Abundance of dissolved polysaccharides in the oxygen minimum layer of the Northern Indian Ocean

Water samples collected from the upper 1500 m at seven stations in the Bay of Bengal and at five stations in the Arabian Sea, were analysed for dissolved carbohydrate by the MBTH (3-methyl-2-benzothiazolenone hydrazone hydrochloride) method without hydrolysis and after hydrolysis with dilute HCl (0.09 N) and concentrated H2SO4 (1.2 M). Monosaccharide (MCHO) concentrations averaged 1.88±1.01 μM and showed small variations with depth at all stations. Polysaccharides (PCHO) were the most abundant form of total dissolved carbohydrates (TCHO) throughout the water column sampled and accounted for 75±11% of the TCHO. Hydrolysis-resistant PCHO (HR-PCHO) contributed 48±16% to the PCHO. Concentrations of PCHO in the lower boundary of the oxygen minimum layer (500 to 1000 m) were generally higher than those observed in the surface waters. Carbohydrate concentrations showed significant negative correlation with dissolved oxygen concentrations. The pattern of carbohydrate distribution reported in this study add to the global picture of carbohydrate distribution.