Observations on the bloom of a diatom Fragilaria oceanica Cleve

Abstract

Fragilaria oceanica the dominant component in a mixed bloom of diatoms and a blue green alga which occurred near Mangalore in August 1972 showed a density of 36.8 x 106 cells/l and constituted 92% of the total number of cells in the bloom. The components of the bloom were Rhizosolenia sp. Pleurosigma sp. Coscinodiscus sp. and the alga Richelia intracellularis. The bloom occurred at a salinity of 32.36 ppt. The values of chlorophyll c and carotenoids were lower than that of chlorophyll a. Species diversity index (0.48) indicated that the bloom was at its peak. During the bloom values of nutrients especially those of inorganic phosphate were fairly high