Seasonal Changes of Chlorophyll a and Environmental Characteristics in the Sea of Oman
Al-Hashmi, Khalid A. Claereboudt*, Michel R. Al-Azri, Adnan, R. Piontovski, Sergey. A.
Sultan Qaboos University, Department Marine Science and Fisheries College Agricultural and Marine Sciences, Box 34
Al-Khod 123 Sultanate of Oman
Monthly estimates of chlorophyll a, temperature, salinity, and nutrients were collected through sampling at two stations from January 2001 to January 2002, in and near Bandar Al-Khyran, the largest semi-enclosed bay on the southern coast of the Sea of Oman. Although the sampling location was at the limit of the tropical range, the seasonal changes of the coastal phytoplankton were more related to temperate dynamics, showing seasonal fluctuation of more than 10o C.
Sharp temperature drops observed in August and July were likely due to rises of the thermocline under the influence of coastal upwelling events or to deep water injections along the north coast of Oman generated by changes in the coastal wind patterns. Overall, small phytoplanktonic cells [0.7-5 μm] dominated the phytoplankton community of the mixed layer with an average of 69.7 % and 73.5 % of the extracted chlorophyll a at the station "Inside" and "Outside" the bay, respectively.
Keywords: Arabian Sea, picoplankton, chlorophyll a, coastal upwelling, phytoplankton blooms.
Coastal upwellings and Mesoscale Eddies of the Western Arabian Sea: Some Biological Implications
S.A. Piontkovski*and S. Al-Jufaili
Sultan Qaboos University, CAMS,
PO Box 34, Al-Khod 123,
Sultanate of Oman
Satellite derived (SeaWIFS, MODIS, TOPEX/Poseidon, and Jason) chlorophyll-a concentration, sea surface heights, sea surface temperature, data on vertical profiles of temperature and salinity from the ARGO drifting floats, wind speed, the Dipole Mode Index, and historical data on sardine landings were employed, to analyze physical-biological coupling in the western Arabian Sea which is known for its vigorous eddy field affecting characteristics of biological productivity. Summer and winter monsoons impose different modes of mesoscale variability. In summer, the East Arabian
Current along with the currents of the Arabian Sea interior generates a dense field of eddies, where as in winter, eddies become less developed and less numerous. Therefore, the chlorophyll distribution is more heterogeneous spatially and more variable temporally during summer monsoon. Interannual changes of eddy field bear footprints of the impact of basin-scale atmospheric
anomaly (the Indian Ocean Dipole). Spatial-temporal characteristics of the eddy field are valuable tools in understanding seasonal and interannual fluctuations of sardine landings contributing ~ 50% to the fishery in the region.