory, and deep-sea fish species were also recovered from sponge tissues, pointing out the ability of sponge natural sampled DNA to detect fishes that were not permanently associated to the biomes where the sponges were sampled. These results highlight the suitability of natural samplers as a cost-effective way to assess vertebrate diversity in hyper-diverse environments.