Seasonal Variation of Diatom Biodiversity With Relation to Environmental Factors In Northern Arabian Sea

Diatoms are planktonic, microscopic and ubiquitous in distribution. In this study, the samples were collected in four seasons from two sites of the Northern Arabian Sea (Gadani shipbreaking area of the Baluchistan coast and Sandspit, Sind coast of Pakistan) for a period of one year. The seasonal distribution of diatom and variations in physico-chemical characteristics of seawater were examined from samples collected on board using Niskin bottles. Eighty five species of diatoms (pennate = 40; centric = 45) were recorded along the Gadani shipbreaking area of the Baluchistan coast of Pakistan. Similarly, from Sandspit, Sind coast of Pakistan seventy four species of diatoms (pennate = 35; centric = 39) were recorded. In Gadani, the highest number of species was recorded in North-East Monsoon (NEM), while in Sandspit, it was recorded in the South-West Monsoon (SWM). The dominant species of pennate diatoms such as Navicula, Nitzschia and Pseudonitzchia were similar in abundance at both the sites, while the dominant centric diatoms were diversified in both coastal sites. The present study indicates that the environmental factors such as temperature, dissolve oxygen, salinity, pH, nitrate, nitrite, phosphate, ammonia, and chlorophyll-a influences the diatom diversity and abundance, and any significant changes in the diversity of phytoplankton species indicate deterioration of the marine ecosystem.