Biochemical components in suspended particles and colloids: carbohydrates in the Potomac and Patuxent Estuaries

Carbohydrates were measured in suspended particles (> 0.4 μm) and colloids over a 187 km segment of the Potomac Estuary and during a summer dinoflagellate bloom in the Patuxent Estuary (U.S.A.). The average carbohydrate composition of suspended particles was 43 ± 18% glucose, 13 ± 7% galactose, 11 + 4% rhamnose, 9 ± 4% fucose, 9 ± 4% xylose, 9 ± 4% mannose and 5 ± 1% arabinose. C/N ratios in suspended particles and colloids averaged 9.3 ± 2, a value typical of single-cell organisms. Colloid-sized (2 nm to 0.4 μm) carbohydrate concentrations ranged from 125 to 255 μg l−1 in the Potomac Estuary and up to 576 μg l−1 during a dinoflagellate bloom in the Patuxent Estuary. Colloid carbohydrates contained 15 ± 5% glucose, 21 ± 3% galactose, 14 ± 3% rhamnose, 16 ± 4% fucose, 16 ± 2% xylose, 9 ± 2% mannose, 7 ± 2% arabinose, and 4 ± 1% ribose. The colloidal material isolated by ultrafiltration comprised up to 70% by weight of the dissolved organic matter (DOC).