Based on investigated results of cruises of the Vietnam - Germany cooperation program "Study on upwelling phenomenon and some relative ecological conditions of the continental shelf waters in the South of Vietnam", the paper aims to identify the shape of chlorophyll-a (Chi-a) distribution in marine region of the southern centre in Vietnam. (1) Chl-a conc.entration varied significantly. The maximum Chl-a concentration was not found in the surface layer at almost study station. It could be located in the water layer at from 20 to 80m, sometimes to 100m. Some stations located in off-shore waters had two peaks of Chl-a concentration, whereas at some stations located in coastal waters with upwelling, the peak of chl-a moved to surface layer. (2) Chl-a concentration was a function of depth. The shapes of Chl-a concentration were shift Gaussian curves (normal shapes), whereas when upwelling exited in marine waters, the shapes were extensional Gaussian curves with two Chl-a peaks (in off-shore regions) or half of shift Gaussian curves (in coastal waters). (3) In addition, the results also identified the mixed depth layers based on distribution of Chl-a concentration in water bodies. Finally, understanding charaCteristics of Chl-a distribution .in water bodies takes an important role of assessment of integrated primary production, biogeochemical cycles, food weblfood chains and other ecological economic fields in tropical marine regions.
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