Seasonal and spatial distribution of Chlorophyll a in the north Arabian Sea bordering Pakistan

The average integrated chlorophyll a values for a 30-m deep surface layer in the north Arabian Sea bordering Pakistan ranged from negligible amounts to as high as 0.53μg chl. a 1ˉ¹(15.9mg mˉ²) during the period January 20, 1977 to June 4, 1977. The values, in general, decreased offshore except for the westernmost part of the Makran shelf, where unexpectedly high values were recorded over deep water. Seasonal distribution showed very high values in January (northeast monsoon season) which, with a few exceptions, gradually decreased to very low values in May, and then increased in June. The January peak may be related to winter cooling of surface waters resulting in convection and the June peak to the onset of southwest monsoon season in May. Coastal water shallower than 30m showed no seasonality and were often sites of intense phytoplankton blooms.