Diurnal variation in phytoplankton pigments in Zuari estuary, Goa

Abstract

Zuari is a large, estuary having strong marine influence. The Zuari water in turn influences the Cumbarjua canal. Two stations, one near the mouth and other in the mid-reaches are studied for diurnal variations of phytoplankton pigments during three seasons of the year 1971-72. Total chlorophyll (range) at the mouth region in August, February and April is 0.13 to 3.09, 6.11 to 15.63 and 4.54 to 13.42 mg/m³ respectively. In mid-reaches the values are 0.06 to 1.94, 3.65 to 7.21 and 4.04 to 14.09 mg/m³ respectively. Maximum concentration is observed in February followed by April and August. Peak values are recorded at mid day when the tide and salinity are high. Chlorophyll (chl.) a is dominant at both the stations except during monsoon and postmonsoon periods when generally chl.c is more in mouth region. The ratios of chl. a to chl. c and chl. d to carotenoids fluctuate, but are mostly greater than one.