Distributions of carbohydrates, including uronic acids, in estuarine waters of Galveston Bay

The concentrations of carbohydrates, including uronic acids, in dissolved (less than or equal to 0.45 mum) and colloidal (1 kDa-0.45 mum) phases were measured in estuarine waters of Galveston Bay, TX, in order to study their role in heavy metal detoxification. The concentrations of dissolved monosaccharides (MCHO) in Galveston Bay ranged from 13 to 62 muM-C, and those of dissolved polysaccharides (PCHO) ranged from 10 to 42 muM-C. On average, MCHO and PCHO contributed about 11% and 7% to dissolved organic carbon (DOC), respectively. The colloidal carbohydrates (CCHO) in Galveston Bay varied from 7 to 54 muM-C, and accounted for 9% to 24% of the colloidal organic carbon (COC), with an average value of 17%, suggesting that CCHO is abundant in the high molecular weight (HMW) fraction of DOG. The concentration of CCHO is generally significantly higher than that of PCHO. This result is attributed to entrainment of low molecular weight (LMW) carbohydrates into the retentate fraction during ultrafiltration. The concentration of total dissolved uronic acids (DUA) in the same samples varied from 1.0 to 8.3 muM-C, with an average value of 6.1 muM-C, while the colloidal uronic acids (CUA) ranged from 0.8 to 6.4 muM-C, with an average value of 4.8 muM-C. The concentrations of DUA are higher than the previously reported values in coastal waters. Furthermore, CUA represent a dominant component of DUA in Galveston Bay waters. More importantly, significant correlations of PCHO and DUA to dissolved Cu concentrations (less than or equal to0.45 mum) were found, suggesting that acid polysaccharides were produced in response to trace metal stressors. (C) 2001 Published by Elsevier Science B.V.