Abstract:
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-3for 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.
