ABUNDANCE AND DISTRIBUTION OF CARBOHYDRATES IN THE OCEAN

Carbohydrate concentrations in depth profiles from the Atlantic and Pacific Oceans, the Gulf of Mexico, and the Gerlache Strait (Antarctica) were determined by MBTH analysis without hydrolysis and after hydrolysis with dilute HCl and concentrated H2SO4. Total carbohydrate (TCHO) concentrations in surface waters varied from 7 to 33 muM C and accounted for 21+/-7% of the dissolved organic carbon (DOC) measured by high-temperature combustion. Polysaccharides (PCHO) were the dominant form of carbohydrate in waters above oxygen minima whereas monosaccharides were dominant in the deep ocean. PCHO comprised 71+/-18% of TCHO and 16+/-9% of the DOC above oxygen minima at all stations. Hydrolysis-resistant PCHO comprised 67+/-30% of the total PCHO. Monosaccharide (MCHO) concentrations averaged 4.3+/-1.9 muM C and varied little with depth at all stations. The large (5-fold) decrease in PCHO concentrations between surface waters and oxygen minima suggested that polysaccharides are an active component of the carbon cycle in the upper ocean.