Seasonal Variation of Phytoplankton Pigments in the Laccadive Sea off Cochin
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Fig. 4. Seasonal distribution of temperature, salinity, dissolved oxygen, oxygen saturation, chlorophyll a, Secchi disk depth and color of the sea
3. Nutrients
In all cases the lowest content was nil and the highest values were 2.7, 2.0, 2.9 and
45.0 ~g-at 1- 1 for PO~--P. NO;--N, No~-N and SiO!--Si respectively. Since the
distribution of nutrients does not have a regular pattern, the totals in a column of water
° -16 m deep are worked out and these values are used in seasonal distribution studies
(Fig. 6). The lowest concentration of inorganic phosphate was recorded in January when
phytoplankton pigments were also practically nil. While nitrite was present during the
SW monsoon months, nitrate was comparatively low throughout the year except in
April. Coincident with the higher concentration of both nitrite and nitrate, in April 1969,
there was a Trichodesmium bloom. Silicate reached its peak value during the SW