New record for Asia-Pacific of Protoperidinium anomaloplaxum (Peridiniales, Dinophyceae) from Vietnamese waters

Minusculum (Lebour) Balech is one of four subgenera of the genus Protoperidinium Bergh 1881. Only five species of this subgenus have been discovered worldwide, most of which are distributed in cold waters. In this study, Protoperidinium anomaloplaxum (Balech) Balech is reported from Vietnam and thus for the first time from Asia-Pacific waters. This species is illustrated with line drawing, light and scanning electron microscopic photographs and described details of the ornamentation of the thecal plates as well as its geographic distribution.

Seasonal variation of phytoplankton in Tuyen Lam reservoir in Da Lat, Vietnam

Seasonal variation and phytoplankton dynamics in Tuyen Lam reservoir in Da Lat city, Viet Nam were studied in the rainy and dry seasons (during January through December, 2014). Samples were taken monthly from 3 stations of Tuyen Lam reservoir. The aim of this study was to analyze the structure of the phytoplankton community on seasonal scales and to identify the environmental factors, such as temperature, conductivity, pH, dissolved oxygen, light intensity, transparency, ammonium, nitrate and phosphate controlling the phytoplankton density and composition of phytoplankton communities. The results showed that phytoplankton comprised 43 taxa, mainly Chlorophyta (58%), Bacillariophyta (14%), Cyanobacteria (14%), Dinophyta (7%), Chrysophyta (5%) and Euglenophyta (2%). There was significant difference in phytoplankton abundance but not species richness between two seasons. Multiple regression analysis between chlorophyll a contents, phytoplankton density with environmental independent variables indicated that ammonium, nitrate concentrations and water temperature were significantly impact to the abundance of phytoplankton, while almost no independent variables were found to correlate to chlorophyll a. CCA analysis phytoplankton and abiotic parameters revealed several species groups with their favorable environmental conditions

A Model for the Prediction of Harmful Algae Blooms in the Vietnamese Upwelling Area

Satellite pictures and in situ observations indicate strong phytoplankton blooms including harmful algae blooms (HABs) during southwest (SW) summer monsoon in the Vietnamese upwelling area. In this period, nutrients are provided by coastal upwelling and by the very high river runoff from the Mekong River. During SW monsoon, in general two circulation patterns exist which allow the prediction of advection and diffusion of HAB patches. A Lagrangian HAB model that is driven by a circulation model and applied to HABs in Vietnamese waters is presented. Advection which is the most complicated part in modelling transport of passive substances is validated with a Lagrangian sediment trap experiment. The model produces realistic results compared to in situ observations and satellite images and might be used for real time forecast in the future

Effects of variations of environmental factors and algal bloom on fish larvae in Southern central Vietnam

A multivariate analysis was conducted to assess the impact of variations of environmental factors such as temperature, salinity, dissolved oxygen (DO), total suspended solid (TSS), nitrite (NO2-N), nitrate (NO3-N), ammonium (NH3,4-N), phosphate (PO4-P), and silicate (SiO3-Si) concentrations, chlorophyll (chlor) and algal bloom on natural fish larvae in Binh Thuan waters, Vietnam. Temporal and spatial variations of environmental factors were correlated with the abundance and diversity of fish larvae. The abundance and diversity of fish larvae decreased at the sites of the algal blooms. Five environmental factors - temperature, salinity, nitrite, phosphate and silicates - showed a statistically significant impact on the fish larvae, but other factors showed weaker and statistically not significant effects. In the months of algal blooms, phosphate, silicate, nitrite, nitrate, ammonium and salinity influenced blooms substantially, while the effects of temperature were mainly confined to the months without blooms of algae. Algal blooms were lethal to fish larvae and juveniles leading to a decline in their abundance and diversity. This will affect and restrict the process of recruitment of fish stocks in the region. Received 19 December 2016, accepted 30 December 2016

TỶ LỆ CHẾT CỦA VI KHUẨN DO PHÂN GIẢI CỦA VIRUS TRONG VỊNH NHA TRANG, NAM TRUNG BỘ, VIỆT NAM

Bacteria play an important role in microbial loop in marine waters and are strongly regulated by top-down controls by two groups, virus and microprotozoa. Bacterial mortality rates, because of viral lysis and microprotozoan grazing, were estimated using dilution method in Nha Trang bay in December 2014. The bacterial mortality rates were marked different among sampling sites and reflected by different in environmental conditions and layers in water column. In Nha Trang bay, the viral lysis on bacteria was, in similar trend with previous studies, high where their main hosts abundance, such as at surface and in the estruarine front area. Bacterial growth rate was low in Cai estuary and higher in mid of Nha Trang Bay and Hon Tam stations. The bacterial mortality rates in Nha Trang Bay were mainly because of the viral lysis (1.59-2.05 day-1) rather than of microprotozoan grazing (0.00-0.36 day-1). The microprotozoan grazing on bacteria in Cai estuary was significantly higher than in others sites (0.36 day-1 versus 0.00-0.05 day-1).Vi khuẩn có vai trò quan trọng trong vi lưới thức ăn ở biển và chịu sự chi phối top-down bởi hai nhóm chính virus và động vật nguyên sinh. Tỉ lệ chết của vi khuẩn (TLCVK) do phân giải của virus và bị ăn bởi động vật nguyên sinh trong vịnh Nha Trang, Khánh Hòa, được đánh giá sử dụng các thí nghiệm nuôi pha loãng. TLCVK có biến động khác nhau theo đặc trưng môi trường của vị trí thu mẫu và theo độ sâu trong cột nước. TLCVK do phân giải của virus cao ở tầng mặt, ở khu vực front cửa sông, và ở khu vực có độ phong phú cao của vi khuẩn thể hiện mối quan hệ giữa virus với các yếu tố môi trường và với độ phong phú của vật chủ. Tốc độ sinh trưởng của vi khuẩn thấp ở vùng cửa sông Cái và cao hơn ở vùng front cửa sông cũng như trạm Hòn Tầm. Lượng vi khuẩn trong vùng nghiên cứu mất đi chủ yếu bởi sự phân giải của virus (TLCVK biến thiên 1,59-2,05 /ngày) hơn là bị ăn bởi động vật nguyên sinh (TLCVK biến thiên 0,00-0,36 /ngày). Ở trạm cửa sông Cái, TLCVK do bị động vật nguyên sinh ăn cao hơn đáng kể so với các trạm khảo sát còn lại (0,36 /ngày so với 0,00-0,05 /ngày)

ĐÁNH GIÁ MỨC ĐỘ ẢNH HƯỞNG CỦA CÁC NGUỒN NƯỚC CHẢY VÀO HỒ ĐAN KIA VÀ ÁP DỤNG MÔ HÌNH AQUATOX QUẢN LÝ CHẤT LƯỢNG

The parameters used for measuring water quality of Dan Kia reservoir were temperature, pH, conductivity, secchi disk depth, dissolved oxygen (DO), chlorophyll a,  nutrients: nitrogen (ammonia, nitrate) and phosphate. There are five influents for the reservoir, therefore the water quality of Dan Kia reservoir depends on activities around these channels. S1 stream has the highest flow into the reservoir (8.2×106m3/year) but most of the nutrients were discharged from S4 and S5 stream. Concentration of ammonia, nitrate and phosphate from these channels is accounting for 89.82, 58.15 and  57.16% into the lake, respectively. The study constructed three scenarios and run them using AQUATOX model. The first scenario, all existing inflows are discharging into the lake, present situation. The second scenario, none is discharging. The third scenario, all are discharging except S4 stream and S5 stream. The result from the first scenario showed that the concentrations from the model consistent with measurements in the reservoir. In case the second and third scenarios happened the concentrations considerably decreased.Các thông số chất lượng nước hồ Đan Kia được khảo sát hàng tháng trong năm 2014 gồm có nhiệt độ, pH, độ dẫn diện, độ sâu secchi, oxy hòa tan, các hợp chất chứa nitơ (amoni, nitrat),  phốt pho (PO43-) và chlorophyll-a. Có 5 nhánh suối dẫn nước vào hồ vì vậy chất lượng nước hồ phụ thuộc vào các hoạt động trên lưu vực hồ và 5 nhánh suối này. Trong đó, nhánh suối S1 có lưu lượng nước chảy vào hồ cao nhất (8.2×106m3/năm) nhưng phần lớn chất dinh dưỡng được đưa vào hồ từ nhánh suối S4 và S5. Nồng độ amoni, nitrat và phốt phát từ hai nhánh suối này lần lượt chiếm đến 89.82, 58.15 và 57.16% tổng tải lượng dinh dưỡng vào hồ. Nghiên cứu đã xây dựng ba kịch bản và mô phỏng ba kịch bản này bằng mô hình AQUATOX. Kịch bản thứ nhất, tất cả các con suối vẫn được dẫn nước vào hồ như hiện tại. Kịch bản thứ hai, không cho bất kỳ con suối nào đổ nước vào hồ. Kịch bản thứ ba, tất cả các nguồn trên vẫn được đưa vào hồ trừ suối S4 và S5. Kết quả từ mô hình AQUATOX cho thấy với kịch bản đầu tiên, nồng độ các chất dinh dưỡng từ mô hình phù hợp với nồng độ đo đạc và đều vượt ngưỡng cho phép. Ở kịch bản thứ 2 và 3, nồng độ các chất dinh dưỡng giảm đáng kể, hầu hết các giá trị đều nằm dưới tiêu chuẩn cho phép đới với nước mặt. Từ kết quả này, nghiên cứu đề nghị các cơ quan chức năng cần tập trung quản lý tình trạng canh tác nông nghiệp trên lưu vực hồ Đan Kia, đặc biệt là khu vực phía Đông Nam hồ. Nghiên cứu cũng đã mô phỏng xu hướng phát triển và thành phần động thực vật phù trong hồ Đan Kia

Radicular cyst in a primary molar following pulp therapy with gutta percha : a case report and literature review

A radicular cyst (RC) in deciduous dentition is relatively rare. This clinical report presents a case of RC that condition derived from a primary molar undergone an endodontic treatment with gutta-percha approximately one year ago. In addition, we also considered whether intracanal medicaments and gutta-percha filling material related to the formation and development of the cyst or not

Biodiversity of Tintinnids (Tintinnida) in Khanh Hoa - Binh Thuan waters

Tintinnidsarean important protozoan group in the aquatic food web and had been widely studied in various waters. There are about 1000 known species in the world. However, there have beenvery few taxonomic studies in Vietnam and therefore the number of Tintinnid taxa and their distribution are poorly known. Thepresent study documents 65 tintinnids species belonging to 30 genera and 13 families in samples collected from Khanh Hoa - Binh Thuan waters in 2016 and 2017. There were 17 new taxa records for Vietnam protozoan fauna, raising the number of tintinnids recorded in Vietnam to 125 taxa. Tintinnid assemblages in Khanh Hoa-Binh Thuan waters shared about 17 species with Ha Long Bay, 32 species with Con Co island and 26 species with coastal waters of South Vietnam. Analysis of species diversity shows that the Shannon diversity index H' varied from 1.5 to 2.6. Distribution of species numbers and diversity in the Khanh Hoa - Binh Thuan waters revealed possible combined effects of hydrographical activities (e.g. upwelling), Mekong river influent (e.g. salinity), and food available on tintinnid communities.   Citation: Nguyen Thi Kieu, Phan Tan Luom, Nguyen Tam Vinh, Nguyen Ngoc Lam, Josepth P. Montoya, Doan Nhu Hai, 2017. Biodiversity of Tintinnids (Tintinnida) in Khanh Hoa - Binh Thuan waters. Tap chi Sinh hoc, 39(4): 421-433. DOI: 10.15625/0866-7160/v39n4.11033. *Corresponding author:[email protected] Received 19 September 2017, accepted 12 December 2017

Habitat Delineation in Highly Variable Marine Environments

The structure of the phytoplankton community in surface waters is the consequence of complex interactions between the physical and chemical properties of the upper water column as well as the interaction within the general biological community. Understanding the structure of phytoplankton communities is especially challenging in highly variable and dynamic marine environments. A variety of strategies have been employed to delineate marine planktonic habitats, including both biogeochemical and water-mass-based approaches. These methods have led to fundamental improvements in our understanding of marine phytoplankton distributions, but they are often difficult to apply to systems with physical and chemical properties and forcings that vary greatly over relatively short spatial or temporal scales. In this study, we have developed a method of dynamic habitat delineation based on environmental variables that are biologically relevant, that integrate over varying time scales, and that are derived from standard oceanographic measurements. As a result, this approach is widely applicable, simple to implement, and effective in resolving the spatial distribution of phytoplankton communities. As a test of our approach, we have applied it to the Amazon River-influenced Western Tropical North Atlantic (WTNA) and to the South China Sea (SCS), which is influenced by both the Mekong River and seasonal coastal upwelling. These two systems differ substantially in their spatial and temporal scales, nutrient sources/sinks, and hydrographic complexity, providing an effective test of the applicability of our analysis. Despite their significant differences in scale and character, our approach generated statistically robust habitat classifications that were clearly relevant to surface phytoplankton communities. Additional analysis of the habitat-defining variables themselves can provide insight into the processes acting to shape phytoplankton communities in each habitat. Finally, by demonstrating the biological relevance of the generated habitats, we gain insights into the conditions promoting the growth of distinct communities and the factors that lead to mismatches between environmental conditions and phytoplankton community structure