Distributions of dissolved monosaccharides and polysaccharides in the surface microlayer and surface water of the Jiaozhou Bay and its adjacent area

• Total dissolved carbohydrates (TDCHO) displayed a seasonal variation in Jiaozhou Bay.
• TDCHO concentrations in the bulk surface water were closely correlated with salinity.
• Monosaccharides (MCHO) and polysaccharides (PCHO) were enriched in the microlayer.
• Microlayer MCHO and PCHO concentrations were correlated with those in the bulk water.

Sea surface microlayer (SML) samples and corresponding bulk surface water (SW) samples were collected in the Jiaozhou Bay and its adjacent area in July and November 2008. The average concentrations of dissolved monosaccharides (MCHO) and polysaccharides (PCHO) revealed similar temporal variability, with higher concentrations during the green-tide period (in July) than during the non-green-tide period (in November). Average enrichment factors (EF) of MCHO and PCHO, defined as the ratio of the concentration in the SML to that in the SW, were 1.3 and 1.4 in July, respectively, while those values in November were 1.9 and 1.6. Our data also showed that the concentrations of MCHO and PCHO in the SML were strongly correlated with those in the SW, indicating that most of the organic materials in the SML came from the SW. The total dissolved carbohydrate concentrations (TDCHO) in the bulk surface water were closely correlated with salinity during the cruises (July: r=−0.580, n=18, P=0.01; November: r=−0.679, n=26, P<0.001), suggesting that riverine input had an important effect on the distribution of TDCHO in surface seawater of the study area.