The distribution of inorganic nutrient salts (NH4, NO2, NO3, PO4 and SiO4) and phytoplankton chlorophyll-a (Chl-a) were investigated in the Gulf of Aden and Arabian Sea coast, Yemen. Seventy tw72o surface water samples were collected during cruises in August 2014 and January 2015. The sampled area extends from As suqayyah in the west of Gulf of Aden to Hawf in the east. The study showed that the average values of nutrient salts (μg/l) on August 2014 and January 2015 were; 0.83 and 0.60, 10.98 and 10.03, 16.41 and 14.73, 10.36 and 8.76, and 29.72 and 22.67 for NH4, NO2, NO3, PO4 and SiO4, respectively. The average values of Chl-a (mg/m3) on August 2014 and January 2015 were; 0.26 and 0.21, respectively. The results showed that, NO3 is very high but NH4 is very low. This may reflect the oxidation of ammonia to nitrite and then nitrate leads to find a very good relation between ammonia and nitrate values. The lowhigh levels of dissolved inorganic nitrogen compounds, DIN (NH4, NO2, and NO3), PO4, SiO4 and Chl-a indicated that, the southern coast of Yemen is not in eutrophic conditions. Hence, surface seawater in Gulf of Aden and Arabian Sea coast under normal environmental conditions. The highest nutrient salts values were in the eastern part of the study area, and may have resulted from water originating from the Indian Ocean and upwelling. Statistical analysis to seek correlations between nutrient salts and Chl-a show very good to excellent correlation which may be due to regular coastal environment.

Keywords: Arabian Sea, Gulf of Aden, Nutrient salts, Chlorophyll-a, Yemen