Variation in the composition of carbohydrates in the Dona Paula Bay (west of India) during May/June 1998

Suspended particulate material was analysed for particulate carbohydrate concentration and composition and for the bulk parameters: suspended particulate matter, chlorophyll a, particulate organic carbon, particulate organic nitrogen and particulate proteins. Chlorophyll a concentrations increased from May 7 to 15 due to the development of a small scale bloom of diatom Navicula sp. and decreased for the remaining period after the premonsoon rain on 16 and 17 May. Concentrations of particulate organic carbon, organic nitrogen, carbohydrates and proteins increased with the increase in chlorophyll a concentration. Together particulate protein-carbon and carbohydrate-carbon accounted for 10 to 30% of the organic carbon. Glucose contributed 26 to 81% to the total particulate carbohydrates. The decrease in glucose concentration was accompanied by the increase in mannose, galactose, xylose, arabinose, rhamnose and fucose. Chlorophyll a showed significant positive relationship with glucose and negative relationships with arabinose and xylose. Conversely, suspended particulate matter showed significant positive relationships with xylose and arabinose and negative relationships with chlorophyll a and glucose. The hexoses to pentoses ratio increased during 7 to 15 May and decreased thereafter. Relatively higher chlorophyll a, particulate protein-carbon plus carbohydrate-carbon, glucose, hexoses:pentoses ratio and lower rhamnose plus fucose suggested the presence of more fresh marine organic matter during May 8 to 15. Subsequently, chlorophyll a, contribution of particulate protein-carbon plus carbohydrates-carbon to organic carbon, hexoses to pentoses ratio, and weight percentage of glucose decreased whereas, weight percentage of rhamnose plus fucose, arabinose and xylose increased, reflecting highly degraded diagenetically altered particulate organic matter from May 16 to June 2. The carbohydrate content and composition as well as protein data suggest that the nature and source of organic matter Varied within a few days ...