The planktonic diatom of the genus Chaetoceros Ehrenberg from northwestern Arabian sea bordering Pakistan

The present paper reports the occurrence of 17 species of chaetoceros including two varieties from the northwestern arabian sea shelf of pakistan and deep sea vicinity. c. coarctatus was the most common and frequent species followed by c. messanensis and c. lorenzianus while others were rare. maximum species diversity occurred during northeast monsoon season. the indus delta shelf was more diverse than the balochistan shelf. all the 17 species were present in the former area and also more frequent than the later area. most species were neritic indicating coastal influence.