Studies on phytoplankton pigments: chlorophyll, total carotenoids and degradation products in Vietnamese waters

Distribution of phytoplankton pigments was investigated in the relation to Chlorophyll a (Chl-a) and light intensity in Vietnamese waters located at longitude 102E - 112W, latitute 23N - 7N. Over 200 samples collected at 58 stations were analyzed for pigments (Chlorophyll a, b, c and carotenoids) and degradation products (Phaeophytill). Chlorophyll a was measured by fluorescence. Results show that average values in the seawater were 0.18 ± 0.04 mg.m-3 for Chl-a; 0.05 ± 0.01 mg.m-3 for Chl-b; 0.062 mg.m-3 for Phaeophytill. Higher value of Chl-a occurred at the thermocline but maxima were found at 75 or 50m depths. Average value of Carotenoids concentration was very low about 0.052 ± 0.12 mg.m-3. The report used a model for the relationship between Chlorophyll a content and light intensity to estimate the primary production. Average value of primary production was about 9.04 mgC.m3.day-1 at the surface and 2.63 mgC.m3.day-1 at the bottom. The relationship between Chlorophyll and some environmental parameters such as temperature, salinity was examined. The effects of thermocline and halocline to the primary production were analyzed

Tracing sediment transport and bed regime in Nha Trang Bay

Three spatial structure groups of radionuclides in U and Th series, 210Pb-excess and 137Cs, and 40K were found based on analyzing temporal and spatial datum of their content by factor analysis with oblique rotation in Nhatrang bay. U and Th spatial structure with their contours decreased toward the offshore, ran longshore and divided seawater of bay into two parts with strong gradient on both sides. Inside part located from center of Nhatrang bay toward the seashore with three main deposit centers of their contents higher than 23 Bq/kg.dry for 238U and 40 Bq/kg.dry for 232Th, indicated unstability of shoreline. Almost sediments coming from river extended toward the offshore, were stopped and transported toward southeastern. The outside part was less than above mentioned content. The boundary line between two parts superposed with the constantly limit line of turbid plume in the rainy season. Direct influence of the continental runoff was limited by the 9 Bq/kg.dry contour of 238U, 19 Bq/kg.dry contour of 232Th. Longshore current was a predominant process whereas lateral transport as sifting and winnowing process of finer grains in sediments of Nhatrang bay. Areas that had very low content of 137Cs and 210 Pb-excess adjoining shoreline showed areas being eroded. Accumulation of 137Cs and 210 Pbexcess nearby river mouth characterized for fine compositions of sediments controlled by seasonal plumes and sites further toward the south indicated finer materials transported from river and accumulated in lack of hydrodynamic process. Near shore accumulation of 40K revealed the sediments there originated from bed erosion

SCIENTIFIC COMMUNICATIONS:

KẾT QUẢ HỘI NGHỊ LẦN THỨ 25 CỦA HỘI ĐỒNG ỦY BAN HẢI DƯƠNG HỌC LIÊN CHÍNH PHỦ, (IOC/UNESCO)Ngày 16 - 25/6/2009, Hội đồng Ủy ban Hải dương học Liên Chính phủ (IOC) đã họp phiên XXV tại trụ sở UNESCO, Paris. Tham dự phiên họp có đại diện của 97 quốc gia (có 37 nước không cử đại diện tham gia) và hơn 20 cơ quan và tổ chức quốc tế liên quan. Đoàn Việt Nam gồm có 6 người: Ông Văn Nghĩa Dũng, Đại sứ, Trưởng phái đoàn UNESCO Việt Nam tại Paris; PGS. TSKH. Nguyễn Tác An, Chủ tịch UBQG IOC Việt Nam, (Trưởng đoàn); TS. Bùi Hồng Long, Viện trưởng Viện Hải dương học, Nha Trang; TS. Đỗ Chiến Thắng, Phó Viện trưởng Viện Địa chất và Địa Vật lý biển, Hà Nội; Ông Lưu Trường Đệ, Phó vụ trưởng, Bộ KH&CN Việt Nam; Bà Phùng Thị Ngọc Ánh, Chuyên viên, Ban Biên giới, Bộ Ngoại giao, Việt Nam. Ngoài ra, còn có sự tham gia, hỗ trợ của bà Trần  Thị  Hoàng  Mai,  chuyên  viên  của  phái  đoàn  UNESCO  Việt  Nam  tại  Paris  và  bà Nguyễn Thị Như Phi, nguyên chuyên viên của UNESCO.Người cung cấp thông tin: PGS.TSKH. Nguyễn Tác An , Chủ tịch UBQG IOC Việt Na

Комплексное управление прибрежными зонами во Вьетнаме: первые шаги, цели, структура

Прибрежная зона Вьетнама является одной из наиболее сверхэксплуатируемых в мире, соответственно с деградацией экосистем и ущербами здоровью людей. Внедрение Комплексного управления прибрежными зонами является чрезвычайно важной задачей для страны. Проанализирована и описана прошлая политическая, правовая и организационная структура, связанная с управлением прибрежными зонами, обрисован научный базис для новой стратегии, сформулированной в статье. Обсуждаются её цели, задачи, первые шаги и приоритеты на ближайшие 10 – 20 лет.Vietnam’s coastal zones are some of the very overexploited in the World with consequent degradation of their ecosystems and damage to public welfare. Implementation of Integrated coastal zone management (ICM) is very important task for Vietnam. We analyse and describe the results of past of Vietnamese policies, legislative and institutional frameworks that are relevant to coastal zone issues and establishing some scientific basis for a management strategy that can be formulated and discussed: goal, objectives, action, and priority activities for the next near 10 – 20 years

ENERGY FLOW OF THE UPWELLING ECOSYSTEM IN SOUTH CENTRAL VIETNAM

This  paper  reviewed  some  approaches  from  studied  results  of upwelling ecosystem in the South Central Vietnam (Khanh Hoa-Binh Thuan) in periods before 2000 and 2003 - 2005 such as primary production and the mechanism of nutrients supply of upwelling in the coastal waters, ecological conditions in southwestern monsoon and transitional period, energy transfer of phytoplankton. The productive habitat area and total fishery landings were estimated on the basis of these results

Water quality assessment in the Nha Trang Bay (Vietnam) by using in-situ and remotely sensed data

The Nha Trang Bay (Vietnam) is an international marine protected area with significant economic, natural and recreational values. Considerable economic development is expected in particularly for tourism, navigation and aquaculture. However, in recent years the environmental quality of the Bay has been degraded by human activities and impacts. Even though the conditions of the Bay are monitored with in-situ measurements in a marine station, the environmental data, measured only in half-yearly intervals, are not sufficient for comprehensively assessing environmental quality at various temporal and spatial scales. Therefore, it is necessary to seek for complementary data sources to assess, control and manage the marine environment of Nha Trang Bay. We conducted three field trips in Nha Trang Bay at 23 stations, including 6 off-shore stations that are not influenced by freshwater from land, and measured the distribution of marine optical properties. These properties include the light extinction coefficient (K) of photosynthetically active radiation (PAR) in the surface layer (i.e. 1m depth) and in water columns. K ranged from 0.099 m-1 off-shore to 0.409 m-1 in coastal waters. In addition, light absorption at various wavelengths were used to assess the concentration of chlorophyll-a, total suspended sediments and primary production. Further, we collected and used spatially explicit data using the OC4 method and the method of band 1, 2 and 3 ratios of the Landsat TM satellite. A data comparison confirms a significant correlation between the different sources of in-situ and remotely sensed data of light absorption. However, the predicted values at stations with a water depth of less than 5 m are significantly affected by sea bottom reflection of, for example, mud, sand, coral reefs and algae. The results indicate that it is appropriate to use remote sensing methods to derive spatially explicit distributed variables of optical properties and derived products for an environmental assessment of coastal waters