Taxonomy and seasonal distribution of Pseudo-nitzschia species (Bacillariophyceae) from the coastal waters of Pakistan

摘要

This is the first detailed record of Pseudo-nitzschia species including their seasonal abundance and taxonomic identification from coastal waters of Pakistan bordering northern Arabian Sea. As reported from other coastal waters, considerably lower cell abundance was encountered. The seasonal abundance was found highest as 2.3×103cells l-lin the month of July 2003 at station A, inside of the Manora Channel which is facing the problem of eutrophication. It shows the possible relation of Pseudo-nitzschia species concentrations with nutrient enrichment. Their abundance coincided with the chlorophyll a values at station A as compared to station B where it showed an inverse correlation, suggesting that other factors like autotrophic species contributed the chlorophyll a concentrations. These studies are based on light microscopy (LM) and scanning electron microscopy (SEM) related with the morphological structure of the Pseudo-nitzschia fraudulenta and Pseudo-nitzschia sub-fraudulenta from the coastal waters of Karachi, Pakistan.