A seasonal survey of carbohydrates and uronic acids in the Trinity River, Texas

Due to their potential significance as indicators of ecological health, the biogeochemical cycling of carbohydrates and uronic acids was investigated in the Trinity River Texas, during 2000-2001. Concentrations of dissolved organic carbon (DOC), total carbohydrates (TCHO), polysaccharides (PCHO), monosaccharides (MCHO), uronic acids (URA), as well as of oxygen, suspended particulate matter, nutrients and trace metals (Cu, Pb, Cd) were assessed at various stages of discharge. TCHO/DOC ratios, as well as nutrient and hydrogen ion concentrations, were inversely related to temperature, which suggests that biological processes in Lake Livingston, the largest freshwater reservoir along the Trinity River, are not only regulating nutrient concentrations but also the preferential degradation of carbohydrates over that of bulk DOC. However, uronic acids were selectively preserved during this temperature controlled biological process, as is evident from the positive correlation of URA/TCHO ratios and temperature. Thus, uronic acids are more refractory compounds than bulk TCHO. Significant correlations between TCHO and dissolved Cu, Pb and Cd suggest that their pathways and cycles are linked through common sources or removal processes.