The coast of Pakistan (North Arabian Sea) is under the influence of the seasonal cycle of monsoons, which may result in 2 periods of elevated phytoplankton productivity, one during the north-east monsoon (December–February) and the other during the south-west monsoon (May–September). | Turkish Journal of Botany Research Article Turk J Bot (2013) 37: 398-410 © TÜBİTAK doi: Seasonal variability of phytoplankton in a coastal lagoon and adjacent open sea in Pakistan Saima LATIF, Zarrien AYUB*, Ghazala SIDDIQUI Centre of Excellence in Marine Biology, University of Karachi, Karachi-75270, Pakistan Received: Accepted: Published Online: Printed: Abstract: The coast of Pakistan (North Arabian Sea) is under the influence of the seasonal cycle of monsoons, which may result in 2 periods of elevated phytoplankton productivity, one during the north-east monsoon (December–February) and the other during the south-west monsoon (May–September). In the present study, elevated primary productivity in the Miani Hor Lagoon and adjacent open sea off Pakistan was found during the south-west monsoon (May–September) and spring inter-monsoon (March–April). The lowest phytoplankton abundance was recorded in the north-east monsoon period at both collection sites. A total of 65 species of diatoms and 32 species of dinoflagellates were identified in the lagoon. In the open sea, 63 species of diatoms and 23 species of dinoflagellates were present. No significant differences were found in salinity, dissolved oxygen, pH, or nitrite, ammonium, or phosphate concentrations during the different seasons at the 2 sites. Temperature and chlorophyll-a varied significantly (P ) in salinity was found between sites or between seasons (Tables 1 and 2). pH value was similar at the 2 sites, but it was significantly (P < ) different between seasons (Table 1). The pH was higher during the spring inter-monsoon as compared to the other seasons, when it was similar (Table 2). Dissolved oxygen in the subsurface water ranged between and mL L–1 in the lagoon and between and mL L–1 in the open sea. No significant difference was found in the concentration of dissolved .
