Nutrient Salts, Inorganic and Organic Carbon Contents in the Waters of the Persian Gulf and the Gulf of Oman

Sea water samples were collected from 32 stations in the southern part of the Persian Gulf and the Gulf of Oman during winter of 1987. Surface water of the Persian Gulf exhibited wide range and higher values of salinity (37.15-43.95, mean 40.02%) compared with lower values and narrow range (36.58-36.95, mean 36.74%) in the Gulf of Oman. Surface salinity did not reflect any significant relationship with nutrients and organic and inorganic carbon except, silicate which showed an increase in concentration with decreasing values of salinity (r= -065, p<0.01) in the Persian Gulf waters. The Gulf of Oman exhibited higher levels of phosphate (0.08-1.65, mean 0.57 μ moles/L), nitrate (0.08- 3.44, mean 0.78 μ moles/L) and silicate (2.49-22.47, mean 6.37 μ moles/L) than the surface water of the southern Persian Gulf, while inorganic carbon (7.5-22.6, mean 13.62 mg/L) and organic carbon (2.1-14.6, mean 6.37 mg/L) of the Gulf of Oman showed nearly comparable results with those of the Persian Gulf,respectively. Atomic ratio of the elements P:N:Si for the surface water showed similar values 1:2.2:11.1 and 1:2.7:11.8 for the Persian Gulf and the Gulf of Oman, respectively, indicating N is the limiting nutrient for this area. The presence of a shallow Oxygen minimum in the Gulf of Oman (0.23-1.30 m1/L) at depth 140-370 m and t values (25.51-26.60) coincide with the layer of maximum PO4 (1.06-2.23 μ moles/L), NO3 (3.39- 19.33 μ moles/L), SiO3 (12.54-29.51 μ moles/L) and PCO2 which could be resulted from mineralization of organic matter. Water mass of Gulf origin was identified at 190-300 m in the Gulf of Oman that exhibit higher density levels 26.05-26.74 and medium concentrations of organic carbon. The nutrients, inorganic and organic carbon budget in the Persian Gulf waters were evaluated as 42608, 20165, 227909, 3395×103 and 4943×103 Ton/year for phosphate, nitrate, silicate, organic and inorganic carbon, respectively, representing the net gain to the Persian Gulf water.