SEASONAL ABUNDANCE AND MORPHOLOGICAL OBSERVATIONS OF A RAPHID PENNATE DIATOM ASTERIONELLA GLACIALIS CASTRACANE FROM THE COASTAL WATERS OF KARACHI, PAKISTAN

Diatom community has thousands of species belonging to the pennate and centric groups in which Asterionella glacialis is a raphid pennate diatom species known to form blooms in various regions including Pakistani waters. Its seasonal abundance and detailed morphological data were missing from coastal waters of Pakistan. To fill the gap of knowledge for these data this species was studied during the period of May 2002 to July 2003 at Manora Channel. Considerably lower cell abundance was encountered during study period. Maximum cell density 127cell -l was observed in the month of July, 2002. The species abundance has a significant positive correlation (Pearson) 0.980 with the salinity but a negative correlation with chlorophyll a -1.00.