Primary Production in the Bay of Bengal during Southwest Monsoon of 1978

Abstract

Measurements of primary production, chlorophyll a and particulate organic carbon were made at 33, 43 and 44 stations respectively during August-September of 1978. The average surface production, chlorophyll a and particulate organic carbon values were 69.4 mg C/m3/day, 0.23 mg/m3 and 472 mg/m3. Average column primary production, chlorophyll a and particulate organic carbon values of the equphotic zone were 0.98 g C/m2/day, 9.81 mg/m2 and 19.7 g/m2. The integral mean concentrations of inorganic phosphate phosphorus and nitrate nitrogen (mu g-at/1) from the euphotic zone were 1.21 plus or minus 0.55 and 2.80 plus or minus 2.46. Nitrite nitrogen was below the detectable level in almost all the stations. The thickness of the surface layer ranged from 5 to 75 m. Surface salinity was less than 30 ppt at the head of the Bay and about 18 ppt at the river mouths. Surface current in the northwestern Bay was found to vary from southwesterly to southerly. Along the coast, alternating features of convergences and divergences have been found. A comparison of primary production value obtained during similar seasons of the previous two years and also with those of the Arabian Sea indicated that the average production value obtained during 1978 was the highest of all the values