Unstudied marine processes discovered in Vietnam

30/11/2023
Scientists from the Institute of Oceanography have discovered an unstudied oceanographic process in Vietnam, the phenomenon of water outcropping due to the activity of the continental flank (shelf-break front) during the transitional wind season from northeast to southwest. The research results of Prof. Dr. Doan Nhu Hai and colleagues are new to Vietnam and the world, making important contributions to plankton characteristics in the narrow and steep continental shelf due to the influence of this continental ridge in a study by the group.

Photos of the research team's specimen collection activities and field data

Plankton includes both producers and 1st and 2nd order consumers, so they play a very important role in any waterbody study in the world. The plankton (SVPD) also includes an abundant composition of the seed of other aquatic animals (fish eggs, juveniles and other organism larvae). Studies on the continental shelf, especially the South Central Narrow Continental Shelf, involving plankton are very limited. The study of the effects of oceanographic processes on plankton in the continental shelf is a broad and complex field due to the diversity of oceanographic processes and the different impacts in different geographic regions of the vast continental shelf in the oceans.

With the aim of elucidating the various impacts of marine processes on SVPD (biome structure and characterization) in the South Central Continental Shelf, in order to enhance the understanding of marine processes and organisms in the continental shelf of Vietnam, as a scientific basis for the assessment of aquatic resources, Prof. Dr. Doan Nhu Hai and the research team of Institute of Oceanography conducted the project "Impacts of marine processes on SVPD biome in the South Central Continental Shelf of Vietnam" (project code KHCBBI.01/20-22). Prof. Dr. Doan Nhu Hai said that in this study, he and his colleagues focused on the fundamental impact of water outcrops on the continental slopes and other effects coming from different physical and hydrological effects on fluctuations of SVPD biomes.

The results show that field analyses and long-term data have provided evidence of shelf-break front formation on the South Central Narrow Continental Shelf due to marine physical factors. This front is evident north of Cape Varella and has influence on currents on the continental shelf interacting with the offshore mass (South China Sea boundary current). For SVPD biomes, changes in composition and abundance are evident in the influence of coastal zones and continental shelf margins due to nutrients. The structure of the SVPD biome, especially Chl-a and zooplankton content, is influenced by continental flanks and from the coastal zone, most pronounced in the maximum Chl-a and basal strata but unknown to the surface layer. Coastal influences are due to nutrient content from land, effects beyond the shelf edge are due to water outcrops at the continental shelf edge (shelf-break front).

Through flow regime modeling, scientists have shown the presence of a relatively stable pair of retrograde (nearshore) and cyclone (offshore) cyclones north of Cape Varella. South of Varella, a cyclone is formed that is bordered close to the shore and may extend further offshore. The model results are consistent with the actual flow measurements with the flow direction at section 1 inverse compared to the other 2 sections located outside Cape Varella. The model results are the same as those analyzed on the HYCOM+CICE model (Metzger et al. 2017) with a resolution of 1/12o at the time of the survey.

Flow mode modeling on April 17 shows a pair of cyclones north of Cape Varella and cyclones south of Cape Varella

The research results have great practical significance, serving as a scientific basis for assessing the food base for aquatic resources in the continental shelf of Central Vietnam. This is the scientific basis of many studies on oceanography, marine biology as well as climate change.  

Prof. Hai added that the project is a new research direction to link the impact of marine physical processes on SVPD as an important group of productive organisms in the narrow continental shelf in South Central Vietnam. The proposal is the first study to compare data from continental shelf cross-sections at high resolution. The results of the project will be the basis for development into a project with coordination between marine sciences and also an opportunity to develop international cooperation in the field of biological oceanography in the next phase. Prof. Hai and his team also wish to further exploit the results achieved, the problems discovered in this mission need to be confirmed and studied at a more extensive level in the future.

The results of the project were published by scientists on 03 prestigious scientific articles on the list of SCIE (Q2/3), 01 VAST2 article and rated B by the Acceptance Council of the Vietnam Academy of Science and Technology.

 

Translated by Phuong Ha
Link to Vietnamese version



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