Tj. Gremm et La. Kaplan, DISSOLVED CARBOHYDRATE CONCENTRATION, COMPOSITION, AND BIOAVAILABILITY TO MICROBIAL HETEROTROPHS IN STREAM WATER, Acta hydrochimica et hydrobiologica, 26(3), 1998, pp. 167-171
Dissolved total carbohydrates (DTCH), dissolved free monosaccharides (
DFMS), dissolved organic carbon (DOC), biodegradable DOC (BDOC), and h
umic substances (HS) were measured in White Clay Creek (WCC), a stream
in southeastern Pennsylvania Piedmont, USA. Samples were collected ov
er different seasons and under baseflow and stormflow conditions. DOC
concentrations ranged from 1.0 to 12.8 mg/L C with the highest concent
rations associated with stormflows. Carbohydrates ranged from 0.42 to
12.4 mu M and accounted for 2.9 to 12.7 % of the DOC. Humic substances
represented the major DOC fraction, accounting for 55 to 72% of the D
OC pool under all flow conditions. The humic fraction had a lower carb
ohydrate content (4.4 %) than the non-humic fraction of DOC (7.2 %). S
tormflow DOC was enriched in carbohydrates relative to baseflow DOG, b
ut the percentage of humic-C changed little. Carbohydrates were primar
ily present as dissolved polysaccharides (55 %), but a significant fra
ction was bound to humic substances (40 %), while a small proportion w
as present as monosaccharides (5 %). The major monosaccharides in stre
am water, listed in order of decreasing concentration, included glucos
e, galactose, rhamnose, xylose, arabinose, mannose, and fucose. On ave
rage (30.6 +/- 7.4)% (n = 44) of the stream water DOC was biodegradabl
e, and carbohydrates accounted for 9.9 to 17.7 % of the BDOC.